stage: Add state tracking

State changes on the Stage are currently deferred to the windowing
system backends, but the code is generally the same, and it should
be abstracted neatly inside the Stage class itself.

There's also the extra caveat for backends that state changes on a
Stage must also emit a ClutterEvent of type CLUTTER_STAGE_STATE, a
requirement that needlessly complicates the backend code.

clutter/clutter-stage-private.h

@@ -109,6 +109,13 @@ ClutterActor *  _clutter_stage_get_drag_actor           (ClutterStage       *sta
 void            _clutter_stage_remove_drag_actor        (ClutterStage       *stage,
                                                          ClutterInputDevice *device);
 
+ClutterStageState       _clutter_stage_get_state        (ClutterStage      *stage);
+gboolean                _clutter_stage_is_activated     (ClutterStage      *stage);
+gboolean                _clutter_stage_is_fullscreen    (ClutterStage      *stage);
+gboolean                _clutter_stage_update_state     (ClutterStage      *stage,
+                                                         ClutterStageState  unset_state,
+                                                         ClutterStageState  set_state);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_STAGE_PRIVATE_H__ */

clutter/clutter-stage.c

@@ -127,6 +127,7 @@ struct _ClutterStagePrivate
   CoglMatrix inverse_projection;
   CoglMatrix view;
   float viewport[4];
+
   ClutterFog fog;
 
   gchar *title;
@@ -159,6 +160,8 @@ struct _ClutterStagePrivate
   gulong redraw_count;
 #endif /* CLUTTER_ENABLE_DEBUG */
 
+  ClutterStageState current_state;
+
   guint relayout_pending       : 1;
   guint redraw_pending         : 1;
   guint is_fullscreen          : 1;
@@ -4397,3 +4400,87 @@ _clutter_stage_remove_drag_actor (ClutterStage       *stage,
   if (g_hash_table_size (drag_actors) == 0)
     g_object_set_data (G_OBJECT (stage), "__clutter_stage_drag_actors", NULL);
 }
+
+/*< private >
+ * _clutter_stage_get_state:
+ * @stage: a #ClutterStage
+ *
+ * Retrieves the current #ClutterStageState flags associated to the @stage.
+ *
+ * Return value: a bitwise OR of #ClutterStageState flags
+ */
+ClutterStageState
+_clutter_stage_get_state (ClutterStage *stage)
+{
+  return stage->priv->current_state;
+}
+
+/*< private >
+ * _clutter_stage_is_activated:
+ * @stage: a #ClutterStage
+ *
+ * Checks whether the @stage state includes %CLUTTER_STAGE_STATE_ACTIVATED.
+ *
+ * Return value: %TRUE if the @stage is active
+ */
+gboolean
+_clutter_stage_is_activated (ClutterStage *stage)
+{
+  return (stage->priv->current_state & CLUTTER_STAGE_STATE_ACTIVATED) != 0;
+}
+
+/*< private >
+ * _clutter_stage_is_fullscreen:
+ * @stage: a #ClutterStage
+ *
+ * Checks whether the @stage state includes %CLUTTER_STAGE_STATE_FULLSCREEN.
+ *
+ * Return value: %TRUE if the @stage is fullscreen
+ */
+gboolean
+_clutter_stage_is_fullscreen (ClutterStage *stage)
+{
+  return (stage->priv->current_state & CLUTTER_STAGE_STATE_FULLSCREEN) != 0;
+}
+
+/*< private >
+ * _clutter_stage_update_state:
+ * @stage: a #ClutterStage
+ * @unset_flags: flags to unset
+ * @set_flags: flags to set
+ *
+ * Updates the state of @stage, by unsetting the @unset_flags and setting
+ * the @set_flags.
+ *
+ * If the stage state has been changed, this function will queue a
+ * #ClutterEvent of type %CLUTTER_STAGE_STATE.
+ *
+ * Return value: %TRUE if the state was updated, and %FALSE otherwise
+ */
+gboolean
+_clutter_stage_update_state (ClutterStage      *stage,
+                             ClutterStageState  unset_flags,
+                             ClutterStageState  set_flags)
+{
+  ClutterStageState new_state;
+  ClutterEvent *event;
+
+  new_state = stage->priv->current_state;
+  new_state |= set_flags;
+  new_state &= ~unset_flags;
+
+  if (new_state == stage->priv->current_state)
+    return FALSE;
+
+  event = clutter_event_new (CLUTTER_STAGE_STATE);
+  clutter_event_set_stage (event, stage);
+
+  event->stage_state.new_state = new_state;
+  event->stage_state.changed_mask = new_state ^ stage->priv->current_state;
+
+  stage->priv->current_state = new_state;
+
+  _clutter_event_push (event, FALSE);
+
+  return TRUE;
+}