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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_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
#define UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
#include "base/basictypes.h"
#include "ui/events/gesture_detection/gesture_detection_export.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/size_f.h"
#include "ui/gfx/geometry/vector2d_f.h"
namespace ui {
class MotionEvent;
// Port of SnapScrollController.java from Chromium
// Controls the scroll snapping behavior based on scroll updates.
class GESTURE_DETECTION_EXPORT SnapScrollController {
public:
SnapScrollController(float snap_bound, const gfx::SizeF& display_size);
~SnapScrollController();
// Sets the snap scroll mode based on the event type.
void SetSnapScrollMode(const MotionEvent& event,
bool is_scale_gesture_detection_in_progress);
// Updates the snap scroll mode based on the given X and Y distance to be
// moved on scroll. If the scroll update is above a threshold, the snapping
// behavior is reset.
void UpdateSnapScrollMode(float distance_x, float distance_y);
bool IsSnapVertical() const;
bool IsSnapHorizontal() const;
bool IsSnappingScrolls() const;
private:
enum SnapMode { SNAP_NONE, SNAP_PENDING, SNAP_HORIZ, SNAP_VERT };
const float snap_bound_;
const float channel_distance_;
SnapMode mode_;
gfx::PointF down_position_;
gfx::Vector2dF accumulated_distance_;
DISALLOW_COPY_AND_ASSIGN(SnapScrollController);
};
} // namespace ui
#endif // UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
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