src/ui/events/gestures/fling_curve.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_EVENTS_GESTURES_FLING_CURVE_H_
   6 #define UI_EVENTS_GESTURES_FLING_CURVE_H_
   7
   8 #include "base/time/time.h"
   9 #include "ui/events/events_base_export.h"
  10 #include "ui/gfx/geometry/point_f.h"
  11 #include "ui/gfx/geometry/vector2d_f.h"
  12
  13 namespace ui {
  14
  15 // FlingCurve can be used to scroll a UI element suitable for touch screen-based
  16 // flings.
  17 class EVENTS_BASE_EXPORT FlingCurve {
  18  public:
  19   FlingCurve(const gfx::Vector2dF& velocity, base::TimeTicks start_timestamp);
  20   ~FlingCurve();
  21
  22   gfx::Vector2dF GetScrollAmountAtTime(base::TimeTicks current_timestamp);
  23   base::TimeTicks start_timestamp() const { return start_timestamp_; }
  24
  25  private:
  26   const float curve_duration_;
  27   const base::TimeTicks start_timestamp_;
  28
  29   gfx::Vector2dF displacement_ratio_;
  30   gfx::Vector2dF cumulative_scroll_;
  31   base::TimeTicks last_timestamp_;
  32   float time_offset_;
  33   float position_offset_;
  34
  35   DISALLOW_COPY_AND_ASSIGN(FlingCurve);
  36 };
  37
  38 }  // namespace ui
  39
  40 #endif  // UI_EVENTS_GESTURES_FLING_CURVE_H_