putty/terminal/terminal.c

/*
 * Terminal emulator.
 */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <limits.h>
#include <wchar.h>

#include <time.h>
#include <assert.h>
#include "putty.h"
#include "terminal.h"

#define VT52_PLUS

#define CL_ANSIMIN      0x0001         /* Codes in all ANSI like terminals. */
#define CL_VT100        0x0002         /* VT100 */
#define CL_VT100AVO     0x0004         /* VT100 +AVO; 132x24 (not 132x14) & attrs */
#define CL_VT102        0x0008         /* VT102 */
#define CL_VT220        0x0010         /* VT220 */
#define CL_VT320        0x0020         /* VT320 */
#define CL_VT420        0x0040         /* VT420 */
#define CL_VT510        0x0080         /* VT510, NB VT510 includes ANSI */
#define CL_VT340TEXT    0x0100         /* VT340 extensions that appear in the VT420 */
#define CL_SCOANSI      0x1000         /* SCOANSI not in ANSIMIN. */
#define CL_ANSI         0x2000         /* ANSI ECMA-48 not in the VT100..VT420 */
#define CL_OTHER        0x4000         /* Others, Xterm, linux, putty, dunno, etc */

#define TM_VT100        (CL_ANSIMIN|CL_VT100)
#define TM_VT100AVO     (TM_VT100|CL_VT100AVO)
#define TM_VT102        (TM_VT100AVO|CL_VT102)
#define TM_VT220        (TM_VT102|CL_VT220)
#define TM_VTXXX        (TM_VT220|CL_VT340TEXT|CL_VT510|CL_VT420|CL_VT320)
#define TM_SCOANSI      (CL_ANSIMIN|CL_SCOANSI)

#define TM_PUTTY        (0xFFFF)

#define UPDATE_DELAY    ((TICKSPERSEC+49)/50)/* ticks to defer window update */
#define TBLINK_DELAY    ((TICKSPERSEC*9+19)/20)/* ticks between text blinks*/
#define CBLINK_DELAY    (CURSORBLINK) /* ticks between cursor blinks */
#define VBELL_DELAY     (VBELL_TIMEOUT) /* visual bell timeout in ticks */

#define compatibility(x) \
    if ( ((CL_##x)&term->compatibility_level) == 0 ) {  \
       term->termstate=TOPLEVEL;                        \
       break;                                           \
    }
#define compatibility2(x,y) \
    if ( ((CL_##x|CL_##y)&term->compatibility_level) == 0 ) { \
       term->termstate=TOPLEVEL;                        \
       break;                                           \
    }

#define has_compat(x) ( ((CL_##x)&term->compatibility_level) != 0 )

static const char *const EMPTY_WINDOW_TITLE = "";

static const char sco2ansicolour[] = { 0, 4, 2, 6, 1, 5, 3, 7 };

#define sel_nl_sz  (sizeof(sel_nl)/sizeof(wchar_t))
static const wchar_t sel_nl[] = SEL_NL;

/* forward declaration */
static void term_userpass_state_free(struct term_userpass_state *s);

/*
 * Fetch the character at a particular position in a line array,
 * for purposes of `wordtype'. The reason this isn't just a simple
 * array reference is that if the character we find is UCSWIDE,
 * then we must look one space further to the left.
 */
#define UCSGET(a, x) \
    ( (x)>0 && (a)[(x)].chr == UCSWIDE ? (a)[(x)-1].chr : (a)[(x)].chr )

/*
 * Detect the various aliases of U+0020 SPACE.
 */
#define IS_SPACE_CHR(chr) \
        ((chr) == 0x20 || (DIRECT_CHAR(chr) && ((chr) & 0xFF) == 0x20))

/*
 * Spot magic CSETs.
 */
#define CSET_OF(chr) (DIRECT_CHAR(chr)||DIRECT_FONT(chr) ? (chr)&CSET_MASK : 0)

/*
 * Internal prototypes.
 */
static void resizeline(Terminal *, termline *, int);
static termline *lineptr(Terminal *, int, int);
static void check_line_size(Terminal *, termline *);
static void do_paint(Terminal *);
static void erase_lots(Terminal *, bool, bool, bool);
static int find_last_nonempty_line(Terminal *, tree234 *);
static void swap_screen(Terminal *, int, bool, bool);
static void update_sbar(Terminal *);
static void deselect(Terminal *);
static void term_print_finish(Terminal *);
static void scroll(Terminal *, int, int, int, bool);
static void parse_optionalrgb(optionalrgb *out, unsigned *values);
static void term_added_data(Terminal *term, bool);
static void term_update_raw_mouse_mode(Terminal *term);
static void term_out_cb(void *);

static termline *newtermline(Terminal *term, int cols, bool bce)
{
    termline *line;
    int j;

    line = snew(termline);
    line->chars = snewn(cols, termchar);
    for (j = 0; j < cols; j++)
        line->chars[j] = (bce ? term->erase_char : term->basic_erase_char);
    line->cols = line->size = cols;
    line->lattr = LATTR_NORM;
    line->trusted = false;
    line->temporary = false;
    line->cc_free = 0;

    return line;
}

static void freetermline(termline *line)
{
    if (line) {
        sfree(line->chars);
        sfree(line);
    }
}

void term_release_line(termline *line)
{
    if (line->temporary)
        freetermline(line);
}

const int colour_indices_conf_to_oscp[CONF_NCOLOURS] = {
    #define COLOUR_ENTRY(id,name) OSCP_COLOUR_##id,
    CONF_COLOUR_LIST(COLOUR_ENTRY)
    #undef COLOUR_ENTRY
};

const int colour_indices_conf_to_osc4[CONF_NCOLOURS] = {
    #define COLOUR_ENTRY(id,name) OSC4_COLOUR_##id,
    CONF_COLOUR_LIST(COLOUR_ENTRY)
    #undef COLOUR_ENTRY
};

const int colour_indices_oscp_to_osc4[OSCP_NCOLOURS] = {
    #define COLOUR_ENTRY(id) OSC4_COLOUR_##id,
    OSCP_COLOUR_LIST(COLOUR_ENTRY)
    #undef COLOUR_ENTRY
};

#ifdef TERM_CC_DIAGS
/*
 * Diagnostic function: verify that a termline has a correct
 * combining character structure.
 *
 * This is a performance-intensive check, so it's no longer enabled
 * by default.
 */
static void cc_check(termline *line)
{
    unsigned char *flags;
    int i, j;

    assert(line->size >= line->cols);

    flags = snewn(line->size, unsigned char);

    for (i = 0; i < line->size; i++)
        flags[i] = (i < line->cols);

    for (i = 0; i < line->cols; i++) {
        j = i;
        while (line->chars[j].cc_next) {
            j += line->chars[j].cc_next;
            assert(j >= line->cols && j < line->size);
            assert(!flags[j]);
            flags[j] = true;
        }
    }

    j = line->cc_free;
    if (j) {
        while (1) {
            assert(j >= line->cols && j < line->size);
            assert(!flags[j]);
            flags[j] = true;
            if (line->chars[j].cc_next)
                j += line->chars[j].cc_next;
            else
                break;
        }
    }

    j = 0;
    for (i = 0; i < line->size; i++)
        j += (flags[i] != 0);

    assert(j == line->size);

    sfree(flags);
}
#endif

static void clear_cc(termline *line, int col);

/*
 * Add a combining character to a character cell.
 */
static void add_cc(termline *line, int col, unsigned long chr)
{
    int newcc;

    assert(col >= 0 && col < line->cols);

    /*
     * Don't add combining characters at all to U+FFFD REPLACEMENT
     * CHARACTER. (Partly it's a slightly incoherent idea in the first
     * place; mostly, U+FFFD is what we generate if a cell already has
     * too many ccs, in which case we want it to be a fixed point when
     * further ccs are added.)
     */
    if (line->chars[col].chr == 0xFFFD)
        return;

    /*
     * Walk the cc list of the cell in question to find its current
     * end point.
     */
    size_t ncc = 0;
    int origcol = col;
    while (line->chars[col].cc_next) {
        col += line->chars[col].cc_next;
        if (++ncc >= CC_LIMIT) {
            /*
             * There are already too many combining characters in this
             * character cell. Change strategy: throw out the entire
             * chain and replace the main character with U+FFFD.
             *
             * (Rationale: extrapolating from UTR #36 section 3.6.2
             * suggests the principle that it's better to substitute
             * U+FFFD than to _ignore_ input completely. Also, if the
             * user copies and pastes an overcombined character cell,
             * this way it will clearly indicate that we haven't
             * reproduced the writer's original intentions, instead of
             * looking as if it was the _writer's_ fault that the 33rd
             * cc is missing.)
             *
             * Per the code above, this will also prevent any further
             * ccs from being added to this cell.
             */
            clear_cc(line, origcol);
            line->chars[origcol].chr = 0xFFFD;
            return;
        }
    }

    /*
     * Extend the cols array if the free list is empty.
     */
    if (!line->cc_free) {
        int n = line->size;

        size_t tmpsize = line->size;
        sgrowarray(line->chars, tmpsize, tmpsize);
        assert(tmpsize <= INT_MAX);
        line->size = tmpsize;

        line->cc_free = n;
        while (n < line->size) {
            if (n+1 < line->size)
                line->chars[n].cc_next = 1;
            else
                line->chars[n].cc_next = 0;
            n++;
        }
    }

    /*
     * `col' now points at the last cc currently in this cell; so
     * we simply add another one.
     */
    newcc = line->cc_free;
    if (line->chars[newcc].cc_next)
        line->cc_free = newcc + line->chars[newcc].cc_next;
    else
        line->cc_free = 0;
    line->chars[newcc].cc_next = 0;
    line->chars[newcc].chr = chr;
    line->chars[col].cc_next = newcc - col;

#ifdef TERM_CC_DIAGS
    cc_check(line);
#endif
}

/*
 * Clear the combining character list in a character cell.
 */
static void clear_cc(termline *line, int col)
{
    int oldfree, origcol = col;

    assert(col >= 0 && col < line->cols);

    if (!line->chars[col].cc_next)
        return;                        /* nothing needs doing */

    oldfree = line->cc_free;
    line->cc_free = col + line->chars[col].cc_next;
    while (line->chars[col].cc_next)
        col += line->chars[col].cc_next;
    if (oldfree)
        line->chars[col].cc_next = oldfree - col;
    else
        line->chars[col].cc_next = 0;

    line->chars[origcol].cc_next = 0;

#ifdef TERM_CC_DIAGS
    cc_check(line);
#endif
}

/*
 * Compare two character cells for equality. Special case required
 * in do_paint() where we override what we expect the chr and attr
 * fields to be.
 */
static bool termchars_equal_override(termchar *a, termchar *b,
                                     unsigned long bchr, unsigned long battr)
{
    /* FULL-TERMCHAR */
    if (!truecolour_equal(a->truecolour, b->truecolour))
        return false;
    if (a->chr != bchr)
        return false;
    if ((a->attr &~ DATTR_MASK) != (battr &~ DATTR_MASK))
        return false;
    while (a->cc_next || b->cc_next) {
        if (!a->cc_next || !b->cc_next)
            return false;              /* one cc-list ends, other does not */
        a += a->cc_next;
        b += b->cc_next;
        if (a->chr != b->chr)
            return false;
    }
    return true;
}

static bool termchars_equal(termchar *a, termchar *b)
{
    return termchars_equal_override(a, b, b->chr, b->attr);
}

/*
 * Copy a character cell. (Requires a pointer to the destination
 * termline, so as to access its free list.)
 */
static void copy_termchar(termline *destline, int x, termchar *src)
{
    clear_cc(destline, x);

    destline->chars[x] = *src;         /* copy everything except cc-list */
    destline->chars[x].cc_next = 0;    /* and make sure this is zero */

    while (src->cc_next) {
        src += src->cc_next;
        add_cc(destline, x, src->chr);
    }

#ifdef TERM_CC_DIAGS
    cc_check(destline);
#endif
}

/*
 * Move a character cell within its termline.
 */
static void move_termchar(termline *line, termchar *dest, termchar *src)
{
    /* First clear the cc list from the original char, just in case. */
    clear_cc(line, dest - line->chars);

    /* Move the character cell and adjust its cc_next. */
    *dest = *src;                      /* copy everything except cc-list */
    if (src->cc_next)
        dest->cc_next = src->cc_next - (dest-src);

    /* Ensure the original cell doesn't have a cc list. */
    src->cc_next = 0;

#ifdef TERM_CC_DIAGS
    cc_check(line);
#endif
}

#ifndef NO_SCROLLBACK_COMPRESSION

/*
 * Compress and decompress a termline into an RLE-based format for
 * storing in scrollback. (Since scrollback almost never needs to
 * be modified and exists in huge quantities, this is a sensible
 * tradeoff, particularly since it allows us to continue adding
 * features to the main termchar structure without proportionally
 * bloating the terminal emulator's memory footprint unless those
 * features are in constant use.)
 */
static void makerle(strbuf *b, termline *ldata,
                    void (*makeliteral)(strbuf *b, termchar *c,
                                        unsigned long *state))
{
    int hdrpos, hdrsize, n, prevlen, prevpos, thislen, thispos;
    bool prev2;
    termchar *c = ldata->chars;
    unsigned long state = 0, oldstate;

    n = ldata->cols;

    hdrpos = b->len;
    hdrsize = 0;
    put_byte(b, 0);
    prevlen = prevpos = 0;
    prev2 = false;

    while (n-- > 0) {
        thispos = b->len;
        makeliteral(b, c++, &state);
        thislen = b->len - thispos;
        if (thislen == prevlen &&
            !memcmp(b->u + prevpos, b->u + thispos, thislen)) {
            /*
             * This literal precisely matches the previous one.
             * Turn it into a run if it's worthwhile.
             *
             * With one-byte literals, it costs us two bytes to
             * encode a run, plus another byte to write the header
             * to resume normal output; so a three-element run is
             * neutral, and anything beyond that is unconditionally
             * worthwhile. With two-byte literals or more, even a
             * 2-run is a win.
             */
            if (thislen > 1 || prev2) {
                int runpos, runlen;

                /*
                 * It's worth encoding a run. Start at prevpos,
                 * unless hdrsize==0 in which case we can back up
                 * another one and start by overwriting hdrpos.
                 */

                hdrsize--;             /* remove the literal at prevpos */
                if (prev2) {
                    assert(hdrsize > 0);
                    hdrsize--;
                    prevpos -= prevlen;/* and possibly another one */
                }

                if (hdrsize == 0) {
                    assert(prevpos == hdrpos + 1);
                    runpos = hdrpos;
                    strbuf_shrink_to(b, prevpos+prevlen);
                } else {
                    memmove(b->u + prevpos+1, b->u + prevpos, prevlen);
                    runpos = prevpos;
                    strbuf_shrink_to(b, prevpos+prevlen+1);
                    /*
                     * Terminate the previous run of ordinary
                     * literals.
                     */
                    assert(hdrsize >= 1 && hdrsize <= 128);
                    b->u[hdrpos] = hdrsize - 1;
                }

                runlen = prev2 ? 3 : 2;

                while (n > 0 && runlen < 129) {
                    int tmppos, tmplen;
                    tmppos = b->len;
                    oldstate = state;
                    makeliteral(b, c, &state);
                    tmplen = b->len - tmppos;
                    bool match = tmplen == thislen &&
                        !memcmp(b->u + runpos+1, b->u + tmppos, tmplen);
                    strbuf_shrink_to(b, tmppos);
                    if (!match) {
                        state = oldstate;
                        break;         /* run over */
                    }
                    n--, c++, runlen++;
                }

                assert(runlen >= 2 && runlen <= 129);
                b->u[runpos] = runlen + 0x80 - 2;

                hdrpos = b->len;
                hdrsize = 0;
                put_byte(b, 0);
                /* And ensure this run doesn't interfere with the next. */
                prevlen = prevpos = 0;
                prev2 = false;

                continue;
            } else {
                /*
                 * Just flag that the previous two literals were
                 * identical, in case we find a third identical one
                 * we want to turn into a run.
                 */
                prev2 = true;
                prevlen = thislen;
                prevpos = thispos;
            }
        } else {
            prev2 = false;
            prevlen = thislen;
            prevpos = thispos;
        }

        /*
         * This character isn't (yet) part of a run. Add it to
         * hdrsize.
         */
        hdrsize++;
        if (hdrsize == 128) {
            b->u[hdrpos] = hdrsize - 1;
            hdrpos = b->len;
            hdrsize = 0;
            put_byte(b, 0);
            prevlen = prevpos = 0;
            prev2 = false;
        }
    }

    /*
     * Clean up.
     */
    if (hdrsize > 0) {
        assert(hdrsize <= 128);
        b->u[hdrpos] = hdrsize - 1;
    } else {
        strbuf_shrink_to(b, hdrpos);
    }
}
static void makeliteral_chr(strbuf *b, termchar *c, unsigned long *state)
{
    /*
     * My encoding for characters is UTF-8-like, in that it stores
     * 7-bit ASCII in one byte and uses high-bit-set bytes as
     * introducers to indicate a longer sequence. However, it's
     * unlike UTF-8 in that it doesn't need to be able to
     * resynchronise, and therefore I don't want to waste two bits
     * per byte on having recognisable continuation characters.
     * Also I don't want to rule out the possibility that I may one
     * day use values 0x80000000-0xFFFFFFFF for interesting
     * purposes, so unlike UTF-8 I need a full 32-bit range.
     * Accordingly, here is my encoding:
     *
     * 00000000-0000007F: 0xxxxxxx (but see below)
     * 00000080-00003FFF: 10xxxxxx xxxxxxxx
     * 00004000-001FFFFF: 110xxxxx xxxxxxxx xxxxxxxx
     * 00200000-0FFFFFFF: 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
     * 10000000-FFFFFFFF: 11110ZZZ xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
     *
     * (`Z' is like `x' but is always going to be zero since the
     * values I'm encoding don't go above 2^32. In principle the
     * five-byte form of the encoding could extend to 2^35, and
     * there could be six-, seven-, eight- and nine-byte forms as
     * well to allow up to 64-bit values to be encoded. But that's
     * completely unnecessary for these purposes!)
     *
     * The encoding as written above would be very simple, except
     * that 7-bit ASCII can occur in several different ways in the
     * terminal data; sometimes it crops up in the D800 page
     * (CSET_ASCII) but at other times it's in the 0000 page (real
     * Unicode). Therefore, this encoding is actually _stateful_:
     * the one-byte encoding of 00-7F actually indicates `reuse the
     * upper three bytes of the last character', and to encode an
     * absolute value of 00-7F you need to use the two-byte form
     * instead.
     */
    if ((c->chr & ~0x7F) == *state) {
        put_byte(b, (unsigned char)(c->chr & 0x7F));
    } else if (c->chr < 0x4000) {
        put_byte(b, (unsigned char)(((c->chr >> 8) & 0x3F) | 0x80));
        put_byte(b, (unsigned char)(c->chr & 0xFF));
    } else if (c->chr < 0x200000) {
        put_byte(b, (unsigned char)(((c->chr >> 16) & 0x1F) | 0xC0));
        put_uint16(b, c->chr & 0xFFFF);
    } else if (c->chr < 0x10000000) {
        put_byte(b, (unsigned char)(((c->chr >> 24) & 0x0F) | 0xE0));
        put_byte(b, (unsigned char)((c->chr >> 16) & 0xFF));
        put_uint16(b, c->chr & 0xFFFF);
    } else {
        put_byte(b, 0xF0);
        put_uint32(b, c->chr);
    }
    *state = c->chr & ~0xFF;
}
static void makeliteral_attr(strbuf *b, termchar *c, unsigned long *state)
{
    /*
     * My encoding for attributes is 16-bit-granular and assumes
     * that the top bit of the word is never required. I either
     * store a two-byte value with the top bit clear (indicating
     * just that value), or a four-byte value with the top bit set
     * (indicating the same value with its top bit clear).
     *
     * However, first I permute the bits of the attribute value, so
     * that the eight bits of colour (four in each of fg and bg)
     * which are never non-zero unless xterm 256-colour mode is in
     * use are placed higher up the word than everything else. This
     * ensures that attribute values remain 16-bit _unless_ the
     * user uses extended colour.
     */
    unsigned attr, colourbits;

    attr = c->attr;

    assert(ATTR_BGSHIFT > ATTR_FGSHIFT);

    colourbits = (attr >> (ATTR_BGSHIFT + 4)) & 0xF;
    colourbits <<= 4;
    colourbits |= (attr >> (ATTR_FGSHIFT + 4)) & 0xF;

    attr = (((attr >> (ATTR_BGSHIFT + 8)) << (ATTR_BGSHIFT + 4)) |
            (attr & ((1 << (ATTR_BGSHIFT + 4))-1)));
    attr = (((attr >> (ATTR_FGSHIFT + 8)) << (ATTR_FGSHIFT + 4)) |
            (attr & ((1 << (ATTR_FGSHIFT + 4))-1)));

    attr |= (colourbits << (32-9));

    if (attr < 0x8000) {
        put_byte(b, (unsigned char)((attr >> 8) & 0xFF));
        put_byte(b, (unsigned char)(attr & 0xFF));
    } else {
        put_byte(b, (unsigned char)(((attr >> 24) & 0x7F) | 0x80));
        put_byte(b, (unsigned char)((attr >> 16) & 0xFF));
        put_byte(b, (unsigned char)((attr >> 8) & 0xFF));
        put_byte(b, (unsigned char)(attr & 0xFF));
    }
}
static void makeliteral_truecolour(strbuf *b, termchar *c, unsigned long *state)
{
    /*
     * Put the used parts of the colour info into the buffer.
     */
    put_byte(b, ((c->truecolour.fg.enabled ? 1 : 0) |
                 (c->truecolour.bg.enabled ? 2 : 0)));
    if (c->truecolour.fg.enabled) {
        put_byte(b, c->truecolour.fg.r);
        put_byte(b, c->truecolour.fg.g);
        put_byte(b, c->truecolour.fg.b);
    }
    if (c->truecolour.bg.enabled) {
        put_byte(b, c->truecolour.bg.r);
        put_byte(b, c->truecolour.bg.g);
        put_byte(b, c->truecolour.bg.b);
    }
}
static void makeliteral_cc(strbuf *b, termchar *c, unsigned long *state)
{
    /*
     * For combining characters, I just encode a bunch of ordinary
     * chars using makeliteral_chr, and terminate with a \0
     * character (which I know won't come up as a combining char
     * itself).
     *
     * I don't use the stateful encoding in makeliteral_chr.
     */
    unsigned long zstate;
    termchar z;

    while (c->cc_next) {
        c += c->cc_next;

        assert(c->chr != 0);

        zstate = 0;
        makeliteral_chr(b, c, &zstate);
    }

    z.chr = 0;
    zstate = 0;
    makeliteral_chr(b, &z, &zstate);
}

typedef struct compressed_scrollback_line {
    size_t len;
    /* compressed data follows after this */
} compressed_scrollback_line;

static termline *decompressline_no_free(compressed_scrollback_line *line);

static compressed_scrollback_line *compressline_no_free(termline *ldata)
{
    strbuf *b = strbuf_new();

    /* Leave space for the header structure */
    strbuf_append(b, sizeof(compressed_scrollback_line));

    /*
     * First, store the column count, 7 bits at a time, least
     * significant `digit' first, with the high bit set on all but
     * the last.
     */
    {
        int n = ldata->cols;
        while (n >= 128) {
            put_byte(b, (unsigned char)((n & 0x7F) | 0x80));
            n >>= 7;
        }
        put_byte(b, (unsigned char)(n));
    }

    /*
     * Next store the lattrs; same principle. We add one extra bit to
     * this to indicate the trust state of the line.
     */
    {
        int n = ldata->lattr | (ldata->trusted ? 0x10000 : 0);
        while (n >= 128) {
            put_byte(b, (unsigned char)((n & 0x7F) | 0x80));
            n >>= 7;
        }
        put_byte(b, (unsigned char)(n));
    }

    /*
     * Now we store a sequence of separate run-length encoded
     * fragments, each containing exactly as many symbols as there
     * are columns in the ldata.
     *
     * All of these have a common basic format:
     *
     *  - a byte 00-7F indicates that X+1 literals follow it
     *  - a byte 80-FF indicates that a single literal follows it
     *    and expects to be repeated (X-0x80)+2 times.
     *
     * The format of the `literals' varies between the fragments.
     */
    makerle(b, ldata, makeliteral_chr);
    makerle(b, ldata, makeliteral_attr);
    makerle(b, ldata, makeliteral_truecolour);
    makerle(b, ldata, makeliteral_cc);

    size_t linelen = b->len - sizeof(compressed_scrollback_line);
    compressed_scrollback_line *line =
        (compressed_scrollback_line *)strbuf_to_str(b);
    line->len = linelen;

    /*
     * Diagnostics: ensure that the compressed data really does
     * decompress to the right thing.
     *
     * This is a bit performance-heavy for production code.
     */
#ifdef TERM_CC_DIAGS
#ifndef CHECK_SB_COMPRESSION
    {
        termline *dcl;
        int i;

#ifdef DIAGNOSTIC_SB_COMPRESSION
        for (i = 0; i < b->len; i++) {
            printf(" %02x ", b->data[i]);
        }
        printf("\n");
#endif

        dcl = decompressline_no_free(line);
        assert(ldata->cols == dcl->cols);
        assert(ldata->lattr == dcl->lattr);
        for (i = 0; i < ldata->cols; i++)
            assert(termchars_equal(&ldata->chars[i], &dcl->chars[i]));

#ifdef DIAGNOSTIC_SB_COMPRESSION
        printf("%d cols (%d bytes) -> %d bytes (factor of %g)\n",
               ldata->cols, 4 * ldata->cols, dused,
               (double)dused / (4 * ldata->cols));
#endif

        freetermline(dcl);
    }
#endif
#endif /* TERM_CC_DIAGS */

    return line;
}

static compressed_scrollback_line *compressline_and_free(termline *ldata)
{
    compressed_scrollback_line *cline = compressline_no_free(ldata);
    freetermline(ldata);
    return cline;
}

static void readrle(BinarySource *bs, termline *ldata,
                    void (*readliteral)(BinarySource *bs, termchar *c,
                                        termline *ldata, unsigned long *state))
{
    int n = 0;
    unsigned long state = 0;

    while (n < ldata->cols) {
        int hdr = get_byte(bs);

        if (hdr >= 0x80) {
            /* A run. */

            size_t pos = bs->pos, count = hdr + 2 - 0x80;
            while (count--) {
                assert(n < ldata->cols);
                bs->pos = pos;
                readliteral(bs, ldata->chars + n, ldata, &state);
                n++;
            }
        } else {
            /* Just a sequence of consecutive literals. */

            int count = hdr + 1;
            while (count--) {
                assert(n < ldata->cols);
                readliteral(bs, ldata->chars + n, ldata, &state);
                n++;
            }
        }
    }

    assert(n == ldata->cols);
}
static void readliteral_chr(BinarySource *bs, termchar *c, termline *ldata,
                            unsigned long *state)
{
    int byte;

    /*
     * 00000000-0000007F: 0xxxxxxx
     * 00000080-00003FFF: 10xxxxxx xxxxxxxx
     * 00004000-001FFFFF: 110xxxxx xxxxxxxx xxxxxxxx
     * 00200000-0FFFFFFF: 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
     * 10000000-FFFFFFFF: 11110ZZZ xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
     */

    byte = get_byte(bs);
    if (byte < 0x80) {
        c->chr = byte | *state;
    } else if (byte < 0xC0) {
        c->chr = (byte &~ 0xC0) << 8;
        c->chr |= get_byte(bs);
    } else if (byte < 0xE0) {
        c->chr = (byte &~ 0xE0) << 16;
        c->chr |= get_uint16(bs);
    } else if (byte < 0xF0) {
        c->chr = (byte &~ 0xF0) << 24;
        c->chr |= get_byte(bs) << 16;
        c->chr |= get_uint16(bs);
    } else {
        assert(byte == 0xF0);
        c->chr = get_uint32(bs);
    }
    *state = c->chr & ~0xFF;
}
static void readliteral_attr(BinarySource *bs, termchar *c, termline *ldata,
                             unsigned long *state)
{
    unsigned val, attr, colourbits;

    val = get_uint16(bs);

    if (val >= 0x8000) {
        val &= ~0x8000;
        val <<= 16;
        val |= get_uint16(bs);
    }

    colourbits = (val >> (32-9)) & 0xFF;
    attr = (val & ((1<<(32-9))-1));

    attr = (((attr >> (ATTR_FGSHIFT + 4)) << (ATTR_FGSHIFT + 8)) |
            (attr & ((1 << (ATTR_FGSHIFT + 4))-1)));
    attr = (((attr >> (ATTR_BGSHIFT + 4)) << (ATTR_BGSHIFT + 8)) |
            (attr & ((1 << (ATTR_BGSHIFT + 4))-1)));

    attr |= (colourbits >> 4) << (ATTR_BGSHIFT + 4);
    attr |= (colourbits & 0xF) << (ATTR_FGSHIFT + 4);

    c->attr = attr;
}
static void readliteral_truecolour(
    BinarySource *bs, termchar *c, termline *ldata, unsigned long *state)
{
    int flags = get_byte(bs);

    if (flags & 1) {
        c->truecolour.fg.enabled = true;
        c->truecolour.fg.r = get_byte(bs);
        c->truecolour.fg.g = get_byte(bs);
        c->truecolour.fg.b = get_byte(bs);
    } else {
        c->truecolour.fg = optionalrgb_none;
    }

    if (flags & 2) {
        c->truecolour.bg.enabled = true;
        c->truecolour.bg.r = get_byte(bs);
        c->truecolour.bg.g = get_byte(bs);
        c->truecolour.bg.b = get_byte(bs);
    } else {
        c->truecolour.bg = optionalrgb_none;
    }
}
static void readliteral_cc(BinarySource *bs, termchar *c, termline *ldata,
                           unsigned long *state)
{
    termchar n;
    unsigned long zstate;
    int x = c - ldata->chars;

    c->cc_next = 0;

    while (1) {
        zstate = 0;
        readliteral_chr(bs, &n, ldata, &zstate);
        if (!n.chr)
            break;
        add_cc(ldata, x, n.chr);
    }
}

static termline *decompressline_no_free(compressed_scrollback_line *line)
{
    int ncols, byte, shift;
    BinarySource bs[1];
    termline *ldata;

    BinarySource_BARE_INIT(bs, line+1, line->len);

    /*
     * First read in the column count.
     */
    ncols = shift = 0;
    do {
        byte = get_byte(bs);
        ncols |= (byte & 0x7F) << shift;
        shift += 7;
    } while (byte & 0x80);

    /*
     * Now create the output termline.
     */
    ldata = snew(termline);
    ldata->chars = snewn(ncols, termchar);
    ldata->cols = ldata->size = ncols;
    ldata->temporary = true;
    ldata->cc_free = 0;

    /*
     * We must set all the cc pointers in ldata->chars to 0 right
     * now, so that cc diagnostics that verify the integrity of the
     * whole line will make sense while we're in the middle of
     * building it up.
     */
    {
        int i;
        for (i = 0; i < ldata->cols; i++)
            ldata->chars[i].cc_next = 0;
    }

    /*
     * Now read in the lattr.
     */
    int lattr = shift = 0;
    do {
        byte = get_byte(bs);
        lattr |= (byte & 0x7F) << shift;
        shift += 7;
    } while (byte & 0x80);
    ldata->lattr = lattr & 0xFFFF;
    ldata->trusted = (lattr & 0x10000) != 0;

    /*
     * Now we read in each of the RLE streams in turn.
     */
    readrle(bs, ldata, readliteral_chr);
    readrle(bs, ldata, readliteral_attr);
    readrle(bs, ldata, readliteral_truecolour);
    readrle(bs, ldata, readliteral_cc);

    /* And we always expect that we ended up exactly at the end of the
     * compressed data. */
    assert(!get_err(bs));
    assert(get_avail(bs) == 0);

    return ldata;
}

static inline void free_compressed_line(compressed_scrollback_line *cline)
{
    sfree(cline);
}

static termline *decompressline_and_free(compressed_scrollback_line *cline)
{
    termline *ldata = decompressline_no_free(cline);
    free_compressed_line(cline);
    return ldata;
}

#else /* NO_SCROLLBACK_COMPRESSION */

static termline *duptermline(termline *oldline)
{
    termline *newline = snew(termline);
    *newline = *oldline;               /* copy the POD structure fields */
    newline->chars = snewn(newline->size, termchar);
    for (int j = 0; j < newline->size; j++)
        newline->chars[j] = oldline->chars[j];
    return newline;
}

typedef termline compressed_scrollback_line;

static inline compressed_scrollback_line *compressline_and_free(
    termline *ldata)
{
    return ldata;
}

static inline compressed_scrollback_line *compressline_no_free(termline *ldata)
{
    return duptermline(ldata);
}

static inline termline *decompressline_no_free(
    compressed_scrollback_line *line)
{
    /* This will return a line without the 'temporary' flag, which
     * means that unlineptr() is already set up to avoid freeing it */
    return line;
}

static inline termline *decompressline_and_free(
    compressed_scrollback_line *line)
{
    /* Same as decompressline_no_free, because the caller will free
     * our returned termline, and that does all the freeing necessary */
    return line;
}

static inline void free_compressed_line(compressed_scrollback_line *line)
{
    freetermline(line);
}

