[mutter] window: unmanage dialog when clearing transient_for

[Jonas Ådahl <jadahl src gnome org>]

commit b443bd42ac738092817addf48e0b363d140cad26
Author: Olivier Fourdan <ofourdan redhat com>
Date:   Tue Jul 10 16:42:42 2018 +0200

    window: unmanage dialog when clearing transient_for
    
    On Wayland, xdg-foreign would leave a modal dialog managed even after
    the imported surface is destroyed.
    
    This is sub-optimal and this breaks the atomic relationship one would
    expect between the parent and its modal dialog.
    
    Make sure we unmanage the dialog if transient_for is unset even for
    Wayland native windows.
    
    Related: https://gitlab.gnome.org/GNOME/mutter/issues/174
    Related: https://gitlab.gnome.org/GNOME/mutter/issues/221

 src/core/window.c | 8 ++++++++
 1 file changed, 8 insertions(+)
---
diff --git a/src/core/window.c b/src/core/window.c
index c06f52c86..a0a986e79 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -7987,7 +7987,15 @@ meta_window_set_transient_for (MetaWindow *window,
             }
         }
     }
+  else if (window->attached && parent == NULL)
+    {
+      guint32 timestamp;
 
+      timestamp =
+        meta_display_get_current_time_roundtrip (window->display);
+      meta_window_unmanage (window, timestamp);
+      return;
+    }
   /* We know this won't create a reference cycle because we check for loops */
   g_clear_object (&window->transient_for);
   window->transient_for = parent ? g_object_ref (parent) : NULL;