descent/2D/MODEX.ASM

;THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
;SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
;END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
;ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
;IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
;SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
;FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
;CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
;AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.  
;COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
;
; $Source: f:/miner/source/2d/rcs/modex.asm $
; $Revision: 1.19 $
; $Author: john $
; $Date: 1995/03/01 15:37:46 $
;
; Routines to access ModeX VGA memory
;
; $Log: modex.asm $
; Revision 1.19  1995/03/01  15:37:46  john
; Better ModeX support.
; 
; Revision 1.18  1994/11/24  13:24:20  john
; Made sure that some rep movs had the cld set first.
; Took some unused functions out.
; 
; Revision 1.17  1994/09/22  18:15:02  john
; Made flip page wait for retrace.
; 
; Revision 1.16  1994/09/22  16:08:27  john
; Fixed some palette stuff.
; 
; Revision 1.15  1994/07/13  12:03:05  john
; Added assembly modex line-drawer.
; 
; Revision 1.14  1994/05/06  12:50:34  john
; Added supertransparency; neatend things up; took out warnings.
; 
; Revision 1.13  1994/05/03  19:39:04  john
; *** empty log message ***
; 
; Revision 1.12  1994/02/18  15:32:32  john
; *** empty log message ***
; 
; Revision 1.11  1993/12/21  11:40:36  john
; *** empty log message ***
; 
; Revision 1.10  1993/12/09  15:02:26  john
; Changed palette stuff majorly
; 
; Revision 1.9  1993/12/03  12:11:32  john
; fixed cx/ecx loop bugs.
; 
; Revision 1.8  1993/11/16  11:28:18  john
; *** empty log message ***
; 
; Revision 1.7  1993/10/15  16:23:23  john
; y
; 
; Revision 1.6  1993/09/28  19:07:19  john
; stripped the waitforretrace out of fade to speed things up.
; 
; Revision 1.5  1993/09/26  18:58:58  john
; fade stuff
; 
; Revision 1.4  1993/09/21  14:01:15  john
; turned off video before mode set to reduce flicker.
; 
; Revision 1.3  1993/09/08  11:38:36  john
; changed rcs stuff at beginning.
; 
;
;


.386

_DATA   SEGMENT BYTE PUBLIC USE32 'DATA'

INCLUDE psmacros.inc
INCLUDE TWEAK.INC
INCLUDE VGAREGS.INC

extd _gr_var_bwidth

extd _modex_line_vertincr
extd _modex_line_incr1		
extd _modex_line_incr2		
	_modex_line_routine	dd ?
extd _modex_line_x1		
extd _modex_line_y1		
extd _modex_line_x2		
extd _modex_line_y2		
extb _modex_line_Color

	SavedColor      db ?

LEFT_MASK1      = 1000b
LEFT_MASK2      = 1100b
LEFT_MASK3      = 1110b
RIGHT_MASK1     = 0001b
RIGHT_MASK2     = 0011b
RIGHT_MASK3     = 0111b
ALL_MASK        = 1111b

tmppal          db 768 dup (0)
fb_pal          dd ?
fb_add          dw ?
fb_count        dd ?

MaskTable1  db  ALL_MASK AND RIGHT_MASK1,
				ALL_MASK AND RIGHT_MASK2,
				ALL_MASK AND RIGHT_MASK3,
				ALL_MASK,
				LEFT_MASK3 AND RIGHT_MASK1,
				LEFT_MASK3 AND RIGHT_MASK2,
				LEFT_MASK3 AND RIGHT_MASK3,
				LEFT_MASK3,
				LEFT_MASK2 AND RIGHT_MASK1,
				LEFT_MASK2 AND RIGHT_MASK2,
				LEFT_MASK2 AND RIGHT_MASK3,
				LEFT_MASK2,
				LEFT_MASK1 AND RIGHT_MASK1,
				LEFT_MASK1 AND RIGHT_MASK2,
				LEFT_MASK1 AND RIGHT_MASK3,
				LEFT_MASK1,

