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/* -*- 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 */
#ifndef mozilla_layers_AsyncPanZoomController_h
#define mozilla_layers_AsyncPanZoomController_h
#include "CrossProcessMutex.h"
#include "mozilla/layers/GeckoContentController.h"
#include "mozilla/layers/RepaintRequest.h"
#include "mozilla/layers/SampleTime.h"
#include "mozilla/layers/ZoomConstraints.h"
#include "mozilla/Atomics.h"
#include "mozilla/Attributes.h"
#include "mozilla/EventForwards.h"
#include "mozilla/Monitor.h"
#include "mozilla/RecursiveMutex.h"
#include "mozilla/RefPtr.h"
#include "mozilla/ScrollTypes.h"
#include "mozilla/StaticPrefs_apz.h"
#include "mozilla/UniquePtr.h"
#include "InputData.h"
#include "Axis.h" // for Axis, Side, etc.
#include "ExpectedGeckoMetrics.h"
#include "FlingAccelerator.h"
#include "InputQueue.h"
#include "APZUtils.h"
#include "Layers.h" // for Layer::ScrollDirection
#include "LayersTypes.h"
#include "mozilla/gfx/Matrix.h"
#include "nsRegion.h"
#include "nsTArray.h"
#include "PotentialCheckerboardDurationTracker.h"
#include "RecentEventsBuffer.h" // for RecentEventsBuffer
#include "SampledAPZCState.h"
namespace mozilla {
namespace ipc {
class SharedMemoryBasic;
} // namespace ipc
namespace layers {
class AsyncDragMetrics;
class APZCTreeManager;
struct ScrollableLayerGuid;
class CompositorController;
class MetricsSharingController;
class GestureEventListener;
struct AsyncTransform;
class AsyncPanZoomAnimation;
class StackScrollerFlingAnimation;
template <typename FlingPhysics>
class GenericFlingAnimation;
class AndroidFlingPhysics;
class DesktopFlingPhysics;
class InputBlockState;
struct FlingHandoffState;
class TouchBlockState;
class PanGestureBlockState;
class OverscrollHandoffChain;
struct OverscrollHandoffState;
class StateChangeNotificationBlocker;
class CheckerboardEvent;
class OverscrollEffectBase;
class WidgetOverscrollEffect;
class GenericOverscrollEffect;
class AndroidSpecificState;
struct KeyboardScrollAction;
// Base class for grouping platform-specific APZC state variables.
class PlatformSpecificStateBase {
virtual ~PlatformSpecificStateBase() = default;
virtual AndroidSpecificState* AsAndroidSpecificState() { return nullptr; }
// PLPPI = "ParentLayer pixels per (Screen) inch"
virtual AsyncPanZoomAnimation* CreateFlingAnimation(
AsyncPanZoomController& aApzc, const FlingHandoffState& aHandoffState,
float aPLPPI);
virtual UniquePtr<VelocityTracker> CreateVelocityTracker(Axis* aAxis);
static void InitializeGlobalState() {}
* Represents a transform from the ParentLayer coordinate space of an APZC
* to the ParentLayer coordinate space of its parent APZC.
* Each layer along the way contributes to the transform. We track
* contributions that are perspective transforms separately, as sometimes
* these require special handling.
struct AncestorTransform {
gfx::Matrix4x4 mTransform;
gfx::Matrix4x4 mPerspectiveTransform;
AncestorTransform() = default;
AncestorTransform(const gfx::Matrix4x4& aTransform,
bool aTransformIsPerspective) {
(aTransformIsPerspective ? mPerspectiveTransform : mTransform) = aTransform;
AncestorTransform(const gfx::Matrix4x4& aTransform,
const gfx::Matrix4x4& aPerspectiveTransform)
: mTransform(aTransform), mPerspectiveTransform(aPerspectiveTransform) {}
gfx::Matrix4x4 CombinedTransform() const {
return mTransform * mPerspectiveTransform;
bool ContainsPerspectiveTransform() const {
return !mPerspectiveTransform.IsIdentity();
gfx::Matrix4x4 GetPerspectiveTransform() const {
return mPerspectiveTransform;
friend AncestorTransform operator*(const AncestorTransform& aA,
const AncestorTransform& aB) {
return AncestorTransform{
aA.mTransform * aB.mTransform,
aA.mPerspectiveTransform * aB.mPerspectiveTransform};
* Controller for all panning and zooming logic. Any time a user input is
* detected and it must be processed in some way to affect what the user sees,
* it goes through here. Listens for any input event from InputData and can
* optionally handle WidgetGUIEvent-derived touch events, but this must be done
* on the main thread. Note that this class completely cross-platform.
* Input events originate on the UI thread of the platform that this runs on,
* and are then sent to this class. This class processes the event in some way;
* for example, a touch move will usually lead to a panning of content (though
* of course there are exceptions, such as if content preventDefaults the event,
* or if the target frame is not scrollable). The compositor interacts with this
* class by locking it and querying it for the current transform matrix based on
* the panning and zooming logic that was invoked on the UI thread.
* Currently, each outer DOM window (i.e. a website in a tab, but not any
* subframes) has its own AsyncPanZoomController. In the future, to support
* asynchronously scrolled subframes, we want to have one AsyncPanZoomController
* per frame.
class AsyncPanZoomController {
typedef mozilla::MonitorAutoLock MonitorAutoLock;
typedef mozilla::gfx::Matrix4x4 Matrix4x4;
typedef mozilla::layers::RepaintRequest::ScrollOffsetUpdateType
enum GestureBehavior {
// The platform code is responsible for forwarding gesture events here. We
// will not attempt to generate gesture events from MultiTouchInputs.
// An instance of GestureEventListener is used to detect gestures. This is
// handled completely internally within this class.
* Gets the DPI from the tree manager.
float GetDPI() const;
* Constant describing the tolerance in distance we use, multiplied by the
* device DPI, before we start panning the screen. This is to prevent us from
* accidentally processing taps as touch moves, and from very short/accidental
* touches moving the screen.
* Note: It's an abuse of the 'Coord' class to use it to represent a 2D
* distance, but it's the closest thing we currently have.
ScreenCoord GetTouchStartTolerance() const;
* Same as GetTouchStartTolerance, but the tolerance for how far the touch
* has to move before it starts allowing touchmove events to be dispatched
* to content, for non-scrollable content.
ScreenCoord GetTouchMoveTolerance() const;
* Same as GetTouchStartTolerance, but the tolerance for how close the second
* tap has to be to the first tap in order to be counted as part of a
* multi-tap gesture (double-tap or one-touch-pinch).
ScreenCoord GetSecondTapTolerance() const;
AsyncPanZoomController(LayersId aLayersId, APZCTreeManager* aTreeManager,
const RefPtr<InputQueue>& aInputQueue,
GeckoContentController* aController,
GestureBehavior aGestures = DEFAULT_GESTURES);
// --------------------------------------------------------------------------
// These methods must only be called on the gecko thread.
* Read the various prefs and do any global initialization for all APZC
* instances. This must be run on the gecko thread before any APZC instances
* are actually used for anything meaningful.
static void InitializeGlobalState();
// --------------------------------------------------------------------------
// These methods must only be called on the controller/UI thread.
