Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1110 insertions, 0 deletions

diff --git a/gfx/layers/apz/src/APZCTreeManager.h b/gfx/layers/apz/src/APZCTreeManager.h
new file mode 100644
index 0000000000..ff9bba51ca
--- /dev/null
+++ b/gfx/layers/apz/src/APZCTreeManager.h
@@ -0,0 +1,1110 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_APZCTreeManager_h
+#define mozilla_layers_APZCTreeManager_h
+
+#include <unordered_map>  // for std::unordered_map
+
+#include "FocusState.h"          // for FocusState
+#include "HitTestingTreeNode.h"  // for HitTestingTreeNodeAutoLock
+#include "IAPZHitTester.h"       // for IAPZHitTester::HitTestResult
+#include "gfxPoint.h"            // for gfxPoint
+#include "mozilla/Assertions.h"  // for MOZ_ASSERT_HELPER2
+#include "mozilla/DataMutex.h"   // for DataMutex
+#include "mozilla/gfx/CompositorHitTestInfo.h"
+#include "mozilla/gfx/Logging.h"              // for gfx::TreeLog
+#include "mozilla/gfx/Matrix.h"               // for Matrix4x4
+#include "mozilla/layers/APZInputBridge.h"    // for APZInputBridge
+#include "mozilla/layers/APZTestData.h"       // for APZTestData
+#include "mozilla/layers/APZUtils.h"          // for GeckoViewMetrics
+#include "mozilla/layers/IAPZCTreeManager.h"  // for IAPZCTreeManager
+#include "mozilla/layers/ScrollbarData.h"
+#include "mozilla/layers/LayersTypes.h"
+#include "mozilla/layers/KeyboardMap.h"      // for KeyboardMap
+#include "mozilla/layers/TouchCounter.h"     // for TouchCounter
+#include "mozilla/layers/ZoomConstraints.h"  // for ZoomConstraints
+#include "mozilla/webrender/webrender_ffi.h"
+#include "mozilla/RecursiveMutex.h"  // for RecursiveMutex
+#include "mozilla/RefPtr.h"          // for RefPtr
+#include "mozilla/TimeStamp.h"       // for mozilla::TimeStamp
+#include "mozilla/UniquePtr.h"       // for UniquePtr
+#include "nsCOMPtr.h"                // for already_AddRefed
+#include "nsTArray.h"
+#include "OvershootDetector.h"
+
+namespace mozilla {
+class MultiTouchInput;
+
+namespace wr {
+class TransactionWrapper;
+class WebRenderAPI;
+}  // namespace wr
+
+namespace layers {
+
+class Layer;
+class AsyncPanZoomController;
+class APZCTreeManagerParent;
+class APZSampler;
+class APZUpdater;
+class CompositorBridgeParent;
+class OverscrollHandoffChain;
+struct OverscrollHandoffState;
+class FocusTarget;
+struct FlingHandoffState;
+class InputQueue;
+struct InputBlockCallbackInfo;
+class GeckoContentController;
+class HitTestingTreeNode;
+class SampleTime;
+class WebRenderScrollDataWrapper;
+struct AncestorTransform;
+struct ScrollThumbData;
+struct ZoomTarget;
+
+/**
+ * ****************** NOTE ON LOCK ORDERING IN APZ **************************
+ *
+ * To avoid deadlock, APZ imposes and respects a global ordering on threads
+ * and locks relevant to APZ.
+ *
+ * Please see the "Threading / Locking Overview" section of
+ * gfx/docs/AsyncPanZoom.rst (hosted in rendered form at
+ * https://firefox-source-docs.mozilla.org/gfx/gfx/AsyncPanZoom.html#threading-locking-overview)
+ * for what the ordering is, and what are the rules for respecting it.
+ * **************************************************************************
+ */
+
+/**
+ * This class manages the tree of AsyncPanZoomController instances. There is one
+ * instance of this class owned by each CompositorBridgeParent, and it contains
+ * as many AsyncPanZoomController instances as there are scrollable container
+ * layers. This class generally lives on the updater thread, although some
+ * functions may be called from other threads as noted; thread safety is ensured
+ * internally.
+ *
+ * The bulk of the work of this class happens as part of the
+ * UpdateHitTestingTree function, which is when a layer tree update is received
+ * by the compositor. This function walks through the layer tree and creates a
+ * tree of HitTestingTreeNode instances to match the layer tree and for use in
+ * hit-testing on the controller thread. APZC instances may be preserved across
+ * calls to this function if the corresponding layers are still present in the
+ * layer tree.
+ *
+ * The other functions on this class are used by various pieces of client code
+ * to notify the APZC instances of events relevant to them. This includes, for
+ * example, user input events that drive panning and zooming, changes to the
+ * scroll viewport area, and changes to pan/zoom constraints.
+ *
+ * Note that the ClearTree function MUST be called when this class is no longer
+ * needed; see the method documentation for details.
+ *
+ * Behaviour of APZ is controlled by a number of preferences shown
+ * \ref APZCPrefs "here".
+ */
+class APZCTreeManager : public IAPZCTreeManager, public APZInputBridge {
+  typedef mozilla::layers::AllowedTouchBehavior AllowedTouchBehavior;
+  typedef mozilla::layers::AsyncDragMetrics AsyncDragMetrics;
+  using HitTestResult = IAPZHitTester::HitTestResult;
+
+  /*
+   * A result from APZCTreeManager::FindHandoffParent.
+   */
+  struct TargetApzcForNodeResult {
+    // The APZC to handoff overscroll to.
+    AsyncPanZoomController* mApzc;
+    // Targeting a document's root APZC from content fixed to the document.
+    bool mIsFixed;
+  };
+
+  // Helper struct to hold some state while we build the hit-testing tree. The
+  // sole purpose of this struct is to shorten the argument list to
+  // UpdateHitTestingTree. All the state that we don't need to
+  // push on the stack during recursion and pop on unwind is stored here.
+  struct TreeBuildingState;
+
+ public:
+  static mozilla::LazyLogModule sLog;
+
+  static already_AddRefed<APZCTreeManager> Create(
+      LayersId aRootLayersId, UniquePtr<IAPZHitTester> aHitTester = nullptr);
+  void SetSampler(APZSampler* aSampler);
+  void SetUpdater(APZUpdater* aUpdater);
+
+  /**
+   * Notifies this APZCTreeManager that the associated compositor is now
+   * responsible for managing another layers id, which got moved over from
+   * some other compositor. That other compositor's APZCTreeManager is also
+   * provided. This allows APZCTreeManager to transfer any necessary state
+   * from the old APZCTreeManager related to that layers id.