MaskTable2  db  ALL_MASK,RIGHT_MASK1,
				ALL_MASK,RIGHT_MASK2,
				ALL_MASK,RIGHT_MASK3,
				ALL_MASK,ALL_MASK,
				LEFT_MASK3,RIGHT_MASK1,
				LEFT_MASK3,RIGHT_MASK2,
				LEFT_MASK3,RIGHT_MASK3,
				LEFT_MASK3,ALL_MASK,
				LEFT_MASK2,RIGHT_MASK1,
				LEFT_MASK2,RIGHT_MASK2,
				LEFT_MASK2,RIGHT_MASK3,
				LEFT_MASK2,ALL_MASK,
				LEFT_MASK1,RIGHT_MASK1,
				LEFT_MASK1,RIGHT_MASK2,
				LEFT_MASK1,RIGHT_MASK3,
				LEFT_MASK1,ALL_MASK

DrawTable   dd  DrawMR,
				DrawMR,
				DrawMR,
				DrawM,
				DrawLMR,
				DrawLMR,
				DrawLMR,
				DrawLM,
				DrawLMR,
				DrawLMR,
				DrawLMR,
				DrawLM,
				DrawLMR,
				DrawLMR,
				DrawLMR,
				DrawLM

_DATA   ENDS

DGROUP  GROUP _DATA


_TEXT   SEGMENT BYTE PUBLIC USE32 'CODE'

		ASSUME  DS:_DATA
		ASSUME  CS:_TEXT

PUBLIC  gr_sync_display_

gr_sync_display_:

		push    ax
		push    dx
		mov     dx, VERT_RESCAN
VS2A:   in      al, dx
		and     al, 08h
		jnz     VS2A        ; Loop until not in vertical retrace
VS2B:   in      al, dx
		and     al, 08h
		jz      VS2B        ; Loop until in vertical retrace

		pop     dx
		pop     ax
		ret


PUBLIC  gr_modex_uscanline_

gr_modex_uscanline_:
		push    edi

		; EAX = X1  (X1 and X2 don't need to be sorted)
		; EDX = X2
		; EBX = Y
		; ECX = Color

		mov     SavedColor, cl

		;mov     ebx, _RowOffset[ebx*4]
		mov	edi, _gr_var_bwidth
		imul	edi, ebx
		add     edi, 0A0000h
		cmp     eax, edx
		jle     @f
		xchg    eax, edx
@@:     mov     bl, al
		shl     bl, 2
		mov     bh, dl
		and     bh, 011b
		or      bl, bh
		and     ebx, 0fh
		; BX = LeftRight switch command. (4bit)
		shr     eax, 2
		shr     edx, 2
		add     edi, eax
		; EDI = Offset into video memory
		mov     ecx, edx
		sub     ecx, eax
		; ECX = X2/4 - X1/4 - 1
		jnz     LargerThan4

;======================= ONE GROUP OF 4 OR LESS TO DRAW ====================

		mov     dx, SC_INDEX
		mov     al, SC_MAP_MASK
		out     dx, al
		inc     dx
		mov     al, MaskTable1[ebx]
		out     dx, al
		mov     al, SavedColor
		mov     [edi], al           ; Write the one pixel
		pop     edi
		ret

LargerThan4:
		dec     ecx
		jnz     LargerThan8

;===================== TWO GROUPS OF 4 OR LESS TO DRAW ====================

		mov     cx, WORD PTR MaskTable2[ebx*2]
		mov     bl, SavedColor
		mov     dx, SC_INDEX
		mov     al, SC_MAP_MASK
		out     dx, al
		inc     dx
		mov     al, cl
		out     dx, al
		mov     [edi], bl           ; Write the left pixel
		mov     al, ch
		out     dx, al
		mov     [edi+1], bl         ; Write the right pixel
		pop     edi
		ret

;========================= MANY GROUPS OF 4 TO DRAW ======================
LargerThan8:
		mov     dx, SC_INDEX
		mov     al, SC_MAP_MASK
		out     dx, al
		inc     dx
		; DX = SC_INDEX
		mov     al, SavedColor
		mov     ah, al
		; AL,AH = color of pixel
		jmp     NEAR32 PTR DrawTable[ebx*4]


DrawM:  ;AH=COLOR, EDI=DEST, CX=X2/4-X1/4-1, BX=Table Index
		mov     al, ALL_MASK
		out     dx, al
		mov     al, ah
		cld
		add     ecx, 2
		shr     ecx, 1
		rep     stosw       ; Write the middle pixels
		jnc     @F
		stosb               ; Write the middle odd pixel
@@:     pop     edi
		ret