* 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.
void ZoomToRect(CSSRect aRect, const uint32_t aFlags);
* Updates any zoom constraints contained in the <meta name="viewport"> tag.
void UpdateZoomConstraints(const ZoomConstraints& aConstraints);
* Return the zoom constraints last set for this APZC (in the constructor
* or in UpdateZoomConstraints()).
ZoomConstraints GetZoomConstraints() const;
* Schedules a runnable to run on the controller/UI thread at some time
* in the future.
void PostDelayedTask(already_AddRefed<Runnable> aTask, int aDelayMs);
// --------------------------------------------------------------------------
// These methods must only be called on the sampler thread.
* Advances any animations currently running to the given timestamp.
* This may be called multiple times with the same timestamp.
* The return value indicates whether or not any currently running animation
* should continue. If true, the compositor should schedule another composite.
bool AdvanceAnimations(const SampleTime& aSampleTime);
bool UpdateAnimation(const RecursiveMutexAutoLock& aProofOfLock,
const SampleTime& aSampleTime,
nsTArray<RefPtr<Runnable>>* aOutDeferredTasks);
// --------------------------------------------------------------------------
// These methods must only be called on the updater thread.
* A shadow layer update has arrived. |aScrollMetdata| is the new
* ScrollMetadata for the container layer corresponding to this APZC.
* |aIsFirstPaint| is a flag passed from the shadow
* layers code indicating that the scroll metadata being sent with this call
* are the initial metadata and the initial paint of the frame has just
* happened.
void NotifyLayersUpdated(const ScrollMetadata& aScrollMetadata,
bool aIsFirstPaint, bool aThisLayerTreeUpdated);
* The platform implementation must set the compositor controller so that we
* can request composites.
void SetCompositorController(CompositorController* aCompositorController);
* If we need to share the frame metrics with some other thread, this
* controller needs to be set and provides relevant information/APIs.
void SetMetricsSharingController(
MetricsSharingController* aMetricsSharingController);
// --------------------------------------------------------------------------
// These methods can be called from any thread.
* Shut down the controller/UI thread state and prepare to be
* deleted (which may happen from any thread).
void Destroy();
* Returns true if Destroy() has already been called on this APZC instance.
bool IsDestroyed() const;
* Returns the transform to take something from the coordinate space of the
* last thing we know gecko painted, to the coordinate space of the last thing
* we asked gecko to paint. In cases where that last request has not yet been
* processed, this is needed to transform input events properly into a space
* gecko will understand.
Matrix4x4 GetTransformToLastDispatchedPaint() const;
* Returns the number of CSS pixels of checkerboard according to the metrics
* in this APZC. The argument provided by the caller is the composition bounds
* of this APZC, additionally clipped by the composition bounds of any
* ancestor APZCs, accounting for all the async transforms.
uint32_t GetCheckerboardMagnitude(
const ParentLayerRect& aClippedCompositionBounds) const;
* Report the number of CSSPixel-milliseconds of checkerboard to telemetry.
* See GetCheckerboardMagnitude for documentation of the
* aClippedCompositionBounds argument that needs to be provided by the caller.
void ReportCheckerboard(const SampleTime& aSampleTime,
const ParentLayerRect& aClippedCompositionBounds);
* Flush any active checkerboard report that's in progress. This basically
* pretends like any in-progress checkerboard event has terminated, and pushes
* out the report to the checkerboard reporting service and telemetry. If the
* checkerboard event has not really finished, it will start a new event
* on the next composite.
void FlushActiveCheckerboardReport();
* See documentation on corresponding method in APZPublicUtils.h
static gfx::IntSize GetDisplayportAlignmentMultiplier(
const ScreenSize& aBaseSize);
enum class ZoomInProgress {
* Recalculates the displayport. Ideally, this should paint an area bigger
* than the composite-to dimensions so that when you scroll down, you don't
* checkerboard immediately. This includes a bunch of logic, including
* algorithms to bias painting in the direction of the velocity and other
* such things.
static const ScreenMargin CalculatePendingDisplayPort(
const FrameMetrics& aFrameMetrics, const ParentLayerPoint& aVelocity,
ZoomInProgress aZoomInProgress);
nsEventStatus HandleDragEvent(const MouseInput& aEvent,
const AsyncDragMetrics& aDragMetrics,
CSSCoord aInitialThumbPos);
* Handler for events which should not be intercepted by the touch listener.
nsEventStatus HandleInputEvent(
const InputData& aEvent,
const ScreenToParentLayerMatrix4x4& aTransformToApzc);
* Handler for gesture events.
* Currently some gestures are detected in GestureEventListener that calls
* APZC back through this handler in order to avoid recursive calls to
* APZC::HandleInputEvent() which is supposed to do the work for
* ReceiveInputEvent().
nsEventStatus HandleGestureEvent(const InputData& aEvent);
* Start autoscrolling this APZC, anchored at the provided location.
void StartAutoscroll(const ScreenPoint& aAnchorLocation);
* Stop autoscrolling this APZC.
void StopAutoscroll();
* Populates the provided object (if non-null) with the scrollable guid of
* this apzc.
void GetGuid(ScrollableLayerGuid* aGuidOut) const;
* Returns the scrollable guid of this apzc.
ScrollableLayerGuid GetGuid() const;
* Returns true if this APZC instance is for the layer identified by the guid.
bool Matches(const ScrollableLayerGuid& aGuid);
* Returns true if the tree manager of this APZC is the same as the one
* passed in.
bool HasTreeManager(const APZCTreeManager* aTreeManager) const;
void StartAnimation(AsyncPanZoomAnimation* aAnimation);
* Cancels any currently running animation.
* aFlags is a bit-field to provide specifics of how to cancel the animation.
* See CancelAnimationFlags.
void CancelAnimation(CancelAnimationFlags aFlags = Default);
* Clear any overscroll on this APZC.
void ClearOverscroll();
* Returns whether this APZC is for an element marked with the 'scrollgrab'
* attribute.
bool HasScrollgrab() const { return mScrollMetadata.GetHasScrollgrab(); }
* Returns whether this APZC has scroll snap points.
bool HasScrollSnapping() const {
return mScrollMetadata.GetSnapInfo().HasScrollSnapping();
* Returns whether this APZC has room to be panned (in any direction).
bool IsPannable() const;
* Returns whether this APZC represents a scroll info layer.
bool IsScrollInfoLayer() const;
* Returns true if the APZC has been flung with a velocity greater than the
* stop-on-tap fling velocity threshold (which is pref-controlled).
bool IsFlingingFast() const;
* Returns the identifier of the touch in the last touch event processed by
* this APZC. This should only be called when the last touch event contained
* only one touch.
int32_t GetLastTouchIdentifier() const;
* Returns the matrix that transforms points from global screen space into
* this APZC's ParentLayer space.
* To respect the lock ordering, mRecursiveMutex must NOT be held when calling
* this function (since this function acquires the tree lock).
ScreenToParentLayerMatrix4x4 GetTransformToThis() const;
* Convert the vector |aVector|, rooted at the point |aAnchor|, from
* this APZC's ParentLayer coordinates into screen coordinates.
* The anchor is necessary because with 3D tranforms, the location of the
* vector can affect the result of the transform.
* To respect the lock ordering, mRecursiveMutex must NOT be held when calling
* this function (since this function acquires the tree lock).
ScreenPoint ToScreenCoordinates(const ParentLayerPoint& aVector,
const ParentLayerPoint& aAnchor) const;
* Convert the vector |aVector|, rooted at the point |aAnchor|, from
* screen coordinates into this APZC's ParentLayer coordinates.