+   * This function must be called on the updater thread.
+   */
+  void NotifyLayerTreeAdopted(LayersId aLayersId,
+                              const RefPtr<APZCTreeManager>& aOldTreeManager);
+
+  /**
+   * Notifies this APZCTreeManager that a layer tree being managed by the
+   * associated compositor has been removed/destroyed. Note that this does
+   * NOT get called during shutdown situations, when the root layer tree is
+   * also getting destroyed.
+   * This function must be called on the updater thread.
+   */
+  void NotifyLayerTreeRemoved(LayersId aLayersId);
+
+  /**
+   * Rebuild the focus state based on the focus target from the layer tree
+   * update that just occurred. This must be called on the updater thread.
+   *
+   * @param aRootLayerTreeId The layer tree ID of the root layer corresponding
+   *                         to this APZCTreeManager
+   * @param aOriginatingLayersId The layer tree ID of the layer corresponding to
+   *                             this layer tree update.
+   */
+  void UpdateFocusState(LayersId aRootLayerTreeId,
+                        LayersId aOriginatingLayersId,
+                        const FocusTarget& aFocusTarget);
+
+  /**
+   * Rebuild the hit-testing tree based on an incoming WebRender transaction.
+   * Preserve nodes and APZC instances where possible, but retire those whose
+   * layers are no longer in the layer tree.
+   * (Note: "layer tree" here refers to the tree of WebRenderLayerScrollData
+   *  nodes sent as part of a WebRender transaction.)
+   *
+   * This must be called on the updater thread.
+   *
+   * @param aRoot The root of the (full) layer tree
+   * @param aOriginatingLayersId The layers id of the subtree that triggered
+   *                             this repaint, and to which aIsFirstPaint
+   *                             applies.
+   * @param aIsFirstPaint True if the transaction that this is called in
+   *                      response to included a first-paint. If this is true,
+   *                      the part of the tree that is affected by the
+   *                      first-paint flag is indicated by the
+   *                      aOriginatingLayersId parameter.
+   * @param aPaintSequenceNumber The sequence number of the paint that triggered
+   *                             this layer update. Note that every child
+   *                             process' layer subtree has its own sequence
+   *                             numbers.
+   */
+  void UpdateHitTestingTree(const WebRenderScrollDataWrapper& aRoot,
+                            bool aIsFirstPaint, LayersId aOriginatingLayersId,
+                            uint32_t aPaintSequenceNumber);
+
+  /**
+   * Called when webrender is enabled, from the sampler thread. This function
+   * populates the provided transaction with any async scroll offsets needed.
+   * It also advances APZ animations to the specified sample time, and requests
+   * another composite if there are still active animations.
+   * In effect it is the webrender equivalent of (part of) the code in
+   * AsyncCompositionManager.
+   */
+  void SampleForWebRender(const Maybe<VsyncId>& aVsyncId,
+                          wr::TransactionWrapper& aTxn,
+                          const SampleTime& aSampleTime);
+
+  /**
+   * Refer to the documentation of APZInputBridge::ReceiveInputEvent() and
+   * APZEventResult.
+   */
+  APZEventResult ReceiveInputEvent(
+      InputData& aEvent,
+      InputBlockCallback&& aCallback = InputBlockCallback()) override;
+
+  /**
+   * Set the keyboard shortcuts to use for translating keyboard events.
+   */
+  void SetKeyboardMap(const KeyboardMap& aKeyboardMap) override;
+
+  /**
+   * Kicks an animation to zoom to a rect. This may be either a zoom out or zoom
+   * in. The actual animation is done on the sampler thread after being set
+   * up. |aRect| must be given in CSS pixels, relative to the document.
+   * |aFlags| is a combination of the ZoomToRectBehavior enum values.
+   */
+  void ZoomToRect(const ScrollableLayerGuid& aGuid,
+                  const ZoomTarget& aZoomTarget,
+                  const uint32_t aFlags = DEFAULT_BEHAVIOR) override;
+
+  /**
+   * If we have touch listeners, this should always be called when we know
+   * definitively whether or not content has preventDefaulted any touch events
+   * that have come in. If |aPreventDefault| is true, any touch events in the
+   * queue will be discarded. This function must be called on the controller
+   * thread.
+   */
+  void ContentReceivedInputBlock(uint64_t aInputBlockId,
+                                 bool aPreventDefault) override;
+
+  /**
+   * When the event regions code is enabled, this function should be invoked to
+   * to confirm the target of the input block. This is only needed in cases
+   * where the initial input event of the block hit a dispatch-to-content region
+   * but is safe to call for all input blocks.
+   * The different elements in the array of targets correspond to the targets
+   * for the different touch points. In the case where the touch point has no
+   * target, or the target is not a scrollable frame, the target's |mScrollId|
+   * should be set to ScrollableLayerGuid::NULL_SCROLL_ID.
+   * Note: For mouse events that start a scrollbar drag, both SetTargetAPZC()
+   *       and StartScrollbarDrag() will be called, and the calls may happen
+   *       in either order. That's fine - whichever arrives first will confirm
+   *       the block, and StartScrollbarDrag() will fill in the drag metrics.
+   *       If the block is confirmed before we have drag metrics, some events
+   *       in the drag block may be handled as no-ops until the drag metrics
+   *       arrive.
+   */
+  void SetTargetAPZC(uint64_t aInputBlockId,
+                     const nsTArray<ScrollableLayerGuid>& aTargets) override;
+
+  /**
+   * Updates any zoom constraints contained in the <meta name="viewport"> tag.
+   * If the |aConstraints| is Nothing() then previously-provided constraints for
+   * the given |aGuid| are cleared.
+   */
+  void UpdateZoomConstraints(
+      const ScrollableLayerGuid& aGuid,
+      const Maybe<ZoomConstraints>& aConstraints) override;
+
+  /**
+   * Calls Destroy() on all APZC instances attached to the tree, and resets the
+   * tree back to empty. This function must be called exactly once during the
+   * lifetime of this APZCTreeManager, when this APZCTreeManager is no longer
+   * needed. Failing to call this function may prevent objects from being freed
+   * properly.
+   * This must be called on the updater thread.
+   */
+  void ClearTree();
+
+  /**
+   * Sets the dpi value used by all AsyncPanZoomControllers attached to this
+   * tree manager.
+   * DPI defaults to 160 if not set using SetDPI() at any point.
