Bug 1503616 - Propagate the zoom animation id over to the APZ code. r=botond

Depends on D11180

Differential Revision: https://phabricator.services.mozilla.com/D11181

--HG--
extra : moz-landing-system : lando

gfx/layers/LayerMetricsWrapper.h

@@ -433,6 +433,15 @@ public:
     return mLayer->GetFixedPositionScrollContainerId();
   }
 
+  Maybe<uint64_t> GetZoomAnimationId() const
+  {
+    MOZ_ASSERT(IsValid());
+    // This function is only really needed for template-compatibility with
+    // WebRenderScrollDataWrapper. Although it will be called, the return
+    // value is not used.
+    return Nothing();
+  }
+
   bool IsBackfaceHidden() const
   {
     MOZ_ASSERT(IsValid());

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -134,6 +134,16 @@ struct APZCTreeManager::TreeBuildingState {
   // children, meaning they are added to the children's ancestor transforms
   // instead. Those deferred transforms are tracked here.
   DeferredTransformMap mPerspectiveTransformsDeferredToChildren;
+
+  // As we recurse down through the tree, this picks up the zoom animation id
+  // from a node in the layer tree, and propagates it downwards to the nearest
+  // APZC instance that is for an RCD node. Generally it will be set on the
+  // root node of the layers (sub-)tree, which may not be same as the RCD node
+  // for the subtree, and so we need this mechanism to ensure it gets propagated
+  // to the RCD's APZC instance. Once it is set on the APZC instance, the value
+  // is cleared back to Nothing(). Note that this is only used in the WebRender
+  // codepath.
+  Maybe<uint64_t> mZoomAnimationId;
 };
 
 class APZCTreeManager::CheckerboardFlushObserver : public nsIObserver {
@@ -885,6 +895,10 @@ APZCTreeManager::PrepareNodeForLayer(const RecursiveMutexAutoLock& aProofOfTreeL
 
   bool parentHasPerspective = aState.mParentHasPerspective.top();
 
+  if (Maybe<uint64_t> zoomAnimationId = aLayer.GetZoomAnimationId()) {
+    aState.mZoomAnimationId = zoomAnimationId;
+  }
+
   RefPtr<HitTestingTreeNode> node = nullptr;
   if (!needsApzc) {
     // Note: if layer properties must be propagated to nodes, RecvUpdate in
@@ -995,6 +1009,11 @@ APZCTreeManager::PrepareNodeForLayer(const RecursiveMutexAutoLock& aProofOfTreeL
       node->SetLastChild(nullptr);
     }
 
+    if (aMetrics.IsRootContent()) {
+      apzc->SetZoomAnimationId(aState.mZoomAnimationId);
+      aState.mZoomAnimationId = Nothing();
+    }
+
     APZCTM_LOG("Using APZC %p for layer %p with identifiers %" PRIx64 " %" PRId64 "\n",
         apzc, aLayer.GetLayer(), uint64_t(aLayersId), aMetrics.GetScrollId());
 

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -5038,5 +5038,15 @@ bool AsyncPanZoomController::MaybeAdjustDestinationForScrollSnapping(
   return false;
 }
 
+void AsyncPanZoomController::SetZoomAnimationId(const Maybe<uint64_t>& aZoomAnimationId)
+{
+  mZoomAnimationId = aZoomAnimationId;
+}
+
+Maybe<uint64_t> AsyncPanZoomController::GetZoomAnimationId() const
+{
+  return mZoomAnimationId;
+}
+
 } // namespace layers
 } // namespace mozilla

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -982,6 +982,15 @@ private:
 
   UniquePtr<OverscrollEffectBase> mOverscrollEffect;
 
+  // Zoom animation id, used for zooming in WebRender. This should only be
+  // set on the APZC instance for the root content document (i.e. the one we
+  // support zooming on), and is only used if WebRender is enabled. The
+  // animation id itself refers to the transform animation id that was set on
+  // the stacking context in the WR display list. By changing the transform
+  // associated with this id, we can adjust the scaling that WebRender applies,
+  // thereby controlling the zoom.
+  Maybe<uint64_t> mZoomAnimationId;
+
   friend class Axis;
 
 public:
@@ -999,6 +1008,9 @@ public:
     return callable(mLastContentPaintMetrics);
   }
 
