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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 "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(const SnapScrollController&) = delete;
- SnapScrollController& operator=(const SnapScrollController&) = delete;
- ~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_;
- };
- } // namespace ui
- #endif // UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
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