Bug 588690 - Part 1: Expose ClearCachedResources on BasicLayerManagers. r=roc

gfx/layers/basic/BasicLayers.cpp

@@ -112,6 +112,13 @@ public:
                      float aOpacity) {}
 
   virtual ShadowableLayer* AsShadowableLayer() { return nsnull; }
+
+  /**
+   * Layers will get this call when their layer manager is destroyed, this
+   * indicates they should clear resources they don't really need after their
+   * LayerManager ceases to exist.
+   */
+  virtual void ClearCachedResources() {}
 };
 
 static BasicImplData*
@@ -290,6 +297,8 @@ public:
                      LayerManager::DrawThebesLayerCallback aCallback,
                      void* aCallbackData,
                      float aOpacity);
+
+  virtual void ClearCachedResources() { mBuffer.Clear(); mValidRegion.SetEmpty(); }
   
   virtual already_AddRefed<gfxASurface>
   CreateBuffer(Buffer::ContentType aType, const nsIntSize& aSize)
@@ -856,6 +865,8 @@ BasicLayerManager::~BasicLayerManager()
 {
   NS_ASSERTION(!InTransaction(), "Died during transaction?");
 
+  ClearCachedResources();
+
   mRoot = nsnull;
 
   MOZ_COUNT_DTOR(BasicLayerManager);
@@ -1078,6 +1089,25 @@ BasicLayerManager::PaintLayer(Layer* aLayer,
   }
 }
 
+void
+BasicLayerManager::ClearCachedResources()
+{
+  if (mRoot) {
+    ClearLayer(mRoot);
+  }
+
+  mCachedSurface.Expire();
+}
+void
+BasicLayerManager::ClearLayer(Layer* aLayer)
+{
+  ToData(aLayer)->ClearResources();
+  for (Layer* child = aLayer->GetFirstChild(); child;
+       child = child->GetNextSibling()) {
+    ClearLayer(child);
+  }
+}
+
 already_AddRefed<ThebesLayer>
 BasicLayerManager::CreateThebesLayer()
 {

gfx/layers/basic/BasicLayers.h

@@ -156,6 +156,9 @@ public:
   virtual const char* Name() const { return "Basic"; }
 #endif // MOZ_LAYERS_HAVE_LOG
 
+  // Clear the cached contents of this layer.
+  void ClearCachedResources();
+
 protected:
 #ifdef DEBUG
   enum TransactionPhase {
@@ -171,6 +174,9 @@ private:
                   void* aCallbackData,
                   float aOpacity);
 
+  // Clear the contents of a layer
+  void ClearLayer(Layer* aLayer);
+
   already_AddRefed<gfxContext> PushGroupWithCachedSurface(gfxContext *aTarget,
                                                           gfxASurface::gfxContentType aContent,
                                                           gfxPoint *aSavedOffset);