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// 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.
#include <memory>
#include "base/time/time.h"
#include "cc/animation/animation_curve.h"
#include "cc/animation/animation_export.h"
#include "ui/gfx/geometry/scroll_offset.h"
namespace cc {
class TimingFunction;
// ScrollOffsetAnimationCurve computes scroll offset as a function of time
// during a scroll offset animation.
// Scroll offset animations can run either in Blink or in cc, in response to
// user input or programmatic scroll operations. For more information about
// scheduling and servicing scroll animations, see blink::ScrollAnimator and
// blink::ProgrammaticScrollAnimator.
class CC_ANIMATION_EXPORT ScrollOffsetAnimationCurve : public AnimationCurve {
// Indicates how the animation duration should be computed.
enum class DurationBehavior {
// Duration proportional to scroll delta; used for programmatic scrolls.
// Constant duration; used for keyboard scrolls.
// Duration inversely proportional to scroll delta within certain bounds.
// Used for mouse wheels, makes fast wheel flings feel "snappy" while
// preserving smoothness of slow wheel movements.
static std::unique_ptr<ScrollOffsetAnimationCurve> Create(
const gfx::ScrollOffset& target_value,
std::unique_ptr<TimingFunction> timing_function,
DurationBehavior = DurationBehavior::DELTA_BASED);
static base::TimeDelta SegmentDuration(const gfx::Vector2dF& delta,
DurationBehavior behavior,
base::TimeDelta delayed_by);
ScrollOffsetAnimationCurve(const ScrollOffsetAnimationCurve&) = delete;
~ScrollOffsetAnimationCurve() override;
ScrollOffsetAnimationCurve& operator=(const ScrollOffsetAnimationCurve&) =
void SetInitialValue(const gfx::ScrollOffset& initial_value,
base::TimeDelta delayed_by = base::TimeDelta());
bool HasSetInitialValue() const;
gfx::ScrollOffset GetValue(base::TimeDelta t) const;
gfx::ScrollOffset target_value() const { return target_value_; }
// Updates the current curve to aim at a new target, starting at time t
// relative to the start of the animation. The duration is recomputed based
// on the DurationBehavior the curve was constructed with. The timing
// function is an ease-in-out cubic bezier modified to preserve velocity at t.
void UpdateTarget(base::TimeDelta t, const gfx::ScrollOffset& new_target);
// Shifts the entire curve by a delta without affecting its shape or timing.
// Used for scroll anchoring adjustments that happen during scroll animations
// (see blink::ScrollAnimator::AdjustAnimationAndSetScrollOffset).
void ApplyAdjustment(const gfx::Vector2dF& adjustment);
// AnimationCurve implementation
base::TimeDelta Duration() const override;
CurveType Type() const override;
std::unique_ptr<AnimationCurve> Clone() const override;
CloneToScrollOffsetAnimationCurve() const;
static void SetAnimationDurationForTesting(base::TimeDelta duration);
ScrollOffsetAnimationCurve(const gfx::ScrollOffset& target_value,
std::unique_ptr<TimingFunction> timing_function,
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_;
std::unique_ptr<TimingFunction> timing_function_;
DurationBehavior duration_behavior_;
bool has_set_initial_value_;
static base::Optional<double> animation_duration_for_testing_;
} // namespace cc