tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

ScrollAnimationBezierPhysics.h (3529B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef mozilla_layout_ScrollAnimationBezierPhysics_h_
      8 #define mozilla_layout_ScrollAnimationBezierPhysics_h_
      9 
     10 #include "ScrollAnimationPhysics.h"
     11 #include "mozilla/SMILKeySpline.h"
     12 
     13 namespace mozilla {
     14 
     15 struct ScrollAnimationBezierPhysicsSettings {
     16  // These values are minimum and maximum animation duration per event,
     17  // and a global ratio which defines how longer is the animation's duration
     18  // compared to the average recent events intervals (such that for a relatively
     19  // consistent events rate, the next event arrives before current animation
     20  // ends)
     21  int32_t mMinMS;
     22  int32_t mMaxMS;
     23  double mIntervalRatio;
     24 };
     25 
     26 // This class implements a cubic bezier timing function and automatically
     27 // adapts the animation duration based on the scrolling rate.
     28 class ScrollAnimationBezierPhysics final : public ScrollAnimationPhysics {
     29 public:
     30  explicit ScrollAnimationBezierPhysics(
     31      const nsPoint& aStartPos,
     32      const ScrollAnimationBezierPhysicsSettings& aSettings);
     33 
     34  void Update(const TimeStamp& aTime, const nsPoint& aDestination,
     35              const nsSize& aCurrentVelocity) override;
     36 
     37  void ApplyContentShift(const CSSPoint& aShiftDelta) override;
     38 
     39  // Get the velocity at a point in time in nscoords/sec.
     40  nsSize VelocityAt(const TimeStamp& aTime) override;
     41 
     42  // Returns the expected scroll position at a given point in time, in app
     43  // units, relative to the scroll frame.
     44  nsPoint PositionAt(const TimeStamp& aTime) override;
     45 
     46  bool IsFinished(const TimeStamp& aTime) override {
     47    return mDuration.IsZero() || aTime > mStartTime + mDuration;
     48  }
     49 
     50 protected:
     51  double ProgressAt(const TimeStamp& aTime) const {
     52    return std::clamp((aTime - mStartTime) / mDuration, 0.0, 1.0);
     53  }
     54 
     55  nscoord VelocityComponent(double aTimeProgress,
     56                            const SMILKeySpline& aTimingFunction,
     57                            nscoord aStart, nscoord aDestination) const;
     58 
     59  // Calculate duration, possibly dynamically according to events rate and
     60  // event origin. (also maintain previous timestamps - which are only used
     61  // here).
     62  TimeDuration ComputeDuration(const TimeStamp& aTime);
     63 
     64  // Initializes the timing function in such a way that the current velocity is
     65  // preserved.
     66  void InitTimingFunction(SMILKeySpline& aTimingFunction, nscoord aCurrentPos,
     67                          nscoord aCurrentVelocity, nscoord aDestination);
     68 
     69  // Initialize event history.
     70  void InitializeHistory(const TimeStamp& aTime);
     71 
     72  // Cached Preferences values.
     73  ScrollAnimationBezierPhysicsSettings mSettings;
     74 
     75  // mPrevEventTime holds previous 3 timestamps for intervals averaging (to
     76  // reduce duration fluctuations). When AsyncScroll is constructed and no
     77  // previous timestamps are available (indicated with mIsFirstIteration),
     78  // initialize mPrevEventTime using imaginary previous timestamps with maximum
     79  // relevant intervals between them.
     80  TimeStamp mPrevEventTime[3];
     81 
     82  TimeStamp mStartTime;
     83 
     84  nsPoint mStartPos;
     85  nsPoint mDestination;
     86  TimeDuration mDuration;
     87  SMILKeySpline mTimingFunctionX;
     88  SMILKeySpline mTimingFunctionY;
     89  bool mIsFirstIteration;
     90 };
     91 
     92 }  // namespace mozilla
     93 
     94 #endif  // mozilla_layout_ScrollAnimationBezierPhysics_h_