Bug 1038781 - Don't reflow/repaint frame when clip changes. r=roc

If an element's existing clip changes, just update overflow areas and let
DLBI handle invalidation.

layout/base/RestyleManager.cpp

@@ -83,8 +83,9 @@ DoApplyRenderingChangeToTree(nsIFrame* aFrame,
  * if aChange has nsChangeHint_SyncFrameView.
  * Calls DoApplyRenderingChangeToTree on all aFrame's out-of-flow descendants
  * (following placeholders), if aChange has nsChangeHint_RepaintFrame.
- * aFrame should be some combination of nsChangeHint_SyncFrameView and
- * nsChangeHint_RepaintFrame and nsChangeHint_UpdateOpacityLayer, nothing else.
+ * aFrame should be some combination of nsChangeHint_SyncFrameView,
+ * nsChangeHint_RepaintFrame, nsChangeHint_UpdateOpacityLayer and
+ * nsChangeHint_SchedulePaint, nothing else.
 */
 static void
 SyncViewsAndInvalidateDescendants(nsIFrame* aFrame,
@@ -94,7 +95,8 @@ SyncViewsAndInvalidateDescendants(nsIFrame* aFrame,
                   "should only be called within ApplyRenderingChangeToTree");
   NS_ASSERTION(aChange == (aChange & (nsChangeHint_RepaintFrame |
                                       nsChangeHint_SyncFrameView |
-                                      nsChangeHint_UpdateOpacityLayer)),
+                                      nsChangeHint_UpdateOpacityLayer |
+                                      nsChangeHint_SchedulePaint)),
                "Invalid change flag");
 
   nsView* view = aFrame->GetView();
@@ -184,7 +186,8 @@ DoApplyRenderingChangeToTree(nsIFrame* aFrame,
     SyncViewsAndInvalidateDescendants(aFrame,
       nsChangeHint(aChange & (nsChangeHint_RepaintFrame |
                               nsChangeHint_SyncFrameView |
-                              nsChangeHint_UpdateOpacityLayer)));
+                              nsChangeHint_UpdateOpacityLayer |
+                              nsChangeHint_SchedulePaint)));
     // This must be set to true if the rendering change needs to
     // invalidate content.  If it's false, a composite-only paint
     // (empty transaction) will be scheduled.
@@ -261,6 +264,9 @@ DoApplyRenderingChangeToTree(nsIFrame* aFrame,
         ActiveLayerTracker::NotifyRestyle(childFrame, eCSSProperty_transform);
       }
     }
+    if (aChange & nsChangeHint_SchedulePaint) {
+      needInvalidatingPaint = true;
+    }
     aFrame->SchedulePaint(needInvalidatingPaint ?
                           nsIFrame::PAINT_DEFAULT :
                           nsIFrame::PAINT_COMPOSITE_ONLY);
@@ -735,7 +741,7 @@ RestyleManager::ProcessRestyledFrames(nsStyleChangeList& aChangeList)
 
       if (hint & (nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView |
                   nsChangeHint_UpdateOpacityLayer | nsChangeHint_UpdateTransformLayer |
-                  nsChangeHint_ChildrenOnlyTransform)) {
+                  nsChangeHint_ChildrenOnlyTransform | nsChangeHint_SchedulePaint)) {
         ApplyRenderingChangeToTree(mPresContext, frame, hint);
       }
       if ((hint & nsChangeHint_RecomputePosition) && !didReflowThisFrame) {

layout/base/nsChangeHint.h

@@ -127,7 +127,13 @@ enum nsChangeHint {
    * SVG textPath needs to be recomputed because the path has changed.
    * This means that the glyph positions of the text need to be recomputed.
    */
-  nsChangeHint_UpdateTextPath = 0x40000
+  nsChangeHint_UpdateTextPath = 0x40000,
+
+  /**
+   * This will schedule an invalidating paint. This is useful if something
+   * has changed which will be invalidated by DLBI.
+   */
+  nsChangeHint_SchedulePaint = 0x80000
 
   // IMPORTANT NOTE: When adding new hints, consider whether you need to
   // add them to NS_HintsNotHandledForDescendantsIn() below.
@@ -228,7 +234,8 @@ inline nsChangeHint NS_HintsNotHandledForDescendantsIn(nsChangeHint aChangeHint)
 #define NS_STYLE_HINT_NONE \
   nsChangeHint(0)
 #define NS_STYLE_HINT_VISUAL \
-  nsChangeHint(nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView)
+  nsChangeHint(nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView | \
+               nsChangeHint_SchedulePaint)
 #define nsChangeHint_AllReflowHints                     \
   nsChangeHint(nsChangeHint_NeedReflow |                \
                nsChangeHint_ClearAncestorIntrinsics |   \

layout/style/nsStyleStruct.cpp

@@ -2501,10 +2501,17 @@ nsChangeHint nsStyleDisplay::CalcDifference(const nsStyleDisplay& aOther) const
       || mAppearance != aOther.mAppearance
       || mOrient != aOther.mOrient
       || mOverflowClipBox != aOther.mOverflowClipBox
-      || mClipFlags != aOther.mClipFlags || !mClip.IsEqualInterior(aOther.mClip))
+      || mClipFlags != aOther.mClipFlags)
     NS_UpdateHint(hint, NS_CombineHint(nsChangeHint_AllReflowHints,
                                        nsChangeHint_RepaintFrame));
 
+  if (!mClip.IsEqualInterior(aOther.mClip)) {
+    // If the clip has changed, we just need to update overflow areas. DLBI
+    // will handle the invalidation.
+    NS_UpdateHint(hint, NS_CombineHint(nsChangeHint_UpdateOverflow,
+                                       nsChangeHint_SchedulePaint));
+  }
+
   if (mOpacity != aOther.mOpacity) {
     // If we're going from the optimized >=0.99 opacity value to 1.0 or back, then
     // repaint the frame because DLBI will not catch the invalidation.  Otherwise,