+  void SetZoomAnimationId(const Maybe<uint64_t>& aZoomAnimationId);
+  Maybe<uint64_t> GetZoomAnimationId() const;
+
   /* ===================================================================
    * The functions and members in this section are used to expose
    * the current async transform state to callers.

gfx/layers/wr/WebRenderCommandBuilder.cpp

@@ -1339,6 +1339,9 @@ WebRenderCommandBuilder::BuildWebRenderCommands(wr::DisplayListBuilder& aBuilder
   // Make a "root" layer data that has everything else as descendants
   mLayerScrollData.emplace_back();
   mLayerScrollData.back().InitializeRoot(mLayerScrollData.size() - 1);
+  if (mZoomProp) {
+    mLayerScrollData.back().SetZoomAnimationId(mZoomProp->id);
+  }
   auto callback = [&aScrollData](ScrollableLayerGuid::ViewID aScrollId) -> bool {
     return aScrollData.HasMetadataFor(aScrollId).isSome();
   };

gfx/layers/wr/WebRenderScrollData.h

@@ -87,6 +87,9 @@ public:
   void SetFixedPositionScrollContainerId(ScrollableLayerGuid::ViewID aId) { mFixedPosScrollContainerId = aId; }
   ScrollableLayerGuid::ViewID GetFixedPositionScrollContainerId() const { return mFixedPosScrollContainerId; }
 
+  void SetZoomAnimationId(const uint64_t& aId) { mZoomAnimationId = Some(aId); }
+  Maybe<uint64_t> GetZoomAnimationId() const { return mZoomAnimationId; }
+
   void Dump(const WebRenderScrollData& aOwner) const;
 
   friend struct IPC::ParamTraits<WebRenderLayerScrollData>;
@@ -117,6 +120,7 @@ private:
   ScrollbarData mScrollbarData;
   uint64_t mScrollbarAnimationId;
   ScrollableLayerGuid::ViewID mFixedPosScrollContainerId;
+  Maybe<uint64_t> mZoomAnimationId;
 };
 
 // Data needed by APZ, for the whole layer tree. One instance of this class
@@ -237,6 +241,7 @@ struct ParamTraits<mozilla::layers::WebRenderLayerScrollData>
     WriteParam(aMsg, aParam.mScrollbarData);
     WriteParam(aMsg, aParam.mScrollbarAnimationId);
     WriteParam(aMsg, aParam.mFixedPosScrollContainerId);
+    WriteParam(aMsg, aParam.mZoomAnimationId);
   }
 
   static bool
@@ -253,7 +258,8 @@ struct ParamTraits<mozilla::layers::WebRenderLayerScrollData>
         && ReadParam(aMsg, aIter, &aResult->mEventRegionsOverride)
         && ReadParam(aMsg, aIter, &aResult->mScrollbarData)
         && ReadParam(aMsg, aIter, &aResult->mScrollbarAnimationId)
-        && ReadParam(aMsg, aIter, &aResult->mFixedPosScrollContainerId);
+        && ReadParam(aMsg, aIter, &aResult->mFixedPosScrollContainerId)
+        && ReadParam(aMsg, aIter, &aResult->mZoomAnimationId);
   }
 };
 

gfx/layers/wr/WebRenderScrollDataWrapper.h

@@ -316,6 +316,12 @@ public:
     return mLayer->GetFixedPositionScrollContainerId();
   }
 
+  Maybe<uint64_t> GetZoomAnimationId() const
+  {
+    MOZ_ASSERT(IsValid());
+    return mLayer->GetZoomAnimationId();
+  }
+
   bool IsBackfaceHidden() const
   {
     // This is only used by APZCTM hit testing, and WR does its own