scale_gesture_detector.h revision 03b57e008b61dfcb1fbad3aea950ae0e001748b0 
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_SCALE_GESTURE_DETECTOR_H_
6#define UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
7
8#include "base/time/time.h"
9#include "ui/events/gesture_detection/gesture_detection_export.h"
10
11namespace ui {
12
13class MotionEvent;
14
15// Port of ScaleGestureDetector.java from Android
16// * platform/frameworks/base/core/java/android/view/ScaleGestureDetector.java
17// * Change-Id: I3e7926a4f6f9ab4951f380bd004499c78b3bda69
18// * Please update the Change-Id as upstream Android changes are pulled.
19class ScaleGestureDetector {
20 public:
21  struct GESTURE_DETECTION_EXPORT Config {
22    Config();
23    ~Config();
24
25    // Distance the current span can deviate from the initial span before
26    // scaling will start (in dips). The span is the diameter of the circle with
27    // a radius of average pointer deviation from the focal point.
28    float span_slop;
29
30    // Minimum accepted value for TouchMajor while scaling (in dips).
31    float min_scaling_touch_major;
32
33    // Minimum span needed to initiate a scaling gesture (in dips).
34    float min_scaling_span;
35
36    // Minimum pinch span change before pinch occurs (in dips). See
37    // crbug.com/373318.
38    float min_pinch_update_span_delta;
39  };
40
41  class ScaleGestureListener {
42   public:
43    virtual ~ScaleGestureListener() {}
44    virtual bool OnScale(const ScaleGestureDetector& detector,
45                         const MotionEvent& e) = 0;
46    virtual bool OnScaleBegin(const ScaleGestureDetector& detector,
47                              const MotionEvent& e) = 0;
48    virtual void OnScaleEnd(const ScaleGestureDetector& detector,
49                            const MotionEvent& e) = 0;
50  };
51
52  // A convenience class to extend when you only want to listen for a subset of
53  // scaling-related events. This implements all methods in
54  // |ScaleGestureListener| but does nothing.
55  // |OnScale()| returns false so that a subclass can retrieve the accumulated
56  // scale factor in an overridden |OnScaleEnd()|.
57  // |OnScaleBegin() returns true.
58  class SimpleScaleGestureListener : public ScaleGestureListener {
59   public:
60    // ScaleGestureListener implementation.
61    virtual bool OnScale(const ScaleGestureDetector&,
62                         const MotionEvent&) OVERRIDE;
63    virtual bool OnScaleBegin(const ScaleGestureDetector&,
64                              const MotionEvent&) OVERRIDