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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CC_INPUT_SNAP_FLING_CURVE_H_
#define CC_INPUT_SNAP_FLING_CURVE_H_
#include "base/time/time.h"
#include "cc/cc_export.h"
#include "ui/gfx/geometry/rect_f.h"
#include "ui/gfx/geometry/vector2d_f.h"
namespace cc {
// The curve for the snap fling animation. The curve would generate a geometric
// sequence of deltas to be scrolled at each frame.
class CC_EXPORT SnapFlingCurve {
public:
// Creates the curve based on the start offset, target offset, and the first
// inertial GSU's time_stamp.
SnapFlingCurve(const gfx::PointF& start_offset,
const gfx::PointF& target_offset,
base::TimeTicks first_gsu_time);
virtual ~SnapFlingCurve();
// Estimate the total distance that will be scrolled given the first GSU's
// delta
static gfx::Vector2dF EstimateDisplacement(const gfx::Vector2dF& first_delta);
// Returns the delta that should be scrolled at |time|.
virtual gfx::Vector2dF GetScrollDelta(base::TimeTicks time);
// Updates |current_displacement_|. This sync is necessary because the node
// might be scrolled by other calls and the scrolls might be clamped.
void UpdateCurrentOffset(const gfx::PointF& current_offset);
// Returns true if the scroll has arrived at the snap destination.
virtual bool IsFinished() const;
base::TimeDelta duration() const { return duration_; }
private:
// Returns the curve's current distance at |current_time|.
double GetCurrentCurveDistance(base::TimeDelta current_time);
// The initial scroll offset of the scroller.
const gfx::PointF start_offset_;
// The total displacement to the snap position.
const gfx::Vector2dF total_displacement_;
// 1D representation of |total_displacement_|.
const double total_distance_;
// The current displacement that has been scrolled.
gfx::Vector2dF current_displacement_;
// The timestamp of the first GSU.
const base::TimeTicks start_time_;
// The number of deltas in the curve's geometric sequence.
const double total_frames_;
// The first delta that defines the curve's geometric sequence.
const double first_delta_;
// The total milliseconds needed to finish the curve.
const base::TimeDelta duration_;
bool is_finished_ = false;
// |total_displacement_.x| / |total_distance_|
double ratio_x_;
// |total_displacement_.y| / |total_distance_|
double ratio_y_;
};
} // namespace cc
#endif // CC_INPUT_SNAP_FLING_CURVE_H_
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