surface: add wlr_surface.opaque_region

include/wlr/types/wlr_surface.h

@@ -66,6 +66,12 @@ struct wlr_surface {
 	 * just like the buffer's texture.
 	 */
 	pixman_region32_t buffer_damage;
+	/**
+	 * The current opaque region, in surface-local coordinates. It is clipped to
+	 * the surface bounds. If the surface's buffer is using a fully opaque
+	 * format, this is set to the whole surface.
+	 */
+	pixman_region32_t opaque_region;
 	/**
 	 * `current` contains the current, committed surface state. `pending`
 	 * accumulates state changes from the client between commits and shouldn't

types/wlr_surface.c

@@ -340,6 +340,25 @@ static void surface_apply_damage(struct wlr_surface *surface) {
 	surface->buffer = buffer;
 }
 
+static void surface_update_opaque_region(struct wlr_surface *surface) {
+	struct wlr_texture *texture = wlr_surface_get_texture(surface);
+	if (texture == NULL) {
+		pixman_region32_clear(&surface->opaque_region);
+		return;
+	}
+
+	if (wlr_texture_is_opaque(texture)) {
+		pixman_region32_init_rect(&surface->opaque_region,
+			0, 0, surface->current.width, surface->current.height);
+		return;
+	}
+
+	pixman_region32_copy(&surface->opaque_region, &surface->current.opaque);
+	pixman_region32_intersect_rect(&surface->opaque_region,
+		&surface->opaque_region,
+		0, 0, surface->current.width, surface->current.height);
+}
+
 static void surface_commit_pending(struct wlr_surface *surface) {
 	bool invalid_buffer = surface->pending.committed & WLR_SURFACE_STATE_BUFFER;
 
@@ -356,6 +375,7 @@ static void surface_commit_pending(struct wlr_surface *surface) {
 	if (invalid_buffer) {
 		surface_apply_damage(surface);
 	}
+	surface_update_opaque_region(surface);
 
 	// commit subsurface order
 	struct wlr_subsurface *subsurface;
@@ -562,6 +582,7 @@ static void surface_handle_resource_destroy(struct wl_resource *resource) {
 	surface_state_finish(&surface->current);
 	surface_state_finish(&surface->previous);
 	pixman_region32_fini(&surface->buffer_damage);
+	pixman_region32_fini(&surface->opaque_region);
 	wlr_buffer_unref(surface->buffer);
 	free(surface);
 }
@@ -607,6 +628,7 @@ struct wlr_surface *wlr_surface_create(struct wl_client *client,
 	wl_list_init(&surface->subsurfaces);
 	wl_list_init(&surface->subsurface_pending_list);
 	pixman_region32_init(&surface->buffer_damage);
+	pixman_region32_init(&surface->opaque_region);
 
 	wl_signal_add(&renderer->events.destroy, &surface->renderer_destroy);
 	surface->renderer_destroy.notify = surface_handle_renderer_destroy;