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// Copyright 2014 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 UI_EVENTS_GESTURES_FLING_CURVE_H_
#define UI_EVENTS_GESTURES_FLING_CURVE_H_
#include "base/macros.h"
#include "base/time/time.h"
#include "ui/events/events_base_export.h"
#include "ui/events/gesture_curve.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/vector2d_f.h"
namespace ui {
// FlingCurve can be used to scroll a UI element suitable for touch screen-based
// flings.
class EVENTS_BASE_EXPORT FlingCurve : public GestureCurve {
public:
FlingCurve(const gfx::Vector2dF& velocity, base::TimeTicks start_timestamp);
~FlingCurve() override;
// GestureCurve implementation.
bool ComputeScrollOffset(base::TimeTicks time,
gfx::Vector2dF* offset,
gfx::Vector2dF* velocity) override;
// In contrast to |ComputeScrollOffset()|, this method is stateful and
// returns the *change* in scroll offset between successive calls.
// Returns true as long as the curve is still active and requires additional
// animation ticks.
bool ComputeScrollDeltaAtTime(base::TimeTicks current, gfx::Vector2dF* delta);
private:
const float curve_duration_;
const base::TimeTicks start_timestamp_;
gfx::Vector2dF displacement_ratio_;
gfx::Vector2dF cumulative_scroll_;
base::TimeTicks previous_timestamp_;
float time_offset_;
float position_offset_;
DISALLOW_COPY_AND_ASSIGN(FlingCurve);
};
} // namespace ui
#endif // UI_EVENTS_GESTURES_FLING_CURVE_H_
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