Source code

Revision control

Copy as Markdown

Other Tools

/* -*- 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_layout_ScrollAnimationPhysics_h_
#define mozilla_layout_ScrollAnimationPhysics_h_
#include "mozilla/TimeStamp.h"
#include "nsPoint.h"
#include "Units.h"
namespace mozilla {
class ScrollAnimationPhysics {
// Update the animation to have |aDestination| as its new destination.
// The animation's current position remains unchanged, and the shape
// of the animation curve is recomputed between the current position
// and the new destination.
// This is used in cases where an input event that would cause another
// animation of this kind is received while this animation is running.
virtual void Update(const TimeStamp& aTime, const nsPoint& aDestination,
const nsSize& aCurrentVelocity) = 0;
// Shift both the current position and the destination of the animation
// by |aShiftDelta|. The progress of the animation along its animation
// curve is unchanged.
// This is used in cases where the main thread changes the scroll offset
// (e.g. via scrollBy()) but we want the "momentum" represented by the
// animation to be preserved.
virtual void ApplyContentShift(const CSSPoint& aShiftDelta) = 0;
// Get the velocity at a point in time in nscoords/sec.
virtual nsSize VelocityAt(const TimeStamp& aTime) = 0;
// Returns the expected scroll position at a given point in time, in app
// units, relative to the scroll frame.
virtual nsPoint PositionAt(const TimeStamp& aTime) = 0;
virtual bool IsFinished(const TimeStamp& aTime) = 0;
virtual ~ScrollAnimationPhysics() = default;
// Helper for accelerated wheel deltas. This can be called from the main thread
// or the APZ Controller thread.
static inline double ComputeAcceleratedWheelDelta(double aDelta,
int32_t aCounter,
int32_t aFactor) {
if (!aDelta) {
return aDelta;
return (aDelta * aCounter * double(aFactor) / 10);
static const uint32_t kScrollSeriesTimeoutMs = 80; // in milliseconds
} // namespace mozilla
#endif // mozilla_layout_ScrollAnimationPhysics_h_