stage/glx: Code clean ups

clutter/glx/clutter-stage-glx.c

@@ -71,10 +71,9 @@ G_DEFINE_TYPE_WITH_CODE (ClutterStageGLX,
 static void
 clutter_stage_glx_unrealize (ClutterStageWindow *stage_window)
 {
-  ClutterBackend *backend = clutter_get_default_backend ();
-  ClutterBackendX11 *backend_x11 = CLUTTER_BACKEND_X11 (backend);
   ClutterStageX11 *stage_x11 = CLUTTER_STAGE_X11 (stage_window);
   ClutterStageGLX *stage_glx = CLUTTER_STAGE_GLX (stage_window);
+  ClutterBackendX11 *backend_x11 = stage_x11->backend;
 
   /* Note unrealize should free up any backend stage related resources */
   CLUTTER_NOTE (BACKEND, "Unrealizing GLX stage [%p]", stage_glx);
@@ -101,19 +100,17 @@ clutter_stage_glx_realize (ClutterStageWindow *stage_window)
   ClutterStageGLX *stage_glx = CLUTTER_STAGE_GLX (stage_window);
   ClutterBackendX11 *backend_x11;
   ClutterBackendGLX *backend_glx;
-  ClutterBackend *backend;
 
   CLUTTER_NOTE (ACTOR, "Realizing stage '%s' [%p]",
                 G_OBJECT_TYPE_NAME (stage_window),
                 stage_window);
 
-  backend     = clutter_get_default_backend ();
-  backend_glx = CLUTTER_BACKEND_GLX (backend);
-  backend_x11 = CLUTTER_BACKEND_X11 (backend);
-
   if (!_clutter_stage_x11_create_window (stage_x11))
     return FALSE;
 
+  backend_x11 = stage_x11->backend;
+  backend_glx = CLUTTER_BACKEND_GLX (backend_x11);
+
   if (stage_glx->glxwin == None)
     {
       int major;
@@ -220,14 +217,12 @@ clutter_stage_glx_ignoring_redraw_clips (ClutterStageWindow *stage_window)
  * - when we come to redraw; if the bounding box is smaller than the
  *   stage we scissor the redraw to that box and use
  *   GLX_MESA_copy_sub_buffer to present the redraw to the front
- *   buffer. Some heuristics are used to decide when a clipped redraw
+ *   buffer.
- *   should be promoted into a full stage redraw.
  *
- * Currently we simply check that the bounding box height is < 300
+ * XXX - In theory, we should have some sort of heuristics to promote
- * pixels.
+ * a clipped redraw to a full screen redraw; in reality, it turns out
- *
+ * that promotion is fairly expensive. See the Clutter bug described
- * XXX: we don't have any empirical data telling us what a sensible
+ * at: http://bugzilla.clutter-project.org/show_bug.cgi?id=2136 .
- * thresholds is!
  *
  * TODO - we should use different heuristics depending on whether the
  * framebuffer is on screen and not redirected by a compositor VS
@@ -251,7 +246,6 @@ clutter_stage_glx_ignoring_redraw_clips (ClutterStageWindow *stage_window)
  * By promoting to a full stage redraw we trade off the cost involved
  * in rasterizing the extra pixels vs avoiding to use a blit to
  * present the back buffer.
- *
  */
 static void
 clutter_stage_glx_add_redraw_clip (ClutterStageWindow *stage_window,
@@ -286,7 +280,8 @@ clutter_stage_glx_add_redraw_clip (ClutterStageWindow *stage_window,
     }
   else if (stage_glx->bounding_redraw_clip.width > 0)
     {
-      clutter_geometry_union (&stage_glx->bounding_redraw_clip, stage_clip,
+      clutter_geometry_union (&stage_glx->bounding_redraw_clip,
+                              stage_clip,
 			      &stage_glx->bounding_redraw_clip);
     }
 
@@ -299,6 +294,11 @@ clutter_stage_glx_add_redraw_clip (ClutterStageWindow *stage_window,
    * expensive than redrawing the additional 30% to avoid the blit.
    *
    * FIXME: This threshold was plucked out of thin air!
+   *
+   * The threshold has been disabled after verifying that it indeed
+   * made redraws more expensive than intended; see bug reference:
+   *
+   * http://bugzilla.clutter-project.org/show_bug.cgi?id=2136
    */
   if (redraw_area > (stage_area * 0.7f))
     {

clutter/glx/clutter-stage-glx.h

@@ -48,18 +48,20 @@ struct _ClutterStageGLX
 {
   ClutterStageX11 parent_instance;
 
-  int pending_swaps;
+  gint pending_swaps;
 
   GLXPixmap glxpixmap;
   GLXWindow glxwin;
 
   /* We only enable clipped redraws after 2 frames, since we've seen
    * a lot of drivers can struggle to get going and may output some
-   * junk frames to start with. */
+   * junk frames to start with.
-  unsigned long frame_count;
+   */
+  guint frame_count;
 
-  gboolean initialized_redraw_clip;
   ClutterGeometry bounding_redraw_clip;
+
+  guint initialized_redraw_clip : 1;
 };
 
 struct _ClutterStageGLXClass