#endif /* NO_SCROLLBACK_COMPRESSION */

/*
 * Resize a line to make it `cols' columns wide.
 */
static void resizeline(Terminal *term, termline *line, int cols)
{
    int i, oldcols;

    if (line->cols != cols) {

        oldcols = line->cols;

        /*
         * This line is the wrong length, which probably means it
         * hasn't been accessed since a resize. Resize it now.
         *
         * First, go through all the characters that will be thrown
         * out in the resize (if we're shrinking the line) and
         * return their cc lists to the cc free list.
         */
        for (i = cols; i < oldcols; i++)
            clear_cc(line, i);

        /*
         * If we're shrinking the line, we now bodily move the
         * entire cc section from where it started to where it now
         * needs to be. (We have to do this before the resize, so
         * that the data we're copying is still there. However, if
         * we're expanding, we have to wait until _after_ the
         * resize so that the space we're copying into is there.)
         */
        if (cols < oldcols)
            memmove(line->chars + cols, line->chars + oldcols,
                    (line->size - line->cols) * TSIZE);

        /*
         * Now do the actual resize, leaving the _same_ amount of
         * cc space as there was to begin with.
         */
        line->size += cols - oldcols;
        line->chars = sresize(line->chars, line->size, TTYPE);
        line->cols = cols;

        /*
         * If we're expanding the line, _now_ we move the cc
         * section.
         */
        if (cols > oldcols)
            memmove(line->chars + cols, line->chars + oldcols,
                    (line->size - line->cols) * TSIZE);

        /*
         * Go through what's left of the original line, and adjust
         * the first cc_next pointer in each list. (All the
         * subsequent ones are still valid because they are
         * relative offsets within the cc block.) Also do the same
         * to the head of the cc_free list.
         */
        for (i = 0; i < oldcols && i < cols; i++)
            if (line->chars[i].cc_next)
                line->chars[i].cc_next += cols - oldcols;
        if (line->cc_free)
            line->cc_free += cols - oldcols;

        /*
         * And finally fill in the new space with erase chars. (We
         * don't have to worry about cc lists here, because we
         * _know_ the erase char doesn't have one.)
         */
        for (i = oldcols; i < cols; i++)
            line->chars[i] = term->basic_erase_char;

#ifdef TERM_CC_DIAGS
        cc_check(line);
#endif
    }
}

/*
 * Get the number of lines in the scrollback.
 */
static int sblines(Terminal *term)
{
    int sblines = count234(term->scrollback);
    if (term->erase_to_scrollback &&
        term->alt_which && term->alt_screen) {
        sblines += term->alt_sblines;
    }
    return sblines;
}

static void null_line_error(Terminal *term, int y, int lineno,
                            tree234 *whichtree, int treeindex,
                            const char *varname)
{
    modalfatalbox("%s==NULL in terminal.c\n"
                  "lineno=%d y=%d w=%d h=%d\n"
                  "count(scrollback=%p)=%d\n"
                  "count(screen=%p)=%d\n"
                  "count(alt=%p)=%d alt_sblines=%d\n"
                  "whichtree=%p treeindex=%d\n"
                  "commitid=%s\n\n"
                  "Please contact <putty@projects.tartarus.org> "
                  "and pass on the above information.",
                  varname, lineno, y, term->cols, term->rows,
                  term->scrollback, count234(term->scrollback),
                  term->screen, count234(term->screen),
                  term->alt_screen, count234(term->alt_screen),
                  term->alt_sblines, whichtree, treeindex, commitid);
}

static inline int checkscr(int y, int lineno)
{
    if (y < 0)
        modalfatalbox("screen line %d < 0 in terminal.c:%d", y, lineno);
    return y;
}

/*
 * Retrieve a line of the screen or of the scrollback, according to
 * whether the y coordinate is non-negative or negative
 * (respectively).
 */
static termline *lineptr(Terminal *term, int y, int lineno)
{
    termline *line;
    tree234 *whichtree;
    int treeindex;

    if (y >= 0) {
        whichtree = term->screen;
        treeindex = y;
    } else {
        int altlines = 0;

        if (term->erase_to_scrollback &&
            term->alt_which && term->alt_screen) {
            altlines = term->alt_sblines;
        }
        if (y < -altlines) {
            whichtree = term->scrollback;
            treeindex = y + altlines + count234(term->scrollback);
        } else {
            whichtree = term->alt_screen;
            treeindex = y + term->alt_sblines;
            /* treeindex = y + count234(term->alt_screen); */
        }
    }
    if (whichtree == term->scrollback) {
        compressed_scrollback_line *cline = index234(whichtree, treeindex);
        if (!cline)
            null_line_error(term, y, lineno, whichtree, treeindex, "cline");
        line = decompressline_no_free(cline);
    } else {
        line = index234(whichtree, treeindex);
    }

    /* We assume that we don't screw up and retrieve something out of range. */
    if (line == NULL)
        null_line_error(term, y, lineno, whichtree, treeindex, "line");
    assert(line != NULL);

    /*
     * Here we resize lines to _at least_ the right length, but we
     * don't truncate them. Truncation is done as a side effect of
     * modifying the line.
     *
     * The point of this policy is to try to arrange that resizing the
     * terminal window repeatedly - e.g. successive steps in an X11
     * opaque window-resize drag, or resizing as a side effect of
     * retiling by tiling WMs such as xmonad - does not throw away
     * data gratuitously. Specifically, we want a sequence of resize
     * operations with no terminal output between them to have the
     * same effect as a single resize to the ultimate terminal size,
     * and also (for the case in which xmonad narrows a window that's
     * scrolling things) we want scrolling up new text at the bottom
     * of a narrowed window to avoid truncating lines further up when
     * the window is re-widened.
     */
    if (term->cols > line->cols)
        resizeline(term, line, term->cols);

    return line;
}

/*
 * Macro wrappers for lineptr. The distinction between lineptr and
 * scrlineptr is that lineptr can retrieve any line, from the screen
 * _or_ from scrollback, and in return, you have to call unlineptr
 * when you're done with it, in case it was a dynamically allocated
 * line decompressed from scrollback that needs freeing. But
 * scrlineptr will only retrieve lines from the active screen (and
 * enforces this by an assertion), which means it's always just
 * returning a pointer to an existing unpacked termline, and you don't
 * have to call unlineptr afterwards. So drawing code (which might
 * need the scrollback) will have to call lineptr/unlineptr, but
 * update code during term_out can call scrlineptr.
 *
 * The 'assertion' in scrlineptr is done using a helper function that
 * returns the input column number, which allows this macro to avoid
 * double-evaluating its argument.
 */
#define lineptr(x) (lineptr)(term,x,__LINE__)
#define scrlineptr(x) (lineptr)(term,checkscr(x,__LINE__),__LINE__)
#define unlineptr(line) term_release_line(line)

/* Wrapper for external use (e.g. tests), without the __LINE__ parameter */
termline *term_get_line(Terminal *term, int y) { return lineptr(y); }

/*
 * Coerce a termline to the terminal's current width. Unlike the
 * optional resize in lineptr() above, this is potentially destructive
 * of text, since it can shrink as well as grow the line.
 *
 * We call this whenever a termline is actually going to be modified.
 * Helpfully, putting a single call to this function in check_boundary
 * deals with _nearly_ all such cases, leaving only a few things like
 * bulk erase and ESC#8 to handle separately.
 */
static void check_line_size(Terminal *term, termline *line)
{
    if (term->cols != line->cols)      /* trivial optimisation */
        resizeline(term, line, term->cols);
}

static void term_schedule_tblink(Terminal *term);
static void term_schedule_cblink(Terminal *term);
static void term_update_callback(void *ctx);

static void term_timer(void *ctx, unsigned long now)
{
    Terminal *term = (Terminal *)ctx;

    if (term->tblink_pending && now == term->next_tblink) {
        term->tblinker = !term->tblinker;
        term->tblink_pending = false;
        term_schedule_tblink(term);
        term->window_update_pending = true;
    }

    if (term->cblink_pending && now == term->next_cblink) {
        term->cblinker = !term->cblinker;
        term->cblink_pending = false;
        term_schedule_cblink(term);
        term->window_update_pending = true;
    }

    if (term->in_vbell && now == term->vbell_end) {
        term->in_vbell = false;
        term->window_update_pending = true;
    }

    if (term->window_update_cooldown &&
        now == term->window_update_cooldown_end) {
        term->window_update_cooldown = false;
    }

    if (term->window_update_pending)
        term_update_callback(term);
}

static void term_update_callback(void *ctx)
{
    Terminal *term = (Terminal *)ctx;
    if (!term->window_update_pending)
        return;
    if (!term->window_update_cooldown) {
        term_update(term);
        term->window_update_cooldown = true;
        term->window_update_cooldown_end = schedule_timer(
            UPDATE_DELAY, term_timer, term);
    }
}

static void term_schedule_update(Terminal *term)
{
    if (!term->window_update_pending) {
        term->window_update_pending = true;
        queue_toplevel_callback(term_update_callback, term);
    }
}

/*
 * Call this whenever the terminal window state changes, to queue an
 * update. This also resets the phase of cursor blinking, so that the
 * cursor remains visible as it moves with the output, and sets a flag
 * to indicate that if we have the 'reset scrollback on display
 * activity' setting enabled, then we should activate it.
 */
static void seen_disp_event(Terminal *term)
{
    if (term->scroll_on_disp) {
        term->disptop = 0;
        term->win_scrollbar_update_pending = true;
    }
    term->cblinker = true;
    term->cblink_pending = false;
    term_schedule_cblink(term);
    term_schedule_update(term);
}

/*
 * Call when the terminal's blinking-text settings change, or when
 * a text blink has just occurred.
 */
static void term_schedule_tblink(Terminal *term)
{
    if (term->blink_is_real) {
        if (!term->tblink_pending)
            term->next_tblink = schedule_timer(TBLINK_DELAY, term_timer, term);
        term->tblink_pending = true;
    } else {
        term->tblinker = true;         /* reset when not in use */
        term->tblink_pending = false;
    }
}

/*
 * Likewise with cursor blinks.
 */
static void term_schedule_cblink(Terminal *term)
{
    if (term->blink_cur && term->has_focus) {
        if (!term->cblink_pending)
            term->next_cblink = schedule_timer(CBLINK_DELAY, term_timer, term);
        term->cblink_pending = true;
    } else {
        term->cblinker = true;         /* reset when not in use */
        term->cblink_pending = false;
    }
}

/*
 * Call to begin a visual bell.
 */
static void term_schedule_vbell(Terminal *term, bool already_started,
                                long startpoint)
{
    long ticks_already_gone;

    if (already_started)
        ticks_already_gone = GETTICKCOUNT() - startpoint;
    else
        ticks_already_gone = 0;

    if (ticks_already_gone < VBELL_DELAY) {
        term->in_vbell = true;
        term->vbell_end = schedule_timer(VBELL_DELAY - ticks_already_gone,
                                         term_timer, term);
    } else {
        term->in_vbell = false;
    }
}

/*
 * Set up power-on settings for the terminal.
 * If 'clear' is false, don't actually clear the primary screen, and
 * position the cursor below the last non-blank line (scrolling if
 * necessary).
 */
static void power_on(Terminal *term, bool clear)
{
    term->alt_x = term->alt_y = 0;
    term->savecurs.x = term->savecurs.y = 0;
    term->alt_savecurs.x = term->alt_savecurs.y = 0;
    term->alt_t = term->marg_t = 0;
    if (term->rows != -1)
        term->alt_b = term->marg_b = term->rows - 1;
    else
        term->alt_b = term->marg_b = 0;
    if (term->cols != -1) {
        int i;
        for (i = 0; i < term->cols; i++)
            term->tabs[i] = (i % 8 == 0 ? true : false);
    }
    term->alt_om = term->dec_om = conf_get_bool(term->conf, CONF_dec_om);
    term->alt_ins = false;
    term->insert = false;
    term->alt_wnext = false;
    term->wrapnext = false;
    term->save_wnext = false;
    term->alt_save_wnext = false;
    term->alt_wrap = term->wrap = conf_get_bool(term->conf, CONF_wrap_mode);
    term->alt_cset = term->cset = term->save_cset = term->alt_save_cset = 0;
    term->alt_utf = false;
    term->utf = false;
    term->save_utf = false;
    term->alt_save_utf = false;
    term->utf8.state = 0;
    term->alt_sco_acs = term->sco_acs =
        term->save_sco_acs = term->alt_save_sco_acs = 0;
    term->cset_attr[0] = term->cset_attr[1] =
        term->save_csattr = term->alt_save_csattr = CSET_ASCII;
    term->rvideo = false;
    term->in_vbell = false;
    term->cursor_on = true;
    term->big_cursor = false;
    term->default_attr = term->save_attr =
        term->alt_save_attr = term->curr_attr = ATTR_DEFAULT;
    term->curr_truecolour.fg = term->curr_truecolour.bg = optionalrgb_none;
    term->save_truecolour = term->alt_save_truecolour = term->curr_truecolour;
    term->app_cursor_keys = conf_get_bool(term->conf, CONF_app_cursor);
    term->app_keypad_keys = conf_get_bool(term->conf, CONF_app_keypad);
    term->use_bce = conf_get_bool(term->conf, CONF_bce);
    term->blink_is_real = conf_get_bool(term->conf, CONF_blinktext);
    term->erase_char = term->basic_erase_char;
    term->alt_which = 0;
    term_print_finish(term);
    term->xterm_mouse = 0;
    term->xterm_extended_mouse = false;
    term->urxvt_extended_mouse = false;
    term->raw_mouse_reported_x = 0;
    term->raw_mouse_reported_y = 0;
    win_set_raw_mouse_mode(term->win, false);
    term->win_pointer_shape_pending = true;
    term->win_pointer_shape_raw = false;
    term->bracketed_paste = false;
    term->srm_echo = false;
    {
        int i;
        for (i = 0; i < 256; i++)
            term->wordness[i] = conf_get_int_int(term->conf, CONF_wordness, i);
    }
    if (term->screen) {
        swap_screen(term, 1, false, false);
        erase_lots(term, false, true, true);
        swap_screen(term, 0, false, false);
        if (clear)
            erase_lots(term, false, true, true);
        term->curs.y = find_last_nonempty_line(term, term->screen) + 1;
        if (term->curs.y == term->rows) {
            term->curs.y--;
            scroll(term, 0, term->rows - 1, 1, true);
        }
    } else {
        term->curs.y = 0;
    }
    term->curs.x = 0;
    term_schedule_tblink(term);
    term_schedule_cblink(term);
    term_schedule_update(term);
}

/*
 * Force a screen update.
 */
void term_update(Terminal *term)
{
    term->window_update_pending = false;

    if (term->win_move_pending) {
        win_move(term->win, term->win_move_pending_x,
                 term->win_move_pending_y);
        term->win_move_pending = false;
    }
    if (term->win_resize_pending == WIN_RESIZE_NEED_SEND) {
        term->win_resize_pending = WIN_RESIZE_AWAIT_REPLY;
        win_request_resize(term->win, term->win_resize_pending_w,
                           term->win_resize_pending_h);
    }
    if (term->win_zorder_pending) {
        win_set_zorder(term->win, term->win_zorder_top);
        term->win_zorder_pending = false;
    }
    if (term->win_minimise_pending) {
        win_set_minimised(term->win, term->win_minimise_enable);
        term->win_minimise_pending = false;
    }
    if (term->win_maximise_pending) {
        win_set_maximised(term->win, term->win_maximise_enable);
        term->win_maximise_pending = false;
    }
    if (term->win_title_pending) {
        win_set_title(term->win, term->window_title,
                      term->wintitle_codepage);
        term->win_title_pending = false;
    }
    if (term->win_icon_title_pending) {
        win_set_icon_title(term->win, term->icon_title,
                           term->icontitle_codepage);
        term->win_icon_title_pending = false;
    }
    if (term->win_pointer_shape_pending) {
        win_set_raw_mouse_mode_pointer(term->win, term->win_pointer_shape_raw);
        term->win_pointer_shape_pending = false;
    }
    if (term->win_refresh_pending) {
        win_refresh(term->win);
        term->win_refresh_pending = false;
    }
    if (term->win_palette_pending) {
        unsigned start = term->win_palette_pending_min;
        unsigned ncolours = term->win_palette_pending_limit - start;
        win_palette_set(term->win, start, ncolours, term->palette + start);
        term->win_palette_pending = false;
    }

    if (win_setup_draw_ctx(term->win)) {
        if (term->win_scrollbar_update_pending) {
            term->win_scrollbar_update_pending = false;
            update_sbar(term);
        }
        do_paint(term);
        win_set_cursor_pos(
            term->win, term->curs.x, term->curs.y - term->disptop);
        win_free_draw_ctx(term->win);
    }
}

/*
 * Called from front end when a keypress occurs, to trigger
 * anything magical that needs to happen in that situation.
 */
void term_seen_key_event(Terminal *term)
{
    /*
     * On any keypress, clear the bell overload mechanism
     * completely, on the grounds that large numbers of
     * beeps coming from deliberate key action are likely
     * to be intended (e.g. beeps from filename completion
     * blocking repeatedly).
     */
    term->beep_overloaded = false;
    while (term->beephead) {
        struct beeptime *tmp = term->beephead;
        term->beephead = tmp->next;
        sfree(tmp);
    }
    term->beeptail = NULL;
    term->nbeeps = 0;

    /*
     * Reset the scrollback on keypress, if we're doing that.
     */
    if (term->scroll_on_key && term->disptop != 0) {
        term->disptop = 0;
        term->win_scrollbar_update_pending = true;
        term_schedule_update(term);
    }
}

/*
 * Same as power_on(), but an external function.
 */
void term_pwron(Terminal *term, bool clear)
{
    power_on(term, clear);
    if (term->ldisc)                   /* cause ldisc to notice changes */
        ldisc_echoedit_update(term->ldisc);
    term->disptop = 0;
    deselect(term);
    term_update(term);
}

static void set_erase_char(Terminal *term)
{
    term->erase_char = term->basic_erase_char;
    if (term->use_bce) {
        term->erase_char.attr = (term->curr_attr &
                                 (ATTR_FGMASK | ATTR_BGMASK));
        term->erase_char.truecolour.bg = term->curr_truecolour.bg;
    }
}

/*
 * We copy a bunch of stuff out of the Conf structure into local
 * fields in the Terminal structure, to avoid the repeated tree234
 * lookups which would be involved in fetching them from the former
 * every time.
 */
static void term_copy_stuff_from_conf(Terminal *term)
{
    term->ansi_colour = conf_get_bool(term->conf, CONF_ansi_colour);
    term->no_arabicshaping = conf_get_bool(term->conf, CONF_no_arabicshaping);
    term->beep = conf_get_int(term->conf, CONF_beep);
    term->bellovl = conf_get_bool(term->conf, CONF_bellovl);
    term->bellovl_n = conf_get_int(term->conf, CONF_bellovl_n);
    term->bellovl_s = conf_get_int(term->conf, CONF_bellovl_s);
    term->bellovl_t = conf_get_int(term->conf, CONF_bellovl_t);
    term->no_bidi = conf_get_bool(term->conf, CONF_no_bidi);
    term->no_bracketed_paste = conf_get_bool(term->conf, CONF_no_bracketed_paste);
    term->bksp_is_delete = conf_get_bool(term->conf, CONF_bksp_is_delete);
    term->blink_cur = conf_get_bool(term->conf, CONF_blink_cur);
    term->blinktext = conf_get_bool(term->conf, CONF_blinktext);
    term->cjk_ambig_wide = conf_get_bool(term->conf, CONF_cjk_ambig_wide);
    term->conf_height = conf_get_int(term->conf, CONF_height);
    term->conf_width = conf_get_int(term->conf, CONF_width);
    term->crhaslf = conf_get_bool(term->conf, CONF_crhaslf);
    term->erase_to_scrollback = conf_get_bool(term->conf, CONF_erase_to_scrollback);
    term->funky_type = conf_get_int(term->conf, CONF_funky_type);
    term->sharrow_type = conf_get_int(term->conf, CONF_sharrow_type);
    term->lfhascr = conf_get_bool(term->conf, CONF_lfhascr);
    term->logflush = conf_get_bool(term->conf, CONF_logflush);
    term->logtype = conf_get_int(term->conf, CONF_logtype);
    term->mouse_override = conf_get_bool(term->conf, CONF_mouse_override);
    term->nethack_keypad = conf_get_bool(term->conf, CONF_nethack_keypad);
    term->no_alt_screen = conf_get_bool(term->conf, CONF_no_alt_screen);
    term->no_applic_c = conf_get_bool(term->conf, CONF_no_applic_c);
    term->no_applic_k = conf_get_bool(term->conf, CONF_no_applic_k);
    term->no_dbackspace = conf_get_bool(term->conf, CONF_no_dbackspace);
    term->no_mouse_rep = conf_get_bool(term->conf, CONF_no_mouse_rep);
    term->no_remote_charset = conf_get_bool(term->conf, CONF_no_remote_charset);
    term->no_remote_resize = conf_get_bool(term->conf, CONF_no_remote_resize);
    term->no_remote_wintitle = conf_get_bool(term->conf, CONF_no_remote_wintitle);
    term->no_remote_clearscroll = conf_get_bool(term->conf, CONF_no_remote_clearscroll);
    term->rawcnp = conf_get_bool(term->conf, CONF_rawcnp);
    term->utf8linedraw = conf_get_bool(term->conf, CONF_utf8linedraw);
    term->rect_select = conf_get_bool(term->conf, CONF_rect_select);
    term->remote_qtitle_action = conf_get_int(term->conf, CONF_remote_qtitle_action);
    term->rxvt_homeend = conf_get_bool(term->conf, CONF_rxvt_homeend);
    term->scroll_on_disp = conf_get_bool(term->conf, CONF_scroll_on_disp);
    term->scroll_on_key = conf_get_bool(term->conf, CONF_scroll_on_key);
    term->xterm_mouse_forbidden = conf_get_bool(term->conf, CONF_no_mouse_rep);
    term->xterm_256_colour = conf_get_bool(term->conf, CONF_xterm_256_colour);
    term->true_colour = conf_get_bool(term->conf, CONF_true_colour);

    /*
     * Parse the control-character escapes in the configured
     * answerback string.
     */
    {
        char *answerback = conf_get_str(term->conf, CONF_answerback);

        strbuf_clear(term->answerback);

        while (*answerback) {
            char *n;
            char c = ctrlparse(answerback, &n);
            if (n) {
                put_byte(term->answerback, c);
                answerback = n;
            } else {
                put_byte(term->answerback, *answerback++);
            }
        }
    }
}

void term_pre_reconfig(Terminal *term, Conf *conf)
{

    /*
     * Copy the current window title into the stored previous
     * configuration, so that doing nothing to the window title field
     * in the config box doesn't reset the title to its startup state.
     */
    conf_set_str(conf, CONF_wintitle, term->window_title);
}

/*
 * When the user reconfigures us, we need to check the forbidden-
 * alternate-screen config option, disable raw mouse mode if the
 * user has disabled mouse reporting, and abandon a print job if
 * the user has disabled printing.
 */
void term_reconfig(Terminal *term, Conf *conf)
{
    /*
     * Before adopting the new config, check all those terminal
     * settings which control power-on defaults; and if they've
     * changed, we will modify the current state as well as the
     * default one. The full list is: Auto wrap mode, DEC Origin
     * Mode, BCE, blinking text, character classes.
     */
    bool reset_wrap, reset_decom, reset_bce, reset_tblink, reset_charclass;
    bool palette_changed = false;
    int i;

    reset_wrap = (conf_get_bool(term->conf, CONF_wrap_mode) !=
                  conf_get_bool(conf, CONF_wrap_mode));
    reset_decom = (conf_get_bool(term->conf, CONF_dec_om) !=
                   conf_get_bool(conf, CONF_dec_om));
    reset_bce = (conf_get_bool(term->conf, CONF_bce) !=
                 conf_get_bool(conf, CONF_bce));
    reset_tblink = (conf_get_bool(term->conf, CONF_blinktext) !=
                    conf_get_bool(conf, CONF_blinktext));
    reset_charclass = false;
    for (i = 0; i < 256; i++)
        if (conf_get_int_int(term->conf, CONF_wordness, i) !=
            conf_get_int_int(conf, CONF_wordness, i))
            reset_charclass = true;

    /*
     * If the bidi or shaping settings have changed, flush the bidi
     * cache completely.
     */
    if (conf_get_bool(term->conf, CONF_no_arabicshaping) !=
        conf_get_bool(conf, CONF_no_arabicshaping) ||
        conf_get_bool(term->conf, CONF_no_bidi) !=
        conf_get_bool(conf, CONF_no_bidi)) {
        for (i = 0; i < term->bidi_cache_size; i++) {
            sfree(term->pre_bidi_cache[i].chars);
            sfree(term->post_bidi_cache[i].chars);
            term->pre_bidi_cache[i].width = -1;
            term->pre_bidi_cache[i].chars = NULL;
            term->post_bidi_cache[i].width = -1;
            term->post_bidi_cache[i].chars = NULL;
        }
    }

    {
        const char *old_title = conf_get_str(term->conf, CONF_wintitle);
        const char *new_title = conf_get_str(conf, CONF_wintitle);
        if (strcmp(old_title, new_title)) {
            sfree(term->window_title);
            term->window_title = dupstr(new_title);
            term->wintitle_codepage = DEFAULT_CODEPAGE;
            term->win_title_pending = true;
            term_schedule_update(term);
        }
    }

    /*
     * Just setting conf is sufficient to cause colour setting changes
     * to appear on the next ESC]R palette reset. But we should also
     * check whether any colour settings have been changed, so that
     * they can be updated immediately if they haven't been overridden
     * by some escape sequence.
     */
    {
        int i, j;
        for (i = 0; i < CONF_NCOLOURS; i++) {
            for (j = 0; j < 3; j++)
                if (conf_get_int_int(term->conf, CONF_colours, i*3+j) !=
                    conf_get_int_int(conf, CONF_colours, i*3+j))
                    break;
            if (j < 3) {
                /* Actually enacting the change has to be deferred 
                 * until the new conf is installed. */
                palette_changed = true;
                break;
            }
        }
    }

    conf_free(term->conf);
    term->conf = conf_copy(conf);

    if (reset_wrap) {
        term->alt_wrap = term->wrap = conf_get_bool(term->conf, CONF_wrap_mode);
        if (!term->wrap)
            term->wrapnext = false;
        if (!term->alt_wrap)
            term->alt_wnext = false;
    }
    if (reset_decom)
        term->alt_om = term->dec_om = conf_get_bool(term->conf, CONF_dec_om);
    if (reset_bce) {
        term->use_bce = conf_get_bool(term->conf, CONF_bce);
        set_erase_char(term);
    }
    if (reset_tblink) {
        term->blink_is_real = conf_get_bool(term->conf, CONF_blinktext);
    }
    if (reset_charclass)
        for (i = 0; i < 256; i++)
            term->wordness[i] = conf_get_int_int(term->conf, CONF_wordness, i);

    if (conf_get_bool(term->conf, CONF_no_alt_screen))
        swap_screen(term, 0, false, false);
    if (conf_get_bool(term->conf, CONF_no_remote_charset)) {
        term->cset_attr[0] = term->cset_attr[1] = CSET_ASCII;
        term->sco_acs = term->alt_sco_acs = 0;
        term->utf = false;
    }
    if (!conf_get_str(term->conf, CONF_printer)) {
        term_print_finish(term);
    }
    if (palette_changed)
        term_notify_palette_changed(term);
    term_schedule_tblink(term);
    term_schedule_cblink(term);
    term_copy_stuff_from_conf(term);
    term_update_raw_mouse_mode(term);
}

/*
 * Clear the scrollback.
 */
void term_clrsb(Terminal *term)
{
    unsigned char *line;
    int i;

    /*
     * Scroll forward to the current screen, if we were back in the
     * scrollback somewhere until now.
     */
    term->disptop = 0;

    /*
     * Clear the actual scrollback.
     */
    while ((line = delpos234(term->scrollback, 0)) != NULL) {
        sfree(line);            /* this is compressed data, not a termline */
    }

    /*
     * When clearing the scrollback, we also truncate any termlines on
     * the current screen which have remembered data from a previous
     * larger window size. Rationale: clearing the scrollback is
     * sometimes done to protect privacy, so the user intention is
     * specifically that we should not retain evidence of what
     * previously happened in the terminal, and that ought to include
     * evidence to the right as well as evidence above.
     */
    for (i = 0; i < term->rows; i++)
        check_line_size(term, scrlineptr(i));

    /*
     * That operation has invalidated the selection, if it overlapped
     * the scrollback at all.
     */
    if (term->selstate != NO_SELECTION && term->selstart.y < 0)
        deselect(term);

    /*
     * There are now no lines of real scrollback which can be pulled
     * back into the screen by a resize, and no lines of the alternate
     * screen which should be displayed as if part of the scrollback.
     */
    term->tempsblines = 0;
    term->alt_sblines = 0;

    /*
     * The scrollbar will need updating to reflect the new state of
     * the world.
     */
    term->win_scrollbar_update_pending = true;
    term_schedule_update(term);
}

const optionalrgb optionalrgb_none = {0, 0, 0, 0};

void term_setup_window_titles(Terminal *term, const char *title_hostname)
{
    const char *conf_title = conf_get_str(term->conf, CONF_wintitle);
    sfree(term->window_title);
    sfree(term->icon_title);
    if (*conf_title) {
        term->window_title = dupstr(conf_title);
        term->icon_title = dupstr(conf_title);
    } else {
        if (title_hostname && *title_hostname)
            term->window_title = dupcat(title_hostname, " - ", appname);
        else
            term->window_title = dupstr(appname);
        term->icon_title = dupstr(term->window_title);
    }
    term->wintitle_codepage = term->icontitle_codepage = DEFAULT_CODEPAGE;
    term->win_title_pending = true;
    term->win_icon_title_pending = true;
}

static void palette_rebuild(Terminal *term)
{
    unsigned min_changed = OSC4_NCOLOURS, max_changed = 0;

    if (term->win_palette_pending) {
        /* Possibly extend existing range. */
        min_changed = term->win_palette_pending_min;
        max_changed = term->win_palette_pending_limit - 1;
    } else {
        /* Start with empty range. */
        min_changed = OSC4_NCOLOURS;
        max_changed = 0;
    }

    for (unsigned i = 0; i < OSC4_NCOLOURS; i++) {
        rgb new_value;
        bool found = false;

        for (unsigned j = lenof(term->subpalettes); j-- > 0 ;) {
            if (term->subpalettes[j].present[i]) {
                new_value = term->subpalettes[j].values[i];
                found = true;
                break;
            }
        }

        assert(found);    /* we expect SUBPAL_CONF to always be set */

        if (new_value.r != term->palette[i].r ||
            new_value.g != term->palette[i].g ||
            new_value.b != term->palette[i].b) {
            term->palette[i] = new_value;
            if (min_changed > i)
                min_changed = i;
            if (max_changed < i)
                max_changed = i;
        }
    }

    if (min_changed <= max_changed) {
        /*
         * At least one colour changed (or we had an update scheduled
         * already). Schedule a redraw event to pass the result back
         * to the TermWin. This also requires invalidating the rest
         * of the window, because usually all the text will need
         * redrawing in the new colours.
         * (If there was an update pending and this palette rebuild
         * didn't actually change anything, we'll harmlessly reinforce
         * the existing update request.)
         */
        term->win_palette_pending = true;
        term->win_palette_pending_min = min_changed;
        term->win_palette_pending_limit = max_changed + 1;
        term_invalidate(term);
    }
}

/*
 * Rebuild the palette from configuration and platform colours.
 * If 'keep_overrides' set, any escape-sequence-specified overrides will
 * remain in place.
 */
static void palette_reset(Terminal *term, bool keep_overrides)
{
    for (unsigned i = 0; i < OSC4_NCOLOURS; i++)
        term->subpalettes[SUBPAL_CONF].present[i] = true;

    /*
     * Copy all the palette information out of the Conf.
     */
    for (unsigned i = 0; i < CONF_NCOLOURS; i++) {
        rgb *col = &term->subpalettes[SUBPAL_CONF].values[
            colour_indices_conf_to_osc4[i]];
        col->r = conf_get_int_int(term->conf, CONF_colours, i*3+0);
        col->g = conf_get_int_int(term->conf, CONF_colours, i*3+1);
        col->b = conf_get_int_int(term->conf, CONF_colours, i*3+2);
    }

    /*
     * Directly invent the rest of the xterm-256 colours.
     */
    for (unsigned i = 0; i < 216; i++) {
        rgb *col = &term->subpalettes[SUBPAL_CONF].values[i + 16];
        int r = i / 36, g = (i / 6) % 6, b = i % 6;
        col->r = r ? r * 40 + 55 : 0;
        col->g = g ? g * 40 + 55 : 0;
        col->b = b ? b * 40 + 55 : 0;
    }
    for (unsigned i = 0; i < 24; i++) {
        rgb *col = &term->subpalettes[SUBPAL_CONF].values[i + 232];
        int shade = i * 10 + 8;
        col->r = col->g = col->b = shade;
    }