+   */
+  void SetDPI(float aDpiValue) override;
+
+  /**
+   * Returns the current dpi value in use.
+   */
+  float GetDPI() const;
+
+  /**
+   * Find the hit testing node for the scrollbar thumb that matches these
+   * drag metrics. Initializes aOutThumbNode with the node, if there is one.
+   */
+  void FindScrollThumbNode(const AsyncDragMetrics& aDragMetrics,
+                           LayersId aLayersId,
+                           HitTestingTreeNodeAutoLock& aOutThumbNode);
+
+  /**
+   * Sets allowed touch behavior values for current touch-session for specific
+   * input block (determined by aInputBlock).
+   * Should be invoked by the widget. Each value of the aValues arrays
+   * corresponds to the different touch point that is currently active.
+   * Must be called after receiving the TOUCH_START event that starts the
+   * touch-session.
+   */
+  void SetAllowedTouchBehavior(
+      uint64_t aInputBlockId,
+      const nsTArray<TouchBehaviorFlags>& aValues) override;
+
+  void SetBrowserGestureResponse(uint64_t aInputBlockId,
+                                 BrowserGestureResponse aResponse) override;
+
+  /**
+   * This is a callback for AsyncPanZoomController to call when it wants to
+   * scroll in response to a touch-move event, or when it needs to hand off
+   * overscroll to the next APZC. Note that because of scroll grabbing, the
+   * first APZC to scroll may not be the one that is receiving the touch events.
+   *
+   * |aPrev| is the APZC that received the touch events triggering the scroll
+   *   (in the case of an initial scroll), or the last APZC to scroll (in the
+   *   case of overscroll)
+   * |aStartPoint| and |aEndPoint| are in |aPrev|'s transformed screen
+   *   coordinates (i.e. the same coordinates in which touch points are given to
+   *   APZCs). The amount of (over)scroll is represented by two points rather
+   *   than a displacement because with certain 3D transforms, the same
+   *   displacement between different points in transformed coordinates can
+   *   represent different displacements in untransformed coordinates.
+   * |aOverscrollHandoffChain| is the overscroll handoff chain used for
+   *   determining the order in which scroll should be handed off between
+   *   APZCs
+   * |aOverscrollHandoffChainIndex| is the next position in the overscroll
+   *   handoff chain that should be scrolled.
+   *
+   * aStartPoint and aEndPoint will be modified depending on how much of the
+   * scroll each APZC consumes. This is to allow the sending APZC to go into
+   * an overscrolled state if no APZC further up in the handoff chain accepted
+   * the entire scroll.
+   *
+   * The function will return true if the entire scroll was consumed, and
+   * false otherwise. As this function also modifies aStartPoint and aEndPoint,
+   * when scroll is consumed, it should always the case that this function
+   * returns true if and only if IsZero(aStartPoint - aEndPoint), using the
+   * modified aStartPoint and aEndPoint after the function returns.
+   *
+   * The way this method works is best illustrated with an example.
+   * Consider three nested APZCs, A, B, and C, with C being the innermost one.
+   * Say B is scroll-grabbing.
+   * The touch events go to C because it's the innermost one (so e.g. taps
+   * should go through C), but the overscroll handoff chain is B -> C -> A
+   * because B is scroll-grabbing.
+   * For convenience I'll refer to the three APZC objects as A, B, and C, and
+   * to the tree manager object as TM.
+   * Here's what happens when C receives a touch-move event:
+   *   - C.TrackTouch() calls TM.DispatchScroll() with index = 0.
+   *   - TM.DispatchScroll() calls B.AttemptScroll() (since B is at index 0 in
+   *     the chain).
+   *   - B.AttemptScroll() scrolls B. If there is overscroll, it calls
+   *     TM.DispatchScroll() with index = 1.
+   *   - TM.DispatchScroll() calls C.AttemptScroll() (since C is at index 1 in
+   *     the chain)
+   *   - C.AttemptScroll() scrolls C. If there is overscroll, it calls
+   *     TM.DispatchScroll() with index = 2.
+   *   - TM.DispatchScroll() calls A.AttemptScroll() (since A is at index 2 in
+   *     the chain)
+   *   - A.AttemptScroll() scrolls A. If there is overscroll, it calls
+   *     TM.DispatchScroll() with index = 3.
+   *   - TM.DispatchScroll() discards the rest of the scroll as there are no
+   *     more elements in the chain.
+   *
+   * Note: this should be used for panning only. For handing off overscroll for
+   *       a fling, use DispatchFling().
+   */
+  bool DispatchScroll(AsyncPanZoomController* aPrev,
+                      ParentLayerPoint& aStartPoint,
+                      ParentLayerPoint& aEndPoint,
+                      OverscrollHandoffState& aOverscrollHandoffState);
+
+  /**
+   * This is a callback for AsyncPanZoomController to call when it wants to
+   * start a fling in response to a touch-end event, or when it needs to hand
+   * off a fling to the next APZC. Note that because of scroll grabbing, the
+   * first APZC to fling may not be the one that is receiving the touch events.
+   *
+   * @param aApzc the APZC that wants to start or hand off the fling
+   * @param aHandoffState a collection of state about the operation,
+   *                      which contains the following:
+   *
+   *        mVelocity the current velocity of the fling, in |aApzc|'s screen
+   *                  pixels per millisecond
+   *        mChain the chain of APZCs along which the fling
+   *                   should be handed off
+   *        mIsHandoff is true if |aApzc| is handing off an existing fling (in
+   *                   this case the fling is given to the next APZC in the
+   *                   handoff chain after |aApzc|), and false is |aApzc| wants
+   *                   start a fling (in this case the fling is given to the
+   *                   first APZC in the chain)
+   *
+   * The return value is the "residual velocity", the portion of
+   * |aHandoffState.mVelocity| that was not consumed by APZCs in the
+   * handoff chain doing flings.
+   * The caller can use this value to determine whether it should consume
+   * the excess velocity by going into overscroll.
+   */
+  ParentLayerPoint DispatchFling(AsyncPanZoomController* aApzc,
+                                 const FlingHandoffState& aHandoffState);
+
+  void StartScrollbarDrag(const ScrollableLayerGuid& aGuid,
+                          const AsyncDragMetrics& aDragMetrics) override;
+
+  bool StartAutoscroll(const ScrollableLayerGuid& aGuid,
+                       const ScreenPoint& aAnchorLocation) override;
+
+  void StopAutoscroll(const ScrollableLayerGuid& aGuid) override;
+
+  /*
+   * Build the chain of APZCs that will handle overscroll for a pan starting at
+   * |aInitialTarget|.
