window: Don't needlessly sync parent and geometry

When a toytoolkit client redraws, the toolkit syncs the parent and
geometry. If a client redraws often (such as the terminal drawing a huge
amount of output), this can spam the compositor with requests and may
result in the client's eventual being killed.

We don't need to send requests for changing the geometry or parent if
these haven't changed. So remember the last geometry and parent, and
update them only if needed.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=83297
Signed-off-by: Ondřej Majerech <majerech.o@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

clients/window.c

@@ -217,6 +217,7 @@ struct window {
 	struct rectangle saved_allocation;
 	struct rectangle min_allocation;
 	struct rectangle pending_allocation;
+	struct rectangle last_geometry;
 	int x, y;
 	int redraw_needed;
 	int redraw_task_scheduled;
@@ -246,6 +247,7 @@ struct window {
 	struct xdg_popup *xdg_popup;
 
 	struct window *parent;
+	struct wl_surface *last_parent_surface;
 
 	struct window_frame *frame;
 
@@ -3993,7 +3995,11 @@ window_sync_parent(struct window *window)
 	else
 		parent_surface = NULL;
 
+	if (parent_surface == window->last_parent_surface)
+		return;
+
 	xdg_surface_set_parent(window->xdg_surface, parent_surface);
+	window->last_parent_surface = parent_surface;
 }
 
 static void
@@ -4018,12 +4024,18 @@ window_sync_geometry(struct window *window)
 		return;
 
 	window_get_geometry(window, &geometry);
+	if (geometry.x == window->last_geometry.x &&
+	    geometry.y == window->last_geometry.y &&
+	    geometry.width == window->last_geometry.width &&
+	    geometry.height == window->last_geometry.height)
+		return;
 
 	xdg_surface_set_window_geometry(window->xdg_surface,
 					geometry.x,
 					geometry.y,
 					geometry.width,
 					geometry.height);
+	window->last_geometry = geometry;
 }
 
 static void