cogl-renderer: Move the XEvent filters to be generic for all renderers

Instead of having cogl_renderer_xlib_add_filter and friends there is
now cogl_renderer_add_native_filter which can be used regardless of
the backend. The callback function for the filter now just takes a
void pointer instead of an XEvent pointer which should be interpreted
differently depending on the backend. For example, on Xlib it would
still be an XEvent but on Windows it could be a MSG. This simplifies
the code somewhat because the _cogl_xlib_add_filter no longer needs to
have its own filter list when a stub renderer is used because there is
always a renderer available.

cogl_renderer_xlib_handle_event has also been renamed to
cogl_renderer_handle_native_event. This just forwards the event on to
all of the listeners. The backend renderer is expected to register its
own event filter if it wants to process the events in some way.

cogl/cogl-renderer.h

@@ -63,27 +63,57 @@ cogl_renderer_new (void);
 
 /* optional configuration APIs */
 
-#ifdef COGL_HAS_XLIB
-
-#define cogl_renderer_xlib_handle_event cogl_renderer_xlib_handle_event_EXP
+#define cogl_renderer_handle_native_event cogl_renderer_handle_native_event_EXP
 /*
- * cogl_renderer_xlib_handle_event:
- * @xevent: pointer to XEvent structure
+ * cogl_renderer_handle_native_event:
+ * @event: pointer to native event structure
  *
- * This function processes a single X event; it can be used to hook
- * into external X event retrieval (for example that done by Clutter
- * or GDK).
+ * This function processes a single event; it can be used to hook into
+ * external event retrieval (for example that done by Clutter or
+ * GDK). The type of the structure that event points to depends on the
+ * window system used for the renderer. On an xlib renderer it would
+ * be a pointer to an XEvent or an a Windows renderer it would be a
+ * pointer to a MSG struct.
  *
- * Return value: #CoglXlibFilterReturn. %COGL_XLIB_FILTER_REMOVE
- * indicates that Cogl has internally handled the event and the
- * caller should do no further processing. %COGL_XLIB_FILTER_CONTINUE
- * indicates that Cogl is either not interested in the event,
- * or has used the event to update internal state without taking
- * any exclusive action.
+ * Return value: #CoglFilterReturn. %COGL_FILTER_REMOVE indicates that
+ * Cogl has internally handled the event and the caller should do no
+ * further processing. %COGL_FILTER_CONTINUE indicates that Cogl is
+ * either not interested in the event, or has used the event to update
+ * internal state without taking any exclusive action.
  */
-CoglXlibFilterReturn
-cogl_renderer_xlib_handle_event (CoglRenderer *renderer,
-                                 XEvent *xevent);
+CoglFilterReturn
+cogl_renderer_handle_native_event (CoglRenderer *renderer,
+                                   void *event);
+
+#define cogl_renderer_add_native_filter cogl_renderer_add_native_filter_EXP
+/*
+ * _cogl_renderer_add_native_filter:
+ *
+ * Adds a callback function that will receive all native events. The
+ * function can stop further processing of the event by return
+ * %COGL_FILTER_REMOVE. What is considered a native event depends on
+ * the type of renderer used. An xlib based renderer would pass all
+ * XEvents whereas a Windows based renderer would pass MSGs.
+ */
+void
+cogl_renderer_add_native_filter (CoglRenderer *renderer,
+                                 CoglNativeFilterFunc func,
+                                 void *data);
+
+#define cogl_renderer_remove_native_filter \
+  cogl_renderer_remove_native_filter_EXP
+/*
+ * _cogl_renderer_remove_native_filter:
+ *
+ * Removes a callback that was previously added with
+ * _cogl_renderer_add_native_filter().
+ */
+void
+cogl_renderer_remove_native_filter (CoglRenderer *renderer,
+                                    CoglNativeFilterFunc func,
+                                    void *data);
+
+#ifdef COGL_HAS_XLIB
 
 #define cogl_renderer_xlib_get_foreign_display \
   cogl_renderer_xlib_get_foreign_display_EXP
@@ -113,30 +143,6 @@ cogl_renderer_xlib_set_foreign_display (CoglRenderer *renderer,
 Display *
 cogl_renderer_xlib_get_display (CoglRenderer *renderer);
 
-#define cogl_renderer_xlib_add_filter cogl_renderer_xlib_add_filter_EXP
-/*
- * _cogl_xlib_add_filter:
- *
- * Adds a callback function that will receive all X11 events. The
- * function can stop further processing of the event by return
- * %COGL_XLIB_FILTER_REMOVE.
- */
-void
-cogl_renderer_xlib_add_filter (CoglRenderer *renderer,
-                               CoglXlibFilterFunc func,
-                               void *data);
-
-#define cogl_renderer_xlib_remove_filter cogl_renderer_xlib_remove_filter_EXP
-/*
- * _cogl_xlib_remove_filter:
- *
- * Removes a callback that was previously added with
- * _cogl_xlib_add_filter().
- */
-void
-cogl_renderer_xlib_remove_filter (CoglRenderer *renderer,
-                                  CoglXlibFilterFunc func,
-                                  void *data);
 #endif /* COGL_HAS_XLIB */
 
 #define cogl_renderer_check_onscreen_template \