tor-browser

GenericFlingAnimation.h (8915B)

---

/* -*- 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_GenericFlingAnimation_h_
#define mozilla_layers_GenericFlingAnimation_h_

#include "APZUtils.h"
#include "AsyncPanZoomAnimation.h"
#include "AsyncPanZoomController.h"
#include "FrameMetrics.h"
#include "Units.h"
#include "OverscrollHandoffState.h"
#include "mozilla/Assertions.h"
#include "mozilla/Monitor.h"
#include "mozilla/RefPtr.h"
#include "mozilla/StaticPrefs_apz.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/ToString.h"
#include "nsThreadUtils.h"

static mozilla::LazyLogModule sApzFlgLog("apz.fling");
#define FLING_LOG(...) MOZ_LOG(sApzFlgLog, LogLevel::Debug, (__VA_ARGS__))

namespace mozilla {
namespace layers {

/**
* The FlingPhysics template parameter determines the physics model
* that the fling animation follows. It must have the following methods:
*
*   - Default constructor.
*
*   - Init(const ParentLayerPoint& aStartingVelocity, float aPLPPI).
*     Called at the beginning of the fling, with the fling's starting velocity,
*     and the number of ParentLayer pixels per (Screen) inch at the point of
*     the fling's start in the fling's direction.
*
*   - Sample(const TimeDuration& aDelta,
*            ParentLayerPoint* aOutVelocity,
*            ParentLayerPoint* aOutOffset);
*     Called on each sample of the fling.
*     |aDelta| is the time elapsed since the last sample.
*     |aOutVelocity| should be the desired velocity after the current sample,
*                    in ParentLayer pixels per millisecond.
*     |aOutOffset| should be the desired _delta_ to the scroll offset after
*     the current sample. |aOutOffset| should _not_ be clamped to the APZC's
*     scrollable bounds; the caller will do the clamping, and it needs to
*     know the unclamped value to handle handoff/overscroll correctly.
*/
template <typename FlingPhysics>
class GenericFlingAnimation : public AsyncPanZoomAnimation,
                             public FlingPhysics {
public:
 GenericFlingAnimation(AsyncPanZoomController& aApzc,
                       const FlingHandoffState& aHandoffState, float aPLPPI)
     : mApzc(aApzc),
       mOverscrollHandoffChain(aHandoffState.mChain),
       mScrolledApzc(aHandoffState.mScrolledApzc) {
   MOZ_ASSERT(mOverscrollHandoffChain);

   // Drop any velocity on axes where we don't have room to scroll anyways
   // (in this APZC, or an APZC further in the handoff chain).
   // This ensures that we don't take the 'overscroll' path in Sample()
   // on account of one axis which can't scroll having a velocity.
   if (!mOverscrollHandoffChain->CanScrollInDirection(
           &mApzc, ScrollDirection::eHorizontal)) {
     RecursiveMutexAutoLock lock(mApzc.mRecursiveMutex);
     mApzc.mX.SetVelocity(0);
   }
   if (!mOverscrollHandoffChain->CanScrollInDirection(
           &mApzc, ScrollDirection::eVertical)) {
     RecursiveMutexAutoLock lock(mApzc.mRecursiveMutex);
     mApzc.mY.SetVelocity(0);
   }

   if (aHandoffState.mIsHandoff) {
     // Only apply acceleration in the APZC that originated the fling, not in
     // APZCs further down the handoff chain during handoff.
     mApzc.mFlingAccelerator.Reset();
   }

   ParentLayerPoint velocity =
       mApzc.mFlingAccelerator.GetFlingStartingVelocity(
           aApzc.GetFrameTime(), mApzc.GetVelocityVector(), aHandoffState);

   mApzc.SetVelocityVector(velocity);

   FlingPhysics::Init(mApzc.GetVelocityVector(), aPLPPI);
 }

 /**
  * Advances a fling by an interpolated amount based on the passed in |aDelta|.
  * This should be called whenever sampling the content transform for this
  * frame. Returns true if the fling animation should be advanced by one frame,
  * or false if there is no fling or the fling has ended.
  */
 virtual bool DoSample(FrameMetrics& aFrameMetrics,
                       const TimeDuration& aDelta) override {
   CSSToParentLayerScale zoom(aFrameMetrics.GetZoom());
   if (zoom == CSSToParentLayerScale(0)) {
     return false;
   }

   ParentLayerPoint velocity;
   ParentLayerPoint offset;
   FlingPhysics::Sample(aDelta, &velocity, &offset);

   mApzc.SetVelocityVector(velocity);

