1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
// Copyright 2014 The Chromium Authors
// 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/events/velocity_tracker/motion_event.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/size_f.h"
#include "ui/gfx/geometry/vector2d_f.h"
namespace ui {
// Port of SnapScrollController.java from Chromium
// Controls the scroll snapping behavior based on scroll updates.
class GESTURE_DETECTION_EXPORT SnapScrollController {
public:
explicit SnapScrollController(const gfx::SizeF& display_size);
SnapScrollController(const SnapScrollController&) = delete;
SnapScrollController& operator=(const SnapScrollController&) = delete;
~SnapScrollController() = default;
// Sets the snap scroll mode based on the event type.
void SetSnapScrollMode(const MotionEvent& event,
bool is_scale_gesture_detection_in_progress,
float slop_distance);
// 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,
float slop_distance);
bool IsSnapVertical() const;
bool IsSnapHorizontal() const;
bool IsSnappingScrolls() const;
private:
enum SnapMode { SNAP_NONE, SNAP_PENDING, SNAP_HORIZ, SNAP_VERT };
gfx::SizeF display_size_;
SnapMode mode_ = SNAP_NONE;
gfx::PointF down_position_;
gfx::Vector2dF accumulated_distance_;
};
} // namespace ui
#endif // UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
|