    /*
     * Re-fetch any OS-local overrides.
     */
    for (unsigned i = 0; i < OSC4_NCOLOURS; i++)
        term->subpalettes[SUBPAL_PLATFORM].present[i] = false;
    win_palette_get_overrides(term->win, term);

    if (!keep_overrides) {
        /*
         * Get rid of all escape-sequence configuration.
         */
        for (unsigned i = 0; i < OSC4_NCOLOURS; i++)
            term->subpalettes[SUBPAL_SESSION].present[i] = false;
    }

    /*
     * Rebuild the composite palette.
     */
    palette_rebuild(term);
}

void term_palette_override(Terminal *term, unsigned osc4_index, rgb rgb)
{
    /*
     * We never expect to be called except as re-entry from our own
     * call to win_palette_get_overrides above, so we need not mess
     * about calling palette_rebuild.
     */
    term->subpalettes[SUBPAL_PLATFORM].present[osc4_index] = true;
    term->subpalettes[SUBPAL_PLATFORM].values[osc4_index] = rgb;
}

/*
 * Initialise the terminal.
 */
Terminal *term_init(Conf *myconf, struct unicode_data *ucsdata, TermWin *win)
{
    Terminal *term;

    /*
     * Allocate a new Terminal structure and initialise the fields
     * that need it.
     */
    term = snew(Terminal);
    memset(term, 0, sizeof(Terminal));
    term->win = win;
    term->ucsdata = ucsdata;
    term->conf = conf_copy(myconf);
    term->compatibility_level = TM_PUTTY;
    strcpy(term->id_string, "\033[?6c");
    bufchain_init(&term->inbuf);
    bufchain_init(&term->printer_buf);
    term->has_focus = true;
    term->termstate = TOPLEVEL;
    term->selstate = NO_SELECTION;
    term->answerback = strbuf_new();

    term_copy_stuff_from_conf(term);

    term->dispcursx = term->dispcursy = -1;
    deselect(term);
    term->rows = term->cols = -1;
    power_on(term, true);
    term->attr_mask = 0xffffffff;

    /* FULL-TERMCHAR */
    term->basic_erase_char.chr = CSET_ASCII | ' ';
    term->basic_erase_char.attr = ATTR_DEFAULT;
    term->basic_erase_char.truecolour.fg = optionalrgb_none;
    term->basic_erase_char.truecolour.bg = optionalrgb_none;
    term->erase_char = term->basic_erase_char;

    /* TermWin implementations will typically extend these with
     * clipboard ids they know about */
    term->mouse_select_clipboards[0] = CLIP_LOCAL;
    term->n_mouse_select_clipboards = 1;
    term->mouse_paste_clipboard = CLIP_NULL;

    term->trusted = true;

    term->window_title = dupstr("");
    term->icon_title = dupstr("");
    term->wintitle_codepage = term->icontitle_codepage = DEFAULT_CODEPAGE;

    term->win_resize_pending = WIN_RESIZE_NO;

    term->bidi_ctx = bidi_new_context();

    palette_reset(term, false);

    return term;
}

void term_free(Terminal *term)
{
    compressed_scrollback_line *cline;
    termline *line;
    struct beeptime *beep;
    int i;

    while ((cline = delpos234(term->scrollback, 0)) != NULL)
        free_compressed_line(cline);
    freetree234(term->scrollback);
    while ((line = delpos234(term->screen, 0)) != NULL)
        freetermline(line);
    freetree234(term->screen);
    while ((line = delpos234(term->alt_screen, 0)) != NULL)
        freetermline(line);
    freetree234(term->alt_screen);
    if (term->disptext) {
        for (i = 0; i < term->rows; i++)
            freetermline(term->disptext[i]);
    }
    sfree(term->disptext);
    while (term->beephead) {
        beep = term->beephead;
        term->beephead = beep->next;
        sfree(beep);
    }
    bufchain_clear(&term->inbuf);
    if (term->print_job)
        printer_finish_job(term->print_job);
    bufchain_clear(&term->printer_buf);
    sfree(term->paste_buffer);
    sfree(term->ltemp);
    sfree(term->wcFrom);
    sfree(term->wcTo);
    strbuf_free(term->answerback);

    for (i = 0; i < term->bidi_cache_size; i++) {
        sfree(term->pre_bidi_cache[i].chars);
        sfree(term->post_bidi_cache[i].chars);
        sfree(term->post_bidi_cache[i].forward);
        sfree(term->post_bidi_cache[i].backward);
    }
    sfree(term->pre_bidi_cache);
    sfree(term->post_bidi_cache);

    sfree(term->tabs);

    expire_timer_context(term);
    delete_callbacks_for_context(term);

    conf_free(term->conf);

    sfree(term->window_title);
    sfree(term->icon_title);

    bidi_free_context(term->bidi_ctx);

    /* In case a term_userpass_state is still around */
    if (term->userpass_state)
        term_userpass_state_free(term->userpass_state);

    sfree(term);
}

void term_set_trust_status(Terminal *term, bool trusted)
{
    term->trusted = trusted;
}

void term_get_cursor_position(Terminal *term, int *x, int *y)
{
    *x = term->curs.x;
    *y = term->curs.y;
}

/*
 * Set up the terminal for a given size.
 */
void term_size(Terminal *term, int newrows, int newcols, int newsavelines)
{
    tree234 *newalt;
    termline **newdisp, *line;
    int i, j, oldrows = term->rows;
    int sblen;
    int save_alt_which = term->alt_which;

    if (newrows == term->rows && newcols == term->cols &&
        newsavelines == term->savelines)
        return;                        /* nothing to do */

    /* Behave sensibly if we're given zero (or negative) rows/cols */

    if (newrows < 1) newrows = 1;
    if (newcols < 1) newcols = 1;

    deselect(term);
    swap_screen(term, 0, false, false);

    term->alt_t = term->marg_t = 0;
    term->alt_b = term->marg_b = newrows - 1;

    if (term->rows == -1) {
        term->scrollback = newtree234(NULL);
        term->screen = newtree234(NULL);
        term->tempsblines = 0;
        term->rows = 0;
    }

    /*
     * Resize the screen and scrollback. We only need to shift
     * lines around within our data structures, because lineptr()
     * will take care of resizing each individual line if
     * necessary. So:
     *
     *  - If the new screen is longer, we shunt lines in from temporary
     *    scrollback if possible, otherwise we add new blank lines at
     *    the bottom.
     *
     *  - If the new screen is shorter, we remove any blank lines at
     *    the bottom if possible, otherwise shunt lines above the cursor
     *    to scrollback if possible, otherwise delete lines below the
     *    cursor.
     *
     *  - Then, if the new scrollback length is less than the
     *    amount of scrollback we actually have, we must throw some
     *    away.
     */
    sblen = count234(term->scrollback);
    /* Do this loop to expand the screen if newrows > rows */
    assert(term->rows == count234(term->screen));
    while (term->rows < newrows) {
        if (term->tempsblines > 0) {
            compressed_scrollback_line *cline;
            /* Insert a line from the scrollback at the top of the screen. */
            assert(sblen >= term->tempsblines);
            cline = delpos234(term->scrollback, --sblen);
            line = decompressline_and_free(cline);
            line->temporary = false;   /* reconstituted line is now real */
            term->tempsblines -= 1;
            addpos234(term->screen, line, 0);
            term->curs.y += 1;
            term->savecurs.y += 1;
            term->alt_y += 1;
            term->alt_savecurs.y += 1;
        } else {
            /* Add a new blank line at the bottom of the screen. */
            line = newtermline(term, newcols, false);
            addpos234(term->screen, line, count234(term->screen));
        }
        term->rows += 1;
    }
    /* Do this loop to shrink the screen if newrows < rows */
    while (term->rows > newrows) {
        if (term->curs.y < term->rows - 1) {
            /* delete bottom row, unless it contains the cursor */
            line = delpos234(term->screen, term->rows - 1);
            freetermline(line);
        } else {
            /* push top row to scrollback */
            line = delpos234(term->screen, 0);
            addpos234(term->scrollback, compressline_and_free(line), sblen++);
            term->tempsblines += 1;
            term->curs.y -= 1;
            term->savecurs.y -= 1;
            term->alt_y -= 1;
            term->alt_savecurs.y -= 1;
        }
        term->rows -= 1;
    }
    assert(term->rows == newrows);
    assert(count234(term->screen) == newrows);

    /* Delete any excess lines from the scrollback. */
    while (sblen > newsavelines) {
        line = delpos234(term->scrollback, 0);
        sfree(line);
        sblen--;
    }
    if (sblen < term->tempsblines)
        term->tempsblines = sblen;
    assert(count234(term->scrollback) <= newsavelines);
    assert(count234(term->scrollback) >= term->tempsblines);
    term->disptop = 0;

    /* Make a new displayed text buffer. */
    newdisp = snewn(newrows, termline *);
    for (i = 0; i < newrows; i++) {
        newdisp[i] = newtermline(term, newcols, false);
        for (j = 0; j < newcols; j++)
            newdisp[i]->chars[j].attr = ATTR_INVALID;
    }
    if (term->disptext) {
        for (i = 0; i < oldrows; i++)
            freetermline(term->disptext[i]);
    }
    sfree(term->disptext);
    term->disptext = newdisp;
    term->dispcursx = term->dispcursy = -1;

    /* Make a new alternate screen. */
    newalt = newtree234(NULL);
    for (i = 0; i < newrows; i++) {
        line = newtermline(term, newcols, true);
        addpos234(newalt, line, i);
    }
    if (term->alt_screen) {
        while (NULL != (line = delpos234(term->alt_screen, 0)))
            freetermline(line);
        freetree234(term->alt_screen);
    }
    term->alt_screen = newalt;
    term->alt_sblines = 0;

    term->tabs = sresize(term->tabs, newcols, unsigned char);
    {
        int i;
        for (i = (term->cols > 0 ? term->cols : 0); i < newcols; i++)
            term->tabs[i] = (i % 8 == 0 ? true : false);
    }

    /* Check that the cursor positions are still valid. */
    if (term->savecurs.y < 0)
        term->savecurs.y = 0;
    if (term->savecurs.y >= newrows)
        term->savecurs.y = newrows - 1;
    if (term->savecurs.x >= newcols)
        term->savecurs.x = newcols - 1;
    if (term->alt_savecurs.y < 0)
        term->alt_savecurs.y = 0;
    if (term->alt_savecurs.y >= newrows)
        term->alt_savecurs.y = newrows - 1;
    if (term->alt_savecurs.x >= newcols)
        term->alt_savecurs.x = newcols - 1;
    if (term->curs.y < 0)
        term->curs.y = 0;
    if (term->curs.y >= newrows)
        term->curs.y = newrows - 1;
    if (term->curs.x >= newcols)
        term->curs.x = newcols - 1;
    if (term->alt_y < 0)
        term->alt_y = 0;
    if (term->alt_y >= newrows)
        term->alt_y = newrows - 1;
    if (term->alt_x >= newcols)
        term->alt_x = newcols - 1;
    term->alt_x = term->alt_y = 0;
    term->wrapnext = false;
    term->alt_wnext = false;

    term->rows = newrows;
    term->cols = newcols;
    term->savelines = newsavelines;

    swap_screen(term, save_alt_which, false, false);

    term->win_scrollbar_update_pending = true;
    term_schedule_update(term);
    if (term->backend)
        backend_size(term->backend, term->cols, term->rows);
}

void term_resize_request_completed(Terminal *term)
{
    assert(term->win_resize_pending == WIN_RESIZE_AWAIT_REPLY);
    term->win_resize_pending = WIN_RESIZE_NO;
    queue_toplevel_callback(term_out_cb, term);
}

/*
 * Hand a backend to the terminal, so it can be notified of resizes.
 */
void term_provide_backend(Terminal *term, Backend *backend)
{
    term->backend = backend;
    if (term->userpass_state)
        term_userpass_state_free(term->userpass_state);
    if (term->backend && term->cols > 0 && term->rows > 0)
        backend_size(term->backend, term->cols, term->rows);
}

/* Find the bottom line on the screen that has any content.
 * If only the top line has content, returns 0.
 * If no lines have content, return -1.
 */
static int find_last_nonempty_line(Terminal *term, tree234 *screen)
{
    int i;
    for (i = count234(screen) - 1; i >= 0; i--) {
        termline *line = index234(screen, i);
        int j;
        for (j = 0; j < line->cols; j++)
            if (!termchars_equal(&line->chars[j], &term->erase_char))
                break;
        if (j != line->cols) break;
    }
    return i;
}

/*
 * Swap screens. If `reset' is true and we have been asked to
 * switch to the alternate screen, we must bring most of its
 * configuration from the main screen and erase the contents of the
 * alternate screen completely. (This is even true if we're already
 * on it! Blame xterm.)
 */
static void swap_screen(Terminal *term, int which,
                        bool reset, bool keep_cur_pos)
{
    int t;
    bool bt;
    pos tp;
    truecolour ttc;
    tree234 *ttr;

    if (!which)
        reset = false;                 /* do no weird resetting if which==0 */

    if (which != term->alt_which) {
        if (term->erase_to_scrollback && term->alt_screen &&
            term->alt_which && term->disptop < 0) {
            /*
             * We're swapping away from the alternate screen, so some
             * lines are about to vanish from the virtual scrollback.
             * Adjust disptop by that much, so that (if we're not
             * resetting the scrollback anyway on a display event) the
             * current scroll position still ends up pointing at the
             * same text.
             */
            term->disptop += term->alt_sblines;
            if (term->disptop > 0)
                term->disptop = 0;
        }

        term->alt_which = which;

        ttr = term->alt_screen;
        term->alt_screen = term->screen;
        term->screen = ttr;
        term->alt_sblines = (
            term->alt_screen ?
            find_last_nonempty_line(term, term->alt_screen) + 1 : 0);
        t = term->curs.x;
        if (!reset && !keep_cur_pos)
            term->curs.x = term->alt_x;
        term->alt_x = t;
        t = term->curs.y;
        if (!reset && !keep_cur_pos)
            term->curs.y = term->alt_y;
        term->alt_y = t;
        t = term->marg_t;
        if (!reset) term->marg_t = term->alt_t;
        term->alt_t = t;
        t = term->marg_b;
        if (!reset) term->marg_b = term->alt_b;
        term->alt_b = t;
        bt = term->dec_om;
        if (!reset) term->dec_om = term->alt_om;
        term->alt_om = bt;
        bt = term->wrap;
        if (!reset) term->wrap = term->alt_wrap;
        term->alt_wrap = bt;
        bt = term->wrapnext;
        if (!reset) term->wrapnext = term->alt_wnext;
        term->alt_wnext = bt;
        bt = term->insert;
        if (!reset) term->insert = term->alt_ins;
        term->alt_ins = bt;
        t = term->cset;
        if (!reset) term->cset = term->alt_cset;
        term->alt_cset = t;
        bt = term->utf;
        if (!reset) term->utf = term->alt_utf;
        term->alt_utf = bt;
        t = term->sco_acs;
        if (!reset) term->sco_acs = term->alt_sco_acs;
        term->alt_sco_acs = t;

        tp = term->savecurs;
        if (!reset)
            term->savecurs = term->alt_savecurs;
        term->alt_savecurs = tp;
        t = term->save_cset;
        if (!reset)
            term->save_cset = term->alt_save_cset;
        term->alt_save_cset = t;
        t = term->save_csattr;
        if (!reset)
            term->save_csattr = term->alt_save_csattr;
        term->alt_save_csattr = t;
        t = term->save_attr;
        if (!reset)
            term->save_attr = term->alt_save_attr;
        term->alt_save_attr = t;
        ttc = term->save_truecolour;
        if (!reset)
            term->save_truecolour = term->alt_save_truecolour;
        term->alt_save_truecolour = ttc;
        bt = term->save_utf;
        if (!reset)
            term->save_utf = term->alt_save_utf;
        term->alt_save_utf = bt;
        bt = term->save_wnext;
        if (!reset)
            term->save_wnext = term->alt_save_wnext;
        term->alt_save_wnext = bt;
        t = term->save_sco_acs;
        if (!reset)
            term->save_sco_acs = term->alt_save_sco_acs;
        term->alt_save_sco_acs = t;

        if (term->erase_to_scrollback && term->alt_screen &&
            term->alt_which && term->disptop < 0) {
            /*
             * Inverse of the adjustment at the top of this function.
             * This time, we're swapping _to_ the alternate screen, so
             * some lines are about to _appear_ in the virtual
             * scrollback, and we adjust disptop in the other
             * direction.
             *
             * Both these adjustments depend on the value stored in
             * term->alt_sblines while the alt screen is selected,
             * which is why we had to do one _before_ switching away
             * from it and the other _after_ switching to it.
             */
            term->disptop -= term->alt_sblines;
            int limit = -sblines(term);
            if (term->disptop < limit)
                term->disptop = limit;
        }
    }

    if (reset && term->screen) {
        /*
         * Yes, this _is_ supposed to honour background-colour-erase.
         */
        erase_lots(term, false, true, true);
    }

    seen_disp_event(term);
}

/*
 * Update the scroll bar.
 */
static void update_sbar(Terminal *term)
{
    int nscroll = sblines(term);
    win_set_scrollbar(term->win, nscroll + term->rows,
                      nscroll + term->disptop, term->rows);
}

/*
 * Check whether the region bounded by the two pointers intersects
 * the scroll region, and de-select the on-screen selection if so.
 */
static void check_selection(Terminal *term, pos from, pos to)
{
    if (poslt(from, term->selend) && poslt(term->selstart, to))
        deselect(term);
}

static void clear_line(Terminal *term, termline *line)
{
    resizeline(term, line, term->cols);
    for (int i = 0; i < term->cols; i++)
        copy_termchar(line, i, &term->erase_char);
    line->lattr = LATTR_NORM;
}

static void check_trust_status(Terminal *term, termline *line)
{
    if (line->trusted != term->trusted) {
        /*
         * If we're displaying trusted output on a previously
         * untrusted line, or vice versa, we need to switch the
         * 'trusted' attribute on this terminal line, and also clear
         * all its previous contents.
         */
        clear_line(term, line);
        line->trusted = term->trusted;
    }
}

/*
 * Scroll the screen. (`lines' is +ve for scrolling forward, -ve
 * for backward.) `sb' is true if the scrolling is permitted to
 * affect the scrollback buffer.
 */
static void scroll(Terminal *term, int topline, int botline,
                   int lines, bool sb)
{
    termline *line;
    int seltop, scrollwinsize;

    if (topline != 0 || term->alt_which != 0)
        sb = false;

    scrollwinsize = botline - topline + 1;

    if (lines < 0) {
        lines = -lines;
        if (lines > scrollwinsize)
            lines = scrollwinsize;
        while (lines-- > 0) {
            line = delpos234(term->screen, botline);
            resizeline(term, line, term->cols);
            clear_line(term, line);
            addpos234(term->screen, line, topline);

            if (term->selstart.y >= topline && term->selstart.y <= botline) {
                term->selstart.y++;
                if (term->selstart.y > botline) {
                    term->selstart.y = botline + 1;
                    term->selstart.x = 0;
                }
            }
            if (term->selend.y >= topline && term->selend.y <= botline) {
                term->selend.y++;
                if (term->selend.y > botline) {
                    term->selend.y = botline + 1;
                    term->selend.x = 0;
                }
            }
        }
    } else {
        if (lines > scrollwinsize)
            lines = scrollwinsize;
        while (lines-- > 0) {
            line = delpos234(term->screen, topline);
#ifdef TERM_CC_DIAGS
            cc_check(line);
#endif
            if (sb && term->savelines > 0) {
                int sblen = count234(term->scrollback);
                /*
                 * We must add this line to the scrollback. We'll
                 * remove a line from the top of the scrollback if
                 * the scrollback is full.
                 */
                if (sblen == term->savelines) {
                    compressed_scrollback_line *cline;

                    sblen--;
                    cline = delpos234(term->scrollback, 0);
                    free_compressed_line(cline);
                } else
                    term->tempsblines += 1;

                addpos234(term->scrollback, compressline_no_free(line), sblen);

                /* now `line' itself can be reused as the bottom line */

                /*
                 * If the user is currently looking at part of the
                 * scrollback, and they haven't enabled any options
                 * that are going to reset the scrollback as a
                 * result of this movement, then the chances are
                 * they'd like to keep looking at the same line. So
                 * we move their viewpoint at the same rate as the
                 * scroll, at least until their viewpoint hits the
                 * top end of the scrollback buffer, at which point
                 * we don't have the choice any more.
                 *
                 * Thanks to Jan Holmen Holsten for the idea and
                 * initial implementation.
                 */
                if (term->disptop > -term->savelines && term->disptop < 0)
                    term->disptop--;

                /*
                 * We've just modified the data that the terminal's
                 * scrollbar is based on, so remember to update it.
                 */
                term->win_scrollbar_update_pending = true;
            }
            resizeline(term, line, term->cols);
            clear_line(term, line);
            line->trusted = false;
            addpos234(term->screen, line, botline);

            /*
             * If the selection endpoints move into the scrollback,
             * we keep them moving until they hit the top. However,
             * of course, if the line _hasn't_ moved into the
             * scrollback then we don't do this, and cut them off
             * at the top of the scroll region.
             *
             * This applies to selstart and selend (for an existing
             * selection), and also selanchor (for one being
             * selected as we speak).
             */
            seltop = sb ? -term->savelines : topline;

            if (term->selstate != NO_SELECTION) {
                if (term->selstart.y >= seltop &&
                    term->selstart.y <= botline) {
                    term->selstart.y--;
                    if (term->selstart.y < seltop) {
                        term->selstart.y = seltop;
                        term->selstart.x = 0;
                    }
                }
                if (term->selend.y >= seltop && term->selend.y <= botline) {
                    term->selend.y--;
                    if (term->selend.y < seltop) {
                        term->selend.y = seltop;
                        term->selend.x = 0;
                    }
                }
                if (term->selanchor.y >= seltop &&
                    term->selanchor.y <= botline) {
                    term->selanchor.y--;
                    if (term->selanchor.y < seltop) {
                        term->selanchor.y = seltop;
                        term->selanchor.x = 0;
                    }
                }
            }
        }
    }

    seen_disp_event(term);
}

/*
 * Move the cursor to a given position, clipping at boundaries. We
 * may or may not want to clip at the scroll margin: marg_clip is 0
 * not to, 1 to disallow _passing_ the margins, and 2 to disallow
 * even _being_ outside the margins.
 */
static void move(Terminal *term, int x, int y, int marg_clip)
{
    if (x < 0)
        x = 0;
    if (x >= term->cols)
        x = term->cols - 1;
    if (marg_clip) {
        if ((term->curs.y >= term->marg_t || marg_clip == 2) &&
            y < term->marg_t)
            y = term->marg_t;
        if ((term->curs.y <= term->marg_b || marg_clip == 2) &&
            y > term->marg_b)
            y = term->marg_b;
    }
    if (y < 0)
        y = 0;
    if (y >= term->rows)
        y = term->rows - 1;
    term->curs.x = x;
    term->curs.y = y;
    term->wrapnext = false;
    seen_disp_event(term);
}

/*
 * Save or restore the cursor and SGR mode.
 */
static void save_cursor(Terminal *term, bool save)
{
    if (save) {
        term->savecurs = term->curs;
        term->save_attr = term->curr_attr;
        term->save_truecolour = term->curr_truecolour;
        term->save_cset = term->cset;
        term->save_utf = term->utf;
        term->save_wnext = term->wrapnext;
        term->save_csattr = term->cset_attr[term->cset];
        term->save_sco_acs = term->sco_acs;
    } else {
        term->curs = term->savecurs;
        /* Make sure the window hasn't shrunk since the save */
        if (term->curs.x >= term->cols)
            term->curs.x = term->cols - 1;
        if (term->curs.y >= term->rows)
            term->curs.y = term->rows - 1;

        term->curr_attr = term->save_attr;
        term->curr_truecolour = term->save_truecolour;
        term->cset = term->save_cset;
        term->utf = term->save_utf;
        term->wrapnext = term->save_wnext;
        /*
         * wrapnext might reset to False if the x position is no
         * longer at the rightmost edge.
         */
        if (term->wrapnext && term->curs.x < term->cols-1)
            term->wrapnext = false;
        term->cset_attr[term->cset] = term->save_csattr;
        term->sco_acs = term->save_sco_acs;
        set_erase_char(term);
        seen_disp_event(term);
    }
}

/*
 * This function is called before doing _anything_ which affects
 * only part of a line of text. It is used to mark the boundary
 * between two character positions, and it indicates that some sort
 * of effect is going to happen on only one side of that boundary.
 *
 * The effect of this function is to check whether a CJK
 * double-width character is straddling the boundary, and to remove
 * it and replace it with two spaces if so. (Of course, one or
 * other of those spaces is then likely to be replaced with
 * something else again, as a result of whatever happens next.)
 *
 * Also, if the boundary is at the right-hand _edge_ of the screen,
 * it implies something deliberate is being done to the rightmost
 * column position; hence we must clear LATTR_WRAPPED2.
 *
 * The input to the function is the coordinates of the _second_
 * character of the pair.
 */
static void check_boundary(Terminal *term, int x, int y)
{
    termline *ldata;

    /* Validate input coordinates, just in case. */
    if (x <= 0 || x > term->cols)
        return;

    ldata = scrlineptr(y);
    check_trust_status(term, ldata);
    check_line_size(term, ldata);
    if (x == term->cols) {
        ldata->lattr &= ~LATTR_WRAPPED2;
    } else {
        if (ldata->chars[x].chr == UCSWIDE) {
            clear_cc(ldata, x-1);
            clear_cc(ldata, x);
            ldata->chars[x-1].chr = ' ' | CSET_ASCII;
            ldata->chars[x] = ldata->chars[x-1];
        }
    }
}

/*
 * Erase a large portion of the screen: the whole screen, or the
 * whole line, or parts thereof.
 */
static void erase_lots(Terminal *term,
                       bool line_only, bool from_begin, bool to_end)
{
    pos start, end;
    bool erase_lattr;
    bool erasing_lines_from_top = false;

    if (line_only) {
        start.y = term->curs.y;
        start.x = 0;
        end.y = term->curs.y + 1;
        end.x = 0;
        erase_lattr = false;
    } else {
        start.y = 0;
        start.x = 0;
        end.y = term->rows;
        end.x = 0;
        erase_lattr = true;
    }

    /* This is the endpoint of the clearing operation that is not
     * either the start or end of the line / screen. */
    pos boundary = term->curs;

    if (!from_begin) {
        /*
         * If we're erasing from the current char to the end of
         * line/screen, then we take account of wrapnext, so as to
         * maintain the invariant that writing a printing character
         * followed by ESC[K should not overwrite the character you
         * _just wrote_. That is, when wrapnext says the cursor is
         * 'logically' at the very rightmost edge of the screen
         * instead of just before the last printing char, ESC[K should
         * do nothing at all, and ESC[J should clear the next line but
         * leave this one unchanged.
         *
         * This adjusted position will also be the position we use for
         * check_boundary (i.e. the thing we ensure isn't in the
         * middle of a double-width printing char).
         */
        if (term->wrapnext)
            incpos(boundary);

        start = boundary;
    }
    if (!to_end) {
        /*
         * If we're erasing from the start of (at least) the line _to_
         * the current position, then that is taken to mean 'inclusive
         * of the cell under the cursor', which means we don't
         * consider wrapnext at all: whether it's set or not, we still
         * clear the cell under the cursor.
         *
         * Again, that incremented boundary position is where we
         * should be careful of a straddling wide character.
         */
        incpos(boundary);
        end = boundary;
    }
    if (!from_begin || !to_end)
        check_boundary(term, boundary.x, boundary.y);
    check_selection(term, start, end);

    /* Clear screen also forces a full window redraw, just in case. */
    if (start.y == 0 && start.x == 0 && end.y == term->rows)
        term_invalidate(term);

    /* Lines scrolled away shouldn't be brought back on if the terminal
     * resizes. */
    if (start.y == 0 && start.x == 0 && end.x == 0 && erase_lattr)
        erasing_lines_from_top = true;

    if (term->erase_to_scrollback && erasing_lines_from_top) {
        /* If it's a whole number of lines, starting at the top, and
         * we're fully erasing them, erase by scrolling and keep the
         * lines in the scrollback. */
        int scrolllines = end.y;
        if (end.y == term->rows) {
            /* Shrink until we find a non-empty row.*/
            scrolllines = find_last_nonempty_line(term, term->screen) + 1;
        }
        if (scrolllines > 0)
            scroll(term, 0, scrolllines - 1, scrolllines, true);
    } else {
        termline *ldata = scrlineptr(start.y);
        check_trust_status(term, ldata);
        while (poslt(start, end)) {
            check_line_size(term, ldata);
            if (start.x == term->cols) {
                if (!erase_lattr)
                    ldata->lattr &= ~(LATTR_WRAPPED | LATTR_WRAPPED2);
                else
                    ldata->lattr = LATTR_NORM;
            } else {
                copy_termchar(ldata, start.x, &term->erase_char);
            }
            if (incpos(start) && start.y < term->rows) {
                ldata = scrlineptr(start.y);
                check_trust_status(term, ldata);
            }
        }
    }

    /* After an erase of lines from the top of the screen, we shouldn't
     * bring the lines back again if the terminal enlarges (since the user or
     * application has explicitly thrown them away). */
    if (erasing_lines_from_top && !(term->alt_which))
        term->tempsblines = 0;

    seen_disp_event(term);
}

/*
 * Insert or delete characters within the current line. n is +ve if
 * insertion is desired, and -ve for deletion.
 */
static void insch(Terminal *term, int n)
{
    int dir = (n < 0 ? -1 : +1);
    int m, j;
    pos eol;
    termline *ldata;

    n = (n < 0 ? -n : n);
    if (n > term->cols - term->curs.x)
        n = term->cols - term->curs.x;
    m = term->cols - term->curs.x - n;

    /*
     * We must de-highlight the selection if it overlaps any part of
     * the region affected by this operation, i.e. the region from the
     * current cursor position to end-of-line, _unless_ the entirety
     * of the selection is going to be moved to the left or right by
     * this operation but otherwise unchanged, in which case we can
     * simply move the highlight with the text.
     */
    eol.y = term->curs.y;
    eol.x = term->cols;
    if (poslt(term->curs, term->selend) && poslt(term->selstart, eol)) {
        pos okstart = term->curs;
        pos okend = eol;
        if (dir > 0) {
            /* Insertion: n characters at EOL will be splatted. */
            okend.x -= n;
        } else {
            /* Deletion: n characters at cursor position will be splatted. */
            okstart.x += n;
        }
        if (posle(okstart, term->selstart) && posle(term->selend, okend)) {
            /* Selection is contained entirely in the interval
             * [okstart,okend), so we need only adjust the selection
             * bounds. */
            term->selstart.x += dir * n;
            term->selend.x += dir * n;
            assert(term->selstart.x >= term->curs.x);
            assert(term->selstart.x < term->cols);
            assert(term->selend.x > term->curs.x);
            assert(term->selend.x <= term->cols);
        } else {
            /* Selection is not wholly contained in that interval, so
             * we must unhighlight it. */
            deselect(term);
        }
    }

    check_boundary(term, term->curs.x, term->curs.y);
    if (dir < 0)
        check_boundary(term, term->curs.x + n, term->curs.y);
    ldata = scrlineptr(term->curs.y);
    check_trust_status(term, ldata);
    if (dir < 0) {
        for (j = 0; j < m; j++)
            move_termchar(ldata,
                          ldata->chars + term->curs.x + j,
                          ldata->chars + term->curs.x + j + n);
        while (n--)
            copy_termchar(ldata, term->curs.x + m++, &term->erase_char);
    } else {
        for (j = m; j-- ;)
            move_termchar(ldata,
                          ldata->chars + term->curs.x + j + n,
                          ldata->chars + term->curs.x + j);
        while (n--)
            copy_termchar(ldata, term->curs.x + n, &term->erase_char);
    }
}

static void term_update_raw_mouse_mode(Terminal *term)
{
    bool want_raw = (term->xterm_mouse != 0 && !term->xterm_mouse_forbidden);
    win_set_raw_mouse_mode(term->win, want_raw);
    term->win_pointer_shape_pending = true;
    term->win_pointer_shape_raw = want_raw;
    term_schedule_update(term);
}

static void term_request_resize(Terminal *term, int cols, int rows)
{
    if (term->cols == cols && term->rows == rows)
        return;                        /* don't need to do anything */

    term->win_resize_pending = WIN_RESIZE_NEED_SEND;
    term->win_resize_pending_w = cols;
    term->win_resize_pending_h = rows;
    term_schedule_update(term);
}

