[mutter/wip/carlosg/theres-no-end] wayland: Warn and fix accounting on missed CLUTTER_TOUCH_END events

[Carlos Garnacho <carlosg src gnome org>]

commit 6e0939ac24f71db211ad7163d7bac6d16bde964a
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

 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 15f0312eb3..0280195e8e 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);