DrawLM:
		;AH=COLOR, EDI=DEST, CX=X2/4-X1/4-1, BX=Table Index
		mov     al, BYTE PTR MaskTable2[ebx*2]
		out     dx, al
		mov     [edi], ah       ; Write leftmost pixels
		inc     edi
		mov     al, ALL_MASK
		out     dx, al
		mov     al, ah
		cld
		inc     ecx
		shr     ecx, 1
		rep     stosw       ; Write the middle pixels
		jnc     @F
		stosb               ; Write the middle odd pixel
@@:     pop     edi
		ret


DrawLMR: ;AH=COLOR, EDI=DEST, CX=X2/4-X1/4-1, BX=Table Index
		mov     bx, WORD PTR MaskTable2[ebx*2]
		mov     al, bl
		out     dx, al
		mov     [edi], ah       ; Write leftmost pixels
		inc     edi
		mov     al, ALL_MASK
		out     dx, al
		mov     al, ah
		cld
		shr     ecx, 1
		rep     stosw       ; Write the middle pixels
		jnc     @F
		stosb               ; Write the middle odd pixel
@@:     mov     al, bh
		out     dx, al
		mov     [edi], ah   ; Write the rightmost pixels
		pop     edi
		ret

DrawMR: ;AH=COLOR, EDI=DEST, CX=X2/4-X1/4-1, BX=Table Index
		mov     bx, WORD PTR MaskTable2[ebx*2]
		mov     al, ALL_MASK
		out     dx, al
		mov     al, ah
		cld
		inc     ecx
		shr     ecx, 1
		rep     stosw       ; Write the middle pixels
		jnc     @F
		stosb               ; Write the middle odd pixel
@@:     mov     al, bh
		out     dx, al
		mov     [edi], ah   ; Write the rightmost pixels
		pop     edi
		ret


PUBLIC gr_modex_setmode_

gr_modex_setmode_:

	push  ebx
	push  ecx
	push  edx
	push  esi
	push  edi

	mov   ecx, eax
	dec   ecx

	cmp   ecx, LAST_X_MODE
	jbe   @f
	mov   ecx, 0
@@:

	;call  turn_screen_off

	push  ecx                   ; some bios's dont preserve cx

	;mov ax, 1201h
	;mov bl, 31h     ; disable palette loading at mode switch
	;int 10h
	mov   ax,13h                ; let the BIOS set standard 256-color
	int   10h                   ;  mode (320x200 linear)
	;mov ax, 1200h
	;mov bl, 31h     ; enable palette loading at mode switch
	;int 10h

	pop   ecx

	mov   dx,SC_INDEX
	mov   ax,0604h
	out   dx,ax                 ; disable chain4 mode

	mov   dx,SC_INDEX
	mov   ax,0100h
	out   dx,ax                 ; synchronous reset while setting Misc
								;  Output for safety, even though clock
								;  unchanged

	mov   esi, dword ptr ModeTable[ecx*4]
	lodsb

	or    al,al
	jz    DontSetDot

	mov   dx,MISC_OUTPUT
	out   dx,al               ; select the dot clock and Horiz
							  ;  scanning rate

	;mov   dx,SC_INDEX
	;mov   al,01h
	;out   dx,al
	;inc   dx
	;in    al, dx
	;or    al, 1000b
	;out   dx, al

DontSetDot:
	mov   dx,SC_INDEX
	mov   ax,0300h
	out   dx,ax        ; undo reset (restart sequencer)

	mov   dx,CRTC_INDEX       ; reprogram the CRT Controller
	mov   al,11h              ; VSync End reg contains register write
	out   dx,al               ; protect bit
	inc   dx                  ; CRT Controller Data register
	in    al,dx               ; get current VSync End register setting
	and   al,07fh             ; remove write protect on various
	out   dx,al               ; CRTC registers
	dec   dx                  ; CRT Controller Index
	cld
	xor   ecx,ecx
	lodsb
	mov   cl,al

SetCRTParmsLoop:
	lodsw                     ; get the next CRT Index/Data pair
	out   dx,ax               ; set the next CRT Index/Data pair
	loop  SetCRTParmsLoop

	mov   dx,SC_INDEX
	mov   ax,0f02h
	out   dx,ax       ; enable writes to all four planes
	mov   edi, 0A0000h        ; point ES:DI to display memory
	xor   ax,ax               ; clear to zero-value pixels
	mov   ecx,8000h           ; # of words in display memory
	rep   stosw               ; clear all of display memory

