clutter/stage: Add infrastructure to track devices and their actors

With the introduction of the input thread, we want to avoid modifying
ClutterInputDevices from the main thread, since they're owned and
updated by the thread.

There's one part of ClutterInputDevice that's still modified from the
main thread though, that is device-actors of pointer devices, and we're
going to move that state-tracking into ClutterStage instead.

So start that by adding the infrastructure to ClutterStage to keep track
of those things. It consists of two hashtables which associate devices
and touch sequences with actors, those hashtables get updated using
clutter_stage_update_device_entry() and
clutter_stage_remove_device_entry(), they can be queried by calling
clutter_stage_get_device_actor(), which will replace
clutter_input_device_get_actor().

clutter_stage_get_device_coords() is added and made available in
clutter-mutter.h because we need to get the coordinates when repicking
in meta_wayland_pointer_repick().

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1633>

clutter/clutter/clutter-mutter.h

@@ -75,6 +75,12 @@ CLUTTER_EXPORT
 gboolean clutter_seat_handle_event_post (ClutterSeat        *seat,
                                          const ClutterEvent *event);
 
+CLUTTER_EXPORT
+void clutter_stage_get_device_coords (ClutterStage         *stage,
+                                      ClutterInputDevice   *device,
+                                      ClutterEventSequence *sequence,
+                                      graphene_point_t     *coords);
+
 #undef __CLUTTER_H_INSIDE__
 
 #endif /* __CLUTTER_MUTTER_H__ */

clutter/clutter/clutter-stage-private.h

@@ -128,6 +128,16 @@ GList * clutter_stage_get_views_for_rect (ClutterStage          *stage,
 
 void clutter_stage_set_actor_needs_immediate_relayout (ClutterStage *stage);
 
+void clutter_stage_update_device_entry (ClutterStage         *self,
+                                        ClutterInputDevice   *device,
+                                        ClutterEventSequence *sequence,
+                                        graphene_point_t      coords,
+                                        ClutterActor         *actor);
+
+void clutter_stage_remove_device_entry (ClutterStage         *self,
+                                        ClutterInputDevice   *device,
+                                        ClutterEventSequence *sequence);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_STAGE_PRIVATE_H__ */

clutter/clutter/clutter-stage.c

@@ -98,6 +98,15 @@ typedef struct _PickClipRecord
   graphene_point_t vertex[4];
 } PickClipRecord;
 
+typedef struct _PointerDeviceEntry
+{
+  ClutterStage *stage;
+  ClutterInputDevice *device;
+  ClutterEventSequence *sequence;
+  graphene_point_t coords;
+  ClutterActor *current_actor;
+} PointerDeviceEntry;
+
 struct _ClutterStagePrivate
 {
   /* the stage implementation */
@@ -126,6 +135,9 @@ struct _ClutterStagePrivate
   gboolean needs_update_devices;
   gboolean pending_finish_queue_redraws;
 
+  GHashTable *pointer_devices;
+  GHashTable *touch_sequences;
+
   guint throttle_motion_events : 1;
   guint min_size_changed       : 1;
   guint motion_events_enabled  : 1;
@@ -165,6 +177,7 @@ static guint stage_signals[LAST_SIGNAL] = { 0, };
 static const ClutterColor default_stage_color = { 255, 255, 255, 255 };
 
 static void free_queue_redraw_entry (QueueRedrawEntry *entry);
+static void free_pointer_device_entry (PointerDeviceEntry *entry);
 static void capture_view_into (ClutterStage          *stage,
                                gboolean               paint,
                                ClutterStageView      *view,
@@ -1301,6 +1314,9 @@ clutter_stage_finalize (GObject *object)
   g_queue_foreach (priv->event_queue, (GFunc) clutter_event_free, NULL);
   g_queue_free (priv->event_queue);
 
+  g_hash_table_destroy (priv->pointer_devices);
+  g_hash_table_destroy (priv->touch_sequences);
+
   g_free (priv->title);
 
   g_array_free (priv->paint_volume_stack, TRUE);
@@ -1596,6 +1612,13 @@ clutter_stage_init (ClutterStage *self)
   priv->sync_delay = -1;
   priv->motion_events_enabled = TRUE;
 
+  priv->pointer_devices =
+    g_hash_table_new_full (NULL, NULL,
+                           NULL, (GDestroyNotify) free_pointer_device_entry);
+  priv->touch_sequences =
+    g_hash_table_new_full (NULL, NULL,
+                           NULL, (GDestroyNotify) free_pointer_device_entry);
+
   clutter_actor_set_background_color (CLUTTER_ACTOR (self),
                                       &default_stage_color);
 
@@ -3392,3 +3415,182 @@ clutter_stage_set_actor_needs_immediate_relayout (ClutterStage *stage)
 