* The anchor is necessary because with 3D tranforms, the location of the
* vector can affect the result of the transform.
* To respect the lock ordering, mRecursiveMutex must NOT be held when calling
* this function (since this function acquires the tree lock).
ParentLayerPoint ToParentLayerCoordinates(const ScreenPoint& aVector,
const ScreenPoint& aAnchor) const;
* Same as above, but uses an ExternalPoint as the anchor.
ParentLayerPoint ToParentLayerCoordinates(const ScreenPoint& aVector,
const ExternalPoint& aAnchor) const;
* Combines an offset defined as an external point, with a window-relative
* offset to give an absolute external point.
static ExternalPoint ToExternalPoint(const ExternalPoint& aScreenOffset,
const ScreenPoint& aScreenPoint);
* Gets a vector where the head is the given point, and the tail is
* the touch start position.
ScreenPoint PanVector(const ExternalPoint& aPos) const;
// Return whether or not a wheel event will be able to scroll in either
// direction.
bool CanScroll(const InputData& aEvent) const;
// Return the directions in which this APZC allows handoff (as governed by
// overscroll-behavior).
ScrollDirections GetAllowedHandoffDirections() const;
// Return whether or not a scroll delta will be able to scroll in either
// direction.
bool CanScroll(const ParentLayerPoint& aDelta) const;
// Return whether or not a scroll delta will be able to scroll in either
// direction with wheel.
bool CanScrollWithWheel(const ParentLayerPoint& aDelta) const;
// Return whether or not there is room to scroll this APZC
// in the given direction.
bool CanScroll(ScrollDirection aDirection) const;
// Return true if there is room to scroll downwards along with moving the
// dynamic toolbar.
// NOTE: This function should be used only for the root content APZC.
bool CanScrollDownwardsWithDynamicToolbar() const;
// Return true if there is room to scroll downwards.
bool CanScrollDownwards() const;
* Convert a point on the scrollbar from this APZC's ParentLayer coordinates
* to CSS coordinates relative to the beginning of the scroll track.
* Only the component in the direction of scrolling is returned.
CSSCoord ConvertScrollbarPoint(const ParentLayerPoint& aScrollbarPoint,
const ScrollbarData& aThumbData) const;
void NotifyMozMouseScrollEvent(const nsString& aString) const;
bool OverscrollBehaviorAllowsSwipe() const;
//|Metrics()| and |Metrics() const| are getter functions that both return
// mScrollMetadata.mMetrics
const FrameMetrics& Metrics() const;
FrameMetrics& Metrics();
* Get the GeckoViewMetrics to be sent to Gecko for the current composite.
GeckoViewMetrics GetGeckoViewMetrics() const;
// Helper function to compare root frame metrics and update them
// Returns true when the metrics have changed and were updated.
bool UpdateRootFrameMetricsIfChanged(GeckoViewMetrics& aMetrics);
// Returns the cached current frame time.
SampleTime GetFrameTime() const;
// Get whether the horizontal content of the honoured target of auto-dir
// scrolling starts from right to left. If you don't know of auto-dir
// scrolling or what a honoured target means,
// @see mozilla::WheelDeltaAdjustmentStrategy
bool IsContentOfHonouredTargetRightToLeft(bool aHonoursRoot) const;
// Protected destructor, to discourage deletion outside of Release():
virtual ~AsyncPanZoomController();
* Helper method for touches beginning. Sets everything up for panning and any
* multitouch gestures.
nsEventStatus OnTouchStart(const MultiTouchInput& aEvent);
* Helper method for touches moving. Does any transforms needed when panning.
nsEventStatus OnTouchMove(const MultiTouchInput& aEvent);
* Helper method for touches ending. Redraws the screen if necessary and does
* any cleanup after a touch has ended.
nsEventStatus OnTouchEnd(const MultiTouchInput& aEvent);
* Helper method for touches being cancelled. Treated roughly the same as a
* touch ending (OnTouchEnd()).
nsEventStatus OnTouchCancel(const MultiTouchInput& aEvent);
* Helper method for scales beginning. Distinct from the OnTouch* handlers in
* that this implies some outside implementation has determined that the user
* is pinching.
nsEventStatus OnScaleBegin(const PinchGestureInput& aEvent);
* Helper method for scaling. As the user moves their fingers when pinching,
* this changes the scale of the page.
nsEventStatus OnScale(const PinchGestureInput& aEvent);
* Helper method for scales ending. Redraws the screen if necessary and does
* any cleanup after a scale has ended.
nsEventStatus OnScaleEnd(const PinchGestureInput& aEvent);
* Helper methods for handling pan events.
nsEventStatus OnPanMayBegin(const PanGestureInput& aEvent);
nsEventStatus OnPanCancelled(const PanGestureInput& aEvent);
nsEventStatus OnPanBegin(const PanGestureInput& aEvent);
nsEventStatus OnPan(const PanGestureInput& aEvent, bool aFingersOnTouchpad);
nsEventStatus OnPanEnd(const PanGestureInput& aEvent);
nsEventStatus OnPanMomentumStart(const PanGestureInput& aEvent);
nsEventStatus OnPanMomentumEnd(const PanGestureInput& aEvent);
nsEventStatus HandleEndOfPan();
* Helper methods for handling scroll wheel events.
nsEventStatus OnScrollWheel(const ScrollWheelInput& aEvent);
* Gets the scroll wheel delta's values in parent-layer pixels from the
* original delta's values of a wheel input.
ParentLayerPoint GetScrollWheelDelta(const ScrollWheelInput& aEvent) const;
* This function is like GetScrollWheelDelta(aEvent).
* The difference is the four added parameters provide values as alternatives
* to the original wheel input's delta values, so |aEvent|'s delta values are
* ignored in this function, we only use some other member variables and
* functions of |aEvent|.
ParentLayerPoint GetScrollWheelDelta(const ScrollWheelInput& aEvent,
double aDeltaX, double aDeltaY,
double aMultiplierX,
double aMultiplierY) const;
* This deleted function is used for:
* 1. avoiding accidental implicit value type conversions of input delta
* values when callers intend to call the above function;
* 2. decoupling the manual relationship between the delta value type and the
* above function. If by any chance the defined delta value type in
* ScrollWheelInput has changed, this will automatically result in build
* time failure, so we can learn of it the first time and accordingly
* redefine those parameters' value types in the above function.
template <typename T>
ParentLayerPoint GetScrollWheelDelta(ScrollWheelInput&, T, T, T, T) = delete;
* Helper methods for handling keyboard events.
nsEventStatus OnKeyboard(const KeyboardInput& aEvent);
CSSPoint GetKeyboardDestination(const KeyboardScrollAction& aAction) const;
* Helper methods for long press gestures.
nsEventStatus OnLongPress(const TapGestureInput& aEvent);
nsEventStatus OnLongPressUp(const TapGestureInput& aEvent);
* Helper method for single tap gestures.
nsEventStatus OnSingleTapUp(const TapGestureInput& aEvent);
* Helper method for a single tap confirmed.
nsEventStatus OnSingleTapConfirmed(const TapGestureInput& aEvent);
* Helper method for double taps.
nsEventStatus OnDoubleTap(const TapGestureInput& aEvent);
* Helper method for double taps where the double-tap gesture is disabled.
nsEventStatus OnSecondTap(const TapGestureInput& aEvent);
* Helper method to cancel any gesture currently going to Gecko. Used
* primarily when a user taps the screen over some clickable content but then
* pans down instead of letting go (i.e. to cancel a previous touch so that a
* new one can properly take effect.
nsEventStatus OnCancelTap(const TapGestureInput& aEvent);
* The following five methods modify the scroll offset. For the APZC
* representing the RCD-RSF, they also recalculate the offset of the layout
* viewport.
