blob: 18a69d3070eb957fedae9bb142c577f7f0724edf [file] [log] [blame]
// 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.
#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 {
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);
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_;
} // namespace ui