snap_scroll_controller.h revision a02191e04bc25c4935f804f2c080ae28663d096d 
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_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
6#define UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
7
8#include "base/basictypes.h"
9#include "ui/events/gesture_detection/gesture_detection_export.h"
10
11namespace gfx {
12class Display;
13}
14
15namespace ui {
16
17class MotionEvent;
18class ZoomManager;
19
20// Port of SnapScrollController.java from Chromium
21// Controls the scroll snapping behavior based on scroll updates.
22class SnapScrollController {
23 public:
24  explicit SnapScrollController(const gfx::Display& display);
25  ~SnapScrollController();
26
27  // Updates the snap scroll mode based on the given X and Y distance to be
28  // moved on scroll.  If the scroll update is above a threshold, the snapping
29  // behavior is reset.
30  void UpdateSnapScrollMode(float distance_x, float distance_y);
31
32  // Sets the snap scroll mode based on the event type.
33  void SetSnapScrollingMode(const MotionEvent& event,
34                            bool is_scale_gesture_detection_in_progress);
35
36  void ResetSnapScrollMode() { snap_scroll_mode_ = SNAP_NONE; }
37  bool IsSnapVertical() const { return snap_scroll_mode_ == SNAP_VERT; }
38  bool IsSnapHorizontal() const { return snap_scroll_mode_ == SNAP_HORIZ; }
39  bool IsSnappingScrolls() const { return snap_scroll_mode_ != SNAP_NONE; }
40
41 private:
42  enum SnapMode {
43    SNAP_NONE,
44    SNAP_HORIZ,
45    SNAP_VERT
46  };
47
48  float channel_distance_;
49  SnapMode snap_scroll_mode_;
50  float first_touch_x_;
51  float first_touch_y_;
52  float distance_x_;
53  float distance_y_;
54
55  DISALLOW_COPY_AND_ASSIGN(SnapScrollController);
56};
57
58}  // namespace ui
59
60#endif  // UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
61