* Scroll the scroll frame to an X,Y offset.
void SetVisualScrollOffset(const CSSPoint& aOffset);
* Scroll the scroll frame to an X,Y offset, clamping the resulting scroll
* offset to the scroll range.
void ClampAndSetVisualScrollOffset(const CSSPoint& aOffset);
* Scroll the scroll frame by an X,Y offset.
* The resulting scroll offset is not clamped to the scrollable rect;
* the caller must ensure it stays within range.
void ScrollBy(const CSSPoint& aOffset);
* Scroll the scroll frame by an X,Y offset, clamping the resulting
* scroll offset to the scroll range.
void ScrollByAndClamp(const CSSPoint& aOffset);
* Scales the viewport by an amount (note that it multiplies this scale in to
* the current scale, it doesn't set it to |aScale|). Also considers a focus
* point so that the page zooms inward/outward from that point.
void ScaleWithFocus(float aScale, const CSSPoint& aFocus);
* Schedules a composite on the compositor thread.
void ScheduleComposite();
* Schedules a composite, and if enough time has elapsed since the last
* paint, a paint.
void ScheduleCompositeAndMaybeRepaint();
* Gets the start point of the current touch.
* This only makes sense if a touch is currently happening and OnTouchMove()
* or the equivalent for pan gestures is being invoked.
ParentLayerPoint PanStart() const;
* Gets a vector of the velocities of each axis.
const ParentLayerPoint GetVelocityVector() const;
* Sets the velocities of each axis.
void SetVelocityVector(const ParentLayerPoint& aVelocityVector);
* Gets the first touch point from a MultiTouchInput. This gets only
* the first one and assumes the rest are either missing or not relevant.
ParentLayerPoint GetFirstTouchPoint(const MultiTouchInput& aEvent);
* Gets the relevant point in the event
* (eg. first touch, or pinch focus point) of the given InputData.
ExternalPoint GetExternalPoint(const InputData& aEvent);
* Gets the relevant point in the event, in external screen coordinates.
ExternalPoint GetFirstExternalTouchPoint(const MultiTouchInput& aEvent);
* Sets the panning state basing on the pan direction angle and current
* touch-action value.
void HandlePanningWithTouchAction(double angle);
* Sets the panning state ignoring the touch action value.
void HandlePanning(double angle);
* Update the panning state and axis locks.
void HandlePanningUpdate(const ScreenPoint& aDelta);
* Set and update the pinch lock
void HandlePinchLocking(const PinchGestureInput& aEvent);
* Sets up anything needed for panning. This takes us out of the "TOUCHING"
* state and starts actually panning us. We provide the physical pixel
* position of the start point so that the pan gesture is calculated
* regardless of if the window/GeckoView moved during the pan.
nsEventStatus StartPanning(const ExternalPoint& aStartPoint,
const TimeStamp& aEventTime);
* Wrapper for Axis::UpdateWithTouchAtDevicePoint(). Calls this function for
* both axes and factors in the time delta from the last update.
void UpdateWithTouchAtDevicePoint(const MultiTouchInput& aEvent);
* Does any panning required due to a new touch event.
void TrackTouch(const MultiTouchInput& aEvent);
* Register the start of a touch or pan gesture at the given position and
* time.
void StartTouch(const ParentLayerPoint& aPoint, TimeStamp aTimestamp);
* Register the end of a touch or pan gesture at the given time.
void EndTouch(TimeStamp aTimestamp);
* Utility function to send updated FrameMetrics to Gecko so that it can paint
* the displayport area. Calls into GeckoContentController to do the actual
* work. This call will use the current metrics. If this function is called
* from a non-main thread, it will redispatch itself to the main thread, and
* use the latest metrics during the redispatch.
void RequestContentRepaint(
RepaintUpdateType aUpdateType = RepaintUpdateType::eUserAction);
* Send the provided metrics to Gecko to trigger a repaint. This function
* may filter duplicate calls with the same metrics. This function must be
* called on the main thread.
void RequestContentRepaint(const FrameMetrics& aFrameMetrics,
const ParentLayerPoint& aVelocity,
const ScreenMargin& aDisplayportMargins,
RepaintUpdateType aUpdateType);
* Gets the current frame metrics. This is *not* the Gecko copy stored in the
* layers code.
const FrameMetrics& GetFrameMetrics() const;
* Gets the current scroll metadata. This is *not* the Gecko copy stored in
* the layers code/
const ScrollMetadata& GetScrollMetadata() const;
* Gets the pointer to the apzc tree manager. All the access to tree manager
* should be made via this method and not via private variable since this
* method ensures that no lock is set.
APZCTreeManager* GetApzcTreeManager() const;
void AssertOnSamplerThread() const;
void AssertOnUpdaterThread() const;
* Convert ScreenPoint relative to the screen to LayoutDevicePoint relative
* to the parent document. This excludes the transient compositor transform.
* NOTE: This must be converted to LayoutDevicePoint relative to the child
* document before sending over IPC to a child process.
Maybe<LayoutDevicePoint> ConvertToGecko(const ScreenIntPoint& aPoint);
enum AxisLockMode {
FREE, /* No locking at all */
STANDARD, /* Default axis locking mode that remains locked until pan ends*/
STICKY, /* Allow lock to be broken, with hysteresis */
static AxisLockMode GetAxisLockMode();
enum PinchLockMode {
PINCH_FREE, /* No locking at all */
PINCH_STANDARD, /* Default pinch locking mode that remains locked until
pinch gesture ends*/
PINCH_STICKY, /* Allow lock to be broken, with hysteresis */
static PinchLockMode GetPinchLockMode();
// Helper function for OnSingleTapUp(), OnSingleTapConfirmed(), and
// OnLongPressUp().
nsEventStatus GenerateSingleTap(GeckoContentController::TapType aType,
const ScreenIntPoint& aPoint,
mozilla::Modifiers aModifiers);
// Common processing at the end of a touch block.
void OnTouchEndOrCancel();
LayersId mLayersId;
RefPtr<CompositorController> mCompositorController;
RefPtr<MetricsSharingController> mMetricsSharingController;
/* Access to the following two fields is protected by the mRefPtrMonitor,
since they are accessed on the UI thread but can be cleared on the
updater thread. */
RefPtr<GeckoContentController> mGeckoContentController;
RefPtr<GestureEventListener> mGestureEventListener;
mutable Monitor mRefPtrMonitor;
// This is a raw pointer to avoid introducing a reference cycle between
// AsyncPanZoomController and APZCTreeManager. Since these objects don't
// live on the main thread, we can't use the cycle collector with them.
// The APZCTreeManager owns the lifetime of the APZCs, so nulling this
// pointer out in Destroy() will prevent accessing deleted memory.
