wlr_scene: Don't render non visible parts of textures/rects

We can also get rid of the intersection checks in the rendering functions
because we are guaranteed to already be in the node do to the prior
intersection checking of the node visibility.

types/scene/wlr_scene.c

@@ -932,28 +932,21 @@ static void scissor_output(struct wlr_output *output, pixman_box32_t *rect) {
 }
 
 static void render_rect(struct wlr_output *output,
-		pixman_region32_t *output_damage, const float color[static 4],
+		pixman_region32_t *damage, const float color[static 4],
 		const struct wlr_box *box, const float matrix[static 9]) {
 	struct wlr_renderer *renderer = output->renderer;
 	assert(renderer);
 
-	pixman_region32_t damage;
-	pixman_region32_init(&damage);
-	pixman_region32_init_rect(&damage, box->x, box->y, box->width, box->height);
-	pixman_region32_intersect(&damage, &damage, output_damage);
-
 	int nrects;
-	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
+	pixman_box32_t *rects = pixman_region32_rectangles(damage, &nrects);
 	for (int i = 0; i < nrects; ++i) {
 		scissor_output(output, &rects[i]);
 		wlr_render_rect(renderer, box, color, matrix);
 	}
-
-	pixman_region32_fini(&damage);
 }
 
 static void render_texture(struct wlr_output *output,
-		pixman_region32_t *output_damage, struct wlr_texture *texture,
+		pixman_region32_t *damage, struct wlr_texture *texture,
 		const struct wlr_fbox *src_box, const struct wlr_box *dst_box,
 		const float matrix[static 9]) {
 	struct wlr_renderer *renderer = output->renderer;
@@ -966,20 +959,12 @@ static void render_texture(struct wlr_output *output,
 		src_box = &default_src_box;
 	}
 
-	pixman_region32_t damage;
-	pixman_region32_init(&damage);
-	pixman_region32_init_rect(&damage, dst_box->x, dst_box->y,
-		dst_box->width, dst_box->height);
-	pixman_region32_intersect(&damage, &damage, output_damage);
-
 	int nrects;
-	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
+	pixman_box32_t *rects = pixman_region32_rectangles(damage, &nrects);
 	for (int i = 0; i < nrects; ++i) {
 		scissor_output(output, &rects[i]);
 		wlr_render_subtexture_with_matrix(renderer, texture, src_box, matrix, 1.0);
 	}
-
-	pixman_region32_fini(&damage);
 }
 
 struct render_data {
@@ -992,7 +977,17 @@ static void render_node_iterator(struct wlr_scene_node *node,
 	struct render_data *data = _data;
 	struct wlr_scene_output *scene_output = data->scene_output;
 	struct wlr_output *output = scene_output->output;
-	pixman_region32_t *output_damage = data->damage;
+
+	pixman_region32_t render_region;
+	pixman_region32_init(&render_region);
+	pixman_region32_copy(&render_region, &node->visible);
+	pixman_region32_translate(&render_region, -scene_output->x, -scene_output->y);
+	wlr_region_scale(&render_region, &render_region, output->scale);
+	pixman_region32_intersect(&render_region, &render_region, data->damage);
+	if (!pixman_region32_not_empty(&render_region)) {
+		pixman_region32_fini(&render_region);
+		return;
+	}
 
 	struct wlr_box dst_box = {
 		.x = x,
@@ -1011,7 +1006,7 @@ static void render_node_iterator(struct wlr_scene_node *node,
 	case WLR_SCENE_NODE_RECT:;
 		struct wlr_scene_rect *scene_rect = scene_rect_from_node(node);
 
-		render_rect(output, output_damage, scene_rect->color, &dst_box,
+		render_rect(output, &render_region, scene_rect->color, &dst_box,
 			output->transform_matrix);
 		break;
 	case WLR_SCENE_NODE_BUFFER:;
@@ -1030,12 +1025,14 @@ static void render_node_iterator(struct wlr_scene_node *node,
 		wlr_matrix_project_box(matrix, &dst_box, transform, 0.0,
 			output->transform_matrix);
 
-		render_texture(output, output_damage, texture, &scene_buffer->src_box,
+		render_texture(output, &render_region, texture, &scene_buffer->src_box,
 			&dst_box, matrix);
 
 		wlr_signal_emit_safe(&scene_buffer->events.output_present, scene_output);
 		break;
 	}
+
+	pixman_region32_fini(&render_region);
 }
 
 static void scene_node_for_each_node(struct wlr_scene_node *node,