Bug 860613 - Add an API to bind an APZC instance to a Layer. r=BenWa

gfx/layers/Layers.cpp

@@ -398,6 +398,38 @@ Layer::SetAnimations(const AnimationArray& aAnimations)
   Mutated();
 }
 
+static uint8_t sPanZoomUserDataKey;
+struct PanZoomUserData : public LayerUserData {
+  PanZoomUserData(AsyncPanZoomController* aController)
+    : mController(aController)
+  { }
+
+  // We don't keep a strong ref here because PanZoomUserData is only
+  // set transiently, and APZC is thread-safe refcounted so
+  // AddRef/Release is expensive.
+  AsyncPanZoomController* mController;
+};
+
+void
+Layer::SetAsyncPanZoomController(AsyncPanZoomController *controller)
+{
+  if (controller) {
+    SetUserData(&sPanZoomUserDataKey, new PanZoomUserData(controller));
+  } else {
+    RemoveUserData(&sPanZoomUserDataKey);
+  }
+}
+
+AsyncPanZoomController*
+Layer::GetAsyncPanZoomController()
+{
+  LayerUserData* data = GetUserData(&sPanZoomUserDataKey);
+  if (!data) {
+    return nullptr;
+  }
+  return static_cast<PanZoomUserData*>(data)->mController;
+}
+
 void
 Layer::ApplyPendingUpdatesToSubtree()
 {

gfx/layers/Layers.h

@@ -48,6 +48,7 @@ namespace layers {
 
 class Animation;
 class AnimationData;
+class AsyncPanZoomController;
 class CommonLayerAttributes;
 class Layer;
 class ThebesLayer;
@@ -896,6 +897,11 @@ public:
   const gfx::Margin& GetFixedPositionMargins() { return mMargins; }
   Layer* GetMaskLayer() { return mMaskLayer; }
 
+  // These functions allow attaching an AsyncPanZoomController to this layer,
+  // and can be used anytime.
+  void SetAsyncPanZoomController(AsyncPanZoomController *controller);
+  AsyncPanZoomController* GetAsyncPanZoomController();
+
   // Note that all lengths in animation data are either in CSS pixels or app
   // units and must be converted to device pixels by the compositor.
   AnimationArray& GetAnimations() { return mAnimations; }

gfx/layers/ipc/CompositorParent.cpp

@@ -67,18 +67,6 @@ struct LayerTreeState {
   TargetConfig mTargetConfig;
 };
 
-static uint8_t sPanZoomUserDataKey;
-struct PanZoomUserData : public LayerUserData {
-  PanZoomUserData(AsyncPanZoomController* aController)
-    : mController(aController)
-  { }
-
-  // We don't keep a strong ref here because PanZoomUserData is only
-  // set transiently, and APZC is thread-safe refcounted so
-  // AddRef/Release is expensive.
-  AsyncPanZoomController* mController;
-};
-
 /**
  * Lookup the indirect shadow tree for |aId| and return it if it
  * exists.  Otherwise null is returned.  This must only be called on
@@ -504,12 +492,11 @@ private:
           if (OP == Resolve) {
             ref->ConnectReferentLayer(referent);
             if (AsyncPanZoomController* apzc = state->mController) {
-              referent->SetUserData(&sPanZoomUserDataKey,
-                                    new PanZoomUserData(apzc));
+              referent->SetAsyncPanZoomController(apzc);
             }
           } else {
             ref->DetachReferentLayer(referent);
-            referent->RemoveUserData(&sPanZoomUserDataKey);
+            referent->SetAsyncPanZoomController(nullptr);
           }
         }
       }
@@ -855,13 +842,7 @@ CompositorParent::ApplyAsyncContentTransformToTree(TimeStamp aCurrentFrame,
     return appliedTransform;
   }
 
-  AsyncPanZoomController* controller = nullptr;
-  // Check if an AsyncPanZoomController is attached to this layer.
-  if (LayerUserData* data = aLayer->GetUserData(&sPanZoomUserDataKey)) {
-    controller = static_cast<PanZoomUserData*>(data)->mController;
-  }
-
-  if (controller) {
+  if (AsyncPanZoomController* controller = aLayer->GetAsyncPanZoomController()) {
     ShadowLayer* shadow = aLayer->AsShadowLayer();
 
     ViewTransform treeTransform;