Atomic<APZCTreeManager*> mTreeManager;
/* Utility functions that return a addrefed pointer to the corresponding
* fields. */
already_AddRefed<GeckoContentController> GetGeckoContentController() const;
already_AddRefed<GestureEventListener> GetGestureEventListener() const;
PlatformSpecificStateBase* GetPlatformSpecificState();
// Both |mScrollMetadata| and |mLastContentPaintMetrics| are protected by the
// monitor. Do not read from or modify them without locking.
ScrollMetadata mScrollMetadata;
// Protects |mScrollMetadata|, |mLastContentPaintMetrics| and |mState|.
// Before manipulating |mScrollMetadata| or |mLastContentPaintMetrics| the
// monitor should be held. When setting |mState|, either the SetState()
// function can be used, or the monitor can be held and then |mState| updated.
// IMPORTANT: See the note about lock ordering at the top of
// APZCTreeManager.h. This is mutable to allow entering it from 'const'
// methods; doing otherwise would significantly limit what methods could be
// 'const'.
// FIXME: Please keep in mind that due to some existing coupled relationships
// among the class members, we should be aware of indirect usage of the
// monitor-protected members. That is, although this monitor isn't required to
// be held before manipulating non-protected class members, some functions on
// those members might indirectly manipulate the protected members; in such
// cases, the monitor should still be held. Let's take mX.CanScroll for
// example:
// Axis::CanScroll(ParentLayerCoord) calls Axis::CanScroll() which calls
// Axis::GetPageLength() which calls Axis::GetFrameMetrics() which calls
// AsyncPanZoomController::GetFrameMetrics(), therefore, this monitor should
// be held before calling the CanScroll function of |mX| and |mY|. These
// coupled relationships bring us the burden of taking care of when the
// monitor should be held, so they should be decoupled in the future.
mutable RecursiveMutex mRecursiveMutex;
// Metadata of the container layer corresponding to this APZC. This is
// stored here so that it is accessible from the UI/controller thread.
// These are the metrics at last content paint, the most recent
// values we were notified of in NotifyLayersUpdate(). Since it represents
// the Gecko state, it should be used as a basis for untransformation when
// sending messages back to Gecko.
ScrollMetadata mLastContentPaintMetadata;
FrameMetrics& mLastContentPaintMetrics; // for convenience, refers to
// mLastContentPaintMetadata.mMetrics
// The last content repaint request.
RepaintRequest mLastPaintRequestMetrics;
// The metrics that we expect content to have. This is updated when we
// request a content repaint, and when we receive a shadow layers update.
// This allows us to transform events into Gecko's coordinate space.
ExpectedGeckoMetrics mExpectedGeckoMetrics;
// This holds important state from the Metrics() at previous times
// SampleCompositedAsyncTransform() was called. This will always have at least
// one item. mRecursiveMutex must be held when using or modifying this member.
// Samples should be inserted to the "back" of the deque and extracted from
// the "front".
std::deque<SampledAPZCState> mSampledState;
// Groups state variables that are specific to a platform.
// Initialized on first use.
UniquePtr<PlatformSpecificStateBase> mPlatformSpecificState;
AxisX mX;
AxisY mY;
// This flag is set to true when we are in a axis-locked pan as a result of
// the touch-action CSS property.
bool mPanDirRestricted;
// This flag is set to true when we are in a pinch-locked state. ie: user
// is performing a two-finger pan rather than a pinch gesture
bool mPinchLocked;
// Stores the pinch events that occured within a given timeframe. Used to
// calculate the focusChange and spanDistance within a fixed timeframe.
// RecentEventsBuffer is not threadsafe. Should only be accessed on the
// controller thread.
RecentEventsBuffer<PinchGestureInput> mPinchEventBuffer;
// Most up-to-date constraints on zooming. These should always be reasonable
// values; for example, allowing a min zoom of 0.0 can cause very bad things
// to happen.
ZoomConstraints mZoomConstraints;
// The last time the compositor has sampled the content transform for this
// frame.
SampleTime mLastSampleTime;
// The last sample time at which we submitted a checkerboarding report.
SampleTime mLastCheckerboardReport;
// Stores the previous focus point if there is a pinch gesture happening. Used
// to allow panning by moving multiple fingers (thus moving the focus point).
ParentLayerPoint mLastZoomFocus;
RefPtr<AsyncPanZoomAnimation> mAnimation;
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;
// Position on screen where user first put their finger down.
ExternalPoint mStartTouch;
// Accessing mScrollPayload needs to be protected by mRecursiveMutex
Maybe<CompositionPayload> mScrollPayload;
friend class Axis;
Maybe<CompositionPayload> NotifyScrollSampling();
* Invoke |callable|, passing |mLastContentPaintMetrics| as argument,
* while holding the APZC lock required to access |mLastContentPaintMetrics|.
* This allows code outside of an AsyncPanZoomController method implementation
* to access |mLastContentPaintMetrics| without having to make a copy of it.
* Passes through the return value of |callable|.
template <typename Callable>
auto CallWithLastContentPaintMetrics(const Callable& callable) const
-> decltype(callable(mLastContentPaintMetrics)) {
RecursiveMutexAutoLock lock(mRecursiveMutex);
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.
* Allows consumers of async transforms to specify for what purpose they are
* using the async transform:
* |eForHitTesting| is intended for hit-testing and other uses that need
* the most up-to-date transform, reflecting all events
* that have been processed so far, even if the transform
* is not yet reflected visually.
* |eForCompositing| is intended for the transform that should be reflected
* visually.
* For example, if an APZC has metrics with the mForceDisableApz flag set,
* then the |eForCompositing| async transform will be empty, while the
* |eForHitTesting| async transform will reflect processed input events
* regardless of mForceDisableApz.
enum AsyncTransformConsumer {
* Get the current layout viewport of the scrollable frame corresponding to
* this APZC.
CSSRect GetCurrentAsyncLayoutViewport(AsyncTransformConsumer aMode) const;
* Get the current scroll offset of the scrollable frame corresponding
* to this APZC, including the effects of any asynchronous panning and
* zooming, in ParentLayer pixels.
ParentLayerPoint GetCurrentAsyncScrollOffset(
AsyncTransformConsumer aMode) const;
* Get the current scroll offset of the scrollable frame corresponding
* to this APZC, including the effects of any asynchronous panning, in
* CSS pixels.
CSSPoint GetCurrentAsyncScrollOffsetInCssPixels(
AsyncTransformConsumer aMode) const;
* Return a visual effect that reflects this apzc's
* overscrolled state, if any.
AsyncTransformComponentMatrix GetOverscrollTransform(
AsyncTransformConsumer aMode) const;
* Returns the incremental transformation corresponding to the async pan/zoom
* in progress. That is, when this transform is multiplied with the layer's
* existing transform, it will make the layer appear with the desired pan/zoom
* amount.
* The transform can have both scroll and zoom components; the caller can
* request just one or the other, or both, via the |aComponents| parameter.
* When only the eLayout component is requested, the returned translation
* should really be a LayerPoint, rather than a ParentLayerPoint, as it will
* not be scaled by the asynchronous zoom.
AsyncTransform GetCurrentAsyncTransform(
AsyncTransformConsumer aMode,
AsyncTransformComponents aComponents = LayoutAndVisual) const;
* Returns the same transform as GetCurrentAsyncTransform(), but includes
* any transform due to axis over-scroll.
