Bug 1328702: ContainerLayer::RemoveAllChildren implementation. r=kats,mattwoodrow

MozReview-Commit-ID: 6zC3v8dQcWD

gfx/layers/Layers.cpp

@@ -1182,6 +1182,43 @@ ContainerLayer::InsertAfter(Layer* aChild, Layer* aAfter)
   return true;
 }
 
+void
+ContainerLayer::RemoveAllChildren()
+{
+  // Optimizes "while (mFirstChild) ContainerLayer::RemoveChild(mFirstChild);"
+  Layer* current = mFirstChild;
+
+  // This is inlining DidRemoveChild() on each layer; we can skip the calls
+  // to NotifyPaintedLayerRemoved as it gets taken care of when as we call
+  // NotifyRemoved prior to removing any layers.
+  while (current) {
+    Layer* next = current->GetNextSibling();
+    if (current->GetType() == TYPE_READBACK) {
+      static_cast<ReadbackLayer*>(current)->NotifyRemoved();
+    }
+    current = next;
+  }
+
+  current = mFirstChild;
+  mFirstChild = nullptr;
+  while (current) {
+    MOZ_ASSERT(!current->GetPrevSibling());
+
+    Layer* next = current->GetNextSibling();
+    current->SetParent(nullptr);
+    current->SetNextSibling(nullptr);
+    if (next) {
+      next->SetPrevSibling(nullptr);
+    }
+    NS_RELEASE(current);
+    current = next;
+  }
+}
+
+// Note that ContainerLayer::RemoveAllChildren is an optimized
+// version of this code; if you make changes to ContainerLayer::RemoveChild
+// consider whether the matching changes need to be made to
+// ContainerLayer::RemoveAllChildren
 bool
 ContainerLayer::RemoveChild(Layer *aChild)
 {
@@ -1625,6 +1662,10 @@ ContainerLayer::HasOpaqueAncestorLayer(Layer* aLayer)
   return false;
 }
 
+// Note that ContainerLayer::RemoveAllChildren contains an optimized
+// version of this code; if you make changes to ContainerLayer::DidRemoveChild
+// consider whether the matching changes need to be made to
+// ContainerLayer::RemoveAllChildren
 void
 ContainerLayer::DidRemoveChild(Layer* aLayer)
 {

gfx/layers/Layers.h

@@ -2257,6 +2257,12 @@ public:
 protected:
   friend class ReadbackProcessor;
 
+  // Note that this is not virtual, and is based on the implementation of
+  // ContainerLayer::RemoveChild, so it should only be called where you would
+  // want to explicitly call the base class implementation of RemoveChild;
+  // e.g., while (mFirstChild) ContainerLayer::RemoveChild(mFirstChild);
+  void RemoveAllChildren();
+
   void DidInsertChild(Layer* aLayer);
   void DidRemoveChild(Layer* aLayer);
 

gfx/layers/basic/BasicContainerLayer.cpp

@@ -23,10 +23,7 @@ namespace layers {
 
 BasicContainerLayer::~BasicContainerLayer()
 {
-  while (mFirstChild) {
+  ContainerLayer::RemoveAllChildren();
-    ContainerLayer::RemoveChild(mFirstChild);
-  }
-
   MOZ_COUNT_DTOR(BasicContainerLayer);
 }
 

gfx/layers/client/ClientContainerLayer.h

@@ -36,10 +36,7 @@ public:
 protected:
   virtual ~ClientContainerLayer()
   {
-    while (mFirstChild) {
+    ContainerLayer::RemoveAllChildren();
-      ContainerLayer::RemoveChild(mFirstChild);
-    }
-
     MOZ_COUNT_DTOR(ClientContainerLayer);
   }