Bug 1418387 - Find the appropriate scrollbar node in GetAPZCAtPointWR. r=botond

MozReview-Commit-ID: Fb4465Gaj7K

--HG--
extra : rebase_source : 647e617326d5e45dde0eb22b3ba9ac7cc03f7096

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -2197,7 +2197,8 @@ APZCTreeManager::GetTargetAPZC(const ScreenPoint& aPoint,
 
   if (gfxPrefs::WebRenderHitTest()) {
     HitTestResult wrHitResult = HitNothing;
-    RefPtr<AsyncPanZoomController> wrTarget = GetAPZCAtPointWR(aPoint, &wrHitResult);
+    HitTestingTreeNode* wrScrollbarNode = nullptr;
+    RefPtr<AsyncPanZoomController> wrTarget = GetAPZCAtPointWR(aPoint, &wrHitResult, &wrScrollbarNode);
     // For now just compare the WR and non-WR results.
     if (wrHitResult != hitResult) {
       printf_stderr("WR hit result mismatch at %s: got %d, expected %d\n",
@@ -2211,6 +2212,11 @@ APZCTreeManager::GetTargetAPZC(const ScreenPoint& aPoint,
           target ? Stringify(target->GetGuid()).c_str() : "null");
       // MOZ_RELEASE_ASSERT(false);
     }
+    if (wrScrollbarNode != scrollbarNode) {
+      printf_stderr("WR scrollbar node mismatch at %s: got %p, expected %p\n",
+          Stringify(aPoint).c_str(), wrScrollbarNode, scrollbarNode);
+      // MOZ_RELEASE_ASSERT(false);
+    }
   }
 
   if (aOutHitResult) {
@@ -2224,9 +2230,11 @@ APZCTreeManager::GetTargetAPZC(const ScreenPoint& aPoint,
 
 already_AddRefed<AsyncPanZoomController>
 APZCTreeManager::GetAPZCAtPointWR(const ScreenPoint& aHitTestPoint,
-                                  HitTestResult* aOutHitResult)
+                                  HitTestResult* aOutHitResult,
+                                  HitTestingTreeNode** aOutScrollbarNode)
 {
   MOZ_ASSERT(aOutHitResult);
+  MOZ_ASSERT(aOutScrollbarNode);
 
   RefPtr<AsyncPanZoomController> result;
   RefPtr<wr::WebRenderAPI> wr = GetWebRenderAPI();
@@ -2256,6 +2264,22 @@ APZCTreeManager::GetAPZCAtPointWR(const ScreenPoint& aHitTestPoint,
     MOZ_ASSERT(result);
   }
 
+  bool isScrollbar = bool(hitInfo & gfx::CompositorHitTestInfo::eScrollbar);
+  bool isScrollbarThumb = bool(hitInfo & gfx::CompositorHitTestInfo::eScrollbarThumb);
+  ScrollDirection direction = (hitInfo & gfx::CompositorHitTestInfo::eScrollbarVertical)
+                            ? ScrollDirection::eVertical
+                            : ScrollDirection::eHorizontal;
+  if (isScrollbar || isScrollbarThumb) {
+    *aOutScrollbarNode = BreadthFirstSearch<ReverseIterator>(mRootNode.get(),
+      [&](HitTestingTreeNode* aNode) {
+        return (aNode->GetLayersId() == layersId) &&
+               (aNode->IsScrollbarNode() == isScrollbar) &&
+               (aNode->IsScrollThumbNode() == isScrollbarThumb) &&
+               (aNode->GetScrollbarDirection() == direction) &&
+               (aNode->GetScrollTargetId() == scrollId);
+      });
+  }
+
   *aOutHitResult = HitLayer;
   if (hitInfo & gfx::CompositorHitTestInfo::eDispatchToContent) {
     *aOutHitResult = HitDispatchToContentRegion;

gfx/layers/apz/src/APZCTreeManager.h

@@ -524,7 +524,8 @@ private:
                                          HitTestResult* aOutHitResult,
                                          HitTestingTreeNode** aOutScrollbarNode);
   already_AddRefed<AsyncPanZoomController> GetAPZCAtPointWR(const ScreenPoint& aHitTestPoint,
-                                                            HitTestResult* aOutHitResult);
+                                                            HitTestResult* aOutHitResult,
+                                                            HitTestingTreeNode** aOutScrollbarNode);
   AsyncPanZoomController* FindRootApzcForLayersId(uint64_t aLayersId) const;
   AsyncPanZoomController* FindRootContentApzcForLayersId(uint64_t aLayersId) const;
   AsyncPanZoomController* FindRootContentOrRootApzc() const;

gfx/layers/apz/src/HitTestingTreeNode.cpp

@@ -124,6 +124,16 @@ HitTestingTreeNode::IsScrollbarNode() const
   return mScrollbarContainerDirection.isSome() || IsScrollThumbNode();
 }
 
+ScrollDirection
+HitTestingTreeNode::GetScrollbarDirection() const
+{
+  MOZ_ASSERT(IsScrollbarNode());
+  if (mScrollThumbData.mDirection.isSome()) {
+    return *(mScrollThumbData.mDirection);
+  }
+  return *mScrollbarContainerDirection;
+}
+
 FrameMetrics::ViewID
 HitTestingTreeNode::GetScrollTargetId() const
 {

gfx/layers/apz/src/HitTestingTreeNode.h

@@ -100,6 +100,8 @@ public:
                         const Maybe<ScrollDirection>& aScrollContainerDirection);
   bool MatchesScrollDragMetrics(const AsyncDragMetrics& aDragMetrics) const;
   bool IsScrollbarNode() const;  // Scroll thumb or scrollbar container layer.
+  // This can only be called if IsScrollbarNode() is true
+  ScrollDirection GetScrollbarDirection() const;
   bool IsScrollThumbNode() const;  // Scroll thumb container layer.
   FrameMetrics::ViewID GetScrollTargetId() const;
   const ScrollThumbData& GetScrollThumbData() const;