cc/animation/scroll_offset_animation_curve.h

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_ANIMATION_SCROLL_OFFSET_ANIMATION_CURVE_H_
#define CC_ANIMATION_SCROLL_OFFSET_ANIMATION_CURVE_H_

#include "base/memory/scoped_ptr.h"
#include "base/time/time.h"
#include "cc/animation/animation_curve.h"
#include "cc/base/cc_export.h"
#include "ui/gfx/geometry/scroll_offset.h"

namespace cc {

class TimingFunction;

class CC_EXPORT ScrollOffsetAnimationCurve : public AnimationCurve {
 public:
  enum class DurationBehavior { DELTA_BASED, CONSTANT };
  static scoped_ptr<ScrollOffsetAnimationCurve> Create(
      const gfx::ScrollOffset& target_value,
      scoped_ptr<TimingFunction> timing_function,
      DurationBehavior = DurationBehavior::DELTA_BASED);

  ~ScrollOffsetAnimationCurve() override;

  void SetInitialValue(const gfx::ScrollOffset& initial_value);
  gfx::ScrollOffset GetValue(base::TimeDelta t) const;
  gfx::ScrollOffset target_value() const { return target_value_; }
  void UpdateTarget(double t, const gfx::ScrollOffset& new_target);

  // AnimationCurve implementation
  base::TimeDelta Duration() const override;
  CurveType Type() const override;
  scoped_ptr<AnimationCurve> Clone() const override;

 private:
  ScrollOffsetAnimationCurve(const gfx::ScrollOffset& target_value,
                             scoped_ptr<TimingFunction> timing_function,
                             DurationBehavior);

  gfx::ScrollOffset initial_value_;
  gfx::ScrollOffset target_value_;
  base::TimeDelta total_animation_duration_;

  // Time from animation start to most recent UpdateTarget.
  base::TimeDelta last_retarget_;

  scoped_ptr<TimingFunction> timing_function_;
  DurationBehavior duration_behavior_;

  DISALLOW_COPY_AND_ASSIGN(ScrollOffsetAnimationCurve);
};

}  // namespace cc

#endif  // CC_ANIMATION_SCROLL_OFFSET_ANIMATION_CURVE_H_