	;  Set pysical screen dimensions

	xor   eax, eax
	lodsw                               ; Load scrn pixel width
	mov   cx, ax
	shl   eax, 16

	mov   dx,CRTC_INDEX
	mov   al,CRTC_OFFSET
	out   dx,al
	inc   dx
	mov   ax,cx
	shr   ax,3
	out   dx,al

	;mov     si, 360
	;@@:
	;mov     ax, 04f06h
	;mov     bl, 0
	;mov     cx, si
	;int     10h
	;cmp     cx, si
	;je      @f
	;inc     si
	;jmp     @B
	;@@:
	;movzx     eax, si

	lodsw                               ; Load Screen Phys. Height

	;call  turn_screen_on

	pop  edi
	pop  esi
	pop  edx
	pop  ecx
	pop  ebx

	ret

PUBLIC gr_modex_setplane_

gr_modex_setplane_:

		push    cx
		push    dx

		mov     cl, al

		; SELECT WRITE PLANE
		and     cl,011b             ;CL = plane
		mov     ax,0100h + MAP_MASK ;AL = index in SC of Map Mask reg
		shl     ah,cl               ;set only the bit for the required
									; plane to 1
		mov     dx,SC_INDEX         ;set the Map Mask to enable only the
	   out     dx,ax               ; pixel's plane

		; SELECT READ PLANE
		mov     ah,cl               ;AH = plane
		mov     al,READ_MAP         ;AL = index in GC of the Read Map reg
		mov     dx,GC_INDEX         ;set the Read Map to read the pixel's
		out     dx,ax               ; plane

		pop     dx
		pop     cx

		ret

PUBLIC  gr_modex_setstart_

gr_modex_setstart_:

		; EAX = X
		; EDX = Y
		; EBX = Wait for retrace

		push    ebx
		push    ecx
		push	ebx

		mov	ecx, _gr_var_bwidth
		imul	ecx, edx

		shr     eax, 2
		add     eax, ecx

		mov     ch, ah
		mov     bh, al

		mov     bl, CC_START_LO
		mov     cl, CC_START_HI

		cli
		mov     dx, VERT_RESCAN
WaitDE: in      al, dx
		test    al, 01h
		jnz     WaitDE

		mov     dx, CRTC_INDEX
		mov     ax, bx
		out     dx, ax      ; Start address low
		mov     ax, cx
		out     dx, ax      ; Start address high
		sti

		pop	ebx
		cmp	ebx, 0
		je	NoWaitVS
		mov     dx, VERT_RESCAN
WaitVS: in      al, dx
		test    al, 08h
		jz      WaitVS      ; Loop until in vertical retrace
NoWaitVS:

		pop     ecx
		pop     ebx

		ret




ModeXAddr       macro
; given: ebx=x, eax=y, return cl=plane mask, ebx=address, trash eax
	mov	cl, bl
	and	cl, 3
	shr	ebx, 2
	imul	eax, _gr_var_bwidth 
	add	ebx, eax
	add	ebx, 0A0000h
	endm


;-----------------------------------------------------------------------
;
; Line drawing function for all MODE X 256 Color resolutions
; Based on code from "PC and PS/2 Video Systems" by Richard Wilton.

PUBLIC gr_modex_line_

gr_modex_line_:
	pusha

	mov	dx,SC_INDEX	; setup for plane mask access

; check for vertical line

	mov	esi,_gr_var_bwidth
	mov	ecx,_modex_line_x2
	sub	ecx,_modex_line_x1
	jz	VertLine

; force x1 < x2

	jns	L01

	neg	ecx

	mov	ebx,_modex_line_x2
	xchg	ebx,_modex_line_x1
	mov	_modex_line_x2,ebx

	mov	ebx,_modex_line_y2
	xchg	ebx,_modex_line_y1
	mov	_modex_line_y2,ebx

; calc dy = abs(y2 - y1)

L01:
	mov	ebx,_modex_line_y2
	sub	ebx,_modex_line_y1
	jnz	short skip
	jmp     HorizLine
skip:		jns	L03

	neg	ebx
	neg	esi

; select appropriate routine for slope of line

L03:
	mov	_modex_line_vertincr,esi
	mov	_modex_line_routine,offset LoSlopeLine
	cmp	ebx,ecx
	jle	L04
	mov	_modex_line_routine,offset HiSlopeLine
	xchg	ebx,ecx

; calc initial decision variable and increments

L04:
	shl	ebx,1
	mov	_modex_line_incr1,ebx
	sub	ebx,ecx
	mov	esi,ebx
	sub	ebx,ecx
	mov	_modex_line_incr2,ebx

