[mutter/gnome-40] wayland: Warn and fix accounting on missed CLUTTER_TOUCH_END events

[Robert Mader <rmader src gnome org>]

commit 6658e125300c724e2422a089bd2a266fcbd0efc6
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Jan 17 13:18:53 2022 +0100

    wayland: Warn and fix accounting on missed CLUTTER_TOUCH_END events
    
    If we happen to handle a CLUTTER_TOUCH_BEGIN without a corresponding
    CLUTTER_TOUCH_END at MetaWaylandTouch, we would still attempt to
    reuse the older MetaWaylandTouchInfo, resulting in an assert triggered
    as there is a stale touch reference on the previous surface.
    
    Warn in place and create a new touch info struct to still fix the
    broken surface accounting, instead of finding out the hard
    way after the surface is destroyed. The assert is preserved to ensure
    the accounting does not sneakily break anymore/further.
    
    Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/584
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2251>
    
    (cherry picked from commit 7bf10de53847d974f38caa663057b8c0a2ed2e38)

 src/wayland/meta-wayland-touch.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/src/wayland/meta-wayland-touch.c b/src/wayland/meta-wayland-touch.c
index 002ff16f72..730a054c91 100644
--- a/src/wayland/meta-wayland-touch.c
+++ b/src/wayland/meta-wayland-touch.c
@@ -177,8 +177,11 @@ touch_get_info (MetaWaylandTouch     *touch,
 
   touch_info = g_hash_table_lookup (touch->touches, sequence);
 
-  if (!touch_info && create)
+  if (create)
     {
+      if (touch_info != NULL)
+        g_warning ("Stale touch information for sequence slot %p", sequence);
+
       touch_info = g_new0 (MetaWaylandTouchInfo, 1);
       touch_info->slot = clutter_event_sequence_get_slot (sequence);
       g_hash_table_insert (touch->touches, sequence, touch_info);