Bug 725981 - Only invalidate the difference in bounds when a solid color moves or resizes. r=roc

layout/base/nsDisplayList.h

@@ -862,6 +862,28 @@ public:
     }
   }
 
+  /**
+   * An alternative default implementation of ComputeInvalidationRegion,
+   * that instead invalidates only the changed area between the two items.
+   */
+  void ComputeInvalidationRegionDifference(nsDisplayListBuilder* aBuilder,
+                                           const nsDisplayItemBoundsGeometry* aGeometry,
+                                           nsRegion* aInvalidRegion)
+  {
+    bool snap;
+    nsRect bounds = GetBounds(aBuilder, &snap);
+
+    if (!aGeometry->mBounds.IsEqualInterior(bounds)) {
+      nscoord radii[8];
+      if (aGeometry->mHasRoundedCorners ||
+          GetUnderlyingFrame()->GetBorderRadii(radii)) {
+        aInvalidRegion->Or(aGeometry->mBounds, bounds);
+      } else {
+        aInvalidRegion->Xor(aGeometry->mBounds, bounds);
+      }
+    }
+  }
+
   /**
    * Called when the area rendered by this display item has changed (been
    * invalidated or changed geometry) since the last paint. This includes
@@ -1815,6 +1837,19 @@ public:
 
   virtual void Paint(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx) MOZ_OVERRIDE;
 
+  virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE
+  {
+    return new nsDisplayItemBoundsGeometry(this, aBuilder);
+  }
+
+  virtual void ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
+                                         const nsDisplayItemGeometry* aGeometry,
+                                         nsRegion* aInvalidRegion)
+  {
+    const nsDisplayItemBoundsGeometry* geometry = static_cast<const nsDisplayItemBoundsGeometry*>(aGeometry);
+    ComputeInvalidationRegionDifference(aBuilder, geometry, aInvalidRegion);
+  }
+
   NS_DISPLAY_DECL_NAME("SolidColor", TYPE_SOLID_COLOR)
 
 private:
@@ -1965,6 +2000,19 @@ public:
     return nsRect(ToReferenceFrame(), GetUnderlyingFrame()->GetSize());
   }
 
+  virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE
+  {
+    return new nsDisplayItemBoundsGeometry(this, aBuilder);
+  }
+
+  virtual void ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
+                                         const nsDisplayItemGeometry* aGeometry,
+                                         nsRegion* aInvalidRegion)
+  {
+    const nsDisplayItemBoundsGeometry* geometry = static_cast<const nsDisplayItemBoundsGeometry*>(aGeometry);
+    ComputeInvalidationRegionDifference(aBuilder, geometry, aInvalidRegion);
+  }
+
   NS_DISPLAY_DECL_NAME("BackgroundColor", TYPE_BACKGROUND_COLOR)
 #ifdef MOZ_DUMP_PAINTING
   virtual void WriteDebugInfo(FILE *aOutput) {

layout/base/nsDisplayListInvalidation.cpp

@@ -30,6 +30,19 @@ nsDisplayItemGenericGeometry::MoveBy(const nsPoint& aOffset)
   mBorderRect.MoveBy(aOffset);
 }
 
+nsDisplayItemBoundsGeometry::nsDisplayItemBoundsGeometry(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder)
+  : nsDisplayItemGeometry(aItem, aBuilder)
+{
+  nscoord radii[8];
+  mHasRoundedCorners = aItem->GetUnderlyingFrame()->GetBorderRadii(radii);
+}
+
+void
+nsDisplayItemBoundsGeometry::MoveBy(const nsPoint& aOffset)
+{
+  mBounds.MoveBy(aOffset);
+}
+
 nsDisplayBorderGeometry::nsDisplayBorderGeometry(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder)
   : nsDisplayItemGeometry(aItem, aBuilder)
   , mContentRect(aItem->GetContentRect())

layout/base/nsDisplayListInvalidation.h

@@ -63,6 +63,16 @@ public:
   nsRect mBorderRect;
 };
 
+class nsDisplayItemBoundsGeometry : public nsDisplayItemGeometry
+{
+public:
+  nsDisplayItemBoundsGeometry(nsDisplayItem* aItem, nsDisplayListBuilder* aBuilder);
+
+  virtual void MoveBy(const nsPoint& aOffset);
+
+  bool mHasRoundedCorners;
+};
+
 class nsDisplayBorderGeometry : public nsDisplayItemGeometry
 {
 public:

layout/generic/nsCanvasFrame.h

@@ -159,6 +159,20 @@ public:
     // We need to override so we don't consider border-radius.
     aOutFrames->AppendElement(mFrame);
   }
+
+  virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE
+  {
+    return new nsDisplayItemBoundsGeometry(this, aBuilder);
+  }
+
+  virtual void ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
+                                         const nsDisplayItemGeometry* aGeometry,
+                                         nsRegion* aInvalidRegion)
+  {
+    const nsDisplayItemBoundsGeometry* geometry = static_cast<const nsDisplayItemBoundsGeometry*>(aGeometry);
+    ComputeInvalidationRegionDifference(aBuilder, geometry, aInvalidRegion);
+  }
+
   virtual void NotifyRenderingChanged() MOZ_OVERRIDE
   {
     mFrame->Properties().Delete(nsIFrame::CachedBackgroundImage());