; calc first pixel address

	push	ecx
	mov	eax,_modex_line_y1
	mov	ebx,_modex_line_x1
	ModeXAddr
	mov	edi,ebx
	mov	al,1
	shl	al,cl
	mov	ah,al		; duplicate nybble
	shl	al,4
	add	ah,al
	mov	bl,ah
	pop	ecx
	inc	ecx
	jmp	[_modex_line_routine]

; routine for verticle lines

VertLine:
	mov	eax,_modex_line_y1
	mov	ebx,_modex_line_y2
	mov	ecx,ebx
	sub	ecx,eax
	jge	L31
	neg	ecx
	mov	eax,ebx

L31:
	inc	ecx
	mov	ebx,_modex_line_x1
	push	ecx
	ModeXAddr

	mov	ah,1
	shl	ah,cl
	mov	al,MAP_MASK
	out	dx,ax
	pop	ecx
	mov	ax, word ptr _modex_line_Color

; draw the line

L32:
	mov	[ebx],al
	add	ebx,esi
	loop	L32
	jmp	Lexit

; routine for horizontal line

HorizLine:

	mov	eax,_modex_line_y1
	mov	ebx,_modex_line_x1
	ModeXAddr

	mov	edi,ebx     ; set dl = first byte mask
	mov	dl,00fh
	shl	dl,cl

	mov	ecx,_modex_line_x2 ; set dh = last byte mask
	and	cl,3
	mov	dh,00eh
	shl	dh,cl
	not	dh

; determine byte offset of first and last pixel in line

	mov	eax,_modex_line_x2
	mov	ebx,_modex_line_x1

	shr	eax,2     ; set ax = last byte column
	shr	ebx,2    ; set bx = first byte column
	mov	ecx,eax    ; cx = ax - bx
	sub	ecx,ebx

	mov    	eax,edx    ; mov end byte masks to ax
	mov	dx,SC_INDEX ; setup dx for VGA outs
	mov     bl,_modex_line_Color

; set pixels in leftmost byte of line

	or	ecx,ecx      ; is start and end pt in same byte
	jnz	L42        ; no !
	and	ah,al      ; combine start and end masks
	jmp	short L44

L42:            push    eax
	mov     ah,al
	mov     al,MAP_MASK
	out     dx,ax
	mov	al,bl
	stosb
	dec	ecx

; draw remainder of the line

L43:
	mov	ah,0Fh
	mov	al,MAP_MASK
	out	dx,ax
	mov	al,bl
	rep	stosb
	pop     eax

; set pixels in rightmost byte of line

L44:	
	mov	al,MAP_MASK
	out	dx, ax
	mov     byte ptr [edi],bl
	jmp	Lexit


; routine for dy >= dx (slope <= 1)

LoSlopeLine:
	mov	al,MAP_MASK
	mov	bh,byte ptr _modex_line_Color
L10:
	mov	ah,bl

L11:
	or	ah,bl
	rol	bl,1
	jc	L14

; bit mask not shifted out

	or	esi,esi
	jns	L12
	add	esi,_modex_line_incr1
	loop	L11

	out	dx,ax
	mov	[edi],bh
	jmp	short Lexit

L12:
	add	esi,_modex_line_incr2
	out	dx,ax
	mov	[edi],bh
	add	edi,_modex_line_vertincr
	loop	L10
	jmp	short Lexit

; bit mask shifted out

L14:            out	dx,ax
	mov	[edi],bh
	inc	edi
	or	esi,esi
	jns	L15
	add	esi,_modex_line_incr1
	loop	L10
	jmp	short Lexit

L15:
	add	esi,_modex_line_incr2
	add	edi,_modex_line_vertincr
	loop	L10
	jmp	short Lexit

; routine for dy > dx (slope > 1)

HiSlopeLine:
	mov	ebx,_modex_line_vertincr
	mov	al,MAP_MASK
L21:    out	dx,ax
	push	eax
	mov	al,_modex_line_Color
	mov	[edi],al
	pop	eax
	add	edi,ebx

L22:
	or	esi,esi
	jns	L23

	add	esi,_modex_line_incr1
	loop	L21
	jmp	short Lexit

L23:
	add	esi,_modex_line_incr2
	rol	ah,1
	adc	edi,0
lx21:	loop	L21

; return to caller

Lexit:
	popa
	ret



_TEXT   ENDS


		END