From c85fb107c0556283062f2bf9b8d990f1e2c0acae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Tue, 29 Oct 2019 17:14:43 +0100
Subject: [PATCH] window-props: Don't look for parent multiple times

Once we set the transient_for, we look for parent MetaWindow, so instead
of overwriting this value for loops check, just use another function
and avoid to look for the xwindow again when setting the MetaWindow parent.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/895
---
 src/x11/window-props.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/src/x11/window-props.c b/src/x11/window-props.c
index 48454befe..2564909a9 100644
--- a/src/x11/window-props.c
+++ b/src/x11/window-props.c
@@ -1625,6 +1625,22 @@ reload_wm_hints (MetaWindow    *window,
   meta_window_queue (window, META_QUEUE_UPDATE_ICON | META_QUEUE_MOVE_RESIZE);
 }
 
+static gboolean
+check_xtransient_for_loop (MetaWindow *window,
+                           MetaWindow *parent)
+{
+  while (parent)
+    {
+      if (parent == window)
+        return TRUE;
+
+      parent = meta_x11_display_lookup_x_window (parent->display->x11_display,
+                                                 parent->xtransient_for);
+    }
+
+  return FALSE;
+}
+
 static void
 reload_transient_for (MetaWindow    *window,
                       MetaPropValue *value,
@@ -1647,18 +1663,11 @@ reload_transient_for (MetaWindow    *window,
         }
 
       /* Make sure there is not a loop */
-      while (parent)
+      if (check_xtransient_for_loop (window, parent))
         {
-          if (parent == window)
-            {
-              meta_warning ("WM_TRANSIENT_FOR window 0x%lx for %s would create loop.\n",
-                            transient_for, window->desc);
-              transient_for = None;
-              break;
-            }
-
-          parent = meta_x11_display_lookup_x_window (parent->display->x11_display,
-                                                     parent->xtransient_for);
+          meta_warning ("WM_TRANSIENT_FOR window 0x%lx for %s would create a "
+                        "loop.\n", transient_for, window->desc);
+          transient_for = None;
         }
     }
   else
@@ -1679,8 +1688,6 @@ reload_transient_for (MetaWindow    *window,
     meta_window_set_transient_for (window, NULL);
   else
     {
-      parent = meta_x11_display_lookup_x_window (window->display->x11_display,
-                                                 window->xtransient_for);
       meta_window_set_transient_for (window, parent);
     }
 }