+   */
+  RefPtr<const OverscrollHandoffChain> BuildOverscrollHandoffChain(
+      const RefPtr<AsyncPanZoomController>& aInitialTarget);
+
+  /**
+   * Function used to disable LongTap gestures.
+   *
+   * On slow running tests, drags and touch events can be misinterpreted
+   * as a long tap. This allows tests to disable long tap gesture detection.
+   */
+  void SetLongTapEnabled(bool aTapGestureEnabled) override;
+
+  APZInputBridge* InputBridge() override { return this; }
+
+  /**
+   * Add a callback to be invoked when |aInputBlockId| is ready for handling.
+   *
+   * Should only be used for input blocks that are not yet ready for handling
+   * at the time this is called. If the input block was already handled,
+   * the callback will never be called.
+   *
+   * Only one callback can be registered for an input block at a time.
+   * Subsequent attempts to register a callback for an input block will be
+   * ignored until the existing callback is triggered.
+   */
+  void AddInputBlockCallback(uint64_t aInputBlockId,
+                             InputBlockCallbackInfo&& aCallbackInfo);
+
+  // Methods to help process WidgetInputEvents (or manage conversion to/from
+  // InputData)
+
+  void ProcessUnhandledEvent(LayoutDeviceIntPoint* aRefPoint,
+                             ScrollableLayerGuid* aOutTargetGuid,
+                             uint64_t* aOutFocusSequenceNumber,
+                             LayersId* aOutLayersId) override;
+
+  void UpdateWheelTransaction(
+      LayoutDeviceIntPoint aRefPoint, EventMessage aEventMessage,
+      const Maybe<ScrollableLayerGuid>& aTargetGuid) override;
+
+  bool GetAPZTestData(LayersId aLayersId, APZTestData* aOutData);
+
+  /**
+   * Iterates over the hit testing tree, collects LayersIds and associated
+   * transforms from layer coordinate space to root coordinate space, and
+   * sends these over to the main thread of the chrome process. If the provided
+   * |aAncestor| argument is non-null, then only the transforms for layer
+   * subtrees scrolled by the aAncestor (i.e. descendants of aAncestor) will be
+   * sent.
+   */
+  void SendSubtreeTransformsToChromeMainThread(
+      const AsyncPanZoomController* aAncestor);
+
+  /**
+   * Set fixed layer margins for dynamic toolbar.
+   */
+  void SetFixedLayerMargins(ScreenIntCoord aTop, ScreenIntCoord aBottom);
+
+  /**
+   * Refer to apz::ComputeTransformForScrollThumb() for a description
+   * of the parameters.
+   */
+  static LayerToParentLayerMatrix4x4 ComputeTransformForScrollThumb(
+      const LayerToParentLayerMatrix4x4& aCurrentTransform,
+      const gfx::Matrix4x4& aScrollableContentTransform,
+      AsyncPanZoomController* aApzc, const FrameMetrics& aMetrics,
+      const ScrollbarData& aScrollbarData, bool aScrollbarIsDescendant);
+
+  /**
+   * Dispatch a flush complete notification from the repaint thread of the
+   * content controller for the given layers id.
+   */
+  static void FlushApzRepaints(LayersId aLayersId);
+
+  /**
+   * Mark |aLayersId| as having been moved from the compositor that owns this
+   * tree manager to a compositor that doesn't use APZ.
+   * See |mDetachedLayersIds| for more details.
+   */
+  void MarkAsDetached(LayersId aLayersId);
+
+  // Assert that the current thread is the sampler thread for this APZCTM.
+  void AssertOnSamplerThread();
+  // Assert that the current thread is the updater thread for this APZCTM.
+  void AssertOnUpdaterThread();
+
+  // Returns a pointer to the WebRenderAPI this APZCTreeManager is for.
+  // This might be null (for example, if WebRender is not enabled).
+  already_AddRefed<wr::WebRenderAPI> GetWebRenderAPI() const;
+
+ protected:
+  APZCTreeManager(LayersId aRootLayersId, UniquePtr<IAPZHitTester> aHitTester);
+
+  void Init();
+
+  // Protected destructor, to discourage deletion outside of Release():
+  virtual ~APZCTreeManager();
+
+  APZSampler* GetSampler() const;
+  APZUpdater* GetUpdater() const;
+
+  bool AdvanceAnimationsInternal(const MutexAutoLock& aProofOfMapLock,
+                                 const SampleTime& aSampleTime);
+
+  // We need to allow APZUpdater to lock and unlock this tree during a WR
+  // scene swap. We do this using private helpers to avoid exposing these
+  // functions to the world.
+ private:
+  friend class APZUpdater;
+  void LockTree() MOZ_CAPABILITY_ACQUIRE(mTreeLock);
+  void UnlockTree() MOZ_CAPABILITY_RELEASE(mTreeLock);
+
+  // Protected hooks for gtests subclass
+  virtual already_AddRefed<AsyncPanZoomController> NewAPZCInstance(
+      LayersId aLayersId, GeckoContentController* aController);
+
+ public:
+  // Public hook for gtests subclass
+  virtual SampleTime GetFrameTime();
+
+  // Also used for controlling time during tests
+  void SetTestSampleTime(const Maybe<TimeStamp>& aTime);
+
+ private:
+  mutable DataMutex<Maybe<TimeStamp>> mTestSampleTime;
+  CopyableTArray<MatrixMessage> mLastMessages;
+
+ public:
+  /* Some helper functions to find an APZC given some identifying input. These
+     functions lock the tree of APZCs while they find the right one, and then
+     return an addref'd pointer to it. This allows caller code to just use the
+     target APZC without worrying about it going away. These are public for
+     testing code and generally should not be used by other production code.
+  */
+  RefPtr<HitTestingTreeNode> GetRootNode() const;
+  HitTestResult GetTargetAPZC(const ScreenPoint& aPoint);
+  already_AddRefed<AsyncPanZoomController> GetTargetAPZC(
+      const LayersId& aLayersId,
+      const ScrollableLayerGuid::ViewID& aScrollId) const;
+  already_AddRefed<AsyncPanZoomController> GetTargetAPZC(
+      const LayersId& aLayersId, const ScrollableLayerGuid::ViewID& aScrollId,
+      const MutexAutoLock& aProofOfMapLock) const;
+  ScreenToParentLayerMatrix4x4 GetScreenToApzcTransform(
+      const AsyncPanZoomController* aApzc) const;
+  ParentLayerToScreenMatrix4x4 GetApzcToGeckoTransformForHit(
+      HitTestResult& aHitResult) const;
+  ParentLayerToScreenMatrix4x4 GetApzcToGeckoTransform(
+      const AsyncPanZoomController* aApzc,
+      const AsyncTransformComponents& aComponents) const;
+
+  /*
+   * A common utility function used for GetApzcToGeckoTransform and
+   * GetOopifApzcToRootContentApzcTransform.
+   *
+   * NOTE: The matrix returned by this function can NOT be used to convert
+   * metrics in |aStartApzc| to |aStopApzc|. If you want the conversion matrix,
+   * you will have to use either GetApzcToGeckoTransform or
+   * GetOopifApzcToRootContentApzcTransform.
+   */
+  ParentLayerToParentLayerMatrix4x4 GetApzcToApzcTransform(
+      const AsyncPanZoomController* aStartApzc,
+      const AsyncPanZoomController* aStopApzc,
+      const AsyncTransformComponents& aComponents) const;
+
+  /*
+   * Returns the matrix which transforms coordinates relative to the layout
+   * viewport of |aApzc|, to be relative to the document origin of the root
+   * content APZC of |aApzc|.
+   * |aApzc| must be the root APZC of an out-of-process iframe.
+   */
+  CSSToCSSMatrix4x4 GetOopifToRootContentTransform(
+      AsyncPanZoomController* aApzc) const;
+
+  /**
+   * Convert the given |aRect| in the document coordinates of |aApzc| to the top
+   * level document coordinates.
+   * |aApzc| must be an in-process root APZC.
+   */
+  CSSRect ConvertRectInApzcToRoot(AsyncPanZoomController* aApzc,
+                                  const CSSRect& aRect) const;
+
+  ScreenPoint GetCurrentMousePosition() const;
+  void SetCurrentMousePosition(const ScreenPoint& aNewPos);
+
+  /**
+   * Convert a screen point of an event targeting |aApzc| to Gecko
+   * coordinates.
+   */
+  Maybe<ScreenIntPoint> ConvertToGecko(const ScreenIntPoint& aPoint,
+                                       AsyncPanZoomController* aApzc);
+
+  /**
+   * Find the zoomable APZC in the same layer subtree (i.e. with the same
+   * layers id) as the given APZC.
+   */
+  already_AddRefed<AsyncPanZoomController> FindZoomableApzc(
+      AsyncPanZoomController* aStart) const;
+
+  AsyncPanZoomController* FindRootApzcFor(LayersId aLayersId) const;
+
+  ScreenMargin GetCompositorFixedLayerMargins() const;
+
+  void AdjustEventPointForDynamicToolbar(ScreenIntPoint& aEventPoint,
+                                         const HitTestResult& aHit);
+
+  APZScrollGeneration NewAPZScrollGeneration() {
+    // In the production code this function gets only called from the sampler
+    // thread but in tests using nsIDOMWindowUtils.setAsyncScrollOffset this
+    // function gets called from the controller thread so we need to lock the
+    // mutex for this counter.
+    MutexAutoLock lock(mScrollGenerationLock);
+    return mScrollGenerationCounter.NewAPZGeneration();
+  }
+
+  template <typename Callback>
+  void CallWithMapLock(Callback& aCallback) {
+    MutexAutoLock lock(mMapLock);
+    aCallback(lock);
+  }
+
+ private:
+  using GuidComparator = ScrollableLayerGuid::Comparator;
+  using ScrollNode = WebRenderScrollDataWrapper;
+
+  /* Helpers */
+
+  void AttachNodeToTree(HitTestingTreeNode* aNode, HitTestingTreeNode* aParent,
+                        HitTestingTreeNode* aNextSibling)
+      MOZ_REQUIRES(mTreeLock);
+  already_AddRefed<AsyncPanZoomController> GetTargetAPZC(
+      const ScrollableLayerGuid& aGuid);
+  already_AddRefed<HitTestingTreeNode> GetTargetNode(
+      const ScrollableLayerGuid& aGuid, GuidComparator aComparator) const;
+  HitTestingTreeNode* FindTargetNode(HitTestingTreeNode* aNode,
+                                     const ScrollableLayerGuid& aGuid,
+                                     GuidComparator aComparator);
+  TargetApzcForNodeResult GetTargetApzcForNode(const HitTestingTreeNode* aNode);
+  TargetApzcForNodeResult FindHandoffParent(
+      const AsyncPanZoomController* aApzc);
+  /**
+   * Find the root __content__ APZC for |aLayersId|.
+   * If |aLayersId| is NOT for the LayersId for the root content, this function
+   * returns nullptr.
+   *
+   * NOTE: Only the top-level content document will have a root content APZC.
+   */
+  HitTestingTreeNode* FindRootNodeForLayersId(LayersId aLayersId) const;
+  AsyncPanZoomController* FindRootContentApzcForLayersId(
+      LayersId aLayersId) const;
+  already_AddRefed<AsyncPanZoomController> GetZoomableTarget(
+      AsyncPanZoomController* aApzc1, AsyncPanZoomController* aApzc2) const;
+  already_AddRefed<AsyncPanZoomController> CommonAncestor(
+      AsyncPanZoomController* aApzc1, AsyncPanZoomController* aApzc2) const;
+
+  struct FixedPositionInfo;
+  struct StickyPositionInfo;
+
+  // Returns true if |aNode| is a fixed layer that is fixed to the root content
+  // APZC.
+  // The map lock is required within these functions; if the map lock is already
+  // being held by the caller, the second overload should be used. If the map
+  // lock is not being held at the call site, the first overload should be used.
+  bool IsFixedToRootContent(const HitTestingTreeNode* aNode) const;
+  bool IsFixedToRootContent(const FixedPositionInfo& aFixedInfo,
+                            const MutexAutoLock& aProofOfMapLock) const;
+
+  // Returns the vertical sides of |aNode| that are stuck to the root content.
+  // The map lock is required within these functions; if the map lock is already
+  // being held by the caller, the second overload should be used. If the map
+  // lock is not being held at the call site, the first overload should be used.
+  SideBits SidesStuckToRootContent(const HitTestingTreeNode* aNode,
+                                   AsyncTransformConsumer aMode) const;
+  SideBits SidesStuckToRootContent(const StickyPositionInfo& aStickyInfo,
+                                   AsyncTransformConsumer aMode,
+                                   const MutexAutoLock& aProofOfMapLock) const;
+
+  /**
+   * Perform hit testing for a touch-start event.