   // If we shouldn't continue the fling, let's just stop and repaint.
   if (IsZero(velocity / zoom)) {
     FLING_LOG("%p ending fling animation. overscrolled=%d\n", &mApzc,
               mApzc.IsOverscrolled());
     // This APZC or an APZC further down the handoff chain may be be
     // overscrolled. Start a snap-back animation on the overscrolled APZC.
     // Note:
     //   This needs to be a deferred task even though it can safely run
     //   while holding mRecursiveMutex, because otherwise, if the overscrolled
     //   APZC is this one, then the SetState(NOTHING) in UpdateAnimation will
     //   stomp on the SetState(SNAP_BACK) it does.
     mDeferredTasks.AppendElement(NewRunnableMethod<AsyncPanZoomController*>(
         "layers::OverscrollHandoffChain::SnapBackOverscrolledApzc",
         mOverscrollHandoffChain.get(),
         &OverscrollHandoffChain::SnapBackOverscrolledApzc, &mApzc));
     return false;
   }

   // Ordinarily we might need to do a ScheduleComposite if either of
   // the following AdjustDisplacement calls returns true, but this
   // is already running as part of a FlingAnimation, so we'll be compositing
   // per frame of animation anyway.
   ParentLayerPoint overscroll;
   ParentLayerPoint adjustedOffset;
   mApzc.mX.AdjustDisplacement(offset.x, adjustedOffset.x, overscroll.x);
   mApzc.mY.AdjustDisplacement(offset.y, adjustedOffset.y, overscroll.y);
   if (aFrameMetrics.GetZoom() != CSSToParentLayerScale(0)) {
     mApzc.ScrollBy(adjustedOffset / aFrameMetrics.GetZoom());
   }

   // The fling may have caused us to reach the end of our scroll range.
   if (!IsZero(overscroll / zoom)) {
     // Hand off the fling to the next APZC in the overscroll handoff chain.

     // We may have reached the end of the scroll range along one axis but
     // not the other. In such a case we only want to hand off the relevant
     // component of the fling.
     if (mApzc.IsZero(overscroll.x)) {
       velocity.x = 0;
     } else if (mApzc.IsZero(overscroll.y)) {
       velocity.y = 0;
     }

     // To hand off the fling, we attempt to find a target APZC and start a new
     // fling with the same velocity on that APZC. For simplicity, the actual
     // overscroll of the current sample is discarded rather than being handed
     // off. The compositor should sample animations sufficiently frequently
     // that this is not noticeable. The target APZC is chosen by seeing if
     // there is an APZC further in the handoff chain which is pannable; if
     // there isn't, we take the new fling ourselves, entering an overscrolled
     // state.
     // Note: APZC is holding mRecursiveMutex, so directly calling
     // HandleFlingOverscroll() (which acquires the tree lock) would violate
     // the lock ordering. Instead we schedule HandleFlingOverscroll() to be
     // called after mRecursiveMutex is released.
     FLING_LOG("%p fling went into overscroll, handing off with velocity %s\n",
               &mApzc, ToString(velocity).c_str());
     mDeferredTasks.AppendElement(
         NewRunnableMethod<ParentLayerPoint, SideBits,
                           RefPtr<const OverscrollHandoffChain>,
                           RefPtr<const AsyncPanZoomController>>(
             "layers::AsyncPanZoomController::HandleFlingOverscroll", &mApzc,
             &AsyncPanZoomController::HandleFlingOverscroll, velocity,
             apz::GetOverscrollSideBits(overscroll), mOverscrollHandoffChain,
             mScrolledApzc));

     // If there is a remaining velocity on this APZC, continue this fling
     // as well. (This fling and the handed-off fling will run concurrently.)
     // Note that AdjustDisplacement() will have zeroed out the velocity
     // along the axes where we're overscrolled.
     return !IsZero(mApzc.GetVelocityVector() / zoom);
   }

   return true;
 }

 void Cancel(CancelAnimationFlags aFlags) override {
   mApzc.mFlingAccelerator.ObserveFlingCanceled(mApzc.GetVelocityVector());
 }

 virtual bool HandleScrollOffsetUpdate(
     const Maybe<CSSPoint>& aRelativeDelta) override {
   return true;
 }

private:
 AsyncPanZoomController& mApzc;
 RefPtr<const OverscrollHandoffChain> mOverscrollHandoffChain;
 RefPtr<const AsyncPanZoomController> mScrolledApzc;
};

}  // namespace layers
}  // namespace mozilla

#endif  // mozilla_layers_GenericFlingAnimation_h_