AsyncTransformComponentMatrix GetCurrentAsyncTransformWithOverscroll(
AsyncTransformConsumer aMode,
AsyncTransformComponents aComponents = LayoutAndVisual) const;
* Returns the "zoom" bits of the transform. This includes both the rasterized
* (layout device to layer scale) and async (layer scale to parent layer
* scale) components of the zoom.
LayoutDeviceToParentLayerScale GetCurrentPinchZoomScale(
AsyncTransformConsumer aMode) const;
ParentLayerRect GetCompositionBounds() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return mScrollMetadata.GetMetrics().GetCompositionBounds();
LayoutDeviceToLayerScale2D GetCumulativeResolution() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return mScrollMetadata.GetMetrics().GetCumulativeResolution();
* Advances to the next sample, if there is one, the list of sampled states
* stored in mSampledState. This will make the result of
* |GetCurrentAsyncTransform(eForCompositing)| and similar functions reflect
* the async scroll offset and zoom of the next sample. See also
* SampleCompositedAsyncTransform which creates the samples.
void AdvanceToNextSample();
* Samples the composited async transform, storing the result into
* mSampledState. This will make the result of
* |GetCurrentAsyncTransform(eForCompositing)| and similar functions reflect
* the async scroll offset and zoom stored in |Metrics()| when the sample
* is activated via some future call to |AdvanceToNextSample|.
* Returns true if the newly sampled value is different from the last
* sampled value.
bool SampleCompositedAsyncTransform(
const RecursiveMutexAutoLock& aProofOfLock);
* Updates the sample at the front of mSampledState with the latest
* metrics. This makes the result of
* |GetCurrentAsyncTransform(eForCompositing)| reflect the current Metrics().
void ResampleCompositedAsyncTransform(
const RecursiveMutexAutoLock& aProofOfLock);
* Helper functions to query the async layout viewport, scroll offset, and
* zoom either directly from |Metrics()|, or from cached variables that
* store the required value from the last time it was sampled by calling
* SampleCompositedAsyncTransform(), depending on who is asking.
CSSRect GetEffectiveLayoutViewport(
AsyncTransformConsumer aMode,
const RecursiveMutexAutoLock& aProofOfLock) const;
CSSPoint GetEffectiveScrollOffset(
AsyncTransformConsumer aMode,
const RecursiveMutexAutoLock& aProofOfLock) const;
CSSToParentLayerScale2D GetEffectiveZoom(
AsyncTransformConsumer aMode,
const RecursiveMutexAutoLock& aProofOfLock) const;
* Returns the visible portion of the content scrolled by this APZC, in
* CSS pixels. The caller must have acquired the mRecursiveMutex lock.
CSSRect GetVisibleRect(const RecursiveMutexAutoLock& aProofOfLock) const;
friend class AutoApplyAsyncTestAttributes;
bool SuppressAsyncScrollOffset() const;
* Applies |mTestAsyncScrollOffset| and |mTestAsyncZoom| to this
* AsyncPanZoomController. Calls |SampleCompositedAsyncTransform| to ensure
* that the GetCurrentAsync* functions consider the test offset and zoom in
* their computations.
void ApplyAsyncTestAttributes(const RecursiveMutexAutoLock& aProofOfLock);
* Sets this AsyncPanZoomController's FrameMetrics to |aPrevFrameMetrics| and
* calls |SampleCompositedAsyncTransform| to unapply any test values applied
* by |ApplyAsyncTestAttributes|.
void UnapplyAsyncTestAttributes(const RecursiveMutexAutoLock& aProofOfLock,
const FrameMetrics& aPrevFrameMetrics);
/* ===================================================================
* The functions and members in this section are used to manage
* the state that tracks what this APZC is doing with the input events.
enum PanZoomState {
NOTHING, /* no touch-start events received */
FLING, /* all touches removed, but we're still scrolling page */
TOUCHING, /* one touch-start event received */
PANNING, /* panning the frame */
PANNING_LOCKED_X, /* touch-start followed by move (i.e. panning with axis
lock) X axis */
PANNING_LOCKED_Y, /* as above for Y axis */
PAN_MOMENTUM, /* like PANNING, but controlled by momentum PanGestureInput
events */
PINCHING, /* nth touch-start, where n > 1. this mode allows pan and zoom */
ANIMATING_ZOOM, /* animated zoom to a new rect */
OVERSCROLL_ANIMATION, /* Spring-based animation used to relieve overscroll
once the finger is lifted. */
SMOOTH_SCROLL, /* Smooth scrolling to destination, with physics
controlled by prefs specific to the scroll origin. */
SMOOTHMSD_SCROLL, /* SmoothMSD scrolling to destination. Used by
CSSOM-View smooth scroll-behavior */
WHEEL_SCROLL, /* Smooth scrolling to a destination for a wheel event. */
KEYBOARD_SCROLL, /* Smooth scrolling to a destination for a keyboard event.
AUTOSCROLL, /* Autoscroll animation. */
SCROLLBAR_DRAG /* Async scrollbar drag. */
// This is in theory protected by |mRecursiveMutex|; that is, it should be
// held whenever this is updated. In practice though... see bug 897017.
PanZoomState mState;
static bool IsPanningState(PanZoomState aState);
* Returns whether the specified PanZoomState does not need to be reset when
* a scroll offset update is processed.
static bool CanHandleScrollOffsetUpdate(PanZoomState aState);
* Determine whether a main-thread scroll offset update should result in
* a call to CancelAnimation() (which interrupts in-progress animations and
* gestures).
* If the update is a relative update, |aRelativeDelta| contains its amount.
* If the update is not a relative update, GetMetrics() should already reflect
* the new offset at the time of the call.
bool ShouldCancelAnimationForScrollUpdate(
const Maybe<CSSPoint>& aRelativeDelta);
friend class StateChangeNotificationBlocker;
* A counter of how many StateChangeNotificationBlockers are active.
* A non-zero count will prevent state change notifications from
* being dispatched. Only code that holds mRecursiveMutex should touch this.
int mNotificationBlockers;
* Helper to set the current state. Holds the monitor before actually setting
* it and fires content controller events based on state changes. Always set
* the state using this call, do not set it directly.
void SetState(PanZoomState aState);
* Fire content controller notifications about state changes, assuming no
* StateChangeNotificationBlocker has been activated.
void DispatchStateChangeNotification(PanZoomState aOldState,
PanZoomState aNewState);
* Internal helpers for checking general state of this apzc.
bool IsInTransformingState() const;
static bool IsTransformingState(PanZoomState aState);
/* ===================================================================
* The functions and members in this section are used to manage
* blocks of touch events and the state needed to deal with content
* listeners.
* Flush a repaint request if one is needed, without throttling it with the
* paint throttler.
void FlushRepaintForNewInputBlock();
* Given an input event and the touch block it belongs to, check if the
* event can lead to a panning/zooming behavior.
* This is primarily used to figure out when to dispatch the pointercancel
* event for the pointer events spec.
bool ArePointerEventsConsumable(TouchBlockState* aBlock,
const MultiTouchInput& aInput);
* Clear internal state relating to touch input handling.
void ResetTouchInputState();
* Gets a ref to the input queue that is shared across the entire tree
* manager.
const RefPtr<InputQueue>& GetInputQueue() const;
void CancelAnimationAndGestureState();
RefPtr<InputQueue> mInputQueue;
InputBlockState* GetCurrentInputBlock() const;
TouchBlockState* GetCurrentTouchBlock() const;
bool HasReadyTouchBlock() const;
PanGestureBlockState* GetCurrentPanGestureBlock() const;
PinchGestureBlockState* GetCurrentPinchGestureBlock() const;
/* ===================================================================
* The functions and members in this section are used to manage
* fling animations, smooth scroll animations, and overscroll
* during a fling or smooth scroll.
