xwayland/window: Queue damage after commits are allowed

Compositors may use XWAYLAND_ALLOW_COMMITS to communicate when Xwayland
may or may not commit new buffers to a wl_surface. If commits are
denied, then later allowed, we'll only get a buffer attached if there is
actual damage posted, which might be long after.

This fixes an issue where the window manager would reparent a window
while denying commits, then after reparenting, allow commits. The window
in question belonged to a game and took several seconds produce the next
frame, resulting in an empty window appearing as if it had just
disappeared.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
(cherry picked from commit 9a55c402aa)

hw/xwayland/xwayland-window.c

@@ -102,9 +102,21 @@ static void
 xwl_window_set_allow_commits(struct xwl_window *xwl_window, Bool allow,
                              const char *debug_msg)
 {
+    struct xwl_screen *xwl_screen = xwl_window->xwl_screen;
+    DamagePtr damage;
+
     xwl_window->allow_commits = allow;
     DebugF("XWAYLAND: win %d allow_commits = %d (%s)\n",
            xwl_window->window->drawable.id, allow, debug_msg);
+
+    damage = window_get_damage(xwl_window->window);
+    if (allow &&
+        xorg_list_is_empty(&xwl_window->link_damage) &&
+        damage &&
+        RegionNotEmpty(DamageRegion(damage))) {
+        xorg_list_add(&xwl_window->link_damage,
+                      &xwl_screen->damage_window_list);
+    }
 }
 
 static void