From: asxpi <asxpi@narayana.im>
Subject: [PATCH] wayland/touch: Forget a touch point once it is cancelled

Jonas Ådahl's proposal on mutter!5375 (note 2904581), completed so it
builds: meta_wayland_touch_cancel() takes the event, and on
CLUTTER_TOUCH_CANCEL the cancelled sequence leaves touch->touches, so no
stale MetaWaylandTouchInfo (focus_surface NULL, slot_serial still set)
is left for touch_can_grab_surface() to find. The other callers cancel
every touch and have no event; they pass NULL and keep today's
behaviour.

LOCAL TEST ONLY: the g_message says which path cancelled, to tell
whether the Tauri double xdg_toplevel.resize goes through
CLUTTER_TOUCH_CANCEL or through the seat's focus change.

Upstream: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/5375#note_2904581
---
--- a/src/wayland/meta-wayland-touch.c
+++ b/src/wayland/meta-wayland-touch.c
@@ -524,7 +524,7 @@
       break;

     case CLUTTER_TOUCH_CANCEL:
-      meta_wayland_touch_cancel (touch);
+      meta_wayland_touch_cancel (touch, event);
       break;

     default:
@@ -561,7 +561,8 @@
 }

 void
-meta_wayland_touch_cancel (MetaWaylandTouch *touch)
+meta_wayland_touch_cancel (MetaWaylandTouch   *touch,
+                           const ClutterEvent *event)
 {
   MetaWaylandInputDevice *input_device = META_WAYLAND_INPUT_DEVICE (touch);
   MetaWaylandSeat *seat = meta_wayland_input_device_get_seat (input_device);
@@ -572,6 +573,9 @@
   if (!meta_wayland_seat_has_touch (seat))
     return;

+  g_message ("touch cancel via %s",
+             event ? "CLUTTER_TOUCH_CANCEL" : "focus change or disable");
+
   surfaces = s = touch_get_surfaces (touch, FALSE);

   for (s = surfaces; s; s = s->next)
@@ -589,6 +593,10 @@
   while (g_hash_table_iter_next (&iter, NULL, (gpointer*) &touch_info))
     g_clear_pointer (&touch_info->focus_surface, touch_surface_decrement_touch);
   g_list_free (surfaces);
+
+  if (event)
+    g_hash_table_remove (touch->touches,
+                         clutter_event_get_event_sequence (event));
 }

 void
@@ -607,7 +615,7 @@
 void
 meta_wayland_touch_disable (MetaWaylandTouch *touch)
 {
-  meta_wayland_touch_cancel (touch);
+  meta_wayland_touch_cancel (touch, NULL);

   g_clear_pointer (&touch->touches, g_hash_table_unref);
   g_clear_pointer (&touch->touch_surfaces, g_hash_table_unref);
--- a/src/wayland/meta-wayland-touch.h
+++ b/src/wayland/meta-wayland-touch.h
@@ -61,7 +61,8 @@
                                              struct wl_client   *client,
                                              struct wl_resource *seat_resource,
                                              uint32_t            id);
-void meta_wayland_touch_cancel (MetaWaylandTouch *touch);
+void meta_wayland_touch_cancel (MetaWaylandTouch   *touch,
+                                const ClutterEvent *event);


 ClutterEventSequence * meta_wayland_touch_find_grab_sequence (MetaWaylandTouch    *touch,
--- a/src/wayland/meta-wayland-seat.c
+++ b/src/wayland/meta-wayland-seat.c
@@ -259,7 +259,7 @@
         sequence = clutter_sprite_get_sequence (CLUTTER_SPRITE (focus));

         if (surface != meta_wayland_touch_get_focus_surface (seat->touch, sequence))
-          meta_wayland_touch_cancel (seat->touch);
+          meta_wayland_touch_cancel (seat->touch, NULL);

         break;
       }
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -608,7 +608,7 @@
   MetaWaylandCompositor *compositor;

   compositor = wayland_compositor_from_display (display);
-  meta_wayland_touch_cancel (compositor->seat->touch);
+  meta_wayland_touch_cancel (compositor->seat->touch, NULL);
 }

 static void