[clutter] stage: implicitly clip to stage window bounds

[Robert Bragg <rbragg src gnome org>]

commit 239fc43c5f5dc15346094bf797ad8e8799424a4b
Author: Robert Bragg <robert linux intel com>
Date:   Mon Sep 19 12:54:31 2011 +0100

    stage: implicitly clip to stage window bounds
    
    This implicitly intersects any clip for redrawing with the stage window
    bounds. Without this we were sometimes trying to set huge off screen
    scissors leading to undefined clipping results.
    
    Reviewed-by: Emmanuele Bassi <ebassi linux intel com>

 clutter/clutter-stage.c |   45 +++++++++++++++++++++++++++++----------------
 1 files changed, 29 insertions(+), 16 deletions(-)
---
diff --git a/clutter/clutter-stage.c b/clutter/clutter-stage.c
index 0abe9e9..e8471bb 100644
--- a/clutter/clutter-stage.c
+++ b/clutter/clutter-stage.c
@@ -529,24 +529,23 @@ _clutter_stage_do_paint (ClutterStage *stage, const ClutterGeometry *clip)
 {
   ClutterStagePrivate *priv = stage->priv;
   float clip_poly[8];
+  ClutterGeometry geom;
+
+  _clutter_stage_window_get_geometry (priv->impl, &geom);
 
   if (clip)
     {
-      clip_poly[0] = clip->x;
-      clip_poly[1] = clip->y;
-      clip_poly[2] = clip->x + clip->width;
-      clip_poly[3] = clip->y;
-      clip_poly[4] = clip->x + clip->width;
-      clip_poly[5] = clip->y + clip->height;
-      clip_poly[6] = clip->x;
-      clip_poly[7] = clip->y + clip->height;
+      clip_poly[0] = MAX (clip->x, 0);
+      clip_poly[1] = MAX (clip->y, 0);
+      clip_poly[2] = MIN (clip->x + clip->width, geom.width);
+      clip_poly[3] = clip_poly[1];
+      clip_poly[4] = clip_poly[2];
+      clip_poly[5] = MIN (clip->y + clip->height, geom.height);
+      clip_poly[6] = clip_poly[0];
+      clip_poly[7] = clip_poly[5];
     }
   else
     {
-      ClutterGeometry geom;
-
-      _clutter_stage_window_get_geometry (priv->impl, &geom);
-
       clip_poly[0] = 0;
       clip_poly[1] = 0;
       clip_poly[2] = geom.width;
@@ -1118,6 +1117,8 @@ clutter_stage_real_queue_redraw (ClutterActor *actor,
   ClutterGeometry stage_clip;
   ClutterPaintVolume *redraw_clip;
   ClutterActorBox bounding_box;
+  ClutterActorBox intersection_box;
+  ClutterGeometry geom;
 
   if (CLUTTER_ACTOR_IN_DESTRUCTION (actor))
     return;
@@ -1151,12 +1152,24 @@ clutter_stage_real_queue_redraw (ClutterActor *actor,
                                              stage,
                                              &bounding_box);
 
+  _clutter_stage_window_get_geometry (stage_window, &geom);
+
+  intersection_box.x1 = MAX (bounding_box.x1, 0);
+  intersection_box.y1 = MAX (bounding_box.y1, 0);
+  intersection_box.x2 = MIN (bounding_box.x2, geom.width);
+  intersection_box.y2 = MIN (bounding_box.y2, geom.height);
+
+  /* There is no need to track degenerate/empty redraw clips */
+  if (intersection_box.x2 <= intersection_box.x1 ||
+      intersection_box.y2 <= intersection_box.y1)
+    return;
+
   /* when converting to integer coordinates make sure we round the edges of the
    * clip rectangle outwards... */
-  stage_clip.x = bounding_box.x1;
-  stage_clip.y = bounding_box.y1;
-  stage_clip.width = bounding_box.x2 - stage_clip.x;
-  stage_clip.height = bounding_box.y2 - stage_clip.y;
+  stage_clip.x = intersection_box.x1;
+  stage_clip.y = intersection_box.y1;
+  stage_clip.width = intersection_box.x2 - stage_clip.x;
+  stage_clip.height = intersection_box.y2 - stage_clip.y;
 
   _clutter_stage_window_add_redraw_clip (stage_window, &stage_clip);
 }