+   *
+   * @param aEvent The touch-start event.
+   *
+   * The remaining parameters are out-parameter used to communicate additional
+   * return values:
+   *
+   * @param aOutTouchBehaviors
+   *     The touch behaviours that should be allowed for this touch block.
+
+   * @return The results of the hit test, including the APZC that was hit.
+   */
+  HitTestResult GetTouchInputBlockAPZC(
+      const MultiTouchInput& aEvent,
+      nsTArray<TouchBehaviorFlags>* aOutTouchBehaviors);
+
+  /**
+   * A helper structure for use by ReceiveInputEvent() and its helpers.
+   */
+  struct InputHandlingState {
+    // A reference to the event being handled.
+    InputData& mEvent;
+
+    // The value that will be returned by ReceiveInputEvent().
+    APZEventResult mResult;
+
+    // If we performed a hit-test while handling this input event, or
+    // reused the result of a previous hit-test in the input block,
+    // this is populated with the result of the hit test.
+    HitTestResult mHit;
+
+    // Called at the end of ReceiveInputEvent() to perform any final
+    // computations, and then return mResult.
+    // If the event will have a delayed result then this takes care of adding
+    // the specified callback to the APZCTreeManager.
+    APZEventResult Finish(APZCTreeManager& aTreeManager,
+                          InputBlockCallback&& aCallback);
+  };
+
+  void ProcessTouchInput(InputHandlingState& aState, MultiTouchInput& aInput);
+  /**
+   * Given a mouse-down event that hit a scroll thumb node, set up APZ
+   * dragging of the scroll thumb.
+   *
+   * Must be called after the mouse event has been sent to InputQueue.
+   *
+   * @param aMouseInput The mouse-down event.
+   * @param aScrollThumbNode Tthe scroll thumb node that was hit.
+   * @param aApzc
+   *     The APZC for the scroll frame scrolled by the scroll thumb, if that
+   *     scroll frame is layerized. (A thumb can be layerized without its
+   *     target scroll frame being layerized.) Otherwise, an enclosing APZC.
+   */
+  void SetupScrollbarDrag(MouseInput& aMouseInput,
+                          const HitTestingTreeNodeAutoLock& aScrollThumbNode,
+                          AsyncPanZoomController* aApzc);
+  /**
+   * Process a touch event that's part of a scrollbar touch-drag gesture.
+   *
+   * @param aInput The touch event.
+   * @param aScrollThumbNode
+   *     If this is the touch-start event, the node representing the scroll
+   *     thumb we are starting to drag. Otherwise nullptr.
+   * @param aHitInfo
+   *     The hit-test flags for the touch input.
+   * @return See ReceiveInputEvent() for what the return value means.
+   */
+  APZEventResult ProcessTouchInputForScrollbarDrag(
+      MultiTouchInput& aInput,
+      const HitTestingTreeNodeAutoLock& aScrollThumbNode,
+      const gfx::CompositorHitTestInfo& aHitInfo);
+  void FlushRepaintsToClearScreenToGeckoTransform();
+
+  void SynthesizePinchGestureFromMouseWheel(
+      const ScrollWheelInput& aWheelInput,
+      const RefPtr<AsyncPanZoomController>& aTarget);
+
+  already_AddRefed<HitTestingTreeNode> RecycleOrCreateNode(
+      const RecursiveMutexAutoLock& aProofOfTreeLock, TreeBuildingState& aState,
+      AsyncPanZoomController* aApzc, LayersId aLayersId);
+  HitTestingTreeNode* PrepareNodeForLayer(
+      const RecursiveMutexAutoLock& aProofOfTreeLock, const ScrollNode& aLayer,
+      const FrameMetrics& aMetrics, LayersId aLayersId,
+      const Maybe<ZoomConstraints>& aZoomConstraints,
+      const AncestorTransform& aAncestorTransform, HitTestingTreeNode* aParent,
+      HitTestingTreeNode* aNextSibling, TreeBuildingState& aState);
+
+  void PrintLayerInfo(const ScrollNode& aLayer);
+
+  void NotifyScrollbarDragInitiated(uint64_t aDragBlockId,
+                                    const ScrollableLayerGuid& aGuid,
+                                    ScrollDirection aDirection) const;
+  void NotifyScrollbarDragRejected(const ScrollableLayerGuid& aGuid) const;
+  void NotifyAutoscrollRejected(const ScrollableLayerGuid& aGuid) const;
+
+  // Returns the transform that converts from |aNode|'s coordinates
+  // to the coordinates of |aNode|'s parent in the hit-testing tree. Requires
+  // the caller to hold mTreeLock.
+  LayerToParentLayerMatrix4x4 ComputeTransformForScrollThumbNode(
+      const HitTestingTreeNode* aNode) const MOZ_REQUIRES(mTreeLock);
+
+  // Look up the GeckoContentController for the given layers id.
+  static already_AddRefed<GeckoContentController> GetContentController(
+      LayersId aLayersId);
+
+  using ClippedCompositionBoundsMap =
+      std::unordered_map<ScrollableLayerGuid, ParentLayerRect,
+                         ScrollableLayerGuid::HashIgnoringPresShellFn,
+                         ScrollableLayerGuid::EqualIgnoringPresShellFn>;
+  // This is a recursive function that populates `aDestMap` with the clipped
+  // composition bounds for the APZC corresponding to `aGuid` and returns those
+  // bounds as a convenience. It recurses to also populate `aDestMap` with that
+  // APZC's ancestors. In order to do this it needs to access mApzcMap
+  // and therefore requires the caller to hold the map lock.
+  ParentLayerRect ComputeClippedCompositionBounds(
+      const MutexAutoLock& aProofOfMapLock,
+      ClippedCompositionBoundsMap& aDestMap, ScrollableLayerGuid aGuid);
+
+  ScreenMargin GetCompositorFixedLayerMargins(
+      const MutexAutoLock& aProofOfMapLock) const;
+
+ protected:
+  /* The input queue where input events are held until we know enough to
+   * figure out where they're going. Protected so gtests can access it.
+   */
+  RefPtr<InputQueue> mInputQueue;
+
+  /** A lock that protects mApzcMap, mScrollThumbInfo, mRootScrollbarInfo,
+   * mFixedPositionInfo, and mStickyPositionInfo.
+   */
+  mutable mozilla::Mutex mMapLock;
+
+ private:
+  /* Layers id for the root CompositorBridgeParent that owns this
+   * APZCTreeManager. */
+  LayersId mRootLayersId;
+
+  /* Pointer to the APZSampler instance that is bound to this APZCTreeManager.
