inaban/output.c

// Copyright 2019-2020 Inaban Authors <https://hacktivis.me/git/inaban>
// SPDX-License-Identifier: BSD-3-Clause
// Based on wlroots's TinyWL which is distributed under CC0

#include "inaban.h"

#include "config.h"

#include <stdlib.h>

static void
render_surface(struct wlr_surface *surface, int sx, int sy, void *data)
{
	/* This function is called for every surface that needs to be rendered. */
	struct render_data *rdata = data;
	struct inaban_view *view  = rdata->view;
	struct wlr_output *output = rdata->output;

	/* We first obtain a wlr_texture, which is a GPU resource. wlroots
	 * automatically handles negotiating these with the client. The underlying
	 * resource could be an opaque handle passed from the client, or the client
	 * could have sent a pixel buffer which we copied to the GPU, or a few other
	 * means. You don't have to worry about this, wlroots takes care of it. */
	struct wlr_texture *texture = wlr_surface_get_texture(surface);
	if(texture == NULL) return;

	/* The view has a position in layout coordinates. If you have two displays,
	 * one next to the other, both 1080p, a view on the rightmost display might
	 * have layout coordinates of 2000,100. We need to translate that to
	 * output-local coordinates, or (2000 - 1920). */
	double ox = 0, oy = 0;
	wlr_output_layout_output_coords(view->server->output_layout, output, &ox, &oy);
	ox += view->x + sx, oy += view->y + sy;

	/* We also have to apply the scale factor for HiDPI outputs. This is only
	 * part of the puzzle, TinyWL does not fully support HiDPI. */
	struct wlr_box box = {
	    .x      = ox * output->scale,
	    .y      = oy * output->scale,
	    .width  = surface->current.width * output->scale,
	    .height = surface->current.height * output->scale,
	};

	/*
	 * Those familiar with OpenGL are also familiar with the role of matricies
	 * in graphics programming. We need to prepare a matrix to render the view
	 * with. wlr_matrix_project_box is a helper which takes a box with a desired
	 * x, y coordinates, width and height, and an output geometry, then
	 * prepares an orthographic projection and multiplies the necessary
	 * transforms to produce a model-view-projection matrix.
	 *
	 * Naturally you can do this any way you like, for example to make a 3D
	 * compositor.
	 */
	float matrix[9];
	enum wl_output_transform transform = wlr_output_transform_invert(surface->current.transform);
	wlr_matrix_project_box(matrix, &box, transform, 0, output->transform_matrix);

	/* This takes our matrix, the texture, and an alpha, and performs the actual
	 * rendering on the GPU. */
	wlr_render_texture_with_matrix(rdata->renderer, texture, matrix, 1);

	/* This lets the client know that we've displayed that frame and it can
	 * prepare another one now if it likes. */
	wlr_surface_send_frame_done(surface, rdata->when);
}

static void
output_frame(struct wl_listener *listener, void *data)
{
	(void)data;
	/* This function is called every time an output is ready to display a frame,
	 * generally at the output's refresh rate (e.g. 60Hz). */
	struct inaban_output *output  = wl_container_of(listener, output, frame);
	struct wlr_renderer *renderer = output->server->renderer;

	struct timespec now;
	clock_gettime(CLOCK_MONOTONIC, &now);

	/* wlr_output_attach_render makes the OpenGL context current. */
	if(!wlr_output_attach_render(output->wlr_output, NULL)) return;
	/* The "effective" resolution can change if you rotate your outputs. */
	int width, height;
	wlr_output_effective_resolution(output->wlr_output, &width, &height);
	/* Begin the renderer (calls glViewport and some other GL sanity checks) */
	wlr_renderer_begin(renderer, width, height);

	float color[4] = {0.11f, 0.11f, 0.11f, 1.0f}; // approx. gruvbox hard-dark
	wlr_renderer_clear(renderer, color);

	/* Each subsequent window we render is rendered on top of the last. Because
	 * our view list is ordered front-to-back, we iterate over it backwards. */
	struct inaban_view *view;
	wl_list_for_each_reverse(view, &output->server->views, link)
	{
		if(!view->mapped) continue; /* An unmapped view should not be rendered. */
		struct render_data rdata = {
		    .output   = output->wlr_output,
		    .view     = view,
		    .renderer = renderer,
		    .when     = &now,
		};
		/* This calls our render_surface function for each surface among the
		 * xdg_surface's toplevel and popups. */
		wlr_xdg_surface_for_each_surface(view->xdg_surface, render_surface, &rdata);
	}

	/* Hardware cursors are rendered by the GPU on a separate plane, and can be
	 * moved around without re-rendering what's beneath them - which is more
	 * efficient. However, not all hardware supports hardware cursors. For this
	 * reason, wlroots provides a software fallback, which we ask it to render
	 * here. wlr_cursor handles configuring hardware vs software cursors for you,
	 * and this function is a no-op when hardware cursors are in use. */
	wlr_output_render_software_cursors(output->wlr_output, NULL);

	/* Conclude rendering and swap the buffers, showing the final frame
	 * on-screen. */
	wlr_renderer_end(renderer);
	wlr_output_commit(output->wlr_output);
}

void
server_new_output(struct wl_listener *listener, void *data)
{
	/* This event is rasied by the backend when a new output (aka a display or
	 * monitor) becomes available. */
	struct inaban_server *server  = wl_container_of(listener, server, new_output);
	struct wlr_output *wlr_output = data;

	/* Some backends don't have modes. DRM+KMS does, and we need to set a mode
	 * before we can use the output. The mode is a tuple of (width, height,
	 * refresh rate), and each monitor supports only a specific set of modes. We
	 * just pick the first, a more sophisticated compositor would let the user
	 * configure it or pick the mode the display advertises as preferred. */
	if(!wl_list_empty(&wlr_output->modes))
	{
		struct wlr_output_mode *mode = wl_container_of(wlr_output->modes.prev, mode, link);
		wlr_output_set_mode(wlr_output, mode);
	}

	/* Allocates and configures our state for this output */
	struct inaban_output *output = calloc(1, sizeof(struct inaban_output));
	output->wlr_output           = wlr_output;
	output->server               = server;
	/* Sets up a listener for the frame notify event. */
	output->frame.notify = output_frame;
	wl_signal_add(&wlr_output->events.frame, &output->frame);
	wl_list_insert(&server->outputs, &output->link);

	/* Adds this to the output layout. The add_auto function arranges outputs
	 * from left-to-right in the order they appear. A more sophisticated
	 * compositor would let the user configure the arrangement of outputs in the
	 * layout. */
	wlr_output_layout_add_auto(server->output_layout, wlr_output);

	/* Creating the global adds a wl_output global to the display, which Wayland
	 * clients can see to find out information about the output (such as
	 * DPI, scale factor, manufacturer, etc). */
	wlr_output_create_global(wlr_output);
}