Bug 1384616 - Save APZ-relevant data from fixed-pos items in the WR scroll data for layers-free transactions. r=jrmuizel

MozReview-Commit-ID: HAFnrCVM9pZ

--HG--
extra : rebase_source : 9b7f5f7a3487501061b0526bfc92b06ef5593a88

gfx/layers/wr/WebRenderScrollData.h

@@ -74,6 +74,7 @@ public:
   const uint64_t& GetScrollbarAnimationId() const { return mScrollbarAnimationId; }
   FrameMetrics::ViewID GetScrollbarTargetContainerId() const { return mScrollbarTargetContainerId; }
   bool IsScrollbarContainer() const { return mIsScrollbarContainer; }
+  void SetFixedPositionScrollContainerId(FrameMetrics::ViewID aId) { mFixedPosScrollContainerId = aId; }
   FrameMetrics::ViewID GetFixedPositionScrollContainerId() const { return mFixedPosScrollContainerId; }
 
   void Dump(const WebRenderScrollData& aOwner) const;

layout/base/nsLayoutUtils.cpp

@@ -2087,13 +2087,20 @@ nsLayoutUtils::SetFixedPositionLayerData(Layer* aLayer,
     }
   }
 
+  ViewID id = ScrollIdForRootScrollFrame(aPresContext);
+  aLayer->SetFixedPositionData(id, anchor, sides);
+}
+
+FrameMetrics::ViewID
+nsLayoutUtils::ScrollIdForRootScrollFrame(nsPresContext* aPresContext)
+{
   ViewID id = FrameMetrics::NULL_SCROLL_ID;
   if (nsIFrame* rootScrollFrame = aPresContext->PresShell()->GetRootScrollFrame()) {
     if (nsIContent* content = rootScrollFrame->GetContent()) {
       id = FindOrCreateIDFor(content);
     }
   }
-  aLayer->SetFixedPositionData(id, anchor, sides);
+  return id;
 }
 
 bool

layout/base/nsLayoutUtils.h

@@ -572,6 +572,12 @@ public:
                                         nsPresContext* aPresContext,
                                         const ContainerLayerParameters& aContainerParameters);
 
+  /**
+   * Get the scroll id for the root scrollframe of the presshell of the given
+   * prescontext. Returns NULL_SCROLL_ID if it couldn't be found.
+   */
+  static FrameMetrics::ViewID ScrollIdForRootScrollFrame(nsPresContext* aPresContext);
+
   /**
    * Return true if aPresContext's viewport has a displayport.
    */

layout/painting/nsDisplayList.cpp

@@ -6688,6 +6688,18 @@ bool nsDisplayFixedPosition::TryMerge(nsDisplayItem* aItem) {
   return true;
 }
 
+bool
+nsDisplayFixedPosition::UpdateScrollData(mozilla::layers::WebRenderScrollData* aData,
+                                         mozilla::layers::WebRenderLayerScrollData* aLayerData)
+{
+  if (aLayerData) {
+    FrameMetrics::ViewID id = nsLayoutUtils::ScrollIdForRootScrollFrame(
+        Frame()->PresContext());
+    aLayerData->SetFixedPositionScrollContainerId(id);
+  }
+  return true;
+}
+
 TableType
 GetTableTypeFromFrame(nsIFrame* aFrame)
 {

layout/painting/nsDisplayList.h

@@ -4297,6 +4297,9 @@ public:
     return mAnimatedGeometryRootForScrollMetadata;
   }
 
+  virtual bool UpdateScrollData(mozilla::layers::WebRenderScrollData* aData,
+                                mozilla::layers::WebRenderLayerScrollData* aLayerData) override;
+
 protected:
   // For background-attachment:fixed
   nsDisplayFixedPosition(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,