path: root/gfx/layers/apz/src/AndroidAPZ.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

#include "AndroidAPZ.h"

#include "AsyncPanZoomController.h"
#include "GeneratedJNIWrappers.h"
#include "gfxPrefs.h"
#include "OverscrollHandoffState.h"
#include "ViewConfiguration.h"

#define ANDROID_APZ_LOG(...)
// #define ANDROID_APZ_LOG(...) printf_stderr("ANDROID_APZ: " __VA_ARGS__)

static float sMaxFlingSpeed = 0.0f;

namespace mozilla {
namespace layers {

AndroidSpecificState::AndroidSpecificState() {
  using namespace mozilla::java;

  sdk::ViewConfiguration::LocalRef config;
  if (sdk::ViewConfiguration::Get(GeckoAppShell::GetApplicationContext(), &config) == NS_OK) {
    int32_t speed = 0;
    if (config->GetScaledMaximumFlingVelocity(&speed) == NS_OK) {
      sMaxFlingSpeed = (float)speed * 0.001f;
    } else {
      ANDROID_APZ_LOG("%p Failed to query ViewConfiguration for scaled maximum fling velocity\n", this);
    }
  } else {
    ANDROID_APZ_LOG("%p Failed to get ViewConfiguration\n", this);
  }

  StackScroller::LocalRef scroller;
  if (StackScroller::New(GeckoAppShell::GetApplicationContext(), &scroller) != NS_OK) {
    ANDROID_APZ_LOG("%p Failed to create Android StackScroller\n", this);
    return;
  }
  mOverScroller = scroller;
}

const float BOUNDS_EPSILON = 1.0f;

// This function is used to convert the scroll offset from a float to an integer
// suitable for using with the Android OverScroller Class.
// The Android OverScroller class (unfortunately) operates in integers instead of floats.
// When casting a float value such as 1.5 to an integer, the value is converted to 1.
// If this value represents the max scroll offset, the OverScroller class will never scroll
// to the end of the page as it will always be 0.5 pixels short. To work around this issue,
// the min and max scroll extents are floor/ceil to convert them to the nearest integer
// just outside of the actual scroll extents. This means, the starting
// scroll offset must be converted the same way so that if the frame has already been
// scrolled 1.5 pixels, it won't be snapped back when converted to an integer. This integer
// rounding error was one of several causes of Bug 1276463.
static int32_t
ClampStart(float aOrigin, float aMin, float aMax)
{
  if (aOrigin <= aMin) {
    return (int32_t)floor(aMin);
  } else if (aOrigin >= aMax) {
    return (int32_t)ceil(aMax);
  }
  return (int32_t)aOrigin;
}

AndroidFlingAnimation::AndroidFlingAnimation(AsyncPanZoomController& aApzc,
                                             PlatformSpecificStateBase* aPlatformSpecificState,
                                             const RefPtr<const OverscrollHandoffChain>& aOverscrollHandoffChain,
                                             bool aFlingIsHandoff,
                                             const RefPtr<const AsyncPanZoomController>& aScrolledApzc)
  : mApzc(aApzc)
  , mOverscrollHandoffChain(aOverscrollHandoffChain)
  , mScrolledApzc(aScrolledApzc)
  , mSentBounceX(false)
  , mSentBounceY(false)
  , mFlingDuration(0)
{
  MOZ_ASSERT(mOverscrollHandoffChain);
  AndroidSpecificState* state = aPlatformSpecificState->AsAndroidSpecificState();
  MOZ_ASSERT(state);
  mOverScroller = state->mOverScroller;
  MOZ_ASSERT(mOverScroller);

  // 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, Layer::HORIZONTAL)) {
    ReentrantMonitorAutoEnter lock(mApzc.mMonitor);
    mApzc.mX.SetVelocity(0);
  }
  if (!mOverscrollHandoffChain->CanScrollInDirection(&mApzc, Layer::VERTICAL)) {
    ReentrantMonitorAutoEnter lock(mApzc.mMonitor);
    mApzc.mY.SetVelocity(0);
  }

  ParentLayerPoint velocity = mApzc.GetVelocityVector();

  float scrollRangeStartX = mApzc.mX.GetPageStart().value;
  float scrollRangeEndX = mApzc.mX.GetScrollRangeEnd().value;
  float scrollRangeStartY = mApzc.mY.GetPageStart().value;
  float scrollRangeEndY = mApzc.mY.GetScrollRangeEnd().value;
  mStartOffset.x = mPreviousOffset.x = mApzc.mX.GetOrigin().value;
  mStartOffset.y = mPreviousOffset.y = mApzc.mY.GetOrigin().value;
  float length = velocity.Length();
  if (length > 0.0f) {
    mFlingDirection = velocity / length;

    if ((sMaxFlingSpeed > 0.0f) && (length > sMaxFlingSpeed)) {
       velocity = mFlingDirection * sMaxFlingSpeed;
    }
  }

  mPreviousVelocity = velocity;

  int32_t originX = ClampStart(mStartOffset.x, scrollRangeStartX, scrollRangeEndX);
  int32_t originY = ClampStart(mStartOffset.y, scrollRangeStartY, scrollRangeEndY);
  if (!state->mLastFling.IsNull()) {
    // If it's been too long since the previous fling, or if the new fling's
    // velocity is too low, don't allow flywheel to kick in. If we do allow
    // flywheel to kick in, then we need to update the timestamp on the
    // StackScroller because otherwise it might use a stale velocity.
    TimeDuration flingDuration = TimeStamp::Now() - state->mLastFling;
    if (flingDuration.ToMilliseconds() < gfxPrefs::APZFlingAccelInterval()
        && velocity.Length() >= gfxPrefs::APZFlingAccelMinVelocity()) {
      bool unused = false;
      mOverScroller->ComputeScrollOffset(flingDuration.ToMilliseconds(), &unused);
    } else {
      mOverScroller->ForceFinished(true);
    }
  }
  mOverScroller->Fling(originX, originY,
                       // Android needs the velocity in pixels per second and it is in pixels per ms.
                       (int32_t)(velocity.x * 1000.0f), (int32_t)(velocity.y * 1000.0f),
                       (int32_t)floor(scrollRangeStartX), (int32_t)ceil(scrollRangeEndX),
                       (int32_t)floor(scrollRangeStartY), (int32_t)ceil(scrollRangeEndY),
                       0, 0, 0);
  state->mLastFling = TimeStamp::Now();
}

