Bug 1442190 - Part 1: Add nsDisplayOpacityGeometry r=mattwoodrow

MozReview-Commit-ID: K7WqIlib10v

--HG--
extra : rebase_source : ccc6a2f531541b0d6dfce79bf0d1685cb9298f01

layout/painting/nsDisplayList.cpp

@@ -6640,6 +6640,20 @@ nsDisplayOpacity::ComputeVisibility(nsDisplayListBuilder* aBuilder,
     nsDisplayWrapList::ComputeVisibility(aBuilder, &visibleUnderChildren);
 }
 
+void
+nsDisplayOpacity::ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
+                                            const nsDisplayItemGeometry* aGeometry,
+                                            nsRegion* aInvalidRegion) const
+{
+  const nsDisplayOpacityGeometry* geometry =
+    static_cast<const nsDisplayOpacityGeometry*>(aGeometry);
+
+  bool snap;
+  if (mOpacity != geometry->mOpacity) {
+    aInvalidRegion->Or(GetBounds(aBuilder, &snap), geometry->mBounds);
+  }
+}
+
 void
 nsDisplayOpacity::WriteDebugInfo(std::stringstream& aStream)
 {

layout/painting/nsDisplayList.h

@@ -5201,12 +5201,15 @@ public:
     return HasSameTypeAndClip(aItem) && HasSameContent(aItem);
   }
 
+  virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) override
+  {
+    return new nsDisplayOpacityGeometry(this, aBuilder, mOpacity);
+  }
+
   virtual void ComputeInvalidationRegion(nsDisplayListBuilder* aBuilder,
                                          const nsDisplayItemGeometry* aGeometry,
-                                         nsRegion* aInvalidRegion) const override
-  {
-    // We don't need to compute an invalidation region since we have LayerTreeInvalidation
-  }
+                                         nsRegion* aInvalidRegion) const override;
+
   virtual bool IsInvalid(nsRect& aRect) const override
   {
     if (mForEventsAndPluginsOnly) {

layout/painting/nsDisplayListInvalidation.h

@@ -353,4 +353,17 @@ public:
   nsPoint mFrameOffsetToViewport;
 };
 
+class nsDisplayOpacityGeometry : public nsDisplayItemGenericGeometry
+{
+public:
+  nsDisplayOpacityGeometry(nsDisplayItem* aItem,
+                           nsDisplayListBuilder* aBuilder,
+                           float aOpacity)
+    : nsDisplayItemGenericGeometry(aItem, aBuilder)
+    , mOpacity(aOpacity)
+  {}
+
+  float mOpacity;
+};
+
 #endif /*NSDISPLAYLISTINVALIDATION_H_*/