events: Add platform-data to allocated Events

Events allocated by Clutter should have a pointer to platform-specific
data; this would allow backends to add separate structures for holding
ancillary data, whilst retaining the ClutterEvent structure for use on
the stack.

In theory, for Clutter 2.x we might just want to drop Event and use an
opaque structure, or a typed data structure inheriting from
GTypeInstance instead.

clutter/clutter-backend.c

@@ -518,6 +518,36 @@ _clutter_backend_get_units_per_em (ClutterBackend       *backend,
   return priv->units_per_em;
 }
 
+void
+_clutter_backend_copy_event_data (ClutterBackend *backend,
+                                  ClutterEvent   *src,
+                                  ClutterEvent   *dest)
+{
+  ClutterBackendClass *klass;
+
+  g_return_if_fail (CLUTTER_IS_BACKEND (backend));
+  g_return_if_fail (src != NULL);
+  g_return_if_fail (dest != NULL);
+
+  klass = CLUTTER_BACKEND_GET_CLASS (backend);
+  if (klass->copy_event_data != NULL)
+    klass->copy_event_data (backend, src, dest);
+}
+
+void
+_clutter_backend_free_event_data (ClutterBackend *backend,
+                                  ClutterEvent   *event)
+{
+  ClutterBackendClass *klass;
+
+  g_return_if_fail (CLUTTER_IS_BACKEND (backend));
+  g_return_if_fail (event != NULL);
+
+  klass = CLUTTER_BACKEND_GET_CLASS (backend);
+  if (klass->free_event_data != NULL)
+    klass->free_event_data (backend, event);
+}
+
 /**
  * clutter_get_default_backend:
  *

clutter/clutter-backend.h

@@ -85,6 +85,12 @@ struct _ClutterBackendClass
                                                 ClutterStage    *stage);
   ClutterDeviceManager *(* get_device_manager) (ClutterBackend  *backend);
 
+  void                  (* copy_event_data)    (ClutterBackend  *backend,
+                                                ClutterEvent    *src,
+                                                ClutterEvent    *dest);
+  void                  (* free_event_data)    (ClutterBackend  *backend,
+                                                ClutterEvent    *event);
+
   /* signals */
   void (* resolution_changed) (ClutterBackend *backend);
   void (* font_changed)       (ClutterBackend *backend);

clutter/clutter-event.c

@@ -43,6 +43,52 @@
  * be synthesized by Clutter itself or by the application code.
  */
 
+typedef struct _ClutterEventPrivate {
+  ClutterEvent base;
+
+  gpointer platform_data;
+} ClutterEventPrivate;
+
+static GHashTable *all_events = NULL;
+
+static gboolean
+is_event_allocated (const ClutterEvent *event)
+{
+  if (all_events == NULL)
+    return FALSE;
+
+  return g_hash_table_lookup (all_events, event) != NULL;
+}
+
+/*
+ * _clutter_event_get_platform_data:
+ * @event: a #ClutterEvent
+ *
+ * Retrieves the pointer to platform-specific data inside an event
+ *
+ * Return value: a pointer to platform-specific data
+ *
+ * Since: 1.4
+ */
+gpointer
+_clutter_event_get_platform_data (const ClutterEvent *event)
+{
+  if (!is_event_allocated (event))
+    return NULL;
+
+  return ((ClutterEventPrivate *) event)->platform_data;
+}
+
+void
+_clutter_event_set_platform_data (ClutterEvent *event,
+                                  gpointer      data)
+{
+  if (!is_event_allocated (event))
+    return;
+
+  ((ClutterEventPrivate *) event)->platform_data = data;
+}
+
 /**
  * clutter_event_type:
  * @event: a #ClutterEvent
@@ -606,10 +652,18 @@ ClutterEvent *
 clutter_event_new (ClutterEventType type)
 {
   ClutterEvent *new_event;
+  ClutterEventPrivate *priv;
 
-  new_event = g_slice_new0 (ClutterEvent);
+  priv = g_slice_new0 (ClutterEventPrivate);
+
+  new_event = (ClutterEvent *) priv;
   new_event->type = new_event->any.type = type;
 
+  if (all_events == NULL)
+    all_events = g_hash_table_new (NULL, NULL);
+
+  g_hash_table_replace (all_events, priv, GUINT_TO_POINTER (1));
+
   return new_event;
 }
 
@@ -631,6 +685,11 @@ clutter_event_copy (ClutterEvent *event)
   new_event = clutter_event_new (CLUTTER_NOTHING);
   *new_event = *event;
 
+  if (is_event_allocated (event))
+    _clutter_backend_copy_event_data (clutter_get_default_backend (),
+                                      event,
+                                      new_event);
+
   return new_event;
 }
 
@@ -644,7 +703,12 @@ void
 clutter_event_free (ClutterEvent *event)
 {
   if (G_LIKELY (event != NULL))
-    g_slice_free (ClutterEvent, event);
+    {
+      _clutter_backend_free_event_data (clutter_get_default_backend (), event);
+
+      g_hash_table_remove (all_events, event);
+      g_slice_free (ClutterEventPrivate, (ClutterEventPrivate *) event);
+    }
 }
 
 /**

clutter/clutter-private.h

@@ -245,7 +245,6 @@ int      _clutter_stage_get_pending_swaps      (ClutterStage *stage);
 
 gboolean _clutter_stage_has_full_redraw_queued (ClutterStage *stage);
 
-
 /* vfuncs implemented by backend */
 GType         _clutter_backend_impl_get_type  (void);
 
@@ -270,6 +269,12 @@ gboolean      _clutter_backend_post_parse     (ClutterBackend  *backend,
                                                GError         **error);
 void          _clutter_backend_init_events    (ClutterBackend  *backend);
 
+void          _clutter_backend_copy_event_data (ClutterBackend  *backend,
+                                                ClutterEvent    *src,
+                                                ClutterEvent    *dest);
+void          _clutter_backend_free_event_data (ClutterBackend  *backend,
+                                                ClutterEvent    *event);
+
 ClutterFeatureFlags _clutter_backend_get_features (ClutterBackend *backend);
 
 gfloat        _clutter_backend_get_units_per_em   (ClutterBackend       *backend,
@@ -341,6 +346,10 @@ void     _clutter_effect_post_paint (ClutterEffect *effect);
 
 GType _clutter_layout_manager_get_child_meta_type (ClutterLayoutManager *manager);
 
+void     _clutter_event_set_platform_data (ClutterEvent       *event,
+                                           gpointer            data);
+gpointer _clutter_event_get_platform_data (const ClutterEvent *event);
+
 G_END_DECLS
 
 #endif /* _HAVE_CLUTTER_PRIVATE_H */