* Attempt a fling with the velocity specified in |aHandoffState|.
* |aHandoffState.mIsHandoff| should be true iff. the fling was handed off
* from a previous APZC, and determines whether acceleration is applied
* to the fling.
* We only accept the fling in the direction(s) in which we are pannable.
* Returns the "residual velocity", i.e. the portion of
* |aHandoffState.mVelocity| that this APZC did not consume.
ParentLayerPoint AttemptFling(const FlingHandoffState& aHandoffState);
ParentLayerPoint AdjustHandoffVelocityForOverscrollBehavior(
ParentLayerPoint& aHandoffVelocity) const;
friend class StackScrollerFlingAnimation;
friend class AutoscrollAnimation;
template <typename FlingPhysics>
friend class GenericFlingAnimation;
friend class AndroidFlingPhysics;
friend class DesktopFlingPhysics;
friend class OverscrollAnimation;
friend class SmoothMsdScrollAnimation;
friend class GenericScrollAnimation;
friend class WheelScrollAnimation;
friend class KeyboardScrollAnimation;
friend class ZoomAnimation;
friend class GenericOverscrollEffect;
friend class WidgetOverscrollEffect;
FlingAccelerator mFlingAccelerator;
// Indicates if the repaint-during-pinch timer is currently set
bool mPinchPaintTimerSet;
// Deal with overscroll resulting from a fling animation. This is only ever
// called on APZC instances that were actually performing a fling.
// The overscroll is handled by trying to hand the fling off to an APZC
// later in the handoff chain, or if there are no takers, continuing the
// fling and entering an overscrolled state.
void HandleFlingOverscroll(
const ParentLayerPoint& aVelocity,
const RefPtr<const OverscrollHandoffChain>& aOverscrollHandoffChain,
const RefPtr<const AsyncPanZoomController>& aScrolledApzc);
void HandleSmoothScrollOverscroll(const ParentLayerPoint& aVelocity);
// Start an overscroll animation with the given initial velocity.
void StartOverscrollAnimation(const ParentLayerPoint& aVelocity);
// Start a smooth-scrolling animation to the given destination, with physics
// based on the prefs for the indicated origin.
void SmoothScrollTo(const CSSPoint& aDestination,
const ScrollOrigin& aOrigin);
// Start a smooth-scrolling animation to the given destination, with MSD
// physics that is suited for scroll-snapping.
void SmoothMsdScrollTo(const CSSPoint& aDestination);
// Returns whether overscroll is allowed during an event.
bool AllowScrollHandoffInCurrentBlock() const;
// Invoked by the pinch repaint timer.
void DoDelayedRequestContentRepaint();
// Compute the number of ParentLayer pixels per (Screen) inch at the given
// point and in the given direction.
float ComputePLPPI(ParentLayerPoint aPoint,
ParentLayerPoint aDirection) const;
Maybe<CSSPoint> GetCurrentAnimationDestination(
const RecursiveMutexAutoLock& aProofOfLock) const;
/* ===================================================================
* The functions and members in this section are used to make ancestor chains
* out of APZC instances. These chains can only be walked or manipulated
* while holding the lock in the associated APZCTreeManager instance.
void SetParent(AsyncPanZoomController* aParent) { mParent = aParent; }
AsyncPanZoomController* GetParent() const { return mParent; }
/* Returns true if there is no APZC higher in the tree with the same
* layers id.
bool HasNoParentWithSameLayersId() const {
return !mParent || (mParent->mLayersId != mLayersId);
bool IsRootForLayersId() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return mScrollMetadata.IsLayersIdRoot();
bool IsRootContent() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return Metrics().IsRootContent();
// |mTreeManager| belongs in this section but it's declaration is a bit
// further above due to initialization-order constraints.
RefPtr<AsyncPanZoomController> mParent;
/* ===================================================================
* The functions and members in this section are used for scrolling,
* including handing off scroll to another APZC, and overscrolling.
ScrollableLayerGuid::ViewID GetScrollId() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return Metrics().GetScrollId();
ScrollableLayerGuid::ViewID GetScrollHandoffParentId() const {
return mScrollMetadata.GetScrollParentId();
* Attempt to scroll in response to a touch-move from |aStartPoint| to
* |aEndPoint|, which are in our (transformed) screen coordinates.
* Due to overscroll handling, there may not actually have been a touch-move
* at these points, but this function will scroll as if there had been.
* If this attempt causes overscroll (i.e. the layer cannot be scrolled
* by the entire amount requested), the overscroll is passed back to the
* tree manager via APZCTreeManager::DispatchScroll(). If the tree manager
* does not find an APZC further in the handoff chain to accept the
* overscroll, and this APZC is pannable, this APZC enters an overscrolled
* state.
* |aOverscrollHandoffChain| and |aOverscrollHandoffChainIndex| are used by
* the tree manager to keep track of which APZC to hand off the overscroll
* to; this function increments the chain and the index and passes it on to
* APZCTreeManager::DispatchScroll() in the event of overscroll.
* Returns true iff. this APZC, or an APZC further down the
* handoff chain, accepted the scroll (possibly entering an overscrolled
* state). If this returns false, the caller APZC knows that it should enter
* an overscrolled state itself if it can.
* aStartPoint and aEndPoint are modified depending on how much of the
* scroll gesture was consumed by APZCs in the handoff chain.
bool AttemptScroll(ParentLayerPoint& aStartPoint, ParentLayerPoint& aEndPoint,
OverscrollHandoffState& aOverscrollHandoffState);
void FlushRepaintForOverscrollHandoff();
* If overscrolled, start a snap-back animation and return true.
* Otherwise return false.
bool SnapBackIfOverscrolled();
* Build the chain of APZCs along which scroll will be handed off when
* this APZC receives input events.
* Notes on lifetime and const-correctness:
* - The returned handoff chain is |const|, to indicate that it cannot be
* changed after being built.
* - When passing the chain to a function that uses it without storing it,
* pass it by reference-to-const (as in |const OverscrollHandoffChain&|).
* - When storing the chain, store it by RefPtr-to-const (as in
* |RefPtr<const OverscrollHandoffChain>|). This ensures the chain is
* kept alive. Note that queueing a task that uses the chain as an
* argument constitutes storing, as the task may outlive its queuer.
* - When passing the chain to a function that will store it, pass it as
* |const RefPtr<const OverscrollHandoffChain>&|. This allows the
* function to copy it into the |RefPtr<const OverscrollHandoffChain>|
* that will store it, while avoiding an unnecessary copy (and thus
* AddRef() and Release()) when passing it.
RefPtr<const OverscrollHandoffChain> BuildOverscrollHandoffChain();
* A helper function for calling APZCTreeManager::DispatchScroll().
