clutter: Always snoop key events for a11y

In the case a11y is required, the screen reader is very much
interested in getting an uninterrupted flow of key events. It attempts
so by setting a ::captured-event callback on the ClutterStage, but
that falls short with our MetaDisplay event handler, as clutter events
can be stopped before a11y gets a chance to see them.

This kind of selective amnesia wrt key events is not new, in X11 those
go unheard of by the WM as long as a client is focused and no grabs hold,
so it is clients' responsibility to talk with AT bridge.

This commit doesn't yet change that for X11, but we can do this right
away from the compositor on Wayland, and without any chance to be
tampered by clients.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1328>

clutter/clutter/cally/cally-util.c

@@ -60,17 +60,6 @@ static const gchar *         cally_util_get_toolkit_name		    (void);
 static const gchar *         cally_util_get_toolkit_version          (void);
 
 /* private */
-static void                  cally_util_simulate_snooper_install     (void);
-static void                  cally_util_simulate_snooper_remove      (void);
-static gboolean              cally_key_snooper                       (ClutterActor *actor,
-                                                                      ClutterEvent *event,
-                                                                      gpointer      user_data);
-static void                  cally_util_stage_added_cb               (ClutterStageManager *stage_manager,
-                                                                      ClutterStage *stage,
-                                                                      gpointer data);
-static void                  cally_util_stage_removed_cb             (ClutterStageManager *stage_manager,
-                                                                      ClutterStage *stage,
-                                                                      gpointer data);
 static gboolean              notify_hf                               (gpointer key,
                                                                       gpointer value,
                                                                       gpointer data);
@@ -153,12 +142,8 @@ cally_util_add_key_event_listener (AtkKeySnoopFunc  listener,
   CallyKeyEventInfo *event_info = NULL;
 
   if (!key_listener_list)
-  {
     key_listener_list = g_hash_table_new_full (NULL, NULL, NULL, g_free);
 
-    cally_util_simulate_snooper_install ();
-  }
-
   event_info = g_new (CallyKeyEventInfo, 1);
   event_info->listener = listener;
   event_info->func_data = data;
@@ -179,75 +164,11 @@ cally_util_remove_key_event_listener (guint remove_listener)
     {
       g_hash_table_destroy (key_listener_list);
       key_listener_list = NULL;
-      cally_util_simulate_snooper_remove ();
     }
 }
 
 /* ------------------------------ PRIVATE FUNCTIONS ------------------------- */
 
-/* Trying to emulate gtk_key_snooper install (a kind of wrapper). This
-   could be implemented without it, but I will maintain it in this
-   way, so if in the future clutter implements it natively it would be
-   easier the transition */
-static void
-cally_util_simulate_snooper_install (void)
-{
-  ClutterStageManager *stage_manager = NULL;
-  ClutterStage *stage = NULL;
-  GSList *stage_list = NULL;
-  GSList *iter = NULL;
-
-  stage_manager = clutter_stage_manager_get_default ();
-  stage_list = clutter_stage_manager_list_stages (stage_manager);
-
-  for (iter = stage_list; iter != NULL; iter = g_slist_next (iter))
-    {
-      stage = CLUTTER_STAGE (iter->data);
-
-      g_signal_connect (G_OBJECT (stage), "captured-event",
-                        G_CALLBACK (cally_key_snooper), NULL);
-    }
-
-  g_signal_connect (G_OBJECT (stage_manager), "stage-added",
-                    G_CALLBACK (cally_util_stage_added_cb), cally_key_snooper);
-  g_signal_connect (G_OBJECT (stage_manager), "stage-removed",
-                    G_CALLBACK (cally_util_stage_removed_cb), cally_key_snooper);
-
-  g_slist_free (stage_list);
-}
-
-static void
-cally_util_simulate_snooper_remove (void)
-{
-  ClutterStageManager *stage_manager = NULL;
-  ClutterStage *stage = NULL;
-  GSList *stage_list = NULL;
-  GSList *iter = NULL;
-  gint num = 0;
-
-  stage_manager = clutter_stage_manager_get_default ();
-  stage_list = clutter_stage_manager_list_stages (stage_manager);
-
-  for (iter = stage_list; iter != NULL; iter = g_slist_next (iter))
-    {
-      stage = CLUTTER_STAGE (iter->data);
-
-      num += g_signal_handlers_disconnect_by_func (stage, cally_key_snooper, NULL);
-    }
-
-  g_signal_handlers_disconnect_by_func (G_OBJECT (stage_manager),
-                                        G_CALLBACK (cally_util_stage_added_cb),
-                                        cally_key_snooper);
-
-  g_signal_handlers_disconnect_by_func (G_OBJECT (stage_manager),
-                                        G_CALLBACK (cally_util_stage_removed_cb),
-                                        cally_key_snooper);
-
-#ifdef CALLY_DEBUG
-  g_print ("Number of snooper callbacks disconnected: %i\n", num);
-#endif
-}
-
 static AtkKeyEventStruct *
 atk_key_event_from_clutter_event_key (ClutterKeyEvent *clutter_event,
                                       gunichar         password_char)
@@ -384,59 +305,34 @@ check_key_visibility (ClutterEvent *event)
     return DEFAULT_PASSWORD_CHAR;
 }
 
