ecore_evas/wayland_egl: Only render if last frame has been presented.

This avoids blocking in eglSwapBuffers and has the side effect of
avoiding doing unnecessary work - painting where a frame won't be
presented.

We do this by using the event that the wayland compositor will send us
to tell us that the frame has been presented. Due to the fact that
evas_render_updates() could do no work and not cause a eglSwapBuffers we
must always have a frame callback listener setup.

Original patch by: Rob Bradford <rob@linux.intel.com>

(I just adjusted the patch to the single efl tree)

SVN revision: 83387

ChangeLog

@@ -380,3 +380,8 @@
 2013-01-28  Daniel Willmann <d.willmann@samsung.com>
 
 				* Use ecore_audio in edje-multisense
+
+2013-01-28 Rafael Antognolli <antognolli@gmail.com>
+
+				* Ecore_Evas wayland-egl only renders now if last frame has
+				been presented.

NEWS

@@ -86,6 +86,7 @@ Improvements:
     * edje entry: remove ecore_imf_context_reset, cursor update in mouse move event because it's useless.
     * edje entry: move ecore_imf_context_cursor_position_set from mouse down event to mouse up event.
     * Use ecore_audio in edje-multisense
+    * Ecore_Evas wayland-egl only renders now if last frame has been presented.
 
 Fixes:
     * Fix PPC (big endian) image codec bug.

src/modules/ecore_evas/engines/wayland/ecore_evas_wayland_common.c

@@ -723,33 +723,6 @@ _ecore_evas_wl_common_pre_render(Ecore_Evas *ee)
    return rend;
 }
 
-int
-_ecore_evas_wl_common_render_updates(Ecore_Evas *ee)
-{
-   int rend = 0;
-   Eina_List *updates = NULL;
-   Ecore_Evas_Engine_Wl_Data *wdata = ee->engine.data;
-
-   LOGFN(__FILE__, __LINE__, __FUNCTION__);
-
-   if ((updates = evas_render_updates(ee->evas)))
-     {
-        Eina_List *l = NULL;
-        Eina_Rectangle *r;
-
-        EINA_LIST_FOREACH(updates, l, r)
-          ecore_wl_window_damage(wdata->win,
-                                 r->x, r->y, r->w, r->h);
-
-        ecore_wl_flush();
-
-        evas_render_updates_free(updates);
-        rend = 1;
-     }
-
-   return rend;
-}
-
 void
 _ecore_evas_wl_common_post_render(Ecore_Evas *ee)
 {

src/modules/ecore_evas/engines/wayland/ecore_evas_wayland_egl.c

@@ -10,6 +10,7 @@
 
 
 /* local function prototypes */
+static int _ecore_evas_wl_render(Ecore_Evas *ee);
 static void _ecore_evas_wl_resize(Ecore_Evas *ee, int w, int h);
 static void _ecore_evas_wl_show(Ecore_Evas *ee);
 static void _ecore_evas_wl_hide(Ecore_Evas *ee);
@@ -72,7 +73,7 @@ static Ecore_Evas_Engine_Func _ecore_wl_engine_func =
    NULL, // modal set
    NULL, // demand attention set
    NULL, // focus skip set
-   _ecore_evas_wl_common_render,
+   _ecore_evas_wl_render,
    _ecore_evas_wl_common_screen_geometry_get,
    _ecore_evas_wl_common_screen_dpi_get
 };
@@ -228,6 +229,108 @@ ecore_evas_wayland_egl_new_internal(const char *disp_name, unsigned int parent,
    return NULL;
 }
 
+static void
+_ecore_evas_wl_frame_complete (void *data, struct wl_callback *callback, uint32_t time EINA_UNUSED);
+
+static const struct wl_callback_listener frame_listener = {
+   _ecore_evas_wl_frame_complete,
+};
+
+static void
+_ecore_evas_wl_frame_complete (void *data, struct wl_callback *callback, uint32_t time EINA_UNUSED)
+{
+   Ecore_Evas *ee = data;
+   Ecore_Evas_Engine_Wl_Data *wdata = ee->engine.data;
+
+   wdata->win->frame_callback = NULL;
+   wdata->win->frame_pending = EINA_FALSE;
+   wl_callback_destroy(callback);
+
+   wdata->win->frame_callback =
+     wl_surface_frame(wdata->win->surface);
+
+   wl_callback_add_listener(wdata->win->frame_callback,
+                            &frame_listener, ee);
+}
+
+int
+_ecore_evas_wl_render_updates(Ecore_Evas *ee)
+{
+   int rend = 0;
+   Eina_List *updates = NULL;
+   Ecore_Evas_Engine_Wl_Data *wdata = ee->engine.data;
+
+   LOGFN(__FILE__, __LINE__, __FUNCTION__);
+
+   /* eglSwapBuffers is ultimately called by evas_render_updates() if
+    * there is some update to make. So we must pre-emptively create a
+    * frame callback handler. We make sure we always have one of these in
+    * available to track if the event is presented.
+    *
+    * This frame callback will be fired when the frame has been presented
+    * and we can safely call eglSwapBuffers without it blocking. Whether
+    * to render or not is handled by the frame_pending boolean which is
+    * reset on the frame callback event.
+    */
+   if (!wdata->win->frame_pending)
+     {
+        /* FIXME - ideally have an evas_changed_get to return the value
+         * of evas->changed to avoid creating this callback and
+         * destroying it again
+         */
+
+        if (!wdata->win->frame_callback)
+          {
+             wdata->win->frame_callback =
+                wl_surface_frame(wdata->win->surface);
+
+             wl_callback_add_listener(wdata->win->frame_callback,
+                                      &frame_listener, ee);
+          }
+
+        if ((updates = evas_render_updates(ee->evas)))
+          {
+             Eina_List *l = NULL;
+             Eina_Rectangle *r;
+
+             EINA_LIST_FOREACH(updates, l, r)
+                ecore_wl_window_damage(wdata->win,
+                                       r->x, r->y, r->w, r->h);
+
+             ecore_wl_flush();
+
+             evas_render_updates_free(updates);
+
+             wdata->win->frame_pending = EINA_TRUE;
+
+             rend = 1;
+          }
+     }
+
+   return rend;
+}
+
+static int
+_ecore_evas_wl_render(Ecore_Evas *ee)
+{
+   int rend = 0;
+
+   LOGFN(__FILE__, __LINE__, __FUNCTION__);
+
+   if (!ee) return 0;
+   if (!ee->visible)
+     {
+        evas_norender(ee->evas);
+        return 0;
+     }
+
+   rend = _ecore_evas_wl_common_pre_render(ee);
+   rend |= _ecore_evas_wl_render_updates(ee);
+   _ecore_evas_wl_common_post_render(ee);
+
+   return rend;
+}
+
 static void 
 _ecore_evas_wl_resize(Ecore_Evas *ee, int w, int h)
 {