clutter-stage: Add clutter_stage_get_redraw_clip_bounds

This adds a public function to get the bounds of the current clipped
redraw on a stage. This should only be called while the stage is being
painted. The function diverts to a virtual function on the
ClutterStageWindow implementation. If the function isn't implemented
or it returns FALSE then the entire stage is reported. The clip bounds
are in integer pixel coordinates in the stage's coordinate space.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2421

clutter/clutter-stage-window.c

@@ -175,6 +175,21 @@ _clutter_stage_window_ignoring_redraw_clips (ClutterStageWindow *window)
   return TRUE;
 }
 
+gboolean
+_clutter_stage_window_get_redraw_clip_bounds (ClutterStageWindow    *window,
+                                              cairo_rectangle_int_t *stage_clip)
+{
+  ClutterStageWindowIface *iface;
+
+  g_return_val_if_fail (CLUTTER_IS_STAGE_WINDOW (window), FALSE);
+
+  iface = CLUTTER_STAGE_WINDOW_GET_IFACE (window);
+  if (iface->get_redraw_clip_bounds)
+    return iface->get_redraw_clip_bounds (window, stage_clip);
+
+  return FALSE;
+}
+
 void
 _clutter_stage_window_set_accept_focus (ClutterStageWindow *window,
                                         gboolean            accept_focus)

clutter/clutter-stage-window.h

@@ -3,6 +3,7 @@
 
 #include <clutter/clutter-actor.h>
 #include <cogl/cogl.h>
+#include <cairo.h>
 
 G_BEGIN_DECLS
 
@@ -64,6 +65,9 @@ struct _ClutterStageWindowIface
                                                  ClutterGeometry    *stage_rectangle);
   gboolean          (* has_redraw_clips)        (ClutterStageWindow *stage_window);
   gboolean          (* ignoring_redraw_clips)   (ClutterStageWindow *stage_window);
+  gboolean          (* get_redraw_clip_bounds)  (ClutterStageWindow *stage_window,
+                                                 cairo_rectangle_int_t *clip);
+
 
   void              (* set_accept_focus)        (ClutterStageWindow *stage_window,
                                                  gboolean            accept_focus);
@@ -104,6 +108,8 @@ void              _clutter_stage_window_add_redraw_clip         (ClutterStageWin
                                                                  ClutterGeometry    *stage_clip);
 gboolean          _clutter_stage_window_has_redraw_clips        (ClutterStageWindow *window);
 gboolean          _clutter_stage_window_ignoring_redraw_clips   (ClutterStageWindow *window);
+gboolean          _clutter_stage_window_get_redraw_clip_bounds  (ClutterStageWindow *window,
+                                                                 cairo_rectangle_int_t *clip);
 
 void              _clutter_stage_window_set_accept_focus        (ClutterStageWindow *window,
                                                            gboolean            accept_focus);

clutter/clutter-stage.c

@@ -1176,6 +1176,47 @@ _clutter_stage_has_full_redraw_queued (ClutterStage *stage)
     return FALSE;
 }
 
+/**
+ * clutter_stage_get_redraw_clip_bounds:
+ * @stage: A #ClutterStage
+ * @clip: (out caller-allocates): Return location for the clip bounds
+ *
+ * Gets the bounds of the current redraw for @stage in stage pixel
+ * coordinates. E.g., if only a single actor has queued a redraw then
+ * Clutter may redraw the stage with a clip so that it doesn't have to
+ * paint every pixel in the stage. This function would then return the
+ * bounds of that clip. An application can use this information to
+ * avoid some extra work if it knows that some regions of the stage
+ * aren't going to be painted. This should only be called while the
+ * stage is being painted. If there is no current redraw clip then
+ * this function will set @clip to the full extents of the stage.
+ *
+ * Since: 1.8
+ */
+void
+clutter_stage_get_redraw_clip_bounds (ClutterStage          *stage,
+                                      cairo_rectangle_int_t *clip)
+{
+  ClutterStagePrivate *priv;
+
+  g_return_if_fail (CLUTTER_IS_STAGE (stage));
+  g_return_if_fail (clip != NULL);
+
+  priv = stage->priv;
+
+  if (!_clutter_stage_window_get_redraw_clip_bounds (priv->impl, clip))
+    {
+      ClutterGeometry geometry;
+
+      /* Set clip to the full extents of the stage */
+      _clutter_stage_window_get_geometry (priv->impl, &geometry);
+      clip->x = 0;
+      clip->y = 0;
+      clip->width = geometry.width;
+      clip->height = geometry.height;
+    }
+}
+
 static void
 read_pixels_to_file (char *filename_stem,
                      int   x,

clutter/clutter-stage.h

@@ -32,6 +32,7 @@
 #include <clutter/clutter-group.h>
 #include <clutter/clutter-color.h>
 #include <clutter/clutter-event.h>
+#include <cairo.h>
 