/**
 * Advances a fling by an interpolated amount based on the Android OverScroller.
 * 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.
 */
bool
AndroidFlingAnimation::DoSample(FrameMetrics& aFrameMetrics,
                                const TimeDuration& aDelta)
{
  bool shouldContinueFling = true;

  mFlingDuration += aDelta.ToMilliseconds();
  mOverScroller->ComputeScrollOffset(mFlingDuration, &shouldContinueFling);

  int32_t currentX = 0;
  int32_t currentY = 0;
  mOverScroller->GetCurrX(&currentX);
  mOverScroller->GetCurrY(&currentY);
  ParentLayerPoint offset((float)currentX, (float)currentY);
  ParentLayerPoint preCheckedOffset(offset);

  bool hitBoundX = CheckBounds(mApzc.mX, offset.x, mFlingDirection.x, &(offset.x));
  bool hitBoundY = CheckBounds(mApzc.mY, offset.y, mFlingDirection.y, &(offset.y));

  ParentLayerPoint velocity = mPreviousVelocity;

  // Sometimes the OverScroller fails to update the offset for a frame.
  // If the frame can still scroll we just use the velocity from the previous
  // frame. However, if the frame can no longer scroll in the direction
  // of the fling, then end the animation.
  if (offset != mPreviousOffset) {
    if (aDelta.ToMilliseconds() > 0) {
      mOverScroller->GetCurrSpeedX(&velocity.x);
      mOverScroller->GetCurrSpeedY(&velocity.y);

      velocity.x /= 1000;
      velocity.y /= 1000;

      mPreviousVelocity = velocity;
    }
  } else if ((fabsf(offset.x - preCheckedOffset.x) > BOUNDS_EPSILON) || (fabsf(offset.y - preCheckedOffset.y) > BOUNDS_EPSILON)) {
    // The page is no longer scrolling but the fling animation is still animating beyond the page bounds. If it goes
    // beyond the BOUNDS_EPSILON then it has overflowed and will never stop. In that case, stop the fling animation.
    shouldContinueFling = false;
  } else if (hitBoundX && hitBoundY) {
    // We can't scroll any farther along either axis.
    shouldContinueFling = false;
  }

  float speed = velocity.Length();

  // gfxPrefs::APZFlingStoppedThreshold is only used in tests.
  if (!shouldContinueFling || (speed < gfxPrefs::APZFlingStoppedThreshold())) {
    if (shouldContinueFling) {
      // The OverScroller thinks it should continue but the speed is below
      // the stopping threshold so abort the animation.
      mOverScroller->AbortAnimation();
    }
    // This animation is going to end. If DeferHandleFlingOverscroll
    // has not been called and there is still some velocity left,
    // call it so that fling hand off may occur if applicable.
    if (!mSentBounceX && !mSentBounceY && (speed > 0.0f)) {
      DeferHandleFlingOverscroll(velocity);
    }
    return false;
  }

  mPreviousOffset = offset;

  mApzc.SetVelocityVector(velocity);
  aFrameMetrics.SetScrollOffset(offset / aFrameMetrics.GetZoom());

  // If we hit a bounds while flinging, send the velocity so that the bounce
  // animation can play.
  if (hitBoundX || hitBoundY) {
    ParentLayerPoint bounceVelocity = velocity;

    if (!mSentBounceX && hitBoundX && fabsf(offset.x - mStartOffset.x) > BOUNDS_EPSILON) {
      mSentBounceX = true;
    } else {
      bounceVelocity.x = 0.0f;
    }

    if (!mSentBounceY && hitBoundY && fabsf(offset.y - mStartOffset.y) > BOUNDS_EPSILON) {
      mSentBounceY = true;
    } else {
      bounceVelocity.y = 0.0f;
    }
    if (!IsZero(bounceVelocity)) {
      DeferHandleFlingOverscroll(bounceVelocity);
    }
  }

  return true;
}

void
AndroidFlingAnimation::DeferHandleFlingOverscroll(ParentLayerPoint& aVelocity)
{
  mDeferredTasks.AppendElement(
      NewRunnableMethod<ParentLayerPoint,
                        RefPtr<const OverscrollHandoffChain>,
                        RefPtr<const AsyncPanZoomController>>(&mApzc,
                                                              &AsyncPanZoomController::HandleFlingOverscroll,
                                                              aVelocity,
                                                              mOverscrollHandoffChain,
                                                              mScrolledApzc));

}

bool
AndroidFlingAnimation::CheckBounds(Axis& aAxis, float aValue, float aDirection, float* aClamped)
{
  if ((aDirection < 0.0f) && (aValue <= aAxis.GetPageStart().value)) {
    if (aClamped) {
      *aClamped = aAxis.GetPageStart().value;
    }
    return true;
  } else if ((aDirection > 0.0f) && (aValue >= aAxis.GetScrollRangeEnd().value)) {
    if (aClamped) {
      *aClamped = aAxis.GetScrollRangeEnd().value;
    }
    return true;
  }
  return false;
}

} // namespace layers
} // namespace mozilla