+   * The sampler has a RefPtr to this class, and this non-owning raw pointer
+   * back to the APZSampler is nulled out in the sampler's destructor, so this
+   * pointer should always be valid.
+   */
+  APZSampler* MOZ_NON_OWNING_REF mSampler;
+  /* Pointer to the APZUpdater instance that is bound to this APZCTreeManager.
+   * The updater has a RefPtr to this class, and this non-owning raw pointer
+   * back to the APZUpdater is nulled out in the updater's destructor, so this
+   * pointer should always be valid.
+   */
+  APZUpdater* MOZ_NON_OWNING_REF mUpdater;
+
+  /* Whenever walking or mutating the tree rooted at mRootNode, mTreeLock must
+   * be held. This lock does not need to be held while manipulating a single
+   * APZC instance in isolation (that is, if its tree pointers are not being
+   * accessed or mutated). The lock also needs to be held when accessing the
+   * mRootNode instance variable, as that is considered part of the APZC tree
+   * management state.
+   * IMPORTANT: See the note about lock ordering at the top of this file. */
+  mutable mozilla::RecursiveMutex mTreeLock;
+  RefPtr<HitTestingTreeNode> mRootNode MOZ_GUARDED_BY(mTreeLock);
+
+  /*
+   * A set of LayersIds for which APZCTM should only send empty
+   * MatrixMessages via NotifyLayerTransform().
+   * This is used in cases where a tab has been transferred to a non-APZ
+   * compositor (and thus will not receive MatrixMessages reflecting its new
+   * transforms) and we need to make sure it doesn't get stuck with transforms
+   * from its old tree manager (us).
+   * Acquire mTreeLock before accessing this.
+   */
+  std::unordered_set<LayersId, LayersId::HashFn> mDetachedLayersIds
+      MOZ_GUARDED_BY(mTreeLock);
+
+  /**
+   * Helper structure to store a bunch of things in mApzcMap so that they can
+   * be used from the sampler thread.
+   */
+  struct ApzcMapData {
+    // A pointer to the APZC itself
+    RefPtr<AsyncPanZoomController> apzc;
+    // The parent APZC's guid, or Nothing() if there is no parent
+    Maybe<ScrollableLayerGuid> parent;
+  };
+
+  /**
+   * A map for quick access to get some APZC data by guid, without having to
+   * acquire the tree lock. mMapLock must be acquired while accessing or
+   * modifying mApzcMap.
+   */
+  std::unordered_map<ScrollableLayerGuid, ApzcMapData,
+                     ScrollableLayerGuid::HashIgnoringPresShellFn,
+                     ScrollableLayerGuid::EqualIgnoringPresShellFn>
+      mApzcMap;
+  /**
+   * A helper structure to store all the information needed to compute the
+   * async transform for a scrollthumb on the sampler thread.
+   */
+  struct ScrollThumbInfo {
+    uint64_t mThumbAnimationId;
+    CSSTransformMatrix mThumbTransform;
+    ScrollbarData mThumbData;
+    ScrollableLayerGuid mTargetGuid;
+    CSSTransformMatrix mTargetTransform;
+    bool mTargetIsAncestor;
+
+    ScrollThumbInfo(const uint64_t& aThumbAnimationId,
+                    const CSSTransformMatrix& aThumbTransform,
+                    const ScrollbarData& aThumbData,
+                    const ScrollableLayerGuid& aTargetGuid,
+                    const CSSTransformMatrix& aTargetTransform,
+                    bool aTargetIsAncestor)
+        : mThumbAnimationId(aThumbAnimationId),
+          mThumbTransform(aThumbTransform),
+          mThumbData(aThumbData),
+          mTargetGuid(aTargetGuid),
+          mTargetTransform(aTargetTransform),
+          mTargetIsAncestor(aTargetIsAncestor) {
+      MOZ_ASSERT(mTargetGuid.mScrollId == mThumbData.mTargetViewId);
+    }
+  };
+  /**
+   * If this APZCTreeManager is being used with WebRender, this vector gets
+   * populated during a layers update. It holds a package of information needed
+   * to compute and set the async transforms on scroll thumbs. This information
+   * is extracted from the HitTestingTreeNodes for the WebRender case because
+   * accessing the HitTestingTreeNodes requires holding the tree lock which
+   * we cannot do on the WR sampler thread. mScrollThumbInfo, however, can
+   * be accessed while just holding the mMapLock which is safe to do on the
+   * sampler thread.
+   * mMapLock must be acquired while accessing or modifying mScrollThumbInfo.
+   */
+  std::vector<ScrollThumbInfo> mScrollThumbInfo;
+
+  /**
+   * A helper structure to store all the information needed to compute the
+   * async transform for a scrollthumb on the sampler thread.
+   */
+  struct RootScrollbarInfo {
+    uint64_t mScrollbarAnimationId;
+    ScrollDirection mScrollDirection;
+
+    RootScrollbarInfo(const uint64_t& aScrollbarAnimationId,
+                      const ScrollDirection aScrollDirection)
+        : mScrollbarAnimationId(aScrollbarAnimationId),
+          mScrollDirection(aScrollDirection) {}
+  };
+  /**
+   * If this APZCTreeManager is being used with WebRender, this vector gets
+   * populated during a layers update. It holds a package of information needed
+   * to compute and set the async transforms on root scrollbars. This
+   * information is extracted from the HitTestingTreeNodes for the WebRender
+   * case because accessing the HitTestingTreeNodes requires holding the tree
+   * lock which we cannot do on the WR sampler thread. mRootScrollbarInfo,
+   * however, can be accessed while just holding the mMapLock which is safe to
+   * do on the sampler thread.
+   * mMapLock must be acquired while accessing or modifying mRootScrollbarInfo.
+   */
+  std::vector<RootScrollbarInfo> mRootScrollbarInfo;
+
+  /**
+   * A helper structure to store all the information needed to compute the
+   * async transform for a fixed position element on the sampler thread.
+   */
+  struct FixedPositionInfo {
+    Maybe<uint64_t> mFixedPositionAnimationId;
+    SideBits mFixedPosSides;
+    ScrollableLayerGuid::ViewID mFixedPosTarget;
+    LayersId mLayersId;
+
+    explicit FixedPositionInfo(const HitTestingTreeNode* aNode);
+  };
+  /**
+   * If this APZCTreeManager is being used with WebRender, this vector gets
+   * populated during a layers update. It holds a package of information needed
+   * to compute and set the async transforms on fixed position content. This
+   * information is extracted from the HitTestingTreeNodes for the WebRender
+   * case because accessing the HitTestingTreeNodes requires holding the tree
+   * lock which we cannot do on the WR sampler thread. mFixedPositionInfo,
+   * however, can be accessed while just holding the mMapLock which is safe to
+   * do on the sampler thread. mMapLock must be acquired while accessing or
+   * modifying mFixedPositionInfo.