 G_BEGIN_DECLS
 
@@ -263,6 +264,9 @@ void                  clutter_stage_set_accept_focus  (ClutterStage *stage,
 gboolean              clutter_stage_get_accept_focus  (ClutterStage *stage);
 
 
+void                  clutter_stage_get_redraw_clip_bounds    (ClutterStage    *stage,
+                                                               cairo_rectangle_int_t *clip);
+
 void                  clutter_stage_set_motion_events_enabled (ClutterStage *stage,
                                                                gboolean      enabled);
 gboolean              clutter_stage_get_motion_events_enabled (ClutterStage *stage);

clutter/cogl/clutter-stage-cogl.c

@@ -324,6 +324,25 @@ clutter_stage_cogl_add_redraw_clip (ClutterStageWindow *stage_window,
   stage_cogl->initialized_redraw_clip = TRUE;
 }
 
+static gboolean
+clutter_stage_cogl_get_redraw_clip_bounds (ClutterStageWindow *stage_window,
+                                           cairo_rectangle_int_t *stage_clip)
+{
+  ClutterStageCogl *stage_cogl = CLUTTER_STAGE_COGL (stage_window);
+
+  if (stage_cogl->using_clipped_redraw)
+    {
+      stage_clip->x = stage_cogl->bounding_redraw_clip.x;
+      stage_clip->y = stage_cogl->bounding_redraw_clip.y;
+      stage_clip->width = stage_cogl->bounding_redraw_clip.width;
+      stage_clip->height = stage_cogl->bounding_redraw_clip.height;
+
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
 /* XXX: This is basically identical to clutter_stage_glx_redraw */
 static void
 clutter_stage_cogl_redraw (ClutterStageWindow *stage_window)
@@ -401,6 +420,9 @@ clutter_stage_cogl_redraw (ClutterStageWindow *stage_window)
                     stage_cogl->bounding_redraw_clip.y,
                     stage_cogl->bounding_redraw_clip.width,
                     stage_cogl->bounding_redraw_clip.height);
+
+      stage_cogl->using_clipped_redraw = TRUE;
+
       cogl_clip_push_window_rectangle (stage_cogl->bounding_redraw_clip.x,
                                        stage_cogl->bounding_redraw_clip.y,
                                        stage_cogl->bounding_redraw_clip.width,
@@ -408,6 +430,8 @@ clutter_stage_cogl_redraw (ClutterStageWindow *stage_window)
       _clutter_stage_do_paint (CLUTTER_STAGE (wrapper),
                                &stage_cogl->bounding_redraw_clip);
       cogl_clip_pop ();
+
+      stage_cogl->using_clipped_redraw = FALSE;
     }
   else
     {
@@ -568,6 +592,7 @@ clutter_stage_window_iface_init (ClutterStageWindowIface *iface)
   iface->add_redraw_clip = clutter_stage_cogl_add_redraw_clip;
   iface->has_redraw_clips = clutter_stage_cogl_has_redraw_clips;
   iface->ignoring_redraw_clips = clutter_stage_cogl_ignoring_redraw_clips;
+  iface->get_redraw_clip_bounds = clutter_stage_cogl_get_redraw_clip_bounds;
   iface->redraw = clutter_stage_cogl_redraw;
   iface->get_active_framebuffer = clutter_stage_cogl_get_active_framebuffer;
 }

clutter/cogl/clutter-stage-cogl.h

@@ -60,6 +60,10 @@ struct _ClutterStageCogl
   ClutterGeometry bounding_redraw_clip;
 
   guint initialized_redraw_clip : 1;
+
+  /* TRUE if the current paint cycle has a clipped redraw. In that
+     case bounding_redraw_clip specifies the the bounds. */
+  guint using_clipped_redraw : 1;
 };
 
 struct _ClutterStageCoglClass

doc/reference/clutter/clutter-sections.txt

@@ -610,6 +610,7 @@ clutter_stage_set_minimum_size
 clutter_stage_get_minimum_size
 clutter_stage_set_no_clear_hint
 clutter_stage_get_no_clear_hint
+clutter_stage_get_redraw_clip_bounds
 clutter_stage_set_accept_focus
 clutter_stage_get_accept_focus
 clutter_stage_get_motion_events_enabled