-static gboolean
+gboolean
-cally_key_snooper (ClutterActor *actor,
+cally_snoop_key_event (ClutterKeyEvent *key)
-                   ClutterEvent *event,
-                   gpointer      user_data)
 {
+  ClutterEvent *event = (ClutterEvent *) key;
   AtkKeyEventStruct *key_event = NULL;
-  gint consumed = 0;
+  gboolean consumed = FALSE;
   gunichar password_char = 0;
 
   /* filter key events */
   if ((event->type != CLUTTER_KEY_PRESS) && (event->type != CLUTTER_KEY_RELEASE))
-    {
+    return FALSE;
-      return FALSE;
-    }
-
-  password_char = check_key_visibility (event);
 
   if (key_listener_list)
     {
       GHashTable *new_hash = g_hash_table_new (NULL, NULL);
 
       g_hash_table_foreach (key_listener_list, insert_hf, new_hash);
-      key_event = atk_key_event_from_clutter_event_key ((ClutterKeyEvent *)event,
+      password_char = check_key_visibility (event);
-                                                        password_char);
+      key_event = atk_key_event_from_clutter_event_key (key, password_char);
       /* func data is inside the hash table */
-      consumed = g_hash_table_foreach_steal (new_hash, notify_hf, key_event);
+      consumed = g_hash_table_foreach_steal (new_hash, notify_hf, key_event) > 0;
       g_hash_table_destroy (new_hash);
 
       g_free (key_event->string);
       g_free (key_event);
     }
 
-  return (consumed ? 1 : 0);
+  return consumed;
-}
-
-static void
-cally_util_stage_added_cb (ClutterStageManager *stage_manager,
-                           ClutterStage *stage,
-                           gpointer data)
-{
-  GCallback cally_key_snooper_cb = G_CALLBACK (data);
-
-  g_signal_connect (G_OBJECT (stage), "captured-event", cally_key_snooper_cb, NULL);
-}
-
-static void
-cally_util_stage_removed_cb (ClutterStageManager *stage_manager,
-                             ClutterStage *stage,
-                             gpointer data)
-{
-  GCallback cally_key_snooper_cb = G_CALLBACK (data);
-
-  g_signal_handlers_disconnect_by_func (stage, cally_key_snooper_cb, NULL);
 }
 
 void

clutter/clutter/cally/cally-util.h

@@ -79,6 +79,8 @@ GType cally_util_get_type (void) G_GNUC_CONST;
 
 void _cally_util_override_atk_util (void);
 
+gboolean cally_snoop_key_event (ClutterKeyEvent *key);
+
 G_END_DECLS
 
 #endif /* __CALLY_UTIL_H__ */

clutter/clutter/clutter-main.c

@@ -762,6 +762,8 @@ static inline void
 process_key_event (ClutterEvent       *event,
                    ClutterInputDevice *device)
 {
+  cally_snoop_key_event ((ClutterKeyEvent *) event);
+
   if (_clutter_event_process_filters (event))
     return;