   priv->actor_needs_immediate_relayout = TRUE;
 }
+
+static void
+on_device_actor_reactive_changed (ClutterActor       *actor,
+                                  GParamSpec         *pspec,
+                                  PointerDeviceEntry *entry)
+{
+}
+
+static void
+on_device_actor_destroyed (ClutterActor       *actor,
+                           PointerDeviceEntry *entry)
+{
+  /* Simply unset the current_actor pointer here, there's no need to
+   * unset has_pointer or to disconnect any signals because the actor
+   * is gone anyway.
+   * Also, as soon as the next repaint happens, a repick should be triggered
+   * and the PointerDeviceEntry will get updated again, so no need to
+   * trigger a repick here.
+   */
+  entry->current_actor = NULL;
+}
+
+static void
+free_pointer_device_entry (PointerDeviceEntry *entry)
+{
+  if (entry->current_actor)
+    {
+      ClutterActor *actor = entry->current_actor;
+
+      g_signal_handlers_disconnect_by_func (actor,
+                                            G_CALLBACK (on_device_actor_reactive_changed),
+                                            entry);
+      g_signal_handlers_disconnect_by_func (actor,
+                                            G_CALLBACK (on_device_actor_destroyed),
+                                            entry);
+
+      _clutter_actor_set_has_pointer (actor, FALSE);
+   }
+
+  g_free (entry);
+}
+
+void
+clutter_stage_update_device_entry (ClutterStage         *self,
+                                   ClutterInputDevice   *device,
+                                   ClutterEventSequence *sequence,
+                                   graphene_point_t      coords,
+                                   ClutterActor         *actor)
+{
+  ClutterStagePrivate *priv = self->priv;
+  PointerDeviceEntry *entry = NULL;
+
+  g_assert (device != NULL);
+
+  if (sequence != NULL)
+    entry = g_hash_table_lookup (priv->touch_sequences, sequence);
+  else
+    entry = g_hash_table_lookup (priv->pointer_devices, device);
+
+  if (!entry)
+    {
+      entry = g_new0 (PointerDeviceEntry, 1);
+
+      if (sequence != NULL)
+        g_hash_table_insert (priv->touch_sequences, sequence, entry);
+      else
+        g_hash_table_insert (priv->pointer_devices, device, entry);
+
+      entry->stage = self;
+      entry->device = device;
+      entry->sequence = sequence;
+    }
+
+  entry->coords = coords;
+
+  if (entry->current_actor != actor)
+    {
+      if (entry->current_actor)
+        {
+          ClutterActor *old_actor = entry->current_actor;
+
+          g_signal_handlers_disconnect_by_func (old_actor,
+                                                G_CALLBACK (on_device_actor_reactive_changed),
+                                                entry);
+          g_signal_handlers_disconnect_by_func (old_actor,
+                                                G_CALLBACK (on_device_actor_destroyed),
+                                                entry);
+
+          _clutter_actor_set_has_pointer (old_actor, FALSE);
+        }
+
+      entry->current_actor = actor;
+
+      if (actor)
+        {
+          g_signal_connect (actor, "notify::reactive",
+                            G_CALLBACK (on_device_actor_reactive_changed), entry);
+          g_signal_connect (actor, "destroy",
+                            G_CALLBACK (on_device_actor_destroyed), entry);
+
+          _clutter_actor_set_has_pointer (actor, TRUE);
+        }
+    }
+}
+
+void
+clutter_stage_remove_device_entry (ClutterStage         *self,
+                                   ClutterInputDevice   *device,
+                                   ClutterEventSequence *sequence)
+{
+  ClutterStagePrivate *priv = self->priv;
+  gboolean removed;
+
+  g_assert (device != NULL);
+
+  if (sequence != NULL)
+    removed = g_hash_table_remove (priv->touch_sequences, sequence);
+  else
+    removed = g_hash_table_remove (priv->pointer_devices, device);
+
+  g_assert (removed);
+}
+
+/**
+ * clutter_stage_get_device_actor:
+ * @stage: a #ClutterStage
+ * @device: a #ClutterInputDevice
+ * @sequence: (allow-none): an optional #ClutterEventSequence
+ *
+ * Retrieves the #ClutterActor underneath the pointer or touch point
+ * of @device and @sequence.
+ *
+ * Return value: (transfer none): a pointer to the #ClutterActor or %NULL
+ */
+ClutterActor *
+clutter_stage_get_device_actor (ClutterStage         *stage,
+                                ClutterInputDevice   *device,
+                                ClutterEventSequence *sequence)
+{
+  ClutterStagePrivate *priv = stage->priv;
+  PointerDeviceEntry *entry = NULL;
+
+  g_return_val_if_fail (CLUTTER_IS_STAGE (stage), NULL);
+  g_return_val_if_fail (device != NULL, NULL);
+
+  if (sequence != NULL)
+    entry = g_hash_table_lookup (priv->touch_sequences, sequence);
+  else
+    entry = g_hash_table_lookup (priv->pointer_devices, device);
+
+  if (entry)
+    return entry->current_actor;
+
+  return NULL;
+}
+
+/**
+ * clutter_stage_get_device_coords: (skip):
+ */
+void
+clutter_stage_get_device_coords (ClutterStage         *stage,
+                                 ClutterInputDevice   *device,
+                                 ClutterEventSequence *sequence,
+                                 graphene_point_t     *coords)
+{
+  ClutterStagePrivate *priv = stage->priv;
+  PointerDeviceEntry *entry = NULL;
+
+  g_return_if_fail (CLUTTER_IS_STAGE (stage));
+  g_return_if_fail (device != NULL);
+
+  if (sequence != NULL)
+    entry = g_hash_table_lookup (priv->touch_sequences, sequence);
+  else
+    entry = g_hash_table_lookup (priv->pointer_devices, device);
+
+  if (entry && coords)
+    *coords = entry->coords;
+}

clutter/clutter/clutter-stage.h

@@ -236,6 +236,11 @@ ClutterStageView * clutter_stage_get_view_at (ClutterStage *stage,
                                               float         x,
                                               float         y);
 
+CLUTTER_EXPORT
+ClutterActor * clutter_stage_get_device_actor (ClutterStage         *stage,
+                                               ClutterInputDevice   *device,
+                                               ClutterEventSequence *sequence);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_STAGE_H__ */