/*
 * Toggle terminal mode `mode' to state `state'. (`query' indicates
 * whether the mode is a DEC private one or a normal one.)
 */
static void toggle_mode(Terminal *term, int mode, int query, bool state)
{
    if (query == 1) {
        switch (mode) {
          case 1:                      /* DECCKM: application cursor keys */
            term->app_cursor_keys = state;
            break;
          case 2:                      /* DECANM: VT52 mode */
            term->vt52_mode = !state;
            if (term->vt52_mode) {
                term->blink_is_real = false;
                term->vt52_bold = false;
            } else {
                term->blink_is_real = term->blinktext;
            }
            term_schedule_tblink(term);
            break;
          case 3:                      /* DECCOLM: 80/132 columns */
            deselect(term);
            if (!term->no_remote_resize)
                term_request_resize(term, state ? 132 : 80, term->rows);
            term->reset_132 = state;
            term->alt_t = term->marg_t = 0;
            term->alt_b = term->marg_b = term->rows - 1;
            move(term, 0, 0, 0);
            erase_lots(term, false, true, true);
            break;
          case 5:                      /* DECSCNM: reverse video */
            /*
             * Toggle reverse video. If we receive an OFF within the
             * visual bell timeout period after an ON, we trigger an
             * effective visual bell, so that ESC[?5hESC[?5l will
             * always be an actually _visible_ visual bell.
             */
            if (term->rvideo && !state) {
                /* This is an OFF, so set up a vbell */
                term_schedule_vbell(term, true, term->rvbell_startpoint);
            } else if (!term->rvideo && state) {
                /* This is an ON, so we notice the time and save it. */
                term->rvbell_startpoint = GETTICKCOUNT();
            }
            term->rvideo = state;
            seen_disp_event(term);
            break;
          case 6:                      /* DECOM: DEC origin mode */
            term->dec_om = state;
            break;
          case 7:                      /* DECAWM: auto wrap */
            term->wrap = state;
            if (!term->wrap)
                term->wrapnext = false;
            break;
          case 8:                      /* DECARM: auto key repeat */
            term->repeat_off = !state;
            break;
          case 25:                     /* DECTCEM: enable/disable cursor */
            compatibility2(OTHER, VT220);
            term->cursor_on = state;
            seen_disp_event(term);
            break;
          case 47:                     /* alternate screen */
            compatibility(OTHER);
            deselect(term);
            swap_screen(term, term->no_alt_screen ? 0 : state, false, false);
            if (term->scroll_on_disp)
                term->disptop = 0;
            break;
          case 1000:                   /* xterm mouse 1 (normal) */
            term->xterm_mouse = state ? 1 : 0;
            term_update_raw_mouse_mode(term);
            break;
          case 1002:                   /* xterm mouse 2 (inc. button drags) */
            term->xterm_mouse = state ? 2 : 0;
            term_update_raw_mouse_mode(term);
            break;
          case 1003:                   /* xterm mouse any-event tracking */
            term->xterm_mouse = state ? 3 : 0;
            term_update_raw_mouse_mode(term);
            break;
          case 1006:                   /* xterm extended mouse */
            term->xterm_extended_mouse = state;
            break;
          case 1015:                   /* urxvt extended mouse */
            term->urxvt_extended_mouse = state;
            break;
          case 1047:                   /* alternate screen */
            compatibility(OTHER);
            deselect(term);
            swap_screen(term, term->no_alt_screen ? 0 : state, true, true);
            if (term->scroll_on_disp)
                term->disptop = 0;
            break;
          case 1048:                   /* save/restore cursor */
            if (!term->no_alt_screen)
                save_cursor(term, state);
            if (!state) seen_disp_event(term);
            break;
          case 1049:                   /* cursor & alternate screen */
            if (state && !term->no_alt_screen)
                save_cursor(term, state);
            if (!state) seen_disp_event(term);
            compatibility(OTHER);
            deselect(term);
            swap_screen(term, term->no_alt_screen ? 0 : state, true, false);
            if (!state && !term->no_alt_screen)
                save_cursor(term, state);
            if (term->scroll_on_disp)
                term->disptop = 0;
            break;
          case 2004:                   /* xterm bracketed paste */
            term->bracketed_paste = state ? true : false;
            break;
        }
    } else if (query == 0) {
        switch (mode) {
          case 4:                      /* IRM: set insert mode */
            compatibility(VT102);
            term->insert = state;
            break;
          case 12:                     /* SRM: set echo mode */
            term->srm_echo = !state;
            break;
          case 20:                     /* LNM: Return sends ... */
            term->cr_lf_return = state;
            break;
          case 34:                     /* WYULCURM: Make cursor BIG */
            compatibility2(OTHER, VT220);
            term->big_cursor = !state;
        }
    }
}

/*
 * Process an OSC or similar sequence, with a whole embedded string,
 * like setting the window title or icon name.
 */
static void do_osc(Terminal *term)
{
    switch (term->osc_type) {
      case OSCLIKE_OSC_W:
        while (term->osc_strlen--)
            term->wordness[(unsigned char)term->osc_string[term->osc_strlen]] =
                term->esc_args[0];
        break;
      case OSCLIKE_OSC:
        term->osc_string[term->osc_strlen] = '\0';
        switch (term->esc_args[0]) {
          case 0:
          case 1:
            if (!term->no_remote_wintitle) {
                sfree(term->icon_title);
                term->icon_title = dupstr(term->osc_string);
                term->icontitle_codepage = term->ucsdata->line_codepage;
                term->win_icon_title_pending = true;
                term_schedule_update(term);
            }
            if (term->esc_args[0] == 1)
                break;
            /* fall through: parameter 0 means set both */
          case 2:
          case 21:
            if (!term->no_remote_wintitle) {
                sfree(term->window_title);
                term->window_title = dupstr(term->osc_string);
                term->wintitle_codepage = term->ucsdata->line_codepage;
                term->win_title_pending = true;
                term_schedule_update(term);
            }
            break;
          case 4:
            if (term->ldisc && !strcmp(term->osc_string, "?")) {
                unsigned index = term->esc_args[1];
                if (index < OSC4_NCOLOURS) {
                    rgb colour = term->palette[index];
                    char *reply_buf = dupprintf(
                        "\033]4;%u;rgb:%04x/%04x/%04x\007", index,
                        (unsigned)colour.r * 0x0101,
                        (unsigned)colour.g * 0x0101,
                        (unsigned)colour.b * 0x0101);
                    ldisc_send(term->ldisc, reply_buf, strlen(reply_buf),
                               false);
                    sfree(reply_buf);
                }
            }
            break;
        }
        break;
      default:
        /* APC, SOS and PM are recognised as control sequences but
         * ignored. PuTTY implements no support for any of them. */
        break;
    }
}

/*
 * ANSI printing routines.
 */
static void term_print_setup(Terminal *term, char *printer)
{
    bufchain_clear(&term->printer_buf);
    term->print_job = printer_start_job(printer);
}
static void term_print_flush(Terminal *term)
{
    size_t size;
    while ((size = bufchain_size(&term->printer_buf)) > 5) {
        ptrlen data = bufchain_prefix(&term->printer_buf);
        if (data.len > size-5)
            data.len = size-5;
        printer_job_data(term->print_job, data.ptr, data.len);
        bufchain_consume(&term->printer_buf, data.len);
    }
}
static void term_print_finish(Terminal *term)
{
    size_t size;
    char c;

    if (!term->printing && !term->only_printing)
        return;                        /* we need do nothing */

    term_print_flush(term);
    while ((size = bufchain_size(&term->printer_buf)) > 0) {
        ptrlen data = bufchain_prefix(&term->printer_buf);
        c = *(char *)data.ptr;
        if (c == '\033' || c == '\233') {
            bufchain_consume(&term->printer_buf, size);
            break;
        } else {
            printer_job_data(term->print_job, &c, 1);
            bufchain_consume(&term->printer_buf, 1);
        }
    }
    printer_finish_job(term->print_job);
    term->print_job = NULL;
    term->printing = term->only_printing = false;
}

static void term_display_graphic_char(Terminal *term, unsigned long c)
{
    termline *cline = scrlineptr(term->curs.y);
    int width = 0;
    if (DIRECT_CHAR(c))
        width = 1;
    if (!width)
        width = term_char_width(term, c);

    if (term->wrapnext && term->wrap && width > 0) {
        cline->lattr |= LATTR_WRAPPED;
        if (term->curs.y == term->marg_b)
            scroll(term, term->marg_t, term->marg_b, 1, true);
        else if (term->curs.y < term->rows - 1)
            term->curs.y++;
        term->curs.x = 0;
        term->wrapnext = false;
        cline = scrlineptr(term->curs.y);
    }
    if (term->insert && width > 0)
        insch(term, width);
    if (term->selstate != NO_SELECTION) {
        pos cursplus = term->curs;
        incpos(cursplus);
        check_selection(term, term->curs, cursplus);
    }
    if (((c & CSET_MASK) == CSET_ASCII ||
         (c & CSET_MASK) == 0) && term->logctx)
        logtraffic(term->logctx, (unsigned char) c, LGTYP_ASCII);

    check_trust_status(term, cline);

    int linecols = term->cols;
    if (cline->trusted)
        linecols -= TRUST_SIGIL_WIDTH;

    /*
     * Before we switch on the character width, do a preliminary check for
     * cases where we might have no room at all to display a double-width
     * character. Our fallback is to substitute REPLACEMENT CHARACTER,
     * which is single-width, and it's easiest to do that _before_ having
     * to 'goto' from one switch case to another.
     */
    if (width == 2 && term->curs.x >= linecols-1) {
        /*
         * If we're in wrapping mode and the terminal is at least 2 cells
         * wide, it's OK, we have a fallback. But otherwise, substitute.
         */
        if (linecols < 2 || !term->wrap) {
            width = 1;
            c = 0xFFFD;
        }
    }

    switch (width) {
      case 2:
        /*
         * If we're about to display a double-width character starting in
         * the rightmost column (and we're in wrapping mode - the other
         * case was disposed of above), then we do something special
         * instead. We must print a space in the last column of the screen,
         * then wrap; and we also set LATTR_WRAPPED2 which instructs
         * subsequent cut-and-pasting not only to splice this line to the
         * one after it, but to ignore the space in the last character
         * position as well. (Because what was actually output to the
         * terminal was presumably just a sequence of CJK characters, and
         * we don't want a space to be pasted in the middle of those just
         * because they had the misfortune to start in the wrong parity
         * column. xterm concurs.)
         */
        check_boundary(term, term->curs.x, term->curs.y);
        check_boundary(term, term->curs.x+2, term->curs.y);
        if (term->curs.x >= linecols-1) {
            assert(term->wrap);    /* we handled the non-wrapping case above */
            copy_termchar(cline, term->curs.x,
                          &term->erase_char);
            cline->lattr |= LATTR_WRAPPED | LATTR_WRAPPED2;
            if (term->curs.y == term->marg_b)
                scroll(term, term->marg_t, term->marg_b,
                       1, true);
            else if (term->curs.y < term->rows - 1)
                term->curs.y++;
            term->curs.x = 0;
            cline = scrlineptr(term->curs.y);
            /* Now we must check_boundary again, of course. */
            check_boundary(term, term->curs.x, term->curs.y);
            check_boundary(term, term->curs.x+2, term->curs.y);
        }

        /* FULL-TERMCHAR */
        clear_cc(cline, term->curs.x);
        cline->chars[term->curs.x].chr = c;
        cline->chars[term->curs.x].attr = term->curr_attr;
        cline->chars[term->curs.x].truecolour =
            term->curr_truecolour;

        term->curs.x++;

        /* FULL-TERMCHAR */
        clear_cc(cline, term->curs.x);
        cline->chars[term->curs.x].chr = UCSWIDE;
        cline->chars[term->curs.x].attr = term->curr_attr;
        cline->chars[term->curs.x].truecolour =
            term->curr_truecolour;

        break;
      case 1:
        check_boundary(term, term->curs.x, term->curs.y);
        check_boundary(term, term->curs.x+1, term->curs.y);

        /* FULL-TERMCHAR */
        clear_cc(cline, term->curs.x);
        cline->chars[term->curs.x].chr = c;
        cline->chars[term->curs.x].attr = term->curr_attr;
        cline->chars[term->curs.x].truecolour =
            term->curr_truecolour;

        break;
      case 0:
        if (term->curs.x > 0) {
            int x = term->curs.x - 1;

            /* If we're in wrapnext state, the character to combine
             * with is _here_, not to our left. */
            if (term->wrapnext)
                x++;

            /*
             * If the previous character is UCSWIDE, back up another
             * one.
             */
            if (cline->chars[x].chr == UCSWIDE) {
                assert(x > 0);
                x--;
            }

            add_cc(cline, x, c);
            seen_disp_event(term);
        }
        return;
      default:
        return;
    }
    term->curs.x++;
    if (term->curs.x >= linecols) {
        term->curs.x = linecols - 1;

        if (term->wrap) {
            if (!term->vt52_mode) {
                /* Set the wrapnext flag, so that the next character
                 * wraps, but this one doesn't. */
                term->wrapnext = true;
            } else {
                /* VT52 mode expects simpler handling, and we just
                 * wrap straight away. */
                cline->lattr |= LATTR_WRAPPED;
                if (term->curs.y == term->marg_b)
                    scroll(term, term->marg_t, term->marg_b, 1, true);
                else if (term->curs.y < term->rows - 1)
                    term->curs.y++;
                term->curs.x = 0;
                term->wrapnext = false;
            }
        }
    }
    seen_disp_event(term);
}

static strbuf *term_input_data_from_unicode(
    Terminal *term, const wchar_t *widebuf, size_t len)
{
    strbuf *buf = strbuf_new();

    if (in_utf(term)) {
        /*
         * Translate input wide characters into UTF-8 to go in the
         * terminal's input data queue.
         */
        for (size_t i = 0; i < len; i++) {
            unsigned long ch = widebuf[i];

            if (IS_SURROGATE(ch)) {
#ifdef PLATFORM_IS_UTF16
                if (i+1 < len) {
                    unsigned long ch2 = widebuf[i+1];
                    if (IS_SURROGATE_PAIR(ch, ch2)) {
                        ch = FROM_SURROGATES(ch, ch2);
                        i++;
                    }
                } else
#endif
                {
                    /* Unrecognised UTF-16 sequence */
                    ch = '.';
                }
            }

            put_utf8_char(buf, ch);
        }
    } else {
        /*
         * Call to the character-set subsystem to translate into
         * whatever charset the terminal is currently configured in.
         *
         * Since the terminal doesn't currently support any multibyte
         * character set other than UTF-8, we can assume here that
         * there will be at most one output byte per input wchar_t.
         * (But also we must allow space for the trailing NUL that
         * wc_to_mb will write.)
         */
        put_wc_to_mb(buf, term->ucsdata->line_codepage, widebuf, len, "");
    }

    return buf;
}

static strbuf *term_input_data_from_charset(
    Terminal *term, int codepage, const char *str, size_t len)
{
    if (codepage < 0) {
        strbuf *buf = strbuf_new();
        put_data(buf, str, len);
        return buf;
    } else {
        strbuf *wide = strbuf_new();
        put_mb_to_wc(wide, codepage, str, len);
        strbuf *buf = term_input_data_from_unicode(
            term, (const wchar_t *)wide->s, wide->len / sizeof(wchar_t));
        strbuf_free(wide);
        return buf;
    }

}

static inline void term_bracketed_paste_start(Terminal *term)
{
    ptrlen seq = PTRLEN_LITERAL("\033[200~");
    if (term->ldisc)
        ldisc_send(term->ldisc, seq.ptr, seq.len, false);
    term->bracketed_paste_active = true;
}

static inline void term_bracketed_paste_stop(Terminal *term)
{
    if (!term->bracketed_paste_active)
        return;

    ptrlen seq = PTRLEN_LITERAL("\033[201~");
    if (term->ldisc)
        ldisc_send(term->ldisc, seq.ptr, seq.len, false);
    term->bracketed_paste_active = false;
}

static inline void term_keyinput_internal(
    Terminal *term, const void *buf, int len, bool interactive)
{
    if (term->srm_echo) {
        /*
         * Implement the terminal-level local echo behaviour that
         * ECMA-48 specifies when terminal mode 12 is configured off
         * (ESC[12l). In this mode, data input to the terminal via the
         * keyboard is also added to the output buffer. But this
         * doesn't apply to escape sequences generated as session
         * input _within_ the terminal, e.g. in response to terminal
         * query sequences, or the bracketing sequences of bracketed
         * paste mode. Those will be sent directly via
         * ldisc_send(term->ldisc, ...) and won't go through this
         * function.
         */

        /* Mimic the special case of negative length in ldisc_send */
        int true_len = len >= 0 ? len : strlen(buf);

        bufchain_add(&term->inbuf, buf, true_len);
        term_added_data(term, false);
    }
    if (interactive)
        term_bracketed_paste_stop(term);
    if (term->ldisc)
        ldisc_send(term->ldisc, buf, len, interactive);
    term_seen_key_event(term);
}

unsigned long term_translate(
    Terminal *term, struct term_utf8_decode *utf8, unsigned char c)
{
    if (in_utf(term)) {
        switch (utf8->state) {
          case 0:
            if (c < 0x80) {
                /* UTF-8 must be stateless so we ignore iso2022. */
                if (term->ucsdata->unitab_ctrl[c] != 0xFF)  {
                    return term->ucsdata->unitab_ctrl[c];
                } else if ((term->utf8linedraw) &&
                           (term->cset_attr[term->cset] == CSET_LINEDRW)) {
                    /* Linedraw characters are explicitly enabled */
                    return c | CSET_LINEDRW;
                } else {
                    return c | CSET_ASCII;
                }
            } else if ((c & 0xe0) == 0xc0) {
                utf8->size = utf8->state = 1;
                utf8->chr = (c & 0x1f);
            } else if ((c & 0xf0) == 0xe0) {
                utf8->size = utf8->state = 2;
                utf8->chr = (c & 0x0f);
            } else if ((c & 0xf8) == 0xf0) {
                utf8->size = utf8->state = 3;
                utf8->chr = (c & 0x07);
            } else if ((c & 0xfc) == 0xf8) {
                utf8->size = utf8->state = 4;
                utf8->chr = (c & 0x03);
            } else if ((c & 0xfe) == 0xfc) {
                utf8->size = utf8->state = 5;
                utf8->chr = (c & 0x01);
            } else {
                return UCSINVALID;
            }
            return UCSINCOMPLETE;
          case 1:
          case 2:
          case 3:
          case 4:
          case 5:
            if ((c & 0xC0) != 0x80) {
                utf8->state = 0;
                return UCSTRUNCATED;   /* caller will then give us the
                                        * same byte again */
            }
            utf8->chr = (utf8->chr << 6) | (c & 0x3f);
            if (--utf8->state)
                return UCSINCOMPLETE;

            unsigned long t = utf8->chr;

            /* Is somebody trying to be evil! */
            if (t < 0x80 ||
                (t < 0x800 && utf8->size >= 2) ||
                (t < 0x10000 && utf8->size >= 3) ||
                (t < 0x200000 && utf8->size >= 4) ||
                (t < 0x4000000 && utf8->size >= 5))
                return UCSINVALID;

            /* Unicode line separator and paragraph separator are CR-LF */
            if (t == 0x2028 || t == 0x2029)
                return 0x85;

            /* High controls are probably a Baaad idea too. */
            if (t < 0xA0)
                return 0xFFFD;

            /* The UTF-16 surrogates are not nice either. */
            /*       The standard give the option of decoding these:
             *       I don't want to! */
            if (t >= 0xD800 && t < 0xE000)
                return UCSINVALID;

            /* ISO 10646 characters now limited to UTF-16 range. */
            if (t > 0x10FFFF)
                return UCSINVALID;

            /* U+FEFF is best seen as a null. */
            if (t == 0xFEFF)
                return UCSINCOMPLETE;
            /* But U+FFFE is an error. */
            if (t == 0xFFFE || t == 0xFFFF)
                return UCSINVALID;

            return t;
        }
    } else if (term->sco_acs &&
               (c!='\033' && c!='\012' && c!='\015' && c!='\b')) {
        /* Are we in the nasty ACS mode? Note: no sco in utf mode. */
        if (term->sco_acs == 2)
            c |= 0x80;

        return c | CSET_SCOACS;
    } else {
        switch (term->cset_attr[term->cset]) {
            /*
             * Linedraw characters are different from 'ESC ( B'
             * only for a small range. For ones outside that
             * range, make sure we use the same font as well as
             * the same encoding.
             */
          case CSET_LINEDRW:
            if (term->ucsdata->unitab_ctrl[c] != 0xFF)
                return term->ucsdata->unitab_ctrl[c];
            else
                return c | CSET_LINEDRW;
            break;

          case CSET_GBCHR:
            /* If UK-ASCII, make the '#' a LineDraw Pound */
            if (c == '#')
                return '}' | CSET_LINEDRW;
            /* fall through */

          case CSET_ASCII:
            if (term->ucsdata->unitab_ctrl[c] != 0xFF)
                return term->ucsdata->unitab_ctrl[c];
            else
                return c | CSET_ASCII;
            break;
          case CSET_SCOACS:
            if (c >= ' ')
                return c | CSET_SCOACS;
            break;
        }
    }
    return c;
}

/*
 * Remove everything currently in `inbuf' and stick it up on the
 * in-memory display. There's a big state machine in here to
 * process escape sequences...
 */
static void term_out(Terminal *term, bool called_from_term_data)
{
    unsigned long c;
    int unget;
    const unsigned char *chars;
    size_t nchars_got = 0, nchars_used = 0;

    /*
     * During drag-selects, we do not process terminal input, because
     * the user will want the screen to hold still to be selected.
     */
    if (term->selstate == DRAGGING)
        return;

    unget = -1;

    chars = NULL;                      /* placate compiler warnings */
    while (nchars_got < nchars_used ||
           unget != -1 ||
           bufchain_size(&term->inbuf) > 0) {
        if (unget != -1) {
            /*
             * Handle a character we left in 'unget' the last time
             * round this loop. This happens if a UTF-8 sequence is
             * aborted early, by containing fewer continuation bytes
             * than its introducer expected: the non-continuation byte
             * that interrupted the sequence must now be processed
             * as a fresh piece of input in its own right.
             */
            c = unget;
            unget = -1;
        } else {
            /*
             * If we're waiting for a terminal resize triggered by an
             * escape sequence, we defer processing the terminal
             * output until we receive acknowledgment from the front
             * end that the resize has happened, so that further
             * output will be processed in the context of the new
             * size.
             *
             * This test goes inside the main while-loop, so that we
             * exit early if we encounter a resize escape sequence
             * part way through term->inbuf.
             *
             * It's also in the branch of this if statement that
             * doesn't deal with a character left in 'unget' by the
             * previous loop iteration, because if we break out of
             * this loop with an ungot character still pending, we'll
             * lose it. (And in any case, if the previous thing that
             * happened was a truncated UTF-8 sequence, then it won't
             * have scheduled a pending resize.)
             */
            if (term->win_resize_pending != WIN_RESIZE_NO)
                break;

            if (nchars_got == nchars_used) {
                /* Delete the previous chunk from the bufchain */
                bufchain_consume(&term->inbuf, nchars_used);
                nchars_used = 0;

                if (bufchain_size(&term->inbuf) == 0)
                    break;             /* no more data */

                ptrlen data = bufchain_prefix(&term->inbuf);
                chars = data.ptr;
                nchars_got = data.len;
                assert(chars != NULL);
                assert(nchars_used < nchars_got);
            }
            c = chars[nchars_used++];

            /*
             * Optionally log the session traffic to a file. Useful for
             * debugging and possibly also useful for actual logging.
             */
            if (term->logtype == LGTYP_DEBUG && term->logctx)
                logtraffic(term->logctx, (unsigned char) c, LGTYP_DEBUG);
        }

        /* Note only VT220+ are 8-bit VT102 is seven bit, it shouldn't even
         * be able to display 8-bit characters, but I'll let that go 'cause
         * of i18n.
         */

        /*
         * If we're printing, add the character to the printer
         * buffer.
         */
        if (term->printing) {
            bufchain_add(&term->printer_buf, &c, 1);

            /*
             * If we're in print-only mode, we use a much simpler
             * state machine designed only to recognise the ESC[4i
             * termination sequence.
             */
            if (term->only_printing) {
                if (c == '\033')
                    term->print_state = 1;
                else if (c == (unsigned char)'\233')
                    term->print_state = 2;
                else if (c == '[' && term->print_state == 1)
                    term->print_state = 2;
                else if (c == '4' && term->print_state == 2)
                    term->print_state = 3;
                else if (c == 'i' && term->print_state == 3)
                    term->print_state = 4;
                else
                    term->print_state = 0;
                if (term->print_state == 4) {
                    term_print_finish(term);
                }
                continue;
            }
        }

        /* Do character-set translation. */
        if (term->termstate == TOPLEVEL) {
            unsigned long t = term_translate(term, &term->utf8, c);
            switch (t) {
              case UCSINCOMPLETE:
                continue;       /* didn't complete a multibyte char */
              case UCSTRUNCATED:
                unget = c;
                /* fall through */
              case UCSINVALID:
                c = UCSERR;
                break;
              default:
                c = t;
                break;
            }
        }

        /*
         * How about C1 controls?
         * Explicitly ignore SCI (0x9a), which we don't translate to DECID.
         */
        if ((c & -32) == 0x80 && term->termstate < DO_CTRLS &&
            !term->vt52_mode && has_compat(VT220)) {
            if (c == 0x9a)
                c = 0;
            else {
                term->termstate = SEEN_ESC;
                term->esc_query = 0;
                c = '@' + (c & 0x1F);
            }
        }

        /* Or the GL control. */
        if (c == '\177' && term->termstate < DO_CTRLS && has_compat(OTHER)) {
            if (term->curs.x && !term->wrapnext)
                term->curs.x--;
            term->wrapnext = false;
            /* destructive backspace might be disabled */
            if (!term->no_dbackspace) {
                check_boundary(term, term->curs.x, term->curs.y);
                check_boundary(term, term->curs.x+1, term->curs.y);
                copy_termchar(scrlineptr(term->curs.y),
                              term->curs.x, &term->erase_char);
            }
            seen_disp_event(term);
        } else
        /* Or normal C0 controls. */
        if ((c & ~0x1F) == 0 && term->termstate < DO_CTRLS) {
            switch (c) {
              case '\005':             /* ENQ: terminal type query */
                /*
                 * Strictly speaking this is VT100 but a VT100 defaults to
                 * no response. Other terminals respond at their option.
                 *
                 * Don't put a CR in the default string as this tends to
                 * upset some weird software.
                 */
                compatibility(ANSIMIN);
                if (term->ldisc) {
                    strbuf *buf = term_input_data_from_charset(
                        term, DEFAULT_CODEPAGE,
                        term->answerback->s, term->answerback->len);
                    ldisc_send(term->ldisc, buf->s, buf->len, false);
                    strbuf_free(buf);
                }
                break;
              case '\007': {            /* BEL: Bell */
                if (term->termstate == SEEN_OSC ||
                    term->termstate == SEEN_OSC_W) {
                    /*
                     * In an OSC context, BEL is one of the ways to terminate
                     * the whole sequence. We process it as such even if we
                     * haven't got into the final OSC_STRING state yet, so that
                     * OSC sequences without a string will be handled cleanly.
                     */
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                }

                struct beeptime *newbeep;
                unsigned long ticks;

                ticks = GETTICKCOUNT();

                if (!term->beep_overloaded) {
                    newbeep = snew(struct beeptime);
                    newbeep->ticks = ticks;
                    newbeep->next = NULL;
                    if (!term->beephead)
                        term->beephead = newbeep;
                    else
                        term->beeptail->next = newbeep;
                    term->beeptail = newbeep;
                    term->nbeeps++;
                }

                /*
                 * Throw out any beeps that happened more than
                 * t seconds ago.
                 */
                while (term->beephead &&
                       term->beephead->ticks < ticks - term->bellovl_t) {
                    struct beeptime *tmp = term->beephead;
                    term->beephead = tmp->next;
                    sfree(tmp);
                    if (!term->beephead)
                        term->beeptail = NULL;
                    term->nbeeps--;
                }

                if (term->bellovl && term->beep_overloaded &&
                    ticks - term->lastbeep >= (unsigned)term->bellovl_s) {
                    /*
                     * If we're currently overloaded and the
                     * last beep was more than s seconds ago,
                     * leave overload mode.
                     */
                    term->beep_overloaded = false;
                } else if (term->bellovl && !term->beep_overloaded &&
                           term->nbeeps >= term->bellovl_n) {
                    /*
                     * Now, if we have n or more beeps
                     * remaining in the queue, go into overload
                     * mode.
                     */
                    term->beep_overloaded = true;
                }
                term->lastbeep = ticks;

                /*
                 * Perform an actual beep if we're not overloaded.
                 */
                if (!term->bellovl || !term->beep_overloaded) {
                    win_bell(term->win, term->beep);

                    if (term->beep == BELL_VISUAL) {
                        term_schedule_vbell(term, false, 0);
                    }
                }
                seen_disp_event(term);
                break;
              }
              case '\b':              /* BS: Back space */
                if (term->wrapnext) {
                    term->wrapnext = false;
                } else if (term->curs.x == 0 &&
                           (term->curs.y == 0 || !term->wrap)) {
                    /* do nothing */
                } else if (term->curs.x == 0 && term->curs.y > 0) {
                    term->curs.x = term->cols - 1, term->curs.y--;

