render/pass: add legacy render pass implementation

Add a render pass implementation which leverages the legacy
rendering API. This is helpful during the migration.

include/render/pass.h

@@ -0,0 +1,9 @@
+#ifndef RENDER_PASS_H
+#define RENDER_PASS_H
+
+#include <wlr/render/interface.h>
+
+struct wlr_render_pass *begin_legacy_buffer_render_pass(struct wlr_renderer *renderer,
+	struct wlr_buffer *buffer);
+
+#endif

render/pass.c

@@ -1,7 +1,16 @@
 #include <assert.h>
+#include <stdlib.h>
 #include <string.h>
 #include <wlr/render/interface.h>
 #include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_matrix.h>
+#include "render/pass.h"
+
+struct wlr_render_pass_legacy {
+	struct wlr_render_pass base;
+	struct wlr_renderer *renderer;
+	int width, height;
+};
 
 void wlr_render_pass_init(struct wlr_render_pass *render_pass,
 		const struct wlr_render_pass_impl *impl) {
@@ -50,3 +59,126 @@ float wlr_render_texture_options_get_alpha(const struct wlr_render_texture_optio
 	}
 	return *options->alpha;
 }
+
+static const struct wlr_render_pass_impl legacy_impl;
+
+static struct wlr_render_pass_legacy *legacy_pass_from_pass(struct wlr_render_pass *pass) {
+	assert(pass->impl == &legacy_impl);
+	struct wlr_render_pass_legacy *legacy = wl_container_of(pass, legacy, base);
+	return legacy;
+}
+
+static bool legacy_submit(struct wlr_render_pass *wlr_pass) {
+	struct wlr_render_pass_legacy *pass = legacy_pass_from_pass(wlr_pass);
+	wlr_renderer_end(pass->renderer);
+	free(pass);
+	return true;
+}
+
+static void get_clip_region(struct wlr_render_pass_legacy *pass,
+		const pixman_region32_t *in, pixman_region32_t *out) {
+	if (in != NULL) {
+		pixman_region32_init(out);
+		pixman_region32_copy(out, in);
+	} else {
+		pixman_region32_init_rect(out, 0, 0, pass->width, pass->height);
+	}
+}
+
+static void scissor(struct wlr_renderer *renderer, const pixman_box32_t *rect) {
+	struct wlr_box box = {
+		.x = rect->x1,
+		.y = rect->y1,
+		.width = rect->x2 - rect->x1,
+		.height = rect->y2 - rect->y1,
+	};
+	wlr_renderer_scissor(renderer, &box);
+}
+
+static void legacy_add_texture(struct wlr_render_pass *wlr_pass,
+		const struct wlr_render_texture_options *options) {
+	struct wlr_render_pass_legacy *pass = legacy_pass_from_pass(wlr_pass);
+	struct wlr_texture *texture = options->texture;
+
+	struct wlr_fbox src_box;
+	wlr_render_texture_options_get_src_box(options, &src_box);
+	struct wlr_box dst_box;
+	wlr_render_texture_options_get_dst_box(options, &dst_box);
+	float alpha = wlr_render_texture_options_get_alpha(options);
+
+	float proj[9], matrix[9];
+	wlr_matrix_identity(proj);
+	wlr_matrix_project_box(matrix, &dst_box, options->transform, 0.0, proj);
+
+	pixman_region32_t clip;
+	get_clip_region(pass, options->clip, &clip);
+
+	int rects_len = 0;
+	const pixman_box32_t *rects = pixman_region32_rectangles(&clip, &rects_len);
+	for (int i = 0; i < rects_len; i++) {
+		scissor(pass->renderer, &rects[i]);
+		wlr_render_subtexture_with_matrix(pass->renderer, texture, &src_box, matrix, alpha);
+	}
+
+	wlr_renderer_scissor(pass->renderer, NULL);
+	pixman_region32_fini(&clip);
+}
+
+static void legacy_add_rect(struct wlr_render_pass *wlr_pass,
+		const struct wlr_render_rect_options *options) {
+	struct wlr_render_pass_legacy *pass = legacy_pass_from_pass(wlr_pass);
+
+	float proj[9], matrix[9];
+	wlr_matrix_identity(proj);
+	wlr_matrix_project_box(matrix, &options->box, WL_OUTPUT_TRANSFORM_NORMAL, 0.0, proj);
+
+	pixman_region32_t clip;
+	get_clip_region(pass, options->clip, &clip);
+
+	float color[4] = {
+		options->color.r,
+		options->color.g,
+		options->color.b,
+		options->color.a,
+	};
+
+	int rects_len = 0;
+	const pixman_box32_t *rects = pixman_region32_rectangles(&clip, &rects_len);
+	for (int i = 0; i < rects_len; i++) {
+		scissor(pass->renderer, &rects[i]);
+		wlr_render_quad_with_matrix(pass->renderer, color, matrix);
+	}
+
+	wlr_renderer_scissor(pass->renderer, NULL);
+	pixman_region32_fini(&clip);
+}
+
+static const struct wlr_render_pass_impl legacy_impl = {
+	.submit = legacy_submit,
+	.add_texture = legacy_add_texture,
+	.add_rect = legacy_add_rect,
+};
+
+struct wlr_render_pass *begin_legacy_buffer_render_pass(struct wlr_renderer *renderer,
+		struct wlr_buffer *buffer) {
+	if (renderer->rendering) {
+		return NULL;
+	}
+
+	struct wlr_render_pass_legacy *pass = calloc(1, sizeof(*pass));
+	if (pass == NULL) {
+		return NULL;
+	}
+
+	wlr_render_pass_init(&pass->base, &legacy_impl);
+	pass->renderer = renderer;
+	pass->width = buffer->width;
+	pass->height = buffer->height;
+
+	if (!wlr_renderer_begin_with_buffer(renderer, buffer)) {
+		free(pass);
+		return NULL;
+	}
+
+	return &pass->base;
+}

render/wlr_renderer.c

@@ -27,6 +27,7 @@
 #endif // WLR_HAS_VULKAN_RENDERER
 
 #include "backend/backend.h"
+#include "render/pass.h"
 #include "render/pixel_format.h"
 #include "render/wlr_renderer.h"
 #include "util/env.h"
@@ -415,7 +416,7 @@ int wlr_renderer_get_drm_fd(struct wlr_renderer *r) {
 struct wlr_render_pass *wlr_renderer_begin_buffer_pass(
 		struct wlr_renderer *renderer, struct wlr_buffer *buffer) {
 	if (!renderer->impl->begin_buffer_pass) {
-		return NULL;
+		return begin_legacy_buffer_render_pass(renderer, buffer);
 	}
 	return renderer->impl->begin_buffer_pass(renderer, buffer);
 }