* Guards against the case where the APZC is being concurrently destroyed
* (and thus mTreeManager is being nulled out).
bool CallDispatchScroll(ParentLayerPoint& aStartPoint,
ParentLayerPoint& aEndPoint,
OverscrollHandoffState& aOverscrollHandoffState);
void RecordScrollPayload(const TimeStamp& aTimeStamp);
* A helper function for overscrolling during panning. This is a wrapper
* around OverscrollBy() that also implements restrictions on entering
* overscroll based on the pan angle.
void OverscrollForPanning(ParentLayerPoint& aOverscroll,
const ScreenPoint& aPanDistance);
* Try to overscroll by 'aOverscroll'.
* If we are pannable on a particular axis, that component of 'aOverscroll'
* is transferred to any existing overscroll.
void OverscrollBy(ParentLayerPoint& aOverscroll);
// Helper function for CanScroll().
ParentLayerPoint GetDeltaForEvent(const InputData& aEvent) const;
/* ===================================================================
* The functions and members in this section are used to maintain the
* area that this APZC instance is responsible for. This is used when
* hit-testing to see which APZC instance should handle touch events.
void SetAncestorTransform(const AncestorTransform& aAncestorTransform) {
mAncestorTransform = aAncestorTransform;
Matrix4x4 GetAncestorTransform() const {
return mAncestorTransform.CombinedTransform();
bool AncestorTransformContainsPerspective() const {
return mAncestorTransform.ContainsPerspectiveTransform();
// Return the perspective transform component of the ancestor transform.
Matrix4x4 GetAncestorTransformPerspective() const {
return mAncestorTransform.GetPerspectiveTransform();
// Returns whether or not this apzc contains the given screen point within
// its composition bounds.
bool Contains(const ScreenIntPoint& aPoint) const;
bool IsOverscrolled() const {
return mX.IsOverscrolled() || mY.IsOverscrolled();
bool IsInPanningState() const;
/* This is the cumulative CSS transform for all the layers from (and
* including) the parent APZC down to (but excluding) this one, and excluding
* any perspective transforms. */
AncestorTransform mAncestorTransform;
/* ===================================================================
* The functions and members in this section are used for sharing the
* FrameMetrics across processes for the progressive tiling code.
/* Unique id assigned to each APZC. Used with ViewID to uniquely identify
* shared FrameMeterics used in progressive tile painting. */
const uint32_t mAPZCId;
RefPtr<ipc::SharedMemoryBasic> mSharedFrameMetricsBuffer;
CrossProcessMutex* mSharedLock;
* Called when ever Metrics() is updated so that if it is being
* shared with the content process the shared FrameMetrics may be updated.
void UpdateSharedCompositorFrameMetrics();
* Create a shared memory buffer for containing the FrameMetrics and
* a CrossProcessMutex that may be shared with the content process
* for use in progressive tiled update calculations.
void ShareCompositorFrameMetrics();
/* ===================================================================
* The functions and members in this section are used for testing
* and assertion purposes only.
* Gets whether this APZC has performed async key scrolling.
bool TestHasAsyncKeyScrolled() const { return mTestHasAsyncKeyScrolled; }
* Set an extra offset for testing async scrolling.
void SetTestAsyncScrollOffset(const CSSPoint& aPoint);
* Set an extra offset for testing async scrolling.
void SetTestAsyncZoom(const LayerToParentLayerScale& aZoom);
void MarkAsyncTransformAppliedToContent() {
mAsyncTransformAppliedToContent = true;
bool GetAsyncTransformAppliedToContent() const {
return mAsyncTransformAppliedToContent;
LayersId GetLayersId() const { return mLayersId; }
bool IsAsyncZooming() const {
RecursiveMutexAutoLock lock(mRecursiveMutex);
return mState == PINCHING || mState == ANIMATING_ZOOM;
// The timestamp of the latest touch start event.
TimeStamp mTouchStartTime;
// The time duration between mTouchStartTime and the touchmove event that
// started the pan (the touchmove event that transitioned this APZC from the
// TOUCHING state to one of the PANNING* states). Only valid while this APZC
// is in a panning state.
TimeDuration mTouchStartRestingTimeBeforePan;
Maybe<ParentLayerCoord> mMinimumVelocityDuringPan;
// Extra offset to add to the async scroll position for testing
CSSPoint mTestAsyncScrollOffset;
// Extra zoom to include in the aync zoom for testing
LayerToParentLayerScale mTestAsyncZoom;
uint8_t mTestAttributeAppliers;
// Flag to track whether or not the APZ transform is not used. This
// flag is recomputed for every composition frame.
bool mAsyncTransformAppliedToContent;
// Flag to track whether or not this APZC has ever async key scrolled.
bool mTestHasAsyncKeyScrolled;
/* ===================================================================
* The functions and members in this section are used for checkerboard
* recording.
// Helper function to update the in-progress checkerboard event, if any.
void UpdateCheckerboardEvent(const MutexAutoLock& aProofOfLock,
uint32_t aMagnitude);
// Mutex protecting mCheckerboardEvent
Mutex mCheckerboardEventLock;
// This is created when this APZC instance is first included as part of a
// composite. If a checkerboard event takes place, this is destroyed at the
// end of the event, and a new one is created on the next composite.
UniquePtr<CheckerboardEvent> mCheckerboardEvent;
// This is used to track the total amount of time that we could reasonably
// be checkerboarding. Combined with other info, this allows us to
// meaningfully say how frequently users actually encounter checkerboarding.
PotentialCheckerboardDurationTracker mPotentialCheckerboardTracker;
/* ===================================================================
* The functions in this section are used for CSS scroll snapping.
// If moving |aStartPosition| by |aDelta| should trigger scroll snapping,
// adjust |aDelta| to reflect the snapping (that is, make it a delta that will
// take us to the desired snap point). The delta is interpreted as being
// relative to |aStartPosition|, and if a target snap point is found,
// |aStartPosition| is also updated, to the value of the snap point.
// |aUnit| affects the snapping behaviour (see ScrollSnapUtils::
// GetSnapPointForDestination).
// Returns true iff. a target snap point was found.
bool MaybeAdjustDeltaForScrollSnapping(ScrollUnit aUnit,
ParentLayerPoint& aDelta,
CSSPoint& aStartPosition);
// A wrapper function of MaybeAdjustDeltaForScrollSnapping for
// ScrollWheelInput.
bool MaybeAdjustDeltaForScrollSnappingOnWheelInput(
const ScrollWheelInput& aEvent, ParentLayerPoint& aDelta,
CSSPoint& aStartPosition);
bool MaybeAdjustDestinationForScrollSnapping(const KeyboardInput& aEvent,
CSSPoint& aDestination);
// Snap to a snap position nearby the current scroll position, if appropriate.
void ScrollSnap();
// Snap to a snap position nearby the destination predicted based on the
// current velocity, if appropriate.
void ScrollSnapToDestination();
// Snap to a snap position nearby the provided destination, if appropriate.
void ScrollSnapNear(const CSSPoint& aDestination);
// Find a snap point near |aDestination| that we should snap to.
// Returns the snap point if one was found, or an empty Maybe otherwise.
// |aUnit| affects the snapping behaviour (see ScrollSnapUtils::
// GetSnapPointForDestination). It should generally be determined by the
// type of event that's triggering the scroll.
Maybe<CSSPoint> FindSnapPointNear(const CSSPoint& aDestination,
ScrollUnit aUnit);
} // namespace layers
} // namespace mozilla
#endif // mozilla_layers_PanZoomController_h