layout/generic/ScrollAnimationPhysics.h

   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_ScrollAnimationPhysics_h_
   8 #define mozilla_layout_ScrollAnimationPhysics_h_
   9
  10 #include "mozilla/TimeStamp.h"
  11 #include "nsPoint.h"
  12 #include "Units.h"
  13
  14 namespace mozilla {
  15
  16 class ScrollAnimationPhysics {
  17  public:
  18   // Update the animation to have |aDestination| as its new destination.
  19   // The animation's current position remains unchanged, and the shape
  20   // of the animation curve is recomputed between the current position
  21   // and the new destination.
  22   // This is used in cases where an input event that would cause another
  23   // animation of this kind is received while this animation is running.
  24   virtual void Update(const TimeStamp& aTime, const nsPoint& aDestination,
  25                       const nsSize& aCurrentVelocity) = 0;
  26
  27   // Shift both the current position and the destination of the animation
  28   // by |aShiftDelta|. The progress of the animation along its animation
  29   // curve is unchanged.
  30   // This is used in cases where the main thread changes the scroll offset
  31   // (e.g. via scrollBy()) but we want the "momentum" represented by the
  32   // animation to be preserved.
  33   virtual void ApplyContentShift(const CSSPoint& aShiftDelta) = 0;
  34
  35   // Get the velocity at a point in time in nscoords/sec.
  36   virtual nsSize VelocityAt(const TimeStamp& aTime) = 0;
  37
  38   // Returns the expected scroll position at a given point in time, in app
  39   // units, relative to the scroll frame.
  40   virtual nsPoint PositionAt(const TimeStamp& aTime) = 0;
  41
  42   virtual bool IsFinished(const TimeStamp& aTime) = 0;
  43
  44   virtual ~ScrollAnimationPhysics() = default;
  45 };
  46
  47 // Helper for accelerated wheel deltas. This can be called from the main thread
  48 // or the APZ Controller thread.
  49 static inline double ComputeAcceleratedWheelDelta(double aDelta,
  50                                                   int32_t aCounter,
  51                                                   int32_t aFactor) {
  52   if (!aDelta) {
  53     return aDelta;
  54   }
  55   return (aDelta * aCounter * double(aFactor) / 10);
  56 }
  57
  58 }  // namespace mozilla
  59
  60 #endif  // mozilla_layout_ScrollAnimationPhysics_h_