window: Stop storing xtransient_for field

Instead retrieve the associated Window from the xwindow property.
Avoids having a vfunc to handle the get_transient_for differences
between Wayland and x11

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3211>

src/core/window-private.h

@@ -203,7 +203,6 @@ struct _MetaWindow
   char *gtk_app_menu_object_path;
   char *gtk_menubar_object_path;
 
-  Window xtransient_for;
   MetaWindow *transient_for;
 
   /* Initial workspace property */

src/core/window.c

@@ -1103,8 +1103,6 @@ meta_window_constructed (GObject *object)
   window->has_valid_cgroup = TRUE;
   window->cgroup_path = NULL;
 
-  window->xtransient_for = None;
-
   window->type = META_WINDOW_NORMAL;
 
   window->struts = NULL;
@@ -6709,13 +6707,7 @@ meta_window_get_transient_for (MetaWindow *window)
 {
   g_return_val_if_fail (META_IS_WINDOW (window), NULL);
 
-  if (window->transient_for)
   return window->transient_for;
-  else if (window->xtransient_for)
-    return meta_x11_display_lookup_x_window (window->display->x11_display,
-                                             window->xtransient_for);
-  else
-    return NULL;
 }
 
 /**

src/x11/window-props.c

@@ -1683,7 +1683,7 @@ check_xtransient_for_loop (MetaWindow *window,
         return TRUE;
 
       parent = meta_x11_display_lookup_x_window (parent->display->x11_display,
-                                                 parent->xtransient_for);
+                                                 meta_window_x11_get_xtransient_for (parent));
     }
 
   return FALSE;
@@ -1695,7 +1695,7 @@ reload_transient_for (MetaWindow    *window,
                       gboolean       initial)
 {
   MetaWindow *parent = NULL;
-  Window transient_for;
+  Window transient_for, current_transient_for;
 
   if (value->type != META_PROP_VALUE_INVALID)
     {
@@ -1713,8 +1713,8 @@ reload_transient_for (MetaWindow    *window,
         {
           const gchar *window_kind = window->override_redirect ?
                                      "override-redirect" : "top-level";
-
+          Window parent_xtransient_for = meta_window_x11_get_xtransient_for (parent);
-          if (parent->xtransient_for != None)
+          if (parent_xtransient_for != None)
             {
               /* We don't have to go through the parents, as per this code it is
                * not possible that a window has the WM_TRANSIENT_FOR set to an
@@ -1724,8 +1724,8 @@ reload_transient_for (MetaWindow    *window,
                             "according to the standard, so we'll fallback to "
                             "the first non-override-redirect window 0x%lx.",
                             parent->desc, window->desc, window_kind,
-                            parent->xtransient_for);
+                            parent_xtransient_for);
-              transient_for = parent->xtransient_for;
+              transient_for = parent_xtransient_for;
               parent =
                 meta_x11_display_lookup_x_window (parent->display->x11_display,
                                                   transient_for);
@@ -1753,18 +1753,19 @@ reload_transient_for (MetaWindow    *window,
   else
     transient_for = None;
 
-  if (transient_for == window->xtransient_for)
+  current_transient_for = meta_window_x11_get_xtransient_for (window);
+  if (transient_for == current_transient_for)
     return;
 
-  window->xtransient_for = transient_for;
 
-  if (window->xtransient_for != None)
+  current_transient_for = transient_for;
-    meta_verbose ("Window %s transient for 0x%lx", window->desc, window->xtransient_for);
+  if (current_transient_for != None)
+    meta_verbose ("Window %s transient for 0x%lx", window->desc, current_transient_for);
   else
     meta_verbose ("Window %s is not transient", window->desc);
 
-  if (window->xtransient_for == None ||
+  if (current_transient_for == None ||
-      window->xtransient_for == window->display->x11_display->xroot)
+      current_transient_for == window->display->x11_display->xroot)
     meta_window_set_transient_for (window, NULL);
   else
     {

src/x11/window-x11-private.h

@@ -98,4 +98,6 @@ Window meta_window_x11_get_xgroup_leader (MetaWindow *window);
 
 Window meta_window_x11_get_user_time_window (MetaWindow *window);
 
+Window meta_window_x11_get_xtransient_for (MetaWindow *window);
+
 G_END_DECLS

src/x11/window-x11.c

@@ -2005,6 +2005,7 @@ meta_window_x11_set_transient_for (MetaWindow *window,
   MetaWindowX11 *window_x11 = META_WINDOW_X11 (window);
   MetaWindowX11Private *priv =
     meta_window_x11_get_instance_private (window_x11);
+  Window xtransient_for;
 
   meta_window_x11_recalc_window_type (window);
   if (!window->constructing)
@@ -2030,9 +2031,10 @@ meta_window_x11_set_transient_for (MetaWindow *window,
    * equivalent to making it your group leader, to work around shortcomings
    * in programs such as xmms-- see #328211.
    */
-  if (window->xtransient_for != None &&
+  xtransient_for = meta_window_x11_get_xtransient_for (window);
+  if (xtransient_for != None &&
       priv->xgroup_leader != None &&
-      window->xtransient_for != priv->xgroup_leader)
+      xtransient_for != priv->xgroup_leader)
     meta_window_group_leader_changed (window);
 
   return TRUE;
@@ -4447,3 +4449,17 @@ meta_window_x11_get_user_time_window (MetaWindow *window)
 
   return priv->user_time_window;
 }
+
+Window
+meta_window_x11_get_xtransient_for (MetaWindow *window)
+{
+  MetaWindow *transient_for;
+
+  g_return_val_if_fail (META_IS_WINDOW (window), None);
+
+  transient_for = meta_window_get_transient_for (window);
+  if (transient_for)
+    return meta_window_x11_get_xwindow (transient_for);
+
+  return None;
+}