+   */
+  std::vector<FixedPositionInfo> mFixedPositionInfo;
+
+  /**
+   * A helper structure to store all the information needed to compute the
+   * async transform for a sticky position element on the sampler thread.
+   */
+  struct StickyPositionInfo {
+    Maybe<uint64_t> mStickyPositionAnimationId;
+    SideBits mFixedPosSides;
+    ScrollableLayerGuid::ViewID mStickyPosTarget;
+    LayersId mLayersId;
+    LayerRectAbsolute mStickyScrollRangeInner;
+    LayerRectAbsolute mStickyScrollRangeOuter;
+
+    explicit StickyPositionInfo(const HitTestingTreeNode* aNode);
+  };
+  /**
+   * If this APZCTreeManager is being used with WebRender, this vector gets
+   * populated during a layers update. It holds a package of information needed
+   * to compute and set the async transforms on sticky position content. This
+   * information is extracted from the HitTestingTreeNodes for the WebRender
+   * case because accessing the HitTestingTreeNodes requires holding the tree
+   * lock which we cannot do on the WR sampler thread. mStickyPositionInfo,
+   * however, can be accessed while just holding the mMapLock which is safe to
+   * do on the sampler thread. mMapLock must be acquired while accessing or
+   * modifying mStickyPositionInfo.
+   */
+  std::vector<StickyPositionInfo> mStickyPositionInfo;
+
+  /* Holds the zoom constraints for scrollable layers, as determined by the
+   * the main-thread gecko code. This can only be accessed on the updater
+   * thread. */
+  std::unordered_map<ScrollableLayerGuid, ZoomConstraints,
+                     ScrollableLayerGuid::HashIgnoringPresShellFn,
+                     ScrollableLayerGuid::EqualIgnoringPresShellFn>
+      mZoomConstraints;
+  /* A list of keyboard shortcuts to use for translating keyboard inputs into
+   * keyboard actions. This is gathered on the main thread from XBL bindings.
+   * This must only be accessed on the controller thread.
+   */
+  KeyboardMap mKeyboardMap;
+  /* This tracks the focus targets of chrome and content and whether we have
+   * a current focus target or whether we are waiting for a new confirmation.
+   */
+  FocusState mFocusState;
+  /* This tracks the hit test result info for the current touch input block.
+   * In particular, it tracks the target APZC, the hit test flags, and the
+   * fixed pos sides. This is populated at the start of a touch block based
+   * on the hit-test result, and used for subsequent touch events in the block.
+   * This allows touch points to move outside the thing they started on, but
+   * still have the touch events delivered to the same initial APZC. This will
+   * only ever be touched on the input delivery thread, and so does not require
+   * locking.
+   */
+  HitTestResult mTouchBlockHitResult;
+  /* Sometimes we want to ignore all touches except one. In such cases, this
+   * is set to the identifier of the touch we are not ignoring; in other cases,
+   * this is set to -1.
+   */
+  int32_t mRetainedTouchIdentifier;
+  /* This tracks whether the current input block represents a touch-drag of
+   * a scrollbar. In this state, touch events are forwarded to content as touch
+   * events, but converted to mouse events before going into InputQueue and
+   * being handled by an APZC (to reuse the APZ code for scrollbar dragging
+   * with a mouse).
+   */
+  bool mInScrollbarTouchDrag;
+  /* Tracks the number of touch points we are tracking that are currently on
+   * the screen. */
+  TouchCounter mTouchCounter;
+  /* If a tap gesture event sent directly by widget code (rather than gesture
+   * detected from touch events by APZ) is being processed, this stores the
+   * result of hit testing for that tap gesture event.
+   */
+  HitTestResult mTapGestureHitResult;
+  /* Stores the current mouse position in screen coordinates.
+   */
+  mutable DataMutex<ScreenPoint> mCurrentMousePosition;
+  /* Extra margins that should be applied to content that fixed wrt. the
+   * RCD-RSF, to account for the dynamic toolbar.
+   * Acquire mMapLock before accessing this.
+   */
+  ScreenMargin mCompositorFixedLayerMargins;
+  /* Similar to above |mCompositorFixedLayerMargins|. But this value is the
+   * margins on the main-thread at the last time position:fixed elements were
+   * updated during the dynamic toolbar transitions.
+   * Acquire mMapLock before accessing this.
+   */
+  ScreenMargin mGeckoFixedLayerMargins;
+  /* For logging the APZC tree for debugging (enabled by the apz.printtree
+   * pref). The purpose of using LOG_CRITICAL is so that you don't also need to
+   * change the gfx.logging.level pref to see the output. */
+  gfx::TreeLog<gfx::LOG_CRITICAL> mApzcTreeLog;
+
+  class CheckerboardFlushObserver;
+  friend class CheckerboardFlushObserver;
+  RefPtr<CheckerboardFlushObserver> mFlushObserver;
+
+  // Map from layers id to APZTestData. Accesses and mutations must be
+  // protected by the mTestDataLock.
+  std::unordered_map<LayersId, UniquePtr<APZTestData>, LayersId::HashFn>
+      mTestData;
+  mutable mozilla::Mutex mTestDataLock;
+
+  // A state machine that tries to record how much users are overshooting
+  // their desired scroll destination while using the scrollwheel.
+  OvershootDetector mOvershootDetector;
+
+  // This must only be touched on the controller thread.
+  float mDPI;
+
+  friend class IAPZHitTester;
+  UniquePtr<IAPZHitTester> mHitTester;
+
+  // NOTE: This ScrollGenerationCounter needs to be per APZCTreeManager since
+  // the generation is bumped up on the sampler theread which is per
+  // APZCTreeManager.
+  ScrollGenerationCounter mScrollGenerationCounter;
+  mozilla::Mutex mScrollGenerationLock;
+
+#if defined(MOZ_WIDGET_ANDROID)
+ private:
+  // Last Frame metrics sent to java through UIController.
+  GeckoViewMetrics mLastRootMetrics;
+#endif  // defined(MOZ_WIDGET_ANDROID)
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_PanZoomController_h