// 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_