                    /*
                     * If the line we've just wrapped back on to had the
                     * LATTR_WRAPPED2 flag set, it means that the line wrapped
                     * because a double-width character was printed with the
                     * cursor in the rightmost column, and the best handling
                     * available was to leave that column empty and move the
                     * whole character to the next line. In that situation,
                     * backspacing needs to put the cursor on the previous
                     * _logical_ character, i.e. skip the empty space left by
                     * the wrapping. This arranges that if an application
                     * unaware of the terminal width or cursor position prints
                     * a number of printing characters and then tries to return
                     * to a particular one of them by emitting the right number
                     * of backspaces, it's still the right number even if a
                     * line break appeared in a maximally awkward position.
                     */
                    termline *ldata = scrlineptr(term->curs.y);
                    if (term->curs.x > 0 && (ldata->lattr & LATTR_WRAPPED2))
                        term->curs.x--;
                } else {
                    term->curs.x--;
                }
                seen_disp_event(term);
                break;
              case '\016':            /* LS1: Locking-shift one */
                compatibility(VT100);
                term->cset = 1;
                break;
              case '\017':            /* LS0: Locking-shift zero */
                compatibility(VT100);
                term->cset = 0;
                break;
              case '\033':            /* ESC: Escape */
                if (term->vt52_mode)
                    term->termstate = VT52_ESC;
                else if (term->termstate == SEEN_OSC ||
                         term->termstate == SEEN_OSC_W) {
                    /* Be prepared to terminate an OSC early */
                    term->termstate = OSC_MAYBE_ST;
                } else {
                    compatibility(ANSIMIN);
                    term->termstate = SEEN_ESC;
                    term->esc_query = 0;
                }
                break;
              case '\015':            /* CR: Carriage return */
                term->curs.x = 0;
                term->wrapnext = false;
                seen_disp_event(term);

                if (term->crhaslf) {
                    if (term->curs.y == term->marg_b)
                        scroll(term, term->marg_t, term->marg_b, 1, true);
                    else if (term->curs.y < term->rows - 1)
                        term->curs.y++;
                }
                if (term->logctx)
                    logtraffic(term->logctx, (unsigned char) c, LGTYP_ASCII);
                break;
              case '\014':            /* FF: Form feed */
                if (has_compat(SCOANSI)) {
                    move(term, 0, 0, 0);
                    erase_lots(term, false, false, true);
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    term->wrapnext = false;
                    seen_disp_event(term);
                    break;
                }
              case '\013':            /* VT: Line tabulation */
                compatibility(VT100);
              case '\012':            /* LF: Line feed */
                if (term->curs.y == term->marg_b)
                    scroll(term, term->marg_t, term->marg_b, 1, true);
                else if (term->curs.y < term->rows - 1)
                    term->curs.y++;
                if (term->lfhascr)
                    term->curs.x = 0;
                term->wrapnext = false;
                seen_disp_event(term);
                if (term->logctx)
                    logtraffic(term->logctx, (unsigned char) c, LGTYP_ASCII);
                break;
              case '\t': {              /* HT: Character tabulation */
                pos old_curs = term->curs;
                termline *ldata = scrlineptr(term->curs.y);

                do {
                    term->curs.x++;
                } while (term->curs.x < term->cols - 1 &&
                         !term->tabs[term->curs.x]);

                if ((ldata->lattr & LATTR_MODE) != LATTR_NORM) {
                    if (term->curs.x >= term->cols / 2)
                        term->curs.x = term->cols / 2 - 1;
                } else {
                    if (term->curs.x >= term->cols)
                        term->curs.x = term->cols - 1;
                }

                check_selection(term, old_curs, term->curs);
                seen_disp_event(term);
                break;
              }
            }
        } else
            switch (term->termstate) {
              case TOPLEVEL:
                /* Only graphic characters get this far;
                 * ctrls are stripped above */
                term_display_graphic_char(term, c);
                term->last_graphic_char = c;
                break;

              case OSC_MAYBE_ST:
                /*
                 * This state is virtually identical to SEEN_ESC, with the
                 * exception that we have an OSC sequence in the pipeline,
                 * and _if_ we see a backslash, we process it.
                 */
                if (c == '\\') {
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                }
                /* else fall through */
              case SEEN_ESC:
                if (c >= ' ' && c <= '/') {
                    if (term->esc_query)
                        term->esc_query = -1;
                    else
                        term->esc_query = c;
                    break;
                }
                term->termstate = TOPLEVEL;
                switch (ANSI(c, term->esc_query)) {
                  case '[':             /* enter CSI mode */
                    term->termstate = SEEN_CSI;
                    term->esc_nargs = 1;
                    term->esc_args[0] = ARG_DEFAULT;
                    term->esc_query = 0;
                    break;
                  case ']':             /* OSC: xterm escape sequences */
                    /* Compatibility is nasty here, xterm, linux, decterm yuk! */
                    compatibility(OTHER);
                    term->termstate = SEEN_OSC;
                    term->osc_type = OSCLIKE_OSC;
                    term->osc_strlen = 0;
                    term->esc_args[0] = 0;
                    term->esc_nargs = 1;
                    break;
                  case 'X':             /* SOS: Start of String */
                  case '^':             /* PM: privacy message */
                  case '_':             /* APC: application program command */
                    /* SOS, PM, and APC sequences are just a string, terminated
                     * by ST or (I've observed in practice for APC) ^G. That
                     * is, they have the same termination convention as OSC. So
                     * we handle them by going straight into OSC_STRING state
                     * and setting a flag indicating that it's not really an
                     * OSC. */
                    compatibility(OTHER);
                    term->termstate = SEEN_OSC;
                    term->osc_type = (c == 'X' ? OSCLIKE_SOS :
                                      c == '^' ? OSCLIKE_PM : OSCLIKE_APC);
                    term->osc_strlen = 0;
                    term->esc_args[0] = 0;
                    term->esc_nargs = 1;
                    break;
                  case '7':             /* DECSC: save cursor */
                    compatibility(VT100);
                    save_cursor(term, true);
                    break;
                  case '8':             /* DECRC: restore cursor */
                    compatibility(VT100);
                    save_cursor(term, false);
                    break;
                  case '=':             /* DECKPAM: Keypad application mode */
                    compatibility(VT100);
                    term->app_keypad_keys = true;
                    break;
                  case '>':             /* DECKPNM: Keypad numeric mode */
                    compatibility(VT100);
                    term->app_keypad_keys = false;
                    break;
                  case 'D':            /* IND: exactly equivalent to LF */
                    compatibility(VT100);
                    if (term->curs.y == term->marg_b)
                        scroll(term, term->marg_t, term->marg_b, 1, true);
                    else if (term->curs.y < term->rows - 1)
                        term->curs.y++;
                    term->wrapnext = false;
                    seen_disp_event(term);
                    break;
                  case 'E':            /* NEL: exactly equivalent to CR-LF */
                    compatibility(VT100);
                    term->curs.x = 0;
                    if (term->curs.y == term->marg_b)
                        scroll(term, term->marg_t, term->marg_b, 1, true);
                    else if (term->curs.y < term->rows - 1)
                        term->curs.y++;
                    term->wrapnext = false;
                    seen_disp_event(term);
                    break;
                  case 'M':            /* RI: reverse index - backwards LF */
                    compatibility(VT100);
                    if (term->curs.y == term->marg_t)
                        scroll(term, term->marg_t, term->marg_b, -1, true);
                    else if (term->curs.y > 0)
                        term->curs.y--;
                    term->wrapnext = false;
                    seen_disp_event(term);
                    break;
                  case 'Z':            /* DECID: terminal type query */
                    compatibility(VT100);
                    if (term->ldisc)
                        ldisc_send(term->ldisc, term->id_string,
                                   strlen(term->id_string), false);
                    break;
                  case 'c':            /* RIS: restore power-on settings */
                    compatibility(VT100);
                    power_on(term, true);
                    if (term->ldisc)   /* cause ldisc to notice changes */
                        ldisc_echoedit_update(term->ldisc);
                    if (term->reset_132) {
                        if (!term->no_remote_resize)
                            term_request_resize(term, 80, term->rows);
                        term->reset_132 = false;
                    }
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    seen_disp_event(term);
                    break;
                  case 'H':            /* HTS: set a tab */
                    compatibility(VT100);
                    term->tabs[term->curs.x] = true;
                    break;

                  case ANSI('8', '#'): { /* DECALN: fills screen with Es :-) */
                    compatibility(VT100);
                    termline *ldata;
                    int i, j;
                    pos scrtop, scrbot;

                    for (i = 0; i < term->rows; i++) {
                        ldata = scrlineptr(i);
                        check_line_size(term, ldata);
                        for (j = 0; j < term->cols; j++) {
                            copy_termchar(ldata, j,
                                          &term->basic_erase_char);
                            ldata->chars[j].chr = 'E';
                        }
                        ldata->lattr = LATTR_NORM;
                    }
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    seen_disp_event(term);
                    scrtop.x = scrtop.y = 0;
                    scrbot.x = 0;
                    scrbot.y = term->rows;
                    check_selection(term, scrtop, scrbot);
                    break;
                  }

                  case ANSI('3', '#'):
                  case ANSI('4', '#'):
                  case ANSI('5', '#'):
                  case ANSI('6', '#'): {
                    compatibility(VT100);
                    int nlattr;
                    termline *ldata;

                    switch (ANSI(c, term->esc_query)) {
                      case ANSI('3', '#'): /* DECDHL: 2*height, top */
                        nlattr = LATTR_TOP;
                        break;
                      case ANSI('4', '#'): /* DECDHL: 2*height, bottom */
                        nlattr = LATTR_BOT;
                        break;
                      case ANSI('5', '#'): /* DECSWL: normal */
                        nlattr = LATTR_NORM;
                        break;
                      default: /* case ANSI('6', '#'): DECDWL: 2*width */
                        nlattr = LATTR_WIDE;
                        break;
                    }
                    ldata = scrlineptr(term->curs.y);
                    check_line_size(term, ldata);
                    check_trust_status(term, ldata);
                    ldata->lattr = nlattr;
                    seen_disp_event(term);
                    break;
                  }
                  /* GZD4: G0 designate 94-set */
                  case ANSI('A', '('):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[0] = CSET_GBCHR;
                    break;
                  case ANSI('B', '('):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[0] = CSET_ASCII;
                    break;
                  case ANSI('0', '('):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[0] = CSET_LINEDRW;
                    break;
                  case ANSI('U', '('):
                    compatibility(OTHER);
                    if (!term->no_remote_charset)
                        term->cset_attr[0] = CSET_SCOACS;
                    break;
                  /* G1D4: G1-designate 94-set */
                  case ANSI('A', ')'):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[1] = CSET_GBCHR;
                    break;
                  case ANSI('B', ')'):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[1] = CSET_ASCII;
                    break;
                  case ANSI('0', ')'):
                    compatibility(VT100);
                    if (!term->no_remote_charset)
                        term->cset_attr[1] = CSET_LINEDRW;
                    break;
                  case ANSI('U', ')'):
                    compatibility(OTHER);
                    if (!term->no_remote_charset)
                        term->cset_attr[1] = CSET_SCOACS;
                    break;
                  /* DOCS: Designate other coding system */
                  case ANSI('8', '%'):  /* Old Linux code */
                  case ANSI('G', '%'):
                    compatibility(OTHER);
                    if (!term->no_remote_charset)
                        term->utf = true;
                    break;
                  case ANSI('@', '%'):
                    compatibility(OTHER);
                    if (!term->no_remote_charset)
                        term->utf = false;
                    break;
                }
                break;
              case SEEN_CSI:
                term->termstate = TOPLEVEL;  /* default */
                if (isdigit(c)) {
                    if (term->esc_nargs <= ARGS_MAX) {
                        if (term->esc_args[term->esc_nargs - 1] == ARG_DEFAULT)
                            term->esc_args[term->esc_nargs - 1] = 0;
                        if (term->esc_args[term->esc_nargs - 1] <=
                            UINT_MAX / 10 &&
                            term->esc_args[term->esc_nargs - 1] * 10 <=
                            UINT_MAX - c - '0')
                            term->esc_args[term->esc_nargs - 1] =
                                10 * term->esc_args[term->esc_nargs - 1] +
                                c - '0';
                        else
                            term->esc_args[term->esc_nargs - 1] = UINT_MAX;
                    }
                    term->termstate = SEEN_CSI;
                } else if (c == ';') {
                    if (term->esc_nargs < ARGS_MAX)
                        term->esc_args[term->esc_nargs++] = ARG_DEFAULT;
                    term->termstate = SEEN_CSI;
                } else if (c < '@') {
                    if (term->esc_query)
                        term->esc_query = -1;
                    else if (c == '?')
                        term->esc_query = 1;
                    else
                        term->esc_query = c;
                    term->termstate = SEEN_CSI;
                } else
#define CLAMP(arg, lim) ((arg) = ((arg) > (lim)) ? (lim) : (arg))
                    switch (ANSI(c, term->esc_query)) {
                      case 'A':       /* CUU: move up N lines */
                        CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             term->curs.y - def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
                        break;
                      case 'e':         /* VPR: move down N lines */
                        compatibility(ANSI);
                        /* FALLTHROUGH */
                      case 'B':         /* CUD: Cursor down */
                        CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             term->curs.y + def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
                        break;
                      case 'b':        /* REP: repeat previous grap */
                        CLAMP(term->esc_args[0], term->rows * term->cols);
                        if (term->last_graphic_char) {
                            unsigned i;
                            for (i = 0; i < term->esc_args[0]; i++)
                                term_display_graphic_char(
                                    term, term->last_graphic_char);
                        }
                        break;
                      case ANSI('c', '>'):      /* DA: report xterm version */
                        compatibility(OTHER);
                        /* this reports xterm version 136 so that VIM can
                           use the drag messages from the mouse reporting */
                        if (term->ldisc)
                            ldisc_send(term->ldisc, "\033[>0;136;0c", 11,
                                       false);
                        break;
                      case 'a':         /* HPR: move right N cols */
                        compatibility(ANSI);
                        /* FALLTHROUGH */
                      case 'C':         /* CUF: Cursor right */
                        CLAMP(term->esc_args[0], term->cols);
                        move(term, term->curs.x + def(term->esc_args[0], 1),
                             term->curs.y, 1);
                        seen_disp_event(term);
                        break;
                      case 'D':       /* CUB: move left N cols */
                        CLAMP(term->esc_args[0], term->cols);
                        move(term, term->curs.x - def(term->esc_args[0], 1),
                             term->curs.y, 1);
                        seen_disp_event(term);
                        break;
                      case 'E':       /* CNL: move down N lines and CR */
                        compatibility(ANSI);
                        CLAMP(term->esc_args[0], term->rows);
                        move(term, 0,
                             term->curs.y + def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
                        break;
                      case 'F':       /* CPL: move up N lines and CR */
                        compatibility(ANSI);
                        CLAMP(term->esc_args[0], term->rows);
                        move(term, 0,
                             term->curs.y - def(term->esc_args[0], 1), 1);
                        seen_disp_event(term);
                        break;
                      case 'G':       /* CHA */
                      case '`':       /* HPA: set horizontal posn */
                        compatibility(ANSI);
                        CLAMP(term->esc_args[0], term->cols);
                        move(term, def(term->esc_args[0], 1) - 1,
                             term->curs.y, 0);
                        seen_disp_event(term);
                        break;
                      case 'd':       /* VPA: set vertical posn */
                        compatibility(ANSI);
                        CLAMP(term->esc_args[0], term->rows);
                        move(term, term->curs.x,
                             ((term->dec_om ? term->marg_t : 0) +
                              def(term->esc_args[0], 1) - 1),
                             (term->dec_om ? 2 : 0));
                        seen_disp_event(term);
                        break;
                      case 'H':      /* CUP */
                      case 'f':      /* HVP: set horz and vert posns at once */
                        if (term->esc_nargs < 2)
                            term->esc_args[1] = ARG_DEFAULT;
                        CLAMP(term->esc_args[0], term->rows);
                        CLAMP(term->esc_args[1], term->cols);
                        move(term, def(term->esc_args[1], 1) - 1,
                             ((term->dec_om ? term->marg_t : 0) +
                              def(term->esc_args[0], 1) - 1),
                             (term->dec_om ? 2 : 0));
                        seen_disp_event(term);
                        break;
                      case 'J': {       /* ED: erase screen or parts of it */
                        unsigned int i = def(term->esc_args[0], 0);
                        if (i == 3) {
                            /* Erase Saved Lines (xterm)
                             * This follows Thomas Dickey's xterm. */
                            if (!term->no_remote_clearscroll)
                                term_clrsb(term);
                        } else {
                            i++;
                            if (i > 3)
                                i = 0;
                            erase_lots(term, false, !!(i & 2), !!(i & 1));
                        }
                        if (term->scroll_on_disp)
                            term->disptop = 0;
                        seen_disp_event(term);
                        break;
                      }
                      case 'K': {       /* EL: erase line or parts of it */
                        unsigned int i = def(term->esc_args[0], 0) + 1;
                        if (i > 3)
                            i = 0;
                        erase_lots(term, true, !!(i & 2), !!(i & 1));
                        seen_disp_event(term);
                        break;
                      }
                      case 'L':       /* IL: insert lines */
                        compatibility(VT102);
                        CLAMP(term->esc_args[0], term->rows);
                        if (term->curs.y <= term->marg_b)
                            scroll(term, term->curs.y, term->marg_b,
                                   -def(term->esc_args[0], 1), false);
                        seen_disp_event(term);
                        break;
                      case 'M':       /* DL: delete lines */
                        compatibility(VT102);
                        CLAMP(term->esc_args[0], term->rows);
                        if (term->curs.y <= term->marg_b)
                            scroll(term, term->curs.y, term->marg_b,
                                   def(term->esc_args[0], 1),
                                   true);
                        seen_disp_event(term);
                        break;
                      case '@':       /* ICH: insert chars */
                        /* XXX VTTEST says this is vt220, vt510 manual says vt102 */
                        compatibility(VT102);
                        CLAMP(term->esc_args[0], term->cols);
                        insch(term, def(term->esc_args[0], 1));
                        seen_disp_event(term);
                        break;
                      case 'P':       /* DCH: delete chars */
                        compatibility(VT102);
                        CLAMP(term->esc_args[0], term->cols);
                        insch(term, -def(term->esc_args[0], 1));
                        seen_disp_event(term);
                        break;
                      case 'c':       /* DA: terminal type query */
                        compatibility(VT100);
                        /* This is the response for a VT102 */
                        if (term->ldisc)
                            ldisc_send(term->ldisc, term->id_string,
                                       strlen(term->id_string), false);
                        break;
                      case 'n':       /* DSR: cursor position query */
                        if (term->ldisc) {
                            if (term->esc_args[0] == 6) {
                                char buf[32];
                                sprintf(buf, "\033[%d;%dR", term->curs.y + 1,
                                        term->curs.x + 1);
                                ldisc_send(term->ldisc, buf, strlen(buf),
                                           false);
                            } else if (term->esc_args[0] == 5) {
                                ldisc_send(term->ldisc, "\033[0n", 4, false);
                            }
                        }
                        break;
                      case 'h':       /* SM: toggle modes to high */
                      case ANSI_QUE('h'):
                        compatibility(VT100);
                        for (int i = 0; i < term->esc_nargs; i++)
                            toggle_mode(term, term->esc_args[i],
                                        term->esc_query, true);
                        break;
                      case 'i':         /* MC: Media copy */
                      case ANSI_QUE('i'): {
                        compatibility(VT100);
                        char *printer;
                        if (term->esc_nargs != 1) break;
                        if (term->esc_args[0] == 5 &&
                            (printer = conf_get_str(term->conf,
                                                    CONF_printer))[0]) {
                            term->printing = true;
                            term->only_printing = !term->esc_query;
                            term->print_state = 0;
                            term_print_setup(term, printer);
                        } else if (term->esc_args[0] == 4 &&
                                   term->printing) {
                            term_print_finish(term);
                        }
                        break;
                      }
                      case 'l':       /* RM: toggle modes to low */
                      case ANSI_QUE('l'):
                        compatibility(VT100);
                        for (int i = 0; i < term->esc_nargs; i++)
                            toggle_mode(term, term->esc_args[i],
                                        term->esc_query, false);
                        break;
                      case 'g':       /* TBC: clear tabs */
                        compatibility(VT100);
                        if (term->esc_nargs == 1) {
                            if (term->esc_args[0] == 0) {
                                term->tabs[term->curs.x] = false;
                            } else if (term->esc_args[0] == 3) {
                                int i;
                                for (i = 0; i < term->cols; i++)
                                    term->tabs[i] = false;
                            }
                        }
                        break;
                      case 'r':       /* DECSTBM: set scroll margins */
                        compatibility(VT100);
                        if (term->esc_nargs <= 2) {
                            int top, bot;
                            CLAMP(term->esc_args[0], term->rows);
                            CLAMP(term->esc_args[1], term->rows);
                            top = def(term->esc_args[0], 1) - 1;
                            bot = (term->esc_nargs <= 1
                                   || term->esc_args[1] == 0 ?
                                   term->rows :
                                   def(term->esc_args[1], term->rows)) - 1;
                            if (bot >= term->rows)
                                bot = term->rows - 1;
                            /* VTTEST Bug 9 - if region is less than 2 lines
                             * don't change region.
                             */
                            if (bot - top > 0) {
                                term->marg_t = top;
                                term->marg_b = bot;
                                term->curs.x = 0;
                                /*
                                 * I used to think the cursor should be
                                 * placed at the top of the newly marginned
                                 * area. Apparently not: VMS TPU falls over
                                 * if so.
                                 *
                                 * Well actually it should for
                                 * Origin mode - RDB
                                 */
                                term->curs.y = (term->dec_om ?
                                                term->marg_t : 0);
                                seen_disp_event(term);
                            }
                        }
                        break;
                      case 'm':       /* SGR: set graphics rendition */
                        /*
                         * A VT100 without the AVO only had one
                         * attribute, either underline or reverse
                         * video depending on the cursor type, this
                         * was selected by CSI 7m.
                         *
                         * case 2:
                         *  This is sometimes DIM, eg on the GIGI and
                         *  Linux
                         * case 8:
                         *  This is sometimes INVIS various ANSI.
                         * case 21:
                         *  This like 22 disables BOLD, DIM and INVIS
                         *
                         * The ANSI colours appear on any terminal
                         * that has colour (obviously) but the
                         * interaction between sgr0 and the colours
                         * varies but is usually related to the
                         * background colour erase item. The
                         * interaction between colour attributes and
                         * the mono ones is also very implementation
                         * dependent.
                         *
                         * The 39 and 49 attributes are likely to be
                         * unimplemented.
                         */
                        for (int i = 0; i < term->esc_nargs; i++)
                        switch (def(term->esc_args[i], 0)) {
                          case 0:       /* restore defaults */
                            term->curr_attr = term->default_attr;
                            term->curr_truecolour =
                                term->basic_erase_char.truecolour;
                            break;
                          case 1:       /* enable bold */
                            compatibility(VT100AVO);
                            term->curr_attr |= ATTR_BOLD;
                            break;
                          case 2:       /* enable dim */
                            compatibility(OTHER);
                            term->curr_attr |= ATTR_DIM;
                            break;
                          case 21:      /* (enable double underline) */
                            compatibility(OTHER);
                          case 4:       /* enable underline */
                            compatibility(VT100AVO);
                            term->curr_attr |= ATTR_UNDER;
                            break;
                          case 5:       /* enable blink */
                            compatibility(VT100AVO);
                            term->curr_attr |= ATTR_BLINK;
                            break;
                          case 6:       /* SCO light bkgrd */
                            compatibility(SCOANSI);
                            term->blink_is_real = false;
                            term->curr_attr |= ATTR_BLINK;
                            term_schedule_tblink(term);
                            break;
                          case 7:       /* enable reverse video */
                            term->curr_attr |= ATTR_REVERSE;
                            break;
                          case 9:       /* enable strikethrough */
                            term->curr_attr |= ATTR_STRIKE;
                            break;
                          case 10:      /* SCO acs off */
                            compatibility(SCOANSI);
                            if (term->no_remote_charset) break;
                            term->sco_acs = 0; break;
                          case 11:      /* SCO acs on */
                            compatibility(SCOANSI);
                            if (term->no_remote_charset) break;
                            term->sco_acs = 1; break;
                          case 12:      /* SCO acs on, |0x80 */
                            compatibility(SCOANSI);
                            if (term->no_remote_charset) break;
                            term->sco_acs = 2; break;
                          case 22:      /* disable bold and dim */
                            compatibility2(OTHER, VT220);
                            term->curr_attr &= ~(ATTR_BOLD | ATTR_DIM);
                            break;
                          case 24:      /* disable underline */
                            compatibility2(OTHER, VT220);
                            term->curr_attr &= ~ATTR_UNDER;
                            break;
                          case 25:      /* disable blink */
                            compatibility2(OTHER, VT220);
                            term->curr_attr &= ~ATTR_BLINK;
                            break;
                          case 27:      /* disable reverse video */
                            compatibility2(OTHER, VT220);
                            term->curr_attr &= ~ATTR_REVERSE;
                            break;
                          case 29:      /* disable strikethrough */
                            term->curr_attr &= ~ATTR_STRIKE;
                            break;
                          case 30:
                          case 31:
                          case 32:
                          case 33:
                          case 34:
                          case 35:
                          case 36:
                          case 37:
                            /* foreground */
                            term->curr_truecolour.fg.enabled = false;
                            term->curr_attr &= ~ATTR_FGMASK;
                            term->curr_attr |=
                                (term->esc_args[i] - 30)<<ATTR_FGSHIFT;
                            break;
                          case 90:
                          case 91:
                          case 92:
                          case 93:
                          case 94:
                          case 95:
                          case 96:
                          case 97:
                            /* aixterm-style bright foreground */
                            term->curr_truecolour.fg.enabled = false;
                            term->curr_attr &= ~ATTR_FGMASK;
                            term->curr_attr |=
                                ((term->esc_args[i] - 90 + 8)
                                 << ATTR_FGSHIFT);
                            break;
                          case 39:      /* default-foreground */
                            term->curr_truecolour.fg.enabled = false;
                            term->curr_attr &= ~ATTR_FGMASK;
                            term->curr_attr |= ATTR_DEFFG;
                            break;
                          case 40:
                          case 41:
                          case 42:
                          case 43:
                          case 44:
                          case 45:
                          case 46:
                          case 47:
                            /* background */
                            term->curr_truecolour.bg.enabled = false;
                            term->curr_attr &= ~ATTR_BGMASK;
                            term->curr_attr |=
                                (term->esc_args[i] - 40)<<ATTR_BGSHIFT;
                            break;
                          case 100:
                          case 101:
                          case 102:
                          case 103:
                          case 104:
                          case 105:
                          case 106:
                          case 107:
                            /* aixterm-style bright background */
                            term->curr_truecolour.bg.enabled = false;
                            term->curr_attr &= ~ATTR_BGMASK;
                            term->curr_attr |=
                                ((term->esc_args[i] - 100 + 8)
                                 << ATTR_BGSHIFT);
                            break;
                          case 49:      /* default-background */
                            term->curr_truecolour.bg.enabled = false;
                            term->curr_attr &= ~ATTR_BGMASK;
                            term->curr_attr |= ATTR_DEFBG;
                            break;

                            /*
                             * 256-colour and true-colour
                             * sequences. A 256-colour
                             * foreground is selected by a
                             * sequence of 3 arguments in the
                             * form 38;5;n, where n is in the
                             * range 0-255. A true-colour RGB
                             * triple is selected by 5 args of
                             * the form 38;2;r;g;b. Replacing
                             * the initial 38 with 48 in both
                             * cases selects the same colour
                             * as the background.
                             */
                          case 38:
                            if (i+2 < term->esc_nargs &&
                                term->esc_args[i+1] == 5) {
                                term->curr_attr &= ~ATTR_FGMASK;
                                term->curr_attr |=
                                    ((term->esc_args[i+2] & 0xFF)
                                     << ATTR_FGSHIFT);
                                term->curr_truecolour.fg =
                                    optionalrgb_none;
                                i += 2;
                            }
                            if (i + 4 < term->esc_nargs &&
                                term->esc_args[i + 1] == 2) {
                                parse_optionalrgb(
                                    &term->curr_truecolour.fg,
                                    term->esc_args + (i+2));
                                i += 4;
                            }
                            break;
                          case 48:
                            if (i+2 < term->esc_nargs &&
                                term->esc_args[i+1] == 5) {
                                term->curr_attr &= ~ATTR_BGMASK;
                                term->curr_attr |=
                                    ((term->esc_args[i+2] & 0xFF)
                                     << ATTR_BGSHIFT);
                                term->curr_truecolour.bg =
                                    optionalrgb_none;
                                i += 2;
                            }
                            if (i + 4 < term->esc_nargs &&
                                term->esc_args[i+1] == 2) {
                                parse_optionalrgb(
                                    &term->curr_truecolour.bg,
                                    term->esc_args + (i+2));
                                i += 4;
                            }
                            break;
                        }
                        set_erase_char(term);
                        break;
                      case 's':       /* save cursor */
                        save_cursor(term, true);
                        break;
                      case 'u':       /* restore cursor */
                        save_cursor(term, false);
                        break;
                      case 't': /* DECSLPP: set page size - ie window height */
                        /*
                         * VT340/VT420 sequence DECSLPP, DEC only allows values
                         *  24/25/36/48/72/144 other emulators (eg dtterm) use
                         * illegal values (eg first arg 1..9) for window changing
                         * and reports.
                         */
                        if (term->esc_nargs <= 1
                            && (term->esc_args[0] < 1 ||
                                term->esc_args[0] >= 24)) {
                            compatibility(VT340TEXT);
                            if (!term->no_remote_resize)
                                term_request_resize(term, term->cols, 24);
                            deselect(term);
                        } else if (term->esc_nargs >= 1 &&
                                   term->esc_args[0] >= 1 &&
                                   term->esc_args[0] < 24) {
                            compatibility(OTHER);

                            switch (term->esc_args[0]) {
                                int len;
                                char buf[80];
                                const char *p;
                              case 1:
                                term->win_minimise_pending = true;
                                term->win_minimise_enable = false;
                                term_schedule_update(term);
                                break;
                              case 2:
                                term->win_minimise_pending = true;
                                term->win_minimise_enable = true;
                                term_schedule_update(term);
                                break;
                              case 3:
                                if (term->esc_nargs >= 3) {
                                    if (!term->no_remote_resize) {
                                        term->win_move_pending = true;
                                        term->win_move_pending_x =
                                            def(term->esc_args[1], 0);
                                        term->win_move_pending_y =
                                            def(term->esc_args[2], 0);
                                        term_schedule_update(term);
                                    }
                                }
                                break;
                              case 4:
                                /* We should resize the window to a given
                                 * size in pixels here, but currently our
                                 * resizing code isn't healthy enough to
                                 * manage it. */
                                break;
                              case 5:
                                /* move to top */
                                term->win_zorder_pending = true;
                                term->win_zorder_top = true;
                                term_schedule_update(term);
                                break;
                              case 6:
                                /* move to bottom */
                                term->win_zorder_pending = true;
                                term->win_zorder_top = false;
                                term_schedule_update(term);
                                break;
                              case 7:
                                term->win_refresh_pending = true;
                                term_schedule_update(term);
                                break;
                              case 8:
                                if (term->esc_nargs >= 3 &&
                                    !term->no_remote_resize) {
                                    term_request_resize(
                                        term,
                                        def(term->esc_args[2],
                                            term->conf_width),
                                        def(term->esc_args[1],
                                            term->conf_height));
                                }
                                break;
                              case 9:
                                if (term->esc_nargs >= 2) {
                                    term->win_maximise_pending = true;
                                    term->win_maximise_enable =
                                        term->esc_args[1];
                                    term_schedule_update(term);
                                }
                                break;
                              case 11:
                                if (term->ldisc)
                                    ldisc_send(term->ldisc, term->minimised ?
                                               "\033[2t" : "\033[1t", 4,
                                               false);
                                break;
                              case 13:
                                if (term->ldisc) {
                                    len = sprintf(buf, "\033[3;%u;%ut",
                                                  term->winpos_x,
                                                  term->winpos_y);
                                    ldisc_send(term->ldisc, buf, len, false);
                                }
                                break;
                              case 14:
                                if (term->ldisc) {
                                    len = sprintf(buf, "\033[4;%u;%ut",
                                                  term->winpixsize_y,
                                                  term->winpixsize_x);
                                    ldisc_send(term->ldisc, buf, len, false);
                                }
                                break;
                              case 18:
                                if (term->ldisc) {
                                    len = sprintf(buf, "\033[8;%d;%dt",
                                                  term->rows, term->cols);
                                    ldisc_send(term->ldisc, buf, len, false);
                                }
                                break;
                              case 19:
                                /*
                                 * Hmmm. Strictly speaking we
                                 * should return `the size of the
                                 * screen in characters', but
                                 * that's not easy: (a) window
                                 * furniture being what it is it's
                                 * hard to compute, and (b) in
                                 * resize-font mode maximising the
                                 * window wouldn't change the
                                 * number of characters. *shrug*. I
                                 * think we'll ignore it for the
                                 * moment and see if anyone
                                 * complains, and then ask them
                                 * what they would like it to do.
                                 */
                                break;
                              case 20:
                                if (term->ldisc &&
                                    term->remote_qtitle_action != TITLE_NONE) {
                                    if(term->remote_qtitle_action == TITLE_REAL)
                                        p = term->icon_title;
                                    else
                                        p = EMPTY_WINDOW_TITLE;
                                    len = strlen(p);
                                    ldisc_send(term->ldisc, "\033]L", 3,
                                               false);
                                    ldisc_send(term->ldisc, p, len, false);
                                    ldisc_send(term->ldisc, "\033\\", 2,
                                               false);
                                }
                                break;
                              case 21:
                                if (term->ldisc &&
                                    term->remote_qtitle_action != TITLE_NONE) {
                                    if(term->remote_qtitle_action == TITLE_REAL)
                                        p = term->window_title;
                                    else
                                        p = EMPTY_WINDOW_TITLE;
                                    len = strlen(p);
                                    ldisc_send(term->ldisc, "\033]l", 3,
                                               false);
                                    ldisc_send(term->ldisc, p, len, false);
                                    ldisc_send(term->ldisc, "\033\\", 2,
                                               false);
                                }
                                break;
                            }
                        }
                        break;
                      case 'S':         /* SU: Scroll up */
                        CLAMP(term->esc_args[0], term->rows);
                        compatibility(SCOANSI);
                        scroll(term, term->marg_t, term->marg_b,
                               def(term->esc_args[0], 1), true);
                        term->wrapnext = false;
                        break;
                      case 'T':         /* SD: Scroll down */
                        CLAMP(term->esc_args[0], term->rows);
                        compatibility(SCOANSI);
                        scroll(term, term->marg_t, term->marg_b,
                               -def(term->esc_args[0], 1), true);
                        term->wrapnext = false;
                        break;
                      case ANSI('|', '*'): /* DECSNLS */
                        /*
                         * Set number of lines on screen
                         * VT420 uses VGA like hardware and can
                         * support any size in reasonable range
                         * (24..49 AIUI) with no default specified.
                         */
                        compatibility(VT420);
                        if (term->esc_nargs == 1 && term->esc_args[0] > 0) {
                            if (!term->no_remote_resize)
                                term_request_resize(
                                    term,
                                    term->cols,
                                    def(term->esc_args[0], term->conf_height));
                            deselect(term);
                        }
                        break;
                      case ANSI('|', '$'): /* DECSCPP */
                        /*
                         * Set number of columns per page
                         * Docs imply range is only 80 or 132, but
                         * I'll allow any.
                         */
                        compatibility(VT340TEXT);
                        if (term->esc_nargs <= 1) {
                            if (!term->no_remote_resize)
                                term_request_resize(
                                    term,
                                    def(term->esc_args[0], term->conf_width),
                                    term->rows);
                            deselect(term);
                        }
                        break;
                      case 'X': {   /* ECH: write N spaces w/o moving cursor */
                        /* XXX VTTEST says this is vt220, vt510 manual
                         * says vt100 */
                        compatibility(ANSIMIN);
                        CLAMP(term->esc_args[0], term->cols);
                        int n = def(term->esc_args[0], 1);
                        pos cursplus;
                        int p = term->curs.x;
                        termline *cline = scrlineptr(term->curs.y);

                        check_trust_status(term, cline);
                        if (n > term->cols - term->curs.x)
                            n = term->cols - term->curs.x;
                        cursplus = term->curs;
                        cursplus.x += n;
                        check_boundary(term, term->curs.x, term->curs.y);
                        check_boundary(term, term->curs.x+n, term->curs.y);
                        check_selection(term, term->curs, cursplus);
                        while (n--)
                            copy_termchar(cline, p++,
                                          &term->erase_char);
                        seen_disp_event(term);
                        break;
                      }
                      case 'x':       /* DECREQTPARM: report terminal characteristics */
                        compatibility(VT100);
                        if (term->ldisc) {
                            char buf[32];
                            int i = def(term->esc_args[0], 0);
                            if (i == 0 || i == 1) {
                                strcpy(buf, "\033[2;1;1;112;112;1;0x");
                                buf[2] += i;
                                ldisc_send(term->ldisc, buf, 20, false);
                            }
                        }
                        break;
                      case 'Z': {         /* CBT */
                        compatibility(OTHER);
                        CLAMP(term->esc_args[0], term->cols);
                        int i = def(term->esc_args[0], 1);
                        pos old_curs = term->curs;

