[metacity/wip/muktupavels/issue-18] window-props: don't set override-redirect window as parent

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 2bbce9f21abbd166d314d1b3346905bb4e234087
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Jun 21 18:30:21 2021 +0300

    window-props: don't set override-redirect window as parent
    
    Before commit c656c658940d override-redirect windows was not
    registered with meta_display_register_x_window. This means
    that Metacity was treating WM_TRANSIENT_FOR hint as invalid
    if it was pointing to override-redirect window.
    
    EWMH specification [1] says that WM_TRANSIENT_FOR property is
    defined for managed windows and extends its usage for
    override-redirect windows. Client should set WM_TRANSIENT_FOR
    on override-redirect window if it is child/popup for another
    window.
    
    As specification does not say anyting about using
    override-redirect windows as parent for managed windows and
    because it causes crashes in Metacity ignore WM_TRANSIENT_FOR
    if it is pointing to override-redirect window.
    
    [1] https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#idm46291029654544
    
    https://gitlab.gnome.org/GNOME/metacity/-/issues/18

 src/core/window-props.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/src/core/window-props.c b/src/core/window-props.c
index a6ad2b03..680b236b 100644
--- a/src/core/window-props.c
+++ b/src/core/window-props.c
@@ -1603,6 +1603,16 @@ reload_transient_for (MetaWindow    *window,
                      transient_for, window->desc);
           transient_for = None;
         }
+      else if (parent->override_redirect)
+        {
+          g_warning ("Ignoring WM_TRANSIENT_FOR for %s because it is pointing "
+                     "to override-redirect window %s.",
+                     window->desc,
+                     parent->desc);
+
+          transient_for = None;
+          parent = NULL;
+        }
 
       /* Make sure there is not a loop */
       while (parent)