                        for (; i>0 && term->curs.x>0; i--) {
                            do {
                                term->curs.x--;
                            } while (term->curs.x >0 &&
                                     !term->tabs[term->curs.x]);
                        }
                        check_selection(term, old_curs, term->curs);
                        break;
                      }
                      case ANSI('c', '='):      /* Hide or Show Cursor */
                        compatibility(SCOANSI);
                        switch(term->esc_args[0]) {
                          case 0:  /* hide cursor */
                            term->cursor_on = false;
                            break;
                          case 1:  /* restore cursor */
                            term->big_cursor = false;
                            term->cursor_on = true;
                            break;
                          case 2:  /* block cursor */
                            term->big_cursor = true;
                            term->cursor_on = true;
                            break;
                        }
                        break;
                      case ANSI('C', '='):
                        /*
                         * set cursor start on scanline esc_args[0] and
                         * end on scanline esc_args[1].If you set
                         * the bottom scan line to a value less than
                         * the top scan line, the cursor will disappear.
                         */
                        compatibility(SCOANSI);
                        if (term->esc_nargs >= 2) {
                            if (term->esc_args[0] > term->esc_args[1])
                                term->cursor_on = false;
                            else
                                term->cursor_on = true;
                        }
                        break;
                      case ANSI('D', '='):
                        compatibility(SCOANSI);
                        term->blink_is_real = false;
                        term_schedule_tblink(term);
                        if (term->esc_args[0]>=1)
                            term->curr_attr |= ATTR_BLINK;
                        else
                            term->curr_attr &= ~ATTR_BLINK;
                        break;
                      case ANSI('E', '='):
                        compatibility(SCOANSI);
                        term->blink_is_real = (term->esc_args[0] >= 1);
                        term_schedule_tblink(term);
                        break;
                      case ANSI('F', '='):      /* set normal foreground */
                        compatibility(SCOANSI);
                        if (term->esc_args[0] < 16) {
                            long colour =
                                (sco2ansicolour[term->esc_args[0] & 0x7] |
                                 (term->esc_args[0] & 0x8)) <<
                                ATTR_FGSHIFT;
                            term->curr_attr &= ~ATTR_FGMASK;
                            term->curr_attr |= colour;
                            term->curr_truecolour.fg = optionalrgb_none;
                            term->default_attr &= ~ATTR_FGMASK;
                            term->default_attr |= colour;
                            set_erase_char(term);
                        }
                        break;
                      case ANSI('G', '='):      /* set normal background */
                        compatibility(SCOANSI);
                        if (term->esc_args[0] < 16) {
                            long colour =
                                (sco2ansicolour[term->esc_args[0] & 0x7] |
                                 (term->esc_args[0] & 0x8)) <<
                                ATTR_BGSHIFT;
                            term->curr_attr &= ~ATTR_BGMASK;
                            term->curr_attr |= colour;
                            term->curr_truecolour.bg = optionalrgb_none;
                            term->default_attr &= ~ATTR_BGMASK;
                            term->default_attr |= colour;
                            set_erase_char(term);
                        }
                        break;
                      case ANSI('L', '='):
                        compatibility(SCOANSI);
                        term->use_bce = (term->esc_args[0] <= 0);
                        set_erase_char(term);
                        break;
                      case ANSI('p', '"'): /* DECSCL: set compat level */
                        /*
                         * Allow the host to make this emulator a
                         * 'perfect' VT102. This first appeared in
                         * the VT220, but we do need to get back to
                         * PuTTY mode so I won't check it.
                         *
                         * The arg in 40..42,50 are a PuTTY extension.
                         * The 2nd arg, 8bit vs 7bit is not checked.
                         *
                         * Setting VT102 mode should also change
                         * the Fkeys to generate PF* codes as a
                         * real VT102 has no Fkeys. The VT220 does
                         * this, F11..F13 become ESC,BS,LF other
                         * Fkeys send nothing.
                         *
                         * Note ESC c will NOT change this!
                         */

                        switch (term->esc_args[0]) {
                          case 61:
                            term->compatibility_level &= ~TM_VTXXX;
                            term->compatibility_level |= TM_VT102;
                            break;
                          case 62:
                            term->compatibility_level &= ~TM_VTXXX;
                            term->compatibility_level |= TM_VT220;
                            break;

                          default:
                            if (term->esc_args[0] > 60 &&
                                term->esc_args[0] < 70)
                                term->compatibility_level |= TM_VTXXX;
                            break;

                          case 40:
                            term->compatibility_level &= TM_VTXXX;
                            break;
                          case 41:
                            term->compatibility_level = TM_PUTTY;
                            break;
                          case 42:
                            term->compatibility_level = TM_SCOANSI;
                            break;

                          case ARG_DEFAULT:
                            term->compatibility_level = TM_PUTTY;
                            break;
                          case 50:
                            break;
                        }

                        /* Change the response to CSI c */
                        if (term->esc_args[0] == 50) {
                            int i;
                            char lbuf[64];
                            strcpy(term->id_string, "\033[?");
                            for (i = 1; i < term->esc_nargs; i++) {
                                if (i != 1)
                                    strcat(term->id_string, ";");
                                sprintf(lbuf, "%u", term->esc_args[i]);
                                strcat(term->id_string, lbuf);
                            }
                            strcat(term->id_string, "c");
                        }
#if 0
                        /* Is this a good idea ?
                         * Well we should do a soft reset at this point ...
                         */
                        if (!has_compat(VT420) && has_compat(VT100)) {
                            if (!term->no_remote_resize)
                                term_request_resize(term,
                                                    term->reset_132 ? 132 : 80,
                                                    24);
                        }
#endif
                        break;
                    }
                break;
              case SEEN_OSC:
                term->osc_type = OSCLIKE_OSC;
                switch (c) {
                  case 'P':            /* Linux palette sequence */
                    term->termstate = SEEN_OSC_P;
                    term->osc_strlen = 0;
                    break;
                  case 'R':            /* Linux palette reset */
                    palette_reset(term, false);
                    term_invalidate(term);
                    term->termstate = TOPLEVEL;
                    break;
                  case 'W':            /* word-set */
                    term->termstate = SEEN_OSC_W;
                    term->osc_type = OSCLIKE_OSC_W;
                    break;
                  case '0':
                  case '1':
                  case '2':
                  case '3':
                  case '4':
                  case '5':
                  case '6':
                  case '7':
                  case '8':
                  case '9':
                    if (term->esc_args[term->esc_nargs-1] <= UINT_MAX / 10 &&
                        term->esc_args[term->esc_nargs-1] * 10 <= UINT_MAX - c - '0')
                        term->esc_args[term->esc_nargs-1] =
                            10 * term->esc_args[term->esc_nargs-1] + c - '0';
                    else
                        term->esc_args[term->esc_nargs-1] = UINT_MAX;
                    break;
                  case 0x9C:
                    /* Terminate even though we aren't in OSC_STRING yet */
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                  case 0xC2:
                    if (in_utf(term)) {
                        /* Or be prepared for the UTF-8 version of that */
                        term->termstate = OSC_MAYBE_ST_UTF8;
                    }
                    break;
                  default:
                    /*
                     * _Most_ other characters here terminate the
                     * immediate parsing of the OSC sequence and go
                     * into OSC_STRING state, but we deal with a
                     * couple of exceptions first.
                     */
                    if (c == 'L' && term->esc_args[0] == 2) {
                        /*
                         * Grotty hack to support xterm and DECterm title
                         * sequences concurrently.
                         */
                        term->esc_args[0] = 1;
                    } else if (c == ';' && term->esc_nargs == 1 &&
                               term->esc_args[0] == 4) {
                        /*
                         * xterm's OSC 4 sequence to query the current
                         * RGB value of a colour takes a second
                         * numeric argument which is easiest to parse
                         * using the existing system rather than in
                         * do_osc.
                         */
                        term->esc_args[term->esc_nargs++] = 0;
                    } else {
                        term->termstate = OSC_STRING;
                        term->osc_strlen = 0;
                    }
                }
                break;
              case OSC_STRING:
                /*
                 * OSC sequences can be terminated or aborted in
                 * various ways.
                 *
                 * The official way to terminate an OSC, per written
                 * standards, is the String Terminator, SC. That can
                 * appear in a 7-bit two-character form ESC \, or as
                 * an 8-bit C1 control 0x9C.
                 *
                 * We only accept 0x9C in circumstances where it
                 * doesn't interfere with our main character set
                 * processing: so in ISO 8859-1, for example, the byte
                 * 0x9C is interpreted as ST, but in CP437 it's
                 * interpreted as an ordinary printing character (as
                 * it happens, the pound sign), because you might
                 * perfectly well want to put it in the window title
                 * like any other printing character.
                 *
                 * In particular, in UTF-8 mode, 0x9C is a perfectly
                 * valid continuation byte for an ordinary printing
                 * character, so we don't accept the C1 control form
                 * of ST unless it appears as a full UTF-8 character
                 * in its own right, i.e. bytes 0xC2 0x9C.
                 *
                 * BEL is also treated as a clean termination of OSC,
                 * which I believe was a behaviour introduced by
                 * xterm.
                 *
                 * To prevent run-on storage of OSC data forever if
                 * emission of a control sequence is interrupted, we
                 * also treat various control characters as illegal,
                 * so that they abort the OSC without processing it
                 * and return to TOPLEVEL state. These are CR, LF, and
                 * any ESC that is *not* followed by \.
                 */

                if (c == '\012' || c == '\015') {
                    /* CR or LF aborts */
                    term->termstate = TOPLEVEL;
                    break;
                }

                if (c == '\033') {
                    /* ESC goes into a state where we wait to see if
                     * the next character is \ */
                    term->termstate = OSC_MAYBE_ST;
                    break;
                }

                if (c == '\007' || (c == 0x9C && !in_utf(term) &&
                                    term->ucsdata->unitab_ctrl[c] != 0xFF)) {
                    /* BEL, or the C1 ST appearing as a one-byte
                     * encoding, cleanly terminates the OSC right here */
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                }

                if (c == 0xC2 && in_utf(term)) {
                    /* 0xC2 is the UTF-8 character that might
                     * introduce the encoding of C1 ST */
                    term->termstate = OSC_MAYBE_ST_UTF8;
                    break;
                }

                /* Anything else gets added to the string */
                if (term->osc_strlen < OSC_STR_MAX)
                    term->osc_string[term->osc_strlen++] = (char)c;
                break;
              case OSC_MAYBE_ST_UTF8:
                /* In UTF-8 mode, we've seen C2, so are we now seeing
                 * 9C? */
                if (c == 0x9C) {
                    /* Yes, so cleanly terminate the OSC */
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                }
                /* No, so append the pending C2 byte to the OSC string
                 * followed by the current character, and go back to
                 * OSC string accumulation */
                if (term->osc_strlen < OSC_STR_MAX)
                    term->osc_string[term->osc_strlen++] = 0xC2;
                if (term->osc_strlen < OSC_STR_MAX)
                    term->osc_string[term->osc_strlen++] = (char)c;
                term->termstate = OSC_STRING;
                break;
              case SEEN_OSC_P: {
                int max = (term->osc_strlen == 0 ? 21 : 15);
                int val;
                if ((int)c >= '0' && (int)c <= '9')
                    val = c - '0';
                else if ((int)c >= 'A' && (int)c <= 'A' + max - 10)
                    val = c - 'A' + 10;
                else if ((int)c >= 'a' && (int)c <= 'a' + max - 10)
                    val = c - 'a' + 10;
                else {
                    term->termstate = TOPLEVEL;
                    break;
                }
                term->osc_string[term->osc_strlen++] = val;
                if (term->osc_strlen >= 7) {
                    unsigned oscp_index = term->osc_string[0];
                    assert(oscp_index < OSCP_NCOLOURS);
                    unsigned osc4_index =
                        colour_indices_oscp_to_osc4[oscp_index];

                    rgb *value = &term->subpalettes[SUBPAL_SESSION].values[
                        osc4_index];
                    value->r = term->osc_string[1] * 16 + term->osc_string[2];
                    value->g = term->osc_string[3] * 16 + term->osc_string[4];
                    value->b = term->osc_string[5] * 16 + term->osc_string[6];
                    term->subpalettes[SUBPAL_SESSION].present[
                        osc4_index] = true;

                    palette_rebuild(term);

                    term->termstate = TOPLEVEL;
                }
                break;
              }
              case SEEN_OSC_W:
                switch (c) {
                  case '0':
                  case '1':
                  case '2':
                  case '3':
                  case '4':
                  case '5':
                  case '6':
                  case '7':
                  case '8':
                  case '9':
                    if (term->esc_args[0] <= UINT_MAX / 10 &&
                        term->esc_args[0] * 10 <= UINT_MAX - c - '0')
                        term->esc_args[0] = 10 * term->esc_args[0] + c - '0';
                    else
                        term->esc_args[0] = UINT_MAX;
                    break;
                  case 0x9C:
                    /* Terminate even though we aren't in OSC_STRING yet */
                    do_osc(term);
                    term->termstate = TOPLEVEL;
                    break;
                  case 0xC2:
                    if (in_utf(term)) {
                        /* Or be prepared for the UTF-8 version of that */
                        term->termstate = OSC_MAYBE_ST_UTF8;
                    }
                    break;
                  default:
                    term->termstate = OSC_STRING;
                    term->osc_strlen = 0;
                }
                break;
              case VT52_ESC:
                term->termstate = TOPLEVEL;
                switch (c) {
                  case 'A':
                    move(term, term->curs.x, term->curs.y - 1, 1);
                    break;
                  case 'B':
                    move(term, term->curs.x, term->curs.y + 1, 1);
                    break;
                  case 'C':
                    move(term, term->curs.x + 1, term->curs.y, 1);
                    break;
                  case 'D':
                    move(term, term->curs.x - 1, term->curs.y, 1);
                    break;
                    /*
                     * From the VT100 Manual
                     * NOTE: The special graphics characters in the VT100
                     *       are different from those in the VT52
                     *
                     * From VT102 manual:
                     *       137 _  Blank             - Same
                     *       140 `  Reserved          - Humm.
                     *       141 a  Solid rectangle   - Similar
                     *       142 b  1/                - Top half of fraction for the
                     *       143 c  3/                - subscript numbers below.
                     *       144 d  5/
                     *       145 e  7/
                     *       146 f  Degrees           - Same
                     *       147 g  Plus or minus     - Same
                     *       150 h  Right arrow
                     *       151 i  Ellipsis (dots)
                     *       152 j  Divide by
                     *       153 k  Down arrow
                     *       154 l  Bar at scan 0
                     *       155 m  Bar at scan 1
                     *       156 n  Bar at scan 2
                     *       157 o  Bar at scan 3     - Similar
                     *       160 p  Bar at scan 4     - Similar
                     *       161 q  Bar at scan 5     - Similar
                     *       162 r  Bar at scan 6     - Same
                     *       163 s  Bar at scan 7     - Similar
                     *       164 t  Subscript 0
                     *       165 u  Subscript 1
                     *       166 v  Subscript 2
                     *       167 w  Subscript 3
                     *       170 x  Subscript 4
                     *       171 y  Subscript 5
                     *       172 z  Subscript 6
                     *       173 {  Subscript 7
                     *       174 |  Subscript 8
                     *       175 }  Subscript 9
                     *       176 ~  Paragraph
                     *
                     */
                  case 'F':
                    term->cset_attr[term->cset = 0] = CSET_LINEDRW;
                    break;
                  case 'G':
                    term->cset_attr[term->cset = 0] = CSET_ASCII;
                    break;
                  case 'H':
                    move(term, 0, 0, 0);
                    break;
                  case 'I':
                    if (term->curs.y == 0) {
                        scroll(term, 0, term->rows - 1, -1, true);
                    } else if (term->curs.y > 0) {
                        term->curs.y--;
                        seen_disp_event(term);
                    }
                    term->wrapnext = false;
                    break;
                  case 'J':
                    erase_lots(term, false, false, true);
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    break;
                  case 'K':
                    erase_lots(term, true, false, true);
                    break;
#if 0
                  case 'V':
                    /* XXX Print cursor line */
                    break;
                  case 'W':
                    /* XXX Start controller mode */
                    break;
                  case 'X':
                    /* XXX Stop controller mode */
                    break;
#endif
                  case 'Y':
                    term->termstate = VT52_Y1;
                    break;
                  case 'Z':
                    if (term->ldisc)
                        ldisc_send(term->ldisc, "\033/Z", 3, false);
                    break;
                  case '=':
                    term->app_keypad_keys = true;
                    break;
                  case '>':
                    term->app_keypad_keys = false;
                    break;
                  case '<':
                    /* XXX This should switch to VT100 mode not current or default
                     *     VT mode. But this will only have effect in a VT220+
                     *     emulation.
                     */
                    term->vt52_mode = false;
                    term->blink_is_real = term->blinktext;
                    term_schedule_tblink(term);
                    break;
#if 0
                  case '^':
                    /* XXX Enter auto print mode */
                    break;
                  case '_':
                    /* XXX Exit auto print mode */
                    break;
                  case ']':
                    /* XXX Print screen */
                    break;
#endif

#ifdef VT52_PLUS
                  case 'E':
                    /* compatibility(ATARI) */
                    move(term, 0, 0, 0);
                    erase_lots(term, false, false, true);
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    break;
                  case 'L':
                    /* compatibility(ATARI) */
                    if (term->curs.y <= term->marg_b)
                        scroll(term, term->curs.y, term->marg_b, -1, false);
                    break;
                  case 'M':
                    /* compatibility(ATARI) */
                    if (term->curs.y <= term->marg_b)
                        scroll(term, term->curs.y, term->marg_b, 1, true);
                    break;
                  case 'b':
                    /* compatibility(ATARI) */
                    term->termstate = VT52_FG;
                    break;
                  case 'c':
                    /* compatibility(ATARI) */
                    term->termstate = VT52_BG;
                    break;
                  case 'd':
                    /* compatibility(ATARI) */
                    erase_lots(term, false, true, false);
                    if (term->scroll_on_disp)
                        term->disptop = 0;
                    break;
                  case 'e':
                    /* compatibility(ATARI) */
                    term->cursor_on = true;
                    seen_disp_event(term);
                    break;
                  case 'f':
                    /* compatibility(ATARI) */
                    term->cursor_on = false;
                    seen_disp_event(term);
                    break;
                    /* case 'j': Save cursor position - broken on ST */
                    /* case 'k': Restore cursor position */
                  case 'l':
                    /* compatibility(ATARI) */
                    erase_lots(term, true, true, true);
                    term->curs.x = 0;
                    term->wrapnext = false;
                    break;
                  case 'o':
                    /* compatibility(ATARI) */
                    erase_lots(term, true, true, false);
                    break;
                  case 'p':
                    /* compatibility(ATARI) */
                    term->curr_attr |= ATTR_REVERSE;
                    break;
                  case 'q':
                    /* compatibility(ATARI) */
                    term->curr_attr &= ~ATTR_REVERSE;
                    break;
                  case 'v':            /* wrap Autowrap on - Wyse style */
                    /* compatibility(ATARI) */
                    term->wrap = true;
                    break;
                  case 'w':            /* Autowrap off */
                    /* compatibility(ATARI) */
                    term->wrap = false;
                    term->wrapnext = false;
                    break;

                  case 'R':
                    /* compatibility(OTHER) */
                    term->vt52_bold = false;
                    term->curr_attr = ATTR_DEFAULT;
                    term->curr_truecolour.fg = optionalrgb_none;
                    term->curr_truecolour.bg = optionalrgb_none;
                    set_erase_char(term);
                    break;
                  case 'S':
                    /* compatibility(VI50) */
                    term->curr_attr |= ATTR_UNDER;
                    break;
                  case 'W':
                    /* compatibility(VI50) */
                    term->curr_attr &= ~ATTR_UNDER;
                    break;
                  case 'U':
                    /* compatibility(VI50) */
                    term->vt52_bold = true;
                    term->curr_attr |= ATTR_BOLD;
                    break;
                  case 'T':
                    /* compatibility(VI50) */
                    term->vt52_bold = false;
                    term->curr_attr &= ~ATTR_BOLD;
                    break;
#endif
                }
                break;
              case VT52_Y1:
                term->termstate = VT52_Y2;
                move(term, term->curs.x, c - ' ', 0);
                break;
              case VT52_Y2:
                term->termstate = TOPLEVEL;
                move(term, c - ' ', term->curs.y, 0);
                break;

#ifdef VT52_PLUS
              case VT52_FG:
                term->termstate = TOPLEVEL;
                term->curr_attr &= ~ATTR_FGMASK;
                term->curr_attr &= ~ATTR_BOLD;
                term->curr_attr |= (c & 0xF) << ATTR_FGSHIFT;
                set_erase_char(term);
                break;
              case VT52_BG:
                term->termstate = TOPLEVEL;
                term->curr_attr &= ~ATTR_BGMASK;
                term->curr_attr &= ~ATTR_BLINK;
                term->curr_attr |= (c & 0xF) << ATTR_BGSHIFT;
                set_erase_char(term);
                break;
#endif
              default: break;          /* placate gcc warning about enum use */
            }
        if (term->selstate != NO_SELECTION) {
            pos cursplus = term->curs;
            incpos(cursplus);
            check_selection(term, term->curs, cursplus);
        }
    }

    bufchain_consume(&term->inbuf, nchars_used);

    if (!called_from_term_data)
        win_unthrottle(term->win, bufchain_size(&term->inbuf));

    term_print_flush(term);
    if (term->logflush && term->logctx)
        logflush(term->logctx);
}

/* Wrapper on term_out with the right prototype to be a toplevel callback */
void term_out_cb(void *ctx)
{
    term_out((Terminal *)ctx, false);
}

/*
 * Small subroutine to parse three consecutive escape-sequence
 * arguments representing a true-colour RGB triple into an
 * optionalrgb.
 */
static void parse_optionalrgb(optionalrgb *out, unsigned *values)
{
    out->enabled = true;
    out->r = values[0] < 256 ? values[0] : 0;
    out->g = values[1] < 256 ? values[1] : 0;
    out->b = values[2] < 256 ? values[2] : 0;
}

/*
 * To prevent having to run the reasonably tricky bidi algorithm
 * too many times, we maintain a cache of the last lineful of data
 * fed to the algorithm on each line of the display.
 */
static bool term_bidi_cache_hit(Terminal *term, int line,
                                termchar *lbefore, int width, bool trusted)
{
    int i;

    if (!term->pre_bidi_cache)
        return false;                  /* cache doesn't even exist yet! */

    if (line >= term->bidi_cache_size)
        return false;                  /* cache doesn't have this many lines */

    if (!term->pre_bidi_cache[line].chars)
        return false;                  /* cache doesn't contain _this_ line */

    if (term->pre_bidi_cache[line].width != width)
        return false;                  /* line is wrong width */

    if (term->pre_bidi_cache[line].trusted != trusted)
        return false;                  /* line has wrong trust state */

    for (i = 0; i < width; i++)
        if (!termchars_equal(term->pre_bidi_cache[line].chars+i, lbefore+i))
            return false;              /* line doesn't match cache */

    return true;                       /* it didn't match. */
}

static void term_bidi_cache_store(Terminal *term, int line, termchar *lbefore,
                                  termchar *lafter, bidi_char *wcTo,
                                  int width, int size, bool trusted)
{
    size_t i, j;

    if (!term->pre_bidi_cache || term->bidi_cache_size <= line) {
        j = term->bidi_cache_size;
        sgrowarray(term->pre_bidi_cache, term->bidi_cache_size, line);
        term->post_bidi_cache = sresize(term->post_bidi_cache,
                                        term->bidi_cache_size,
                                        struct bidi_cache_entry);
        while (j < term->bidi_cache_size) {
            term->pre_bidi_cache[j].chars =
                term->post_bidi_cache[j].chars = NULL;
            term->pre_bidi_cache[j].width =
                term->post_bidi_cache[j].width = -1;
            term->pre_bidi_cache[j].trusted = false;
            term->post_bidi_cache[j].trusted = false;
            term->pre_bidi_cache[j].forward =
                term->post_bidi_cache[j].forward = NULL;
            term->pre_bidi_cache[j].backward =
                term->post_bidi_cache[j].backward = NULL;
            j++;
        }
    }

    sfree(term->pre_bidi_cache[line].chars);
    sfree(term->post_bidi_cache[line].chars);
    sfree(term->post_bidi_cache[line].forward);
    sfree(term->post_bidi_cache[line].backward);

    term->pre_bidi_cache[line].width = width;
    term->pre_bidi_cache[line].trusted = trusted;
    term->pre_bidi_cache[line].chars = snewn(size, termchar);
    term->post_bidi_cache[line].width = width;
    term->post_bidi_cache[line].trusted = trusted;
    term->post_bidi_cache[line].chars = snewn(size, termchar);
    term->post_bidi_cache[line].forward = snewn(width, int);
    term->post_bidi_cache[line].backward = snewn(width, int);

    memcpy(term->pre_bidi_cache[line].chars, lbefore, size * TSIZE);
    memcpy(term->post_bidi_cache[line].chars, lafter, size * TSIZE);
    memset(term->post_bidi_cache[line].forward, 0, width * sizeof(int));
    memset(term->post_bidi_cache[line].backward, 0, width * sizeof(int));

    for (i = j = 0; j < width; j += wcTo[i].nchars, i++) {
        int p = wcTo[i].index;

        if (p != BIDI_CHAR_INDEX_NONE) {
            assert(0 <= p && p < width);

            for (int x = 0; x < wcTo[i].nchars; x++) {
                term->post_bidi_cache[line].backward[j+x] = p+x;
                term->post_bidi_cache[line].forward[p+x] = j+x;
            }
        }
    }
}

/*
 * Prepare the bidi information for a screen line. Returns the
 * transformed list of termchars, or NULL if no transformation at
 * all took place (because bidi is disabled). If return was
 * non-NULL, auxiliary information such as the forward and reverse
 * mappings of permutation position are available in
 * term->post_bidi_cache[scr_y].*.
 */
static termchar *term_bidi_line(Terminal *term, struct termline *ldata,
                                int scr_y)
{
    termchar *lchars;
    int it;

    /* Do Arabic shaping and bidi. */
    if (!term->no_bidi || !term->no_arabicshaping ||
        (ldata->trusted && term->cols > TRUST_SIGIL_WIDTH)) {

        if (!term_bidi_cache_hit(term, scr_y, ldata->chars, term->cols,
                                 ldata->trusted)) {

            if (term->wcFromTo_size < term->cols) {
                term->wcFromTo_size = term->cols;
                term->wcFrom = sresize(term->wcFrom, term->wcFromTo_size,
                                       bidi_char);
                term->wcTo = sresize(term->wcTo, term->wcFromTo_size,
                                     bidi_char);
            }

            for (it=0; it<term->cols ; it++) {
                unsigned long uc = (ldata->chars[it].chr);

                switch (uc & CSET_MASK) {
                  case CSET_LINEDRW:
                    if (!term->rawcnp) {
                        uc = term->ucsdata->unitab_xterm[uc & 0xFF];
                        break;
                    }
                  case CSET_ASCII:
                    uc = term->ucsdata->unitab_line[uc & 0xFF];
                    break;
                  case CSET_SCOACS:
                    uc = term->ucsdata->unitab_scoacs[uc&0xFF];
                    break;
                }
                switch (uc & CSET_MASK) {
                  case CSET_ACP:
                    uc = term->ucsdata->unitab_font[uc & 0xFF];
                    break;
                  case CSET_OEMCP:
                    uc = term->ucsdata->unitab_oemcp[uc & 0xFF];
                    break;
                }

                term->wcFrom[it].origwc = term->wcFrom[it].wc =
                    (unsigned int)uc;
                term->wcFrom[it].index = it;
                term->wcFrom[it].nchars = 1;
            }

            if (ldata->trusted && term->cols > TRUST_SIGIL_WIDTH) {
                memmove(
                    term->wcFrom + TRUST_SIGIL_WIDTH, term->wcFrom,
                    (term->cols - TRUST_SIGIL_WIDTH) * sizeof(*term->wcFrom));
                for (it = 0; it < TRUST_SIGIL_WIDTH; it++) {
                    term->wcFrom[it].origwc = term->wcFrom[it].wc =
                        (it == 0 ? TRUST_SIGIL_CHAR :
                         it == 1 ? UCSWIDE : ' ');
                    term->wcFrom[it].index = BIDI_CHAR_INDEX_NONE;
                    term->wcFrom[it].nchars = 1;
                }
            }

            int nbc = 0;
            for (it = 0; it < term->cols; it++) {
                term->wcFrom[nbc] = term->wcFrom[it];
                if (it+1 < term->cols && term->wcFrom[it+1].wc == UCSWIDE) {
                    term->wcFrom[nbc].nchars++;
                    it++;
                }
                nbc++;
            }

            if (!term->no_bidi)
                do_bidi(term->bidi_ctx, term->wcFrom, nbc);

            if (!term->no_arabicshaping) {
                do_shape(term->wcFrom, term->wcTo, nbc);
            } else {
                /* If we're not calling do_shape, we must copy the
                 * data into wcTo anyway, unchanged */
                memcpy(term->wcTo, term->wcFrom, nbc * sizeof(*term->wcTo));
            }

            if (term->ltemp_size < ldata->size) {
                term->ltemp_size = ldata->size;
                term->ltemp = sresize(term->ltemp, term->ltemp_size,
                                      termchar);
            }

            memcpy(term->ltemp, ldata->chars, ldata->size * TSIZE);

            int opos = 0;
            for (it=0; it<nbc; it++) {
                int ipos = term->wcTo[it].index;
                for (int j = 0; j < term->wcTo[it].nchars; j++) {
                    if (ipos != BIDI_CHAR_INDEX_NONE) {
                        term->ltemp[opos] = ldata->chars[ipos];
                        if (term->ltemp[opos].cc_next)
                            term->ltemp[opos].cc_next -= opos - ipos;

                        if (j > 0)
                            term->ltemp[opos].chr = UCSWIDE;
                        else if (term->wcTo[it].origwc != term->wcTo[it].wc)
                            term->ltemp[opos].chr = term->wcTo[it].wc;
                    } else {
                        term->ltemp[opos] = term->basic_erase_char;
                        term->ltemp[opos].chr =
                            j > 0 ? UCSWIDE : term->wcTo[it].origwc;
                    }
                    opos++;
                }
            }
            assert(opos == term->cols);
            term_bidi_cache_store(term, scr_y, ldata->chars,
                                  term->ltemp, term->wcTo,
                                  term->cols, ldata->size, ldata->trusted);

            lchars = term->ltemp;
        } else {
            lchars = term->post_bidi_cache[scr_y].chars;
        }
    } else {
        lchars = NULL;
    }

    return lchars;
}

static void do_paint_draw(Terminal *term, termline *ldata, int x, int y,
                          wchar_t *ch, int ccount,
                          unsigned long attr, truecolour tc)
{
    if (ch[0] == TRUST_SIGIL_CHAR) {
        assert(ldata->trusted);
        assert(ccount == 1);
        assert(attr & ATTR_WIDE);
        wchar_t tch[2];
        tch[0] = tch[1] = L' ';
        win_draw_text(term->win, x, y, tch, 2, term->basic_erase_char.attr,
                      ldata->lattr, term->basic_erase_char.truecolour);
        win_draw_trust_sigil(term->win, x, y);
    } else {
        if (ccount == 2 &&
            IS_REGIONAL_INDICATOR_LETTER(ch[0]) &&
            IS_REGIONAL_INDICATOR_LETTER(ch[1]))
            attr |= ATTR_WIDE | TATTR_COMBINING;
        win_draw_text(term->win, x, y, ch, ccount, attr, ldata->lattr, tc);
        if (attr & (TATTR_ACTCURS | TATTR_PASCURS))
            win_draw_cursor(term->win, x, y, ch, ccount,
                            attr, ldata->lattr, tc);
    }
}

/*
 * Given a context, update the window.
 */
static void do_paint(Terminal *term)
{
    int i, j, our_curs_y, our_curs_x;
    int rv, cursor;
    pos scrpos;
    wchar_t *ch;
    size_t chlen;
    termchar *newline;

    chlen = 1024;
    ch = snewn(chlen, wchar_t);

    newline = snewn(term->cols, termchar);

    rv = (!term->rvideo ^ !term->in_vbell ? ATTR_REVERSE : 0);

    /* Depends on:
     * screen array, disptop, scrtop,
     * selection, rv,
     * blinkpc, blink_is_real, tblinker,
     * curs.y, curs.x, cblinker, blink_cur, cursor_on, has_focus, wrapnext
     */

    /* Has the cursor position or type changed ? */
    if (term->cursor_on) {
        if (term->has_focus) {
            if (term->cblinker || !term->blink_cur)
                cursor = TATTR_ACTCURS;
            else
                cursor = 0;
        } else
            cursor = TATTR_PASCURS;
        if (term->wrapnext)
            cursor |= TATTR_RIGHTCURS;
    } else
        cursor = 0;
    our_curs_y = term->curs.y - term->disptop;
    {
        /*
         * Adjust the cursor position:
         *  - for bidi
         *  - in the case where it's resting on the right-hand half
         *    of a CJK wide character. xterm's behaviour here,
         *    which seems adequate to me, is to display the cursor
         *    covering the _whole_ character, exactly as if it were
         *    one space to the left.
         */
        termline *ldata = lineptr(term->curs.y);
        termchar *lchars;

        our_curs_x = term->curs.x;

        if ( (lchars = term_bidi_line(term, ldata, our_curs_y)) != NULL) {
            our_curs_x = term->post_bidi_cache[our_curs_y].forward[our_curs_x];
        } else
            lchars = ldata->chars;

        if (our_curs_x > 0 &&
            lchars[our_curs_x].chr == UCSWIDE)
            our_curs_x--;

        unlineptr(ldata);
    }

    /*
     * If the cursor is not where it was last time we painted, and
     * its previous position is visible on screen, invalidate its
     * previous position.
     */
    if (term->dispcursy >= 0 &&
        (term->curstype != cursor ||
         term->dispcursy != our_curs_y ||
         term->dispcursx != our_curs_x)) {
        termchar *dispcurs = term->disptext[term->dispcursy]->chars +
            term->dispcursx;

        if (term->dispcursx > 0 && dispcurs->chr == UCSWIDE)
            dispcurs[-1].attr |= ATTR_INVALID;
        if (term->dispcursx < term->cols-1 && dispcurs[1].chr == UCSWIDE)
            dispcurs[1].attr |= ATTR_INVALID;
        dispcurs->attr |= ATTR_INVALID;

        term->curstype = 0;
    }
    term->dispcursx = term->dispcursy = -1;

    /* The normal screen data */
    for (i = 0; i < term->rows; i++) {
        termline *ldata;
        termchar *lchars;
        bool dirty_line, dirty_run, selected;
        unsigned long attr = 0, cset = 0;
        int start = 0;
        int ccount = 0;
        bool last_run_dirty = false;
        int laststart;
        bool dirtyrect;
        int *backward;
        truecolour tc;

        scrpos.y = i + term->disptop;
        ldata = lineptr(scrpos.y);

        /* Do Arabic shaping and bidi. */
        lchars = term_bidi_line(term, ldata, i);
        if (lchars) {
            backward = term->post_bidi_cache[i].backward;
        } else {
            lchars = ldata->chars;
            backward = NULL;
        }

        /*
         * First loop: work along the line deciding what we want
         * each character cell to look like.
         */
        for (j = 0; j < term->cols; j++) {
            unsigned long tattr, tchar;
            termchar *d = lchars + j;
            scrpos.x = backward ? backward[j] : j;

            tchar = d->chr;
            tattr = d->attr;

            if (!term->ansi_colour)
                tattr = (tattr & ~(ATTR_FGMASK | ATTR_BGMASK)) |
                    ATTR_DEFFG | ATTR_DEFBG;

            if (!term->xterm_256_colour) {
                int colour;
                colour = (tattr & ATTR_FGMASK) >> ATTR_FGSHIFT;
                if (colour >= 16 && colour < 256)
                    tattr = (tattr &~ ATTR_FGMASK) | ATTR_DEFFG;
                colour = (tattr & ATTR_BGMASK) >> ATTR_BGSHIFT;
                if (colour >= 16 && colour < 256)
                    tattr = (tattr &~ ATTR_BGMASK) | ATTR_DEFBG;
            }

            if (term->true_colour) {
                tc = d->truecolour;
            } else {
                tc.fg = tc.bg = optionalrgb_none;
            }

            switch (tchar & CSET_MASK) {
              case CSET_ASCII:
                tchar = term->ucsdata->unitab_line[tchar & 0xFF];
                break;
              case CSET_LINEDRW:
                tchar = term->ucsdata->unitab_xterm[tchar & 0xFF];
                break;
              case CSET_SCOACS:
                tchar = term->ucsdata->unitab_scoacs[tchar&0xFF];
                break;
            }
            if (j < term->cols-1 && d[1].chr == UCSWIDE)
                tattr |= ATTR_WIDE;

            /* Video reversing things */
            if (term->selstate == DRAGGING || term->selstate == SELECTED) {
                if (term->seltype == LEXICOGRAPHIC)
                    selected = (posle(term->selstart, scrpos) &&
                                poslt(scrpos, term->selend));
                else
                    selected = (posPle(term->selstart, scrpos) &&
                                posPle_left(scrpos, term->selend));
            } else
                selected = false;
            tattr = (tattr ^ rv
                     ^ (selected ? ATTR_REVERSE : 0));

            /* 'Real' blinking ? */
            if (term->blink_is_real && (tattr & ATTR_BLINK)) {
                if (term->has_focus && term->tblinker) {
                    tchar = term->ucsdata->unitab_line[(unsigned char)' '];
                }
                tattr &= ~ATTR_BLINK;
            }

            /*
             * Check the font we'll _probably_ be using to see if
             * the character is wide when we don't want it to be.
             */
            if (tchar != term->disptext[i]->chars[j].chr ||
                tattr != (term->disptext[i]->chars[j].attr &~
                          (ATTR_NARROW | DATTR_MASK))) {
                if ((tattr & ATTR_WIDE) == 0 &&
                    win_char_width(term->win, tchar) == 2)
                    tattr |= ATTR_NARROW;
            } else if (term->disptext[i]->chars[j].attr & ATTR_NARROW)
                tattr |= ATTR_NARROW;

            if (i == our_curs_y && j == our_curs_x) {
                tattr |= cursor;
                term->curstype = cursor;
                term->dispcursx = j;
                term->dispcursy = i;
            }

            /* FULL-TERMCHAR */
            newline[j].attr = tattr;
            newline[j].chr = tchar;
            newline[j].truecolour = tc;
            /* Combining characters are still read from lchars */
            newline[j].cc_next = 0;
        }

        /*
         * Now loop over the line again, noting where things have
         * changed.
         *
         * During this loop, we keep track of where we last saw
         * DATTR_STARTRUN. Any mismatch automatically invalidates
         * _all_ of the containing run that was last printed: that
         * is, any rectangle that was drawn in one go in the
         * previous update should be either left completely alone
         * or overwritten in its entirety. This, along with the
         * expectation that front ends clip all text runs to their
         * bounding rectangle, should solve any possible problems
         * with fonts that overflow their character cells.
         */
        laststart = 0;
        dirtyrect = false;
        for (j = 0; j < term->cols; j++) {
            if (term->disptext[i]->chars[j].attr & DATTR_STARTRUN) {
                laststart = j;
                dirtyrect = false;
            }

            if (term->disptext[i]->chars[j].chr != newline[j].chr ||
                (term->disptext[i]->chars[j].attr &~ DATTR_MASK)
                != newline[j].attr) {
                int k;

                if (!dirtyrect) {
                    for (k = laststart; k < j; k++)
                        term->disptext[i]->chars[k].attr |= ATTR_INVALID;

                    dirtyrect = true;
                }
            }

            if (dirtyrect)
                term->disptext[i]->chars[j].attr |= ATTR_INVALID;
        }

        /*
         * Finally, loop once more and actually do the drawing.
         */
        dirty_run = dirty_line = (ldata->lattr !=
                                  term->disptext[i]->lattr);
        term->disptext[i]->lattr = ldata->lattr;

        tc = term->erase_char.truecolour;
        for (j = 0; j < term->cols; j++) {
            unsigned long tattr, tchar;
            bool break_run, do_copy, next_run_dirty = false;
            termchar *d = lchars + j;

            tattr = newline[j].attr;
            tchar = newline[j].chr;

            if ((term->disptext[i]->chars[j].attr ^ tattr) & ATTR_WIDE)
                dirty_line = true;

            break_run = ((tattr ^ attr) & term->attr_mask) != 0;

            if (!truecolour_equal(newline[j].truecolour, tc))
                break_run = true;

#ifdef USES_VTLINE_HACK
            /* Special hack for VT100 Linedraw glyphs */
            if ((tchar >= 0x23BA && tchar <= 0x23BD) ||
                (j > 0 && (newline[j-1].chr >= 0x23BA &&
                           newline[j-1].chr <= 0x23BD)))
                break_run = true;
#endif

            /*
             * Separate out sequences of characters that have the
             * same CSET, if that CSET is a magic one.
             */
            if (CSET_OF(tchar) != cset)
                break_run = true;

            /*
             * Break on both sides of any combined-character cell.
             */
            if (d->cc_next != 0 ||
                (j > 0 && d[-1].cc_next != 0))
                break_run = true;

            /*
             * Break on both sides of a regional indicator letter.
             */
            if (IS_REGIONAL_INDICATOR_LETTER(tchar)) {
                break_run = true;
                if (j+1 < term->cols) {
                    /* Also, check if there are any changes to whether or
                     * not we're drawing this and the next character as a
                     * single flag glyph. */
                    bool flag_now = IS_REGIONAL_INDICATOR_LETTER(d[1].chr);
                    bool flag_before = (
                        IS_REGIONAL_INDICATOR_LETTER(
                            term->disptext[i]->chars[j].chr) &&
                        IS_REGIONAL_INDICATOR_LETTER(
                            term->disptext[i]->chars[j+1].chr) &&
                        (term->disptext[i]->chars[j].attr & DATTR_STARTRUN));
                    if (flag_now != flag_before)
                        next_run_dirty = true; /* must redraw this flag */
                }
            } else if (j>0 && IS_REGIONAL_INDICATOR_LETTER(d[-1].chr)) {
                break_run = true;
            }

            /*
             * Break on both sides of a trust sigil.
             */
            if (d->chr == TRUST_SIGIL_CHAR ||
                (j >= 2 && d[-1].chr == UCSWIDE &&
                 d[-2].chr == TRUST_SIGIL_CHAR))
                break_run = true;

            if (!term->ucsdata->dbcs_screenfont && !dirty_line) {
                if (term->disptext[i]->chars[j].chr == tchar &&
                    (term->disptext[i]->chars[j].attr &~ DATTR_MASK)==tattr &&
                    truecolour_equal(
                        term->disptext[i]->chars[j].truecolour, tc))
                    break_run = true;
                else if (!dirty_run && ccount == 1)
                    break_run = true;
            }

            if (break_run) {
                if ((dirty_run || last_run_dirty) && ccount > 0)
                    do_paint_draw(term, ldata, start, i, ch, ccount, attr, tc);
                start = j;
                ccount = 0;
                attr = tattr;
                tc = newline[j].truecolour;
                cset = CSET_OF(tchar);
                if (term->ucsdata->dbcs_screenfont)
                    last_run_dirty = dirty_run;
                dirty_run = dirty_line || next_run_dirty;
            }

            do_copy = false;
            if (!termchars_equal_override(&term->disptext[i]->chars[j],
                                          d, tchar, tattr)) {
                do_copy = true;
                dirty_run = true;
            }

            sgrowarrayn(ch, chlen, ccount, 2);

#ifdef PLATFORM_IS_UTF16
            if (tchar > 0x10000 && tchar < 0x110000) {
                ch[ccount++] = (wchar_t) HIGH_SURROGATE_OF(tchar);
                ch[ccount++] = (wchar_t) LOW_SURROGATE_OF(tchar);
            } else
#endif /* PLATFORM_IS_UTF16 */
            ch[ccount++] = (wchar_t) tchar;

            if (d->cc_next) {
                termchar *dd = d;

                while (dd->cc_next) {
                    unsigned long schar;

                    dd += dd->cc_next;

                    schar = dd->chr;
                    switch (schar & CSET_MASK) {
                      case CSET_ASCII:
                        schar = term->ucsdata->unitab_line[schar & 0xFF];
                        break;
                      case CSET_LINEDRW:
                        schar = term->ucsdata->unitab_xterm[schar & 0xFF];
                        break;
                      case CSET_SCOACS:
                        schar = term->ucsdata->unitab_scoacs[schar&0xFF];
                        break;
                    }

                    sgrowarrayn(ch, chlen, ccount, 2);

#ifdef PLATFORM_IS_UTF16
                    if (schar > 0x10000 && schar < 0x110000) {
                        ch[ccount++] = (wchar_t) HIGH_SURROGATE_OF(schar);
                        ch[ccount++] = (wchar_t) LOW_SURROGATE_OF(schar);
                    } else
#endif /* PLATFORM_IS_UTF16 */
                    ch[ccount++] = (wchar_t) schar;
                }

                attr |= TATTR_COMBINING;
            }

            if (do_copy) {
                copy_termchar(term->disptext[i], j, d);
                term->disptext[i]->chars[j].chr = tchar;
                term->disptext[i]->chars[j].attr = tattr;
                term->disptext[i]->chars[j].truecolour = tc;
                if (start == j)
                    term->disptext[i]->chars[j].attr |= DATTR_STARTRUN;
            }

            /* If it's a wide char step along to the next one. */
            if (tattr & ATTR_WIDE) {
                if (++j < term->cols) {
                    d++;
                    /*
                     * By construction above, the cursor should not
                     * be on the right-hand half of this character.
                     * Ever.
                     */
                    assert(!(i == our_curs_y && j == our_curs_x));
                    if (!termchars_equal(&term->disptext[i]->chars[j], d))
                        dirty_run = true;
                    copy_termchar(term->disptext[i], j, d);
                }
            }

            /* If it's a regional indicator letter, and so is the next
             * one, then also step to the next one, keeping the flag
             * sequence together. */
            if (IS_REGIONAL_INDICATOR_LETTER(d->chr) &&
                (j+1 < term->cols && IS_REGIONAL_INDICATOR_LETTER(d[1].chr))) {
                j++;
                d++;

                /* Set ATTR_WIDE, so that the pair is displayed as one */
                attr |= ATTR_WIDE;

                /* Include the second letter in the text buffer */
                unsigned long rchar = d->chr;
#ifdef PLATFORM_IS_UTF16
                sgrowarrayn(ch, chlen, ccount, 2);
                ch[ccount++] = (wchar_t)HIGH_SURROGATE_OF(rchar);
                ch[ccount++] = (wchar_t)LOW_SURROGATE_OF(rchar);
#else
                sgrowarrayn(ch, chlen, ccount, 1);
                ch[ccount++] = (wchar_t)rchar;
#endif

                /* Display the cursor, if it's on the right half */
                if (i == our_curs_y && j == our_curs_x) {
                    attr |= cursor;
                    term->disptext[i]->chars[j-1].attr |= cursor;
                }

                if (!termchars_equal_override(
                        &term->disptext[i]->chars[j],
                        d, rchar, term->disptext[i]->chars[j-1].attr))
                    dirty_run = true;

                copy_termchar(term->disptext[i], j, d);
                term->disptext[i]->chars[j].attr =
                    term->disptext[i]->chars[j-1].attr & ~DATTR_STARTRUN;
            }
        }
        if (dirty_run && ccount > 0)
            do_paint_draw(term, ldata, start, i, ch, ccount, attr, tc);

        unlineptr(ldata);
    }

    sfree(newline);
    sfree(ch);
}

/*
 * Invalidate the whole screen so it will be repainted in full.
 */
void term_invalidate(Terminal *term)
{
    int i, j;

    for (i = 0; i < term->rows; i++)
        for (j = 0; j < term->cols; j++)
            term->disptext[i]->chars[j].attr |= ATTR_INVALID;

    term_schedule_update(term);
}

/*
 * Paint the window in response to a WM_PAINT message.
 */
void term_paint(Terminal *term,
                int left, int top, int right, int bottom, bool immediately)
{
    int i, j;
    if (left < 0) left = 0;
    if (top < 0) top = 0;
    if (right >= term->cols) right = term->cols-1;
    if (bottom >= term->rows) bottom = term->rows-1;

    for (i = top; i <= bottom && i < term->rows; i++) {
        if ((term->disptext[i]->lattr & LATTR_MODE) == LATTR_NORM)
            for (j = left; j <= right && j < term->cols; j++)
                term->disptext[i]->chars[j].attr |= ATTR_INVALID;
        else
            for (j = left / 2; j <= right / 2 + 1 && j < term->cols; j++)
                term->disptext[i]->chars[j].attr |= ATTR_INVALID;
    }

    if (immediately) {
        do_paint(term);
    } else {
        term_schedule_update(term);
    }
}

/*
 * Attempt to scroll the scrollback. The second parameter gives the
 * position we want to scroll to; the first is +1 to denote that
 * this position is relative to the beginning of the scrollback, -1
 * to denote it is relative to the end, and 0 to denote that it is
 * relative to the current position.
 */
void term_scroll(Terminal *term, int rel, int where)
{
    int sbtop = -sblines(term);

    term->disptop = (rel < 0 ? 0 : rel > 0 ? sbtop : term->disptop) + where;
    if (term->disptop < sbtop)
        term->disptop = sbtop;
    if (term->disptop > 0)
        term->disptop = 0;
    term->win_scrollbar_update_pending = true;
    term_schedule_update(term);
}

/*
 * Scroll the scrollback to centre it on the beginning or end of the
 * current selection, if any.
 */
void term_scroll_to_selection(Terminal *term, int which_end)
{
    pos target;
    int y;
    int sbtop = -sblines(term);

    if (term->selstate != SELECTED)
        return;
    if (which_end)
        target = term->selend;
    else
        target = term->selstart;

    y = target.y - term->rows/2;
    if (y < sbtop)
        y = sbtop;
    else if (y > 0)
        y = 0;
    term_scroll(term, -1, y);
}

/*
 * Helper routine for clipme(): growing buffer.
 */
typedef struct {
    size_t bufsize;         /* amount of allocated space in textbuf/attrbuf */
    size_t bufpos;          /* amount of actual data */
    wchar_t *textbuf;       /* buffer for copied text */
    wchar_t *textptr;       /* = textbuf + bufpos (current insertion point) */
    int *attrbuf;           /* buffer for copied attributes */
    int *attrptr;           /* = attrbuf + bufpos */
    truecolour *tcbuf;      /* buffer for copied colours */
    truecolour *tcptr;      /* = tcbuf + bufpos */
} clip_workbuf;

static void clip_addchar(clip_workbuf *b, wchar_t chr, int attr, truecolour tc)
{
    if (b->bufpos >= b->bufsize) {
        sgrowarray(b->textbuf, b->bufsize, b->bufpos);
        b->textptr = b->textbuf + b->bufpos;
        b->attrbuf = sresize(b->attrbuf, b->bufsize, int);
        b->attrptr = b->attrbuf + b->bufpos;
        b->tcbuf = sresize(b->tcbuf, b->bufsize, truecolour);
        b->tcptr = b->tcbuf + b->bufpos;
    }
    *b->textptr++ = chr;
    *b->attrptr++ = attr;
    *b->tcptr++ = tc;
    b->bufpos++;
}

static void clipme(Terminal *term, pos top, pos bottom, bool rect, bool desel,
                   const int *clipboards, int n_clipboards)
{
    clip_workbuf buf;
    int old_top_x;
    int attr;
    truecolour tc;

    buf.bufsize = 5120;
    buf.bufpos = 0;
    buf.textptr = buf.textbuf = snewn(buf.bufsize, wchar_t);
    buf.attrptr = buf.attrbuf = snewn(buf.bufsize, int);
    buf.tcptr = buf.tcbuf = snewn(buf.bufsize, truecolour);

    old_top_x = top.x;                 /* needed for rect==1 */

    while (poslt(top, bottom)) {
        bool nl = false;
        termline *ldata = lineptr(top.y);
        pos nlpos;

        /*
         * nlpos will point at the maximum position on this line we
         * should copy up to. So we start it at the end of the
         * line...
         */
        nlpos.y = top.y;
        nlpos.x = term->cols;

        /*
         * ... move it backwards if there's unused space at the end
         * of the line (and also set `nl' if this is the case,
         * because in normal selection mode this means we need a
         * newline at the end)...
         */
        if (!(ldata->lattr & LATTR_WRAPPED)) {
            while (nlpos.x &&
                   IS_SPACE_CHR(ldata->chars[nlpos.x - 1].chr) &&
                   !ldata->chars[nlpos.x - 1].cc_next &&
                   poslt(top, nlpos))
                decpos(nlpos);
            if (poslt(nlpos, bottom))
                nl = true;
        } else {
            if (ldata->trusted) {
                /* A wrapped line with a trust sigil on it terminates
                 * a few characters earlier. */
                nlpos.x = (nlpos.x < TRUST_SIGIL_WIDTH ? 0 :
                           nlpos.x - TRUST_SIGIL_WIDTH);
            }
            if (ldata->lattr & LATTR_WRAPPED2) {
                /* Ignore the last char on the line in a WRAPPED2 line. */
                decpos(nlpos);
            }
        }

        /*
         * ... and then clip it to the terminal x coordinate if
         * we're doing rectangular selection. (In this case we
         * still did the above, so that copying e.g. the right-hand
         * column from a table doesn't fill with spaces on the
         * right.)
         */
        if (rect) {
            if (nlpos.x > bottom.x)
                nlpos.x = bottom.x;
            nl = (top.y < bottom.y);
        }

        while (poslt(top, bottom) && poslt(top, nlpos)) {
            wchar_t cbuf[16], *p;
            int c;
            int x = top.x;

            if (ldata->chars[x].chr == UCSWIDE) {
                top.x++;
                continue;
            }

            while (1) {
                int uc = ldata->chars[x].chr;
                attr = ldata->chars[x].attr;
                tc = ldata->chars[x].truecolour;

                switch (uc & CSET_MASK) {
                  case CSET_LINEDRW:
                    if (!term->rawcnp) {
                        uc = term->ucsdata->unitab_xterm[uc & 0xFF];
                        break;
                    }
                  case CSET_ASCII:
                    uc = term->ucsdata->unitab_line[uc & 0xFF];
                    break;
                  case CSET_SCOACS:
                    uc = term->ucsdata->unitab_scoacs[uc&0xFF];
                    break;
                }
                switch (uc & CSET_MASK) {
                  case CSET_ACP:
                    uc = term->ucsdata->unitab_font[uc & 0xFF];
                    break;
                  case CSET_OEMCP:
                    uc = term->ucsdata->unitab_oemcp[uc & 0xFF];
                    break;
                }

                c = (uc & ~CSET_MASK);
#ifdef PLATFORM_IS_UTF16
                if (uc > 0x10000 && uc < 0x110000) {
                    cbuf[0] = 0xD800 | ((uc - 0x10000) >> 10);
                    cbuf[1] = 0xDC00 | ((uc - 0x10000) & 0x3FF);
                    cbuf[2] = 0;
                } else
#endif
                {
                    cbuf[0] = uc;
                    cbuf[1] = 0;
                }

                if (DIRECT_FONT(uc)) {
                    if (c >= ' ' && c != 0x7F) {
                        char buf[2];
                        buffer_sink bs[1];
                        buffer_sink_init(bs, cbuf,
                                         sizeof(cbuf) - sizeof(wchar_t));
                        if (is_dbcs_leadbyte(term->ucsdata->font_codepage, (BYTE) c)) {
                            buf[0] = c;
                            buf[1] = (char) (0xFF & ldata->chars[top.x + 1].chr);
                            put_mb_to_wc(bs, term->ucsdata->font_codepage,
                                         buf, 2);
                            top.x++;
                        } else {
                            buf[0] = c;
                            put_mb_to_wc(bs, term->ucsdata->font_codepage,
                                         buf, 1);
                        }

                        assert(!bs->overflowed);
                        *(wchar_t *)bs->out = L'\0';
                    }
                }

                for (p = cbuf; *p; p++)
                    clip_addchar(&buf, *p, attr, tc);

                if (ldata->chars[x].cc_next)
                    x += ldata->chars[x].cc_next;
                else
                    break;
            }
            top.x++;
        }
        if (nl) {
            int i;
            for (i = 0; i < sel_nl_sz; i++)
                clip_addchar(&buf, sel_nl[i], 0, term->basic_erase_char.truecolour);
        }
        top.y++;
        top.x = rect ? old_top_x : 0;

        unlineptr(ldata);
    }
#if SELECTION_NUL_TERMINATED
    clip_addchar(&buf, 0, 0, term->basic_erase_char.truecolour);
#endif
    /* Finally, transfer all that to the clipboard(s). */
    {
        int i;
        bool clip_local = false;
        for (i = 0; i < n_clipboards; i++) {
            if (clipboards[i] == CLIP_LOCAL) {
                clip_local = true;
            } else if (clipboards[i] != CLIP_NULL) {
                win_clip_write(
                    term->win, clipboards[i], buf.textbuf, buf.attrbuf,
                    buf.tcbuf, buf.bufpos, desel);
            }
        }
        if (clip_local) {
            sfree(term->last_selected_text);
            sfree(term->last_selected_attr);
            sfree(term->last_selected_tc);
            term->last_selected_text = buf.textbuf;
            term->last_selected_attr = buf.attrbuf;
            term->last_selected_tc = buf.tcbuf;
            term->last_selected_len = buf.bufpos;
        } else {
            sfree(buf.textbuf);
            sfree(buf.attrbuf);
            sfree(buf.tcbuf);
        }
    }
}

void term_copyall(Terminal *term, const int *clipboards, int n_clipboards)
{
    pos top;
    pos bottom;
    tree234 *screen = term->screen;
    top.y = -sblines(term);
    top.x = 0;
    bottom.y = find_last_nonempty_line(term, screen);
    bottom.x = term->cols;
    clipme(term, top, bottom, false, true, clipboards, n_clipboards);
}

static void paste_from_clip_local(void *vterm)
{
    Terminal *term = (Terminal *)vterm;
    term_do_paste(term, term->last_selected_text, term->last_selected_len);
}

void term_request_copy(Terminal *term, const int *clipboards, int n_clipboards)
{
    int i;
    for (i = 0; i < n_clipboards; i++) {
        assert(clipboards[i] != CLIP_LOCAL);
        if (clipboards[i] != CLIP_NULL) {
            win_clip_write(term->win, clipboards[i],
                           term->last_selected_text, term->last_selected_attr,
                           term->last_selected_tc, term->last_selected_len,
                           false);
        }
    }
}

void term_request_paste(Terminal *term, int clipboard)
{
    switch (clipboard) {
      case CLIP_NULL:
        /* Do nothing: CLIP_NULL never has data in it. */
        break;
      case CLIP_LOCAL:
        queue_toplevel_callback(paste_from_clip_local, term);
        break;
      default:
        win_clip_request_paste(term->win, clipboard);
        break;
    }
}

/*
 * The wordness array is mainly for deciding the disposition of the
 * US-ASCII characters.
 */
static int wordtype(Terminal *term, int uc)
{
    struct ucsword {
        int start, end, ctype;
    };
    static const struct ucsword ucs_words[] = {
        {128, 160, 0},
        {161, 191, 1},
        {215, 215, 1},
        {247, 247, 1},
        {0x037e, 0x037e, 1},           /* Greek question mark */
        {0x0387, 0x0387, 1},           /* Greek ano teleia */
        {0x055a, 0x055f, 1},           /* Armenian punctuation */
        {0x0589, 0x0589, 1},           /* Armenian full stop */
        {0x0700, 0x070d, 1},           /* Syriac punctuation */
        {0x104a, 0x104f, 1},           /* Myanmar punctuation */
        {0x10fb, 0x10fb, 1},           /* Georgian punctuation */
        {0x1361, 0x1368, 1},           /* Ethiopic punctuation */
        {0x166d, 0x166e, 1},           /* Canadian Syl. punctuation */
        {0x17d4, 0x17dc, 1},           /* Khmer punctuation */
        {0x1800, 0x180a, 1},           /* Mongolian punctuation */
        {0x2000, 0x200a, 0},           /* Various spaces */
        {0x2070, 0x207f, 2},           /* superscript */
        {0x2080, 0x208f, 2},           /* subscript */
        {0x200b, 0x27ff, 1},           /* punctuation and symbols */
        {0x3000, 0x3000, 0},           /* ideographic space */
        {0x3001, 0x3020, 1},           /* ideographic punctuation */
        {0x303f, 0x309f, 3},           /* Hiragana */
        {0x30a0, 0x30ff, 3},           /* Katakana */
        {0x3300, 0x9fff, 3},           /* CJK Ideographs */
        {0xac00, 0xd7a3, 3},           /* Hangul Syllables */
        {0xf900, 0xfaff, 3},           /* CJK Ideographs */
        {0xfe30, 0xfe6b, 1},           /* punctuation forms */
        {0xff00, 0xff0f, 1},           /* half/fullwidth ASCII */
        {0xff1a, 0xff20, 1},           /* half/fullwidth ASCII */
        {0xff3b, 0xff40, 1},           /* half/fullwidth ASCII */
        {0xff5b, 0xff64, 1},           /* half/fullwidth ASCII */
        {0xfff0, 0xffff, 0},           /* half/fullwidth ASCII */
        {0, 0, 0}
    };
    const struct ucsword *wptr;

    switch (uc & CSET_MASK) {
      case CSET_LINEDRW:
        uc = term->ucsdata->unitab_xterm[uc & 0xFF];
        break;
      case CSET_ASCII:
        uc = term->ucsdata->unitab_line[uc & 0xFF];
        break;
      case CSET_SCOACS:
        uc = term->ucsdata->unitab_scoacs[uc&0xFF];
        break;
    }
    switch (uc & CSET_MASK) {
      case CSET_ACP:
        uc = term->ucsdata->unitab_font[uc & 0xFF];
        break;
      case CSET_OEMCP:
        uc = term->ucsdata->unitab_oemcp[uc & 0xFF];
        break;
    }

    /* For DBCS fonts I can't do anything useful. Even this will sometimes
     * fail as there's such a thing as a double width space. :-(
     */
    if (term->ucsdata->dbcs_screenfont &&
        term->ucsdata->font_codepage == term->ucsdata->line_codepage)
        return (uc != ' ');

    if (uc < 0x80)
        return term->wordness[uc];

    for (wptr = ucs_words; wptr->start; wptr++) {
        if (uc >= wptr->start && uc <= wptr->end)
            return wptr->ctype;
    }

    return 2;
}

static int line_cols(Terminal *term, termline *ldata)
{
    int cols = term->cols;
    if (ldata->trusted) {
        cols -= TRUST_SIGIL_WIDTH;
    }
    if (ldata->lattr & LATTR_WRAPPED2)
        cols--;
    if (cols < 0)
        cols = 0;
    return cols;
}

/*
 * Spread the selection outwards according to the selection mode.
 */
static pos sel_spread_half(Terminal *term, pos p, int dir)
{
    termline *ldata;
    short wvalue;
    int topy = -sblines(term);

    ldata = lineptr(p.y);

    switch (term->selmode) {
      case SM_CHAR:
        /*
         * In this mode, every character is a separate unit, except
         * for runs of spaces at the end of a non-wrapping line.
         */
        if (!(ldata->lattr & LATTR_WRAPPED)) {
            termchar *q = ldata->chars + line_cols(term, ldata);
            while (q > ldata->chars &&
                   IS_SPACE_CHR(q[-1].chr) && !q[-1].cc_next)
                q--;
            if (q == ldata->chars + term->cols)
                q--;
            if (p.x >= q - ldata->chars)
                p.x = (dir == -1 ? q - ldata->chars : term->cols - 1);
        }
        break;
      case SM_WORD:
        /*
         * In this mode, the units are maximal runs of characters
         * whose `wordness' has the same value.
         */
        wvalue = wordtype(term, UCSGET(ldata->chars, p.x));
        if (dir == +1) {
            while (1) {
                int maxcols = line_cols(term, ldata);
                if (p.x < maxcols-1) {
                    if (wordtype(term, UCSGET(ldata->chars, p.x+1)) == wvalue)
                        p.x++;
                    else
                        break;
                } else {
                    if (p.y+1 < term->rows &&
                        (ldata->lattr & LATTR_WRAPPED)) {
                        termline *ldata2;
                        ldata2 = lineptr(p.y+1);
                        if (wordtype(term, UCSGET(ldata2->chars, 0))
                            == wvalue) {
                            p.x = 0;
                            p.y++;
                            unlineptr(ldata);
                            ldata = ldata2;
                        } else {
                            unlineptr(ldata2);
                            break;
                        }
                    } else
                        break;
                }
            }
        } else {
            while (1) {
                if (p.x > 0) {
                    if (wordtype(term, UCSGET(ldata->chars, p.x-1)) == wvalue)
                        p.x--;
                    else
                        break;
                } else {
                    termline *ldata2;
                    int maxcols;
                    if (p.y <= topy)
                        break;
                    ldata2 = lineptr(p.y-1);
                    maxcols = line_cols(term, ldata2);
                    if (ldata2->lattr & LATTR_WRAPPED) {
                        if (wordtype(term, UCSGET(ldata2->chars, maxcols-1))
                            == wvalue) {
                            p.x = maxcols-1;
                            p.y--;
                            unlineptr(ldata);
                            ldata = ldata2;
                        } else {
                            unlineptr(ldata2);
                            break;
                        }
                    } else
                        break;
                }
            }
        }
        break;
      case SM_LINE:
        /*
         * In this mode, every line is a unit.
         */
        p.x = (dir == -1 ? 0 : term->cols - 1);
        break;
    }

    unlineptr(ldata);
    return p;
}

static void sel_spread(Terminal *term)
{
    if (term->seltype == LEXICOGRAPHIC) {
        term->selstart = sel_spread_half(term, term->selstart, -1);
        decpos(term->selend);
        term->selend = sel_spread_half(term, term->selend, +1);
        incpos(term->selend);
    }
}

static void term_paste_callback(void *vterm)
{
    Terminal *term = (Terminal *)vterm;

    if (term->paste_len == 0)
        return;

    while (term->paste_pos < term->paste_len) {
        size_t n = 0;
        while (n + term->paste_pos < term->paste_len) {
            if (term->paste_buffer[term->paste_pos + n++] == '\015')
                break;
        }
        if (term->ldisc) {
            strbuf *buf = term_input_data_from_unicode(
                term, term->paste_buffer + term->paste_pos, n);
            term_keyinput_internal(term, buf->s, buf->len, false);
            strbuf_free(buf);
        }
        term->paste_pos += n;

        if (term->paste_pos < term->paste_len) {
            queue_toplevel_callback(term_paste_callback, term);
            return;
        }
    }
    term_bracketed_paste_stop(term);
    sfree(term->paste_buffer);
    term->paste_buffer = NULL;
    term->paste_len = 0;
}

/*
 * Specialist string compare function. Returns true if the buffer of
 * alen wide characters starting at a has as a prefix the buffer of
 * blen characters starting at b.
 */
static bool wstartswith(const wchar_t *a, size_t alen,
                        const wchar_t *b, size_t blen)
{
    return alen >= blen && !wcsncmp(a, b, blen);
}

void term_do_paste(Terminal *term, const wchar_t *data, size_t len)
{
    const wchar_t *p;
    bool paste_controls = conf_get_bool(term->conf, CONF_paste_controls);

    /*
     * Pasting data into the terminal counts as a keyboard event (for
     * purposes of the 'Reset scrollback on keypress' config option),
     * unless the paste is zero-length.
     */
    if (len == 0)
        return;
    term_seen_key_event(term);

    if (term->paste_buffer)
        sfree(term->paste_buffer);
    term->paste_pos = term->paste_len = 0;
    term->paste_buffer = snewn(len + 12, wchar_t);

    if (term->bracketed_paste && !term->no_bracketed_paste)
        term_bracketed_paste_start(term);

    p = data;
    while (p < data + len) {
        wchar_t wc = *p++;

        if (wc == sel_nl[0] &&
            wstartswith(p-1, data+len-(p-1), sel_nl, sel_nl_sz)) {
            /*
             * This is the (platform-dependent) sequence that the host
             * OS uses to represent newlines in clipboard data.
             * Normalise it to a press of CR.
             */
            p += sel_nl_sz - 1;
            wc = '\015';
        }

        if ((wc & ~(wint_t)0x9F) == 0) {
            /*
             * This is a control code, either in the range 0x00-0x1F
             * or 0x80-0x9F. We reject all of these in pastecontrols
             * mode, except for a small set of permitted ones.
             */
            if (!paste_controls) {
                /* In line with xterm 292, accepted control chars are:
                 * CR, LF, tab, backspace. (And DEL, i.e. 0x7F, but
                 * that's permitted by virtue of not matching the bit
                 * mask that got us into this if statement, so we
                 * don't have to permit it here. */
                static const unsigned mask =
                    (1<<13) | (1<<10) | (1<<9) | (1<<8);

                if (wc > 15 || !((mask >> wc) & 1))
                    continue;
            }

            if (wc == '\033' && term->bracketed_paste &&
                wstartswith(p-1, data+len-(p-1), L"\033[201~", 6)) {
                /*
                 * Also, in bracketed-paste mode, reject the ESC
                 * character that begins the end-of-paste sequence.
                 */
                continue;
            }
        }

        term->paste_buffer[term->paste_len++] = wc;
    }

    /* Assume a small paste will be OK in one go. */
    if (term->paste_len < 256) {
        if (term->ldisc) {
            strbuf *buf = term_input_data_from_unicode(
                term, term->paste_buffer, term->paste_len);
            assert(buf->len <= INT_MAX); /* because paste_len was also small */
            term_keyinput_internal(term, buf->s, buf->len, false);
            strbuf_free(buf);
        }
        if (term->paste_buffer)
            sfree(term->paste_buffer);
        term_bracketed_paste_stop(term);
        term->paste_buffer = NULL;
        term->paste_pos = term->paste_len = 0;
    }

    queue_toplevel_callback(term_paste_callback, term);
}

void term_mouse(Terminal *term, Mouse_Button braw, Mouse_Button bcooked,
                Mouse_Action a, int x, int y, bool shift, bool ctrl, bool alt)
{
    pos selpoint;
    termline *ldata;
    bool raw_mouse = (term->xterm_mouse &&
                      !term->no_mouse_rep &&
                      !(term->mouse_override && shift));
    int default_seltype;

    // Don't do anything if mouse movement events weren't requested;
    // Note: return early to avoid doing all of this code on every mouse move
    // event only to throw it away.
    if (a == MA_MOVE && (!raw_mouse || term->xterm_mouse < 3)) {
        return;
    }

    if (y < 0) {
        y = 0;
        if (a == MA_DRAG && !raw_mouse)
            term_scroll(term, 0, -1);
    }
    if (y >= term->rows) {
        y = term->rows - 1;
        if (a == MA_DRAG && !raw_mouse)
            term_scroll(term, 0, +1);
    }
    if (x < 0) {
        if (y > 0 && !raw_mouse && term->seltype != RECTANGULAR) {
            /*
             * When we're using the mouse for normal raster-based
             * selection, dragging off the left edge of a terminal row
             * is treated the same as the right-hand end of the
             * previous row, in that it's considered to identify a
             * point _before_ the first character on row y.
             *
             * But if the mouse action is going to be used for
             * anything else - rectangular selection, or xterm mouse
             * tracking - then we disable this special treatment.
             */
            x = term->cols - 1;
            y--;
        } else
            x = 0;
    }
    if (x >= term->cols)
        x = term->cols - 1;

    selpoint.y = y + term->disptop;
    ldata = lineptr(selpoint.y);

    if ((ldata->lattr & LATTR_MODE) != LATTR_NORM)
        x /= 2;

    /*
     * Transform x through the bidi algorithm to find the _logical_
     * click point from the physical one.
     */
    if (term_bidi_line(term, ldata, y) != NULL) {
        x = term->post_bidi_cache[y].backward[x];
    }

    selpoint.x = x;
    unlineptr(ldata);

    /*
     * If we're in the middle of a selection operation, we ignore raw
     * mouse mode until it's done (we must have been not in raw mouse
     * mode when it started).
     * This makes use of Shift for selection reliable, and avoids the
     * host seeing mouse releases for which they never saw corresponding
     * presses.
     */
    if (raw_mouse &&
        (term->selstate != ABOUT_TO) && (term->selstate != DRAGGING)) {
        int encstate = 0, r, c;
        bool wheel;
        char *response = NULL;

        if (term->ldisc) {

            switch (braw) {
              case MBT_LEFT:
                encstate = 0x00;               /* left button down */
                wheel = false;
                break;
              case MBT_MIDDLE:
                encstate = 0x01;
                wheel = false;
                break;
              case MBT_RIGHT:
                encstate = 0x02;
                wheel = false;
                break;
              case MBT_WHEEL_UP:
                encstate = 0x40;
                wheel = true;
                break;
              case MBT_WHEEL_DOWN:
                encstate = 0x41;
                wheel = true;
                break;
              case MBT_WHEEL_LEFT:
                encstate = 0x42;
                wheel = true;
                break;
              case MBT_WHEEL_RIGHT:
                encstate = 0x43;
                wheel = true;
                break;
              case MBT_NOTHING:
                assert( a == MA_MOVE );
                encstate = 0x03; // release; no buttons pressed
                wheel = false;
                break;
              default:
                return;
            }
            if (wheel) {
                /* For mouse wheel buttons, we only ever expect to see
                 * MA_CLICK actions, and we don't try to keep track of
                 * the buttons being 'pressed' (since without matching
                 * click/release pairs that's pointless). */
                if (a != MA_CLICK)
                    return;
            } else switch (a) {
              case MA_DRAG:
                if (term->xterm_mouse == 1)
                    return;
                encstate += 0x20; // motion indicator
                break;
              case MA_MOVE:    // mouse move without buttons
                assert( braw == MBT_NOTHING && bcooked == MBT_NOTHING  );
                if (term->xterm_mouse < 3)
                    return;

                if (selpoint.x == term->raw_mouse_reported_x &&
                    selpoint.y == term->raw_mouse_reported_y)
                    return;

                term->raw_mouse_reported_x = x;
                term->raw_mouse_reported_y = y;

                encstate += 0x20; // motion indicator
                break;
              case MA_RELEASE:
                /* If multiple extensions are enabled, the xterm 1006 is used, so it's okay to check for only that */
                if (!term->xterm_extended_mouse)
                    encstate = 0x03;
                term->mouse_is_down = 0;
                break;
              case MA_CLICK:
                if (term->mouse_is_down == braw)
                    return;
                term->mouse_is_down = braw;
                break;
              default:
                return;
            }
            if (shift)
                encstate += 0x04;
            if (ctrl)
                encstate += 0x10;
            r = y + 1;
            c = x + 1;

            /* Check the extensions in decreasing order of preference. Encoding the release event above assumes that 1006 comes first. */
            if (term->xterm_extended_mouse) {
                response = dupprintf("\033[<%d;%d;%d%c", encstate, c, r,
                                     a == MA_RELEASE ? 'm' : 'M');
            } else if (term->urxvt_extended_mouse) {
                response = dupprintf("\033[%d;%d;%dM", encstate + 32, c, r);
            } else if (c <= 223 && r <= 223) {
                response = dupprintf("\033[M%c%c%c", encstate + 32,
                                     c + 32, r + 32);
            }
            if (response) {
                ldisc_send(term->ldisc, response, strlen(response), false);
                sfree(response);
            }
        }
        return;
    }

    /*
     * Set the selection type (rectangular or normal) at the start
     * of a selection attempt, from the state of Alt.
     */
    if (!alt ^ !term->rect_select)
        default_seltype = RECTANGULAR;
    else
        default_seltype = LEXICOGRAPHIC;

    if (term->selstate == NO_SELECTION) {
        term->seltype = default_seltype;
    }

    if (bcooked == MBT_SELECT && a == MA_CLICK) {
        deselect(term);
        term->selstate = ABOUT_TO;
        term->seltype = default_seltype;
        term->selanchor = selpoint;
        term->selmode = SM_CHAR;
    } else if (bcooked == MBT_SELECT && (a == MA_2CLK || a == MA_3CLK)) {
        deselect(term);
        term->selmode = (a == MA_2CLK ? SM_WORD : SM_LINE);
        term->selstate = DRAGGING;
        term->selstart = term->selanchor = selpoint;
        term->selend = term->selstart;
        incpos(term->selend);
        sel_spread(term);
    } else if ((bcooked == MBT_SELECT && a == MA_DRAG) ||
               (bcooked == MBT_EXTEND && a != MA_RELEASE)) {
        if (a == MA_DRAG &&
            (term->selstate == NO_SELECTION || term->selstate == SELECTED)) {
            /*
             * This can happen if a front end has passed us a MA_DRAG
             * without a prior MA_CLICK. OS X GTK does so, for
             * example, if the initial button press was eaten by the
             * WM when it activated the window in the first place. The
             * nicest thing to do in this situation is to ignore
             * further drags, and wait for the user to click in the
             * window again properly if they want to select.
             */
            return;
        }
        if (term->selstate == ABOUT_TO && poseq(term->selanchor, selpoint))
            return;
        if (bcooked == MBT_EXTEND && a != MA_DRAG &&
            term->selstate == SELECTED) {
            if (term->seltype == LEXICOGRAPHIC) {
                /*
                 * For normal selection, we extend by moving
                 * whichever end of the current selection is closer
                 * to the mouse.
                 */
                if (posdiff(selpoint, term->selstart) <
                    posdiff(term->selend, term->selstart) / 2) {
                    term->selanchor = term->selend;
                    decpos(term->selanchor);
                } else {
                    term->selanchor = term->selstart;
                }
            } else {
                /*
                 * For rectangular selection, we have a choice of
                 * _four_ places to put selanchor and selpoint: the
                 * four corners of the selection.
                 */
                if (2*selpoint.x < term->selstart.x + term->selend.x)
                    term->selanchor.x = term->selend.x-1;
                else
                    term->selanchor.x = term->selstart.x;

                if (2*selpoint.y < term->selstart.y + term->selend.y)
                    term->selanchor.y = term->selend.y;
                else
                    term->selanchor.y = term->selstart.y;
            }
            term->selstate = DRAGGING;
        }
        if (term->selstate != ABOUT_TO && term->selstate != DRAGGING)
            term->selanchor = selpoint;
        term->selstate = DRAGGING;
        if (term->seltype == LEXICOGRAPHIC) {
            /*
             * For normal selection, we set (selstart,selend) to
             * (selpoint,selanchor) in some order.
             */
            if (poslt(selpoint, term->selanchor)) {
                term->selstart = selpoint;
                term->selend = term->selanchor;
                incpos(term->selend);
            } else {
                term->selstart = term->selanchor;
                term->selend = selpoint;
                incpos(term->selend);
            }
        } else {
            /*
             * For rectangular selection, we may need to
             * interchange x and y coordinates (if the user has
             * dragged in the -x and +y directions, or vice versa).
             */
            term->selstart.x = min(term->selanchor.x, selpoint.x);
            term->selend.x = 1+max(term->selanchor.x, selpoint.x);
            term->selstart.y = min(term->selanchor.y, selpoint.y);
            term->selend.y =   max(term->selanchor.y, selpoint.y);
        }
        sel_spread(term);
    } else if ((bcooked == MBT_SELECT || bcooked == MBT_EXTEND) &&
               a == MA_RELEASE) {
        if (term->selstate == DRAGGING) {
            /*
             * We've completed a selection. We now transfer the
             * data to the clipboard.
             */
            clipme(term, term->selstart, term->selend,
                   (term->seltype == RECTANGULAR), false,
                   term->mouse_select_clipboards,
                   term->n_mouse_select_clipboards);
            term->selstate = SELECTED;
        } else
            term->selstate = NO_SELECTION;
    } else if (bcooked == MBT_PASTE
               && (a == MA_CLICK
#if MULTICLICK_ONLY_EVENT
                   || a == MA_2CLK || a == MA_3CLK
#endif
                   )) {
        term_request_paste(term, term->mouse_paste_clipboard);
    }

    /*
     * Since terminal output is suppressed during drag-selects, we
     * should make sure to write any pending output if one has just
     * finished.
     */
    term_out(term, false);
    term_schedule_update(term);
}

void term_cancel_selection_drag(Terminal *term)
{
    /*
     * In unusual circumstances, a mouse drag might be interrupted by
     * something that steals the rest of the mouse gesture. An example
     * is the GTK popup menu appearing. In that situation, we'll never
     * receive the MA_RELEASE that finishes the DRAGGING state, which
     * means terminal output could be suppressed indefinitely. Call
     * this function from the front end in such situations to restore
     * sensibleness.
     */
    if (term->selstate == DRAGGING)
        term->selstate = NO_SELECTION;
    term_out(term, false);
    term_schedule_update(term);
}

static int shift_bitmap(bool shift, bool ctrl, bool alt, bool *consumed_alt)
{
    int bitmap = (shift ? 1 : 0) + (alt ? 2 : 0) + (ctrl ? 4 : 0);
    if (bitmap)
        bitmap++;
    if (alt && consumed_alt)
        *consumed_alt = true;
    return bitmap;
}

int format_arrow_key(char *buf, Terminal *term, int xkey,
                     bool shift, bool ctrl, bool alt, bool *consumed_alt)
{
    char *p = buf;

    if (term->vt52_mode)
        p += sprintf(p, "\x1B%c", xkey);
    else {
        bool app_flg = (term->app_cursor_keys && !term->no_applic_c);
#if 0
        /*
         * RDB: VT100 & VT102 manuals both state the app cursor
         * keys only work if the app keypad is on.
         *
         * SGT: That may well be true, but xterm disagrees and so
         * does at least one application, so I've #if'ed this out
         * and the behaviour is back to PuTTY's original: app
         * cursor and app keypad are independently switchable
         * modes. If anyone complains about _this_ I'll have to
         * put in a configurable option.
         */
        if (!term->app_keypad_keys)
            app_flg = 0;
#endif

        int bitmap = 0;

        /* Adjustment based on Shift, Ctrl and/or Alt */
        switch (term->sharrow_type) {
          case SHARROW_APPLICATION:
            if (ctrl)
                app_flg = !app_flg;
            break;
          case SHARROW_BITMAP:
            bitmap = shift_bitmap(shift, ctrl, alt, consumed_alt);
            break;
        }

        if (app_flg)
            p += sprintf(p, "\x1BO%c", xkey);
        else if (bitmap)
            p += sprintf(p, "\x1B[1;%d%c", bitmap, xkey);
        else
            p += sprintf(p, "\x1B[%c", xkey);
    }

    return p - buf;
}

int format_function_key(char *buf, Terminal *term, int key_number,
                        bool shift, bool ctrl, bool alt, bool *consumed_alt)
{
    char *p = buf;

    static const int key_number_to_tilde_code[] = {
        -1,                 /* no such key as F0 */
        11, 12, 13, 14, 15, /*gap*/ 17, 18, 19, 20, 21, /*gap*/
        23, 24, 25, 26, /*gap*/ 28, 29, /*gap*/ 31, 32, 33, 34,
    };

    assert(key_number > 0);
    assert(key_number < lenof(key_number_to_tilde_code));

    int index = key_number;
    if (term->funky_type != FUNKY_XTERM_216 && term->funky_type != FUNKY_SCO) {
        if (shift && index <= 10) {
            shift = false;
            index += 10;
        }
    }

    int code = key_number_to_tilde_code[index];

    if (term->funky_type == FUNKY_SCO) {
        /* SCO function keys */
        static const char sco_codes[] =
            "MNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz@[\\]^_`{";
        index = (key_number >= 1 && key_number <= 12) ? key_number - 1 : 0;
        if (shift) index += 12;
        if (ctrl) index += 24;
        p += sprintf(p, "\x1B[%c", sco_codes[index]);
    } else if ((term->vt52_mode || term->funky_type == FUNKY_VT100P) &&
               code >= 11 && code <= 24) {
        int offt = 0;
        if (code > 15)
            offt++;
        if (code > 21)
            offt++;
        if (term->vt52_mode)
            p += sprintf(p, "\x1B%c", code + 'P' - 11 - offt);
        else
            p += sprintf(p, "\x1BO%c", code + 'P' - 11 - offt);
    } else if (term->funky_type == FUNKY_LINUX && code >= 11 && code <= 15) {
        p += sprintf(p, "\x1B[[%c", code + 'A' - 11);
    } else if ((term->funky_type == FUNKY_XTERM ||
                term->funky_type == FUNKY_XTERM_216) &&
               code >= 11 && code <= 14) {
        if (term->vt52_mode)
            p += sprintf(p, "\x1B%c", code + 'P' - 11);
        else {
            int bitmap = 0;
            if (term->funky_type == FUNKY_XTERM_216)
                bitmap = shift_bitmap(shift, ctrl, alt, consumed_alt);
            if (bitmap)
                p += sprintf(p, "\x1B[1;%d%c", bitmap, code + 'P' - 11);
            else
                p += sprintf(p, "\x1BO%c", code + 'P' - 11);
        }
    } else {
        int bitmap = 0;
        if (term->funky_type == FUNKY_XTERM_216)
            bitmap = shift_bitmap(shift, ctrl, alt, consumed_alt);
        if (bitmap)
            p += sprintf(p, "\x1B[%d;%d~", code, bitmap);
        else
            p += sprintf(p, "\x1B[%d~", code);
    }

    return p - buf;
}

int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key,
                            bool shift, bool ctrl, bool alt,
                            bool *consumed_alt)
{
    char *p = buf;

    int code;
    switch (key) {
      case SKK_HOME: code = 1; break;
      case SKK_INSERT: code = 2; break;
      case SKK_DELETE: code = 3; break;
      case SKK_END: code = 4; break;
      case SKK_PGUP: code = 5; break;
      case SKK_PGDN: code = 6; break;
      default: unreachable("bad small keypad key enum value");
    }

    /* Reorder edit keys to physical order */
    if (term->funky_type == FUNKY_VT400 && code <= 6)
        code = "\0\2\1\4\5\3\6"[code];

    if (term->vt52_mode && code > 0 && code <= 6) {
        p += sprintf(p, "\x1B%c", " HLMEIG"[code]);
    } else if (term->funky_type == FUNKY_SCO) {
        static const char codes[] = "HL.FIG";
        if (code == 3) {
            *p++ = '\x7F';
        } else {
            p += sprintf(p, "\x1B[%c", codes[code-1]);
        }
    } else if ((code == 1 || code == 4) && term->rxvt_homeend) {
        p += sprintf(p, code == 1 ? "\x1B[H" : "\x1BOw");
    } else {
        if (term->vt52_mode) {
	    p += sprintf(p, "\x1B[%d~", code);
        } else {
            int bitmap = 0;
            if (term->funky_type == FUNKY_XTERM_216)
                bitmap = shift_bitmap(shift, ctrl, alt, consumed_alt);
            if (bitmap)
                p += sprintf(p, "\x1B[%d;%d~", code, bitmap);
            else
                p += sprintf(p, "\x1B[%d~", code);
        }
    }

    return p - buf;
}

int format_numeric_keypad_key(char *buf, Terminal *term, char key,
                              bool shift, bool ctrl)
{
    char *p = buf;
    bool app_keypad = (term->app_keypad_keys && !term->no_applic_k);

    if (term->nethack_keypad && (key >= '1' && key <= '9')) {
        static const char nh_base[] = "bjnh.lyku";
        char c = nh_base[key - '1'];
        if (ctrl && c != '.')
            c &= 0x1F;
        else if (shift && c != '.')
            c += 'A'-'a';
        *p++ = c;
    } else {
        int xkey = 0;

        if (term->funky_type == FUNKY_VT400 ||
            (term->funky_type <= FUNKY_LINUX && app_keypad)) {
            switch (key) {
              case 'G': xkey = 'P'; break;
              case '/': xkey = 'Q'; break;
              case '*': xkey = 'R'; break;
              case '-': xkey = 'S'; break;
            }
        }

        if (app_keypad) {
            switch (key) {
              case '0': xkey = 'p'; break;
              case '1': xkey = 'q'; break;
              case '2': xkey = 'r'; break;
              case '3': xkey = 's'; break;
              case '4': xkey = 't'; break;
              case '5': xkey = 'u'; break;
              case '6': xkey = 'v'; break;
              case '7': xkey = 'w'; break;
              case '8': xkey = 'x'; break;
              case '9': xkey = 'y'; break;
              case '.': xkey = 'n'; break;
              case '\r': xkey = 'M'; break;

              case '+':
                /*
                 * Keypad + is tricky. It covers a space that would
                 * be taken up on the VT100 by _two_ keys; so we
                 * let Shift select between the two. Worse still,
                 * in xterm function key mode we change which two...
                 */
                if (term->funky_type == FUNKY_XTERM)
                    xkey = shift ? 'l' : 'k';
                else
                    xkey = shift ? 'm' : 'l';
                break;

              case '/':
                if (term->funky_type == FUNKY_XTERM)
                    xkey = 'o';
                break;
              case '*':
                if (term->funky_type == FUNKY_XTERM)
                    xkey = 'j';
                break;
              case '-':
                if (term->funky_type == FUNKY_XTERM)
                    xkey = 'm';
                break;
            }
        }

        if (xkey) {
            if (term->vt52_mode) {
                if (xkey >= 'P' && xkey <= 'S')
                    p += sprintf(p, "\x1B%c", xkey);
                else
                    p += sprintf(p, "\x1B?%c", xkey);
            } else
                p += sprintf(p, "\x1BO%c", xkey);
        }
    }

    return p - buf;
}

void term_keyinputw(Terminal *term, const wchar_t *widebuf, int len)
{
    strbuf *buf = term_input_data_from_unicode(term, widebuf, len);
    if (buf->len)
        term_keyinput_internal(term, buf->s, buf->len, true);
    strbuf_free(buf);
}

void term_keyinput(Terminal *term, int codepage, const void *str, int len)
{
    if (codepage < 0 || codepage == term->ucsdata->line_codepage) {
        /*
         * This text needs no translation, either because it's already
         * in the right character set, or because we got the special
         * codepage value -1 from our caller which means 'this data
         * should be charset-agnostic, just send it raw' (for really
         * simple things like control characters).
         */
        term_keyinput_internal(term, str, len, true);
    } else {
        strbuf *buf = term_input_data_from_charset(term, codepage, str, len);
        if (buf->len)
            term_keyinput_internal(term, buf->s, buf->len, true);
        strbuf_free(buf);
    }
}

void term_nopaste(Terminal *term)
{
    if (term->paste_len == 0)
        return;
    sfree(term->paste_buffer);
    term_bracketed_paste_stop(term);
    term->paste_buffer = NULL;
    term->paste_len = 0;
}

static void deselect(Terminal *term)
{
    term->selstate = NO_SELECTION;
    term->selstart.x = term->selstart.y = term->selend.x = term->selend.y = 0;
}

void term_lost_clipboard_ownership(Terminal *term, int clipboard)
{
    if (!(term->n_mouse_select_clipboards > 1 &&
          clipboard == term->mouse_select_clipboards[1]))
        return;

    deselect(term);
    term_update(term);

    /*
     * Since terminal output is suppressed during drag-selects, we
     * should make sure to write any pending output if one has just
     * finished.
     */
    term_out(term, false);
}

static void term_added_data(Terminal *term, bool called_from_term_data)
{
    if (!term->in_term_out) {
        term->in_term_out = true;
        term_out(term, called_from_term_data);
        term->in_term_out = false;
    }
}

size_t term_data(Terminal *term, const void *data, size_t len)
{
    bufchain_add(&term->inbuf, data, len);
    term_added_data(term, true);
    return bufchain_size(&term->inbuf);
}

void term_provide_logctx(Terminal *term, LogContext *logctx)
{
    term->logctx = logctx;
}

void term_set_focus(Terminal *term, bool has_focus)
{
    term->has_focus = has_focus;
    term_schedule_cblink(term);
}

/*
 * Provide "auto" settings for remote tty modes, suitable for an
 * application with a terminal window.
 */
char *term_get_ttymode(Terminal *term, const char *mode)
{
    const char *val = NULL;
    if (strcmp(mode, "ERASE") == 0) {
        val = term->bksp_is_delete ? "^?" : "^H";
    } else if (strcmp(mode, "IUTF8") == 0) {
        val = (term->ucsdata->line_codepage == CP_UTF8) ? "yes" : "no";
    }
    /* FIXME: perhaps we should set ONLCR based on lfhascr as well? */
    /* FIXME: or ECHO and friends based on local echo state? */
    return dupstr(val);
}

struct term_userpass_state {
    prompts_t *prompts;
    size_t curr_prompt;
    enum TermUserpassPromptState {
        TUS_INITIAL,         /* haven't even printed the prompt yet */
        TUS_ACTIVE,          /* prompt is currently receiving user input */
        TUS_ABORTED,         /* user pressed ^C or ^D to cancel prompt */
    } prompt_state;
    Terminal *term;
    TermLineEditor *le;
    TermLineEditorCallbackReceiver le_rcv;
};

static void term_userpass_next_prompt(struct term_userpass_state *s);

/*
 * Signal that a prompts_t is done. This involves sending a
 * notification to the caller, and also turning off our own callback
 * that listens for more data arriving in the ldisc's input queue.
 */
static inline SeatPromptResult signal_prompts_t(Terminal *term, prompts_t *p,
                                                SeatPromptResult spr)
{
    assert(p->callback && "Asynchronous userpass input requires a callback");
    queue_toplevel_callback(p->callback, p->callback_ctx);
    if (term->ldisc)
        ldisc_provide_userpass_le(term->ldisc, NULL);
    p->spr = spr;
    if (p->data) {
        term_userpass_state_free(p->data);
        p->data = NULL;
    }
    return spr;
}

/* Tiny wrapper to make it easier to write lots of little strings */
static inline void term_write(Terminal *term, ptrlen data)
{
    term_data(term, data.ptr, data.len);
}

static void term_lineedit_to_terminal(
    TermLineEditorCallbackReceiver *rcv, ptrlen data)
{
    struct term_userpass_state *s = container_of(
        rcv, struct term_userpass_state, le_rcv);
    prompt_t *pr = s->prompts->prompts[s->curr_prompt];
    if (pr->echo)
        term_write(s->term, data);
}

static void term_lineedit_to_backend(
    TermLineEditorCallbackReceiver *rcv, ptrlen data)
{
    struct term_userpass_state *s = container_of(
        rcv, struct term_userpass_state, le_rcv);
    prompt_t *pr = s->prompts->prompts[s->curr_prompt];
    put_datapl(pr->result, data);
}

static void term_lineedit_newline(TermLineEditorCallbackReceiver *rcv)
{
    struct term_userpass_state *s = container_of(
        rcv, struct term_userpass_state, le_rcv);

    prompt_t *pr = s->prompts->prompts[s->curr_prompt];
    if (!pr->echo) {
        /* If echo is disabled, we won't have printed the newline in
         * term_lineedit_to_terminal, so print it now */
        term_write(s->term, PTRLEN_LITERAL("\x0D\x0A"));
    }

    ldisc_provide_userpass_le(s->term->ldisc, NULL);
    s->curr_prompt++;
    s->prompt_state = TUS_INITIAL;
    term_userpass_next_prompt(s);
}

static void term_lineedit_special(
    TermLineEditorCallbackReceiver *rcv, SessionSpecialCode code, int arg)
{
    struct term_userpass_state *s = container_of(
        rcv, struct term_userpass_state, le_rcv);
    switch (code) {
      case SS_IP:
      case SS_EOF:
        ldisc_provide_userpass_le(s->term->ldisc, NULL);
        s->prompt_state = TUS_ABORTED;
        signal_prompts_t(s->term, s->prompts, SPR_USER_ABORT);
      default:
        break;
    }
}

static const TermLineEditorCallbackReceiverVtable
term_userpass_lineedit_receiver_vt = {
    .to_terminal = term_lineedit_to_terminal,
    .to_backend = term_lineedit_to_backend,
    .special = term_lineedit_special,
    .newline = term_lineedit_newline,
};

static struct term_userpass_state *term_userpass_state_new(
    Terminal *term, prompts_t *prompts)
{
    struct term_userpass_state *s = snew(struct term_userpass_state);
    s->prompts = prompts;
    s->curr_prompt = 0;
    s->prompt_state = TUS_INITIAL;
    s->term = term;
    s->le_rcv.vt = &term_userpass_lineedit_receiver_vt;
    s->le = lineedit_new(term, LE_INTERRUPT | LE_EOF_ALWAYS | LE_ESC_ERASES,
                         &s->le_rcv);
    assert(!term->userpass_state);
    term->userpass_state = s;
    return s;
}

static void term_userpass_state_free(struct term_userpass_state *s)
{
    assert(s->term->userpass_state == s);
    s->term->userpass_state = NULL;
    lineedit_free(s->le);
    sfree(s);
}

static void term_userpass_next_prompt(struct term_userpass_state *s)
{
    if (s->prompt_state != TUS_INITIAL)
        return;
    if (s->curr_prompt < s->prompts->n_prompts) {
        prompt_t *pr = s->prompts->prompts[s->curr_prompt];
        term_write(s->term, ptrlen_from_asciz(pr->prompt));
        s->prompt_state = TUS_ACTIVE;
        ldisc_provide_userpass_le(s->term->ldisc, s->le);
    } else {
        /* This triggers the callback provided by the userpass client,
         * which will call term_userpass_state to fetch the result
         * we're storing here */
        signal_prompts_t(s->term, s->prompts, SPR_OK);
    }
}

static bool terminal_use_utf8 = true;
bool set_legacy_charset_handling(bool newvalue)
{
    terminal_use_utf8 = !newvalue;
    return true;
}

/*
 * Process some terminal data in the course of username/password
 * input.
 */
SeatPromptResult term_get_userpass_input(Terminal *term, prompts_t *p)
{
    if (!term->ldisc) {
        /* Can't handle interactive prompts without an ldisc */
        return signal_prompts_t(term, p, SPR_SW_ABORT(
            "Terminal not prepared for interactive prompts"));
    }

    if (p->spr.kind != SPRK_INCOMPLETE) {
        /* We've already finished these prompts, so return the same
         * result again */
        return p->spr;
    }

    struct term_userpass_state *s = (struct term_userpass_state *)p->data;

    if (!s) {
        /*
         * First call. Set some stuff up.
         */
        p->data = s = term_userpass_state_new(term, p);
        p->spr = SPR_INCOMPLETE;
        term->userpass_utf8_override = p->utf8 && terminal_use_utf8;
        /* We only print the `name' caption if we have to... */
        if (p->name_reqd && p->name) {
            ptrlen plname = ptrlen_from_asciz(p->name);
            term_write(term, plname);
            if (!ptrlen_endswith(plname, PTRLEN_LITERAL("\n"), NULL))
                term_write(term, PTRLEN_LITERAL("\r\n"));
        }
        /* ...but we always print any `instruction'. */
        if (p->instruction) {
            ptrlen plinst = ptrlen_from_asciz(p->instruction);
            term_write(term, plinst);
            if (!ptrlen_endswith(plinst, PTRLEN_LITERAL("\n"), NULL))
                term_write(term, PTRLEN_LITERAL("\r\n"));
        }
        /*
         * Zero all the results, in case we abort half-way through.
         */
        {
            int i;
            for (i = 0; i < (int)p->n_prompts; i++)
                prompt_set_result(p->prompts[i], "");
        }
        /* And print the first prompt. */
        term_userpass_next_prompt(s);
    }

    return SPR_INCOMPLETE;
}

void term_notify_minimised(Terminal *term, bool minimised)
{
    term->minimised = minimised;
}

void term_notify_palette_changed(Terminal *term)
{
    palette_reset(term, true);
}

void term_notify_window_pos(Terminal *term, int x, int y)
{
    term->winpos_x = x;
    term->winpos_y = y;
}

void term_notify_window_size_pixels(Terminal *term, int x, int y)
{
    term->winpixsize_x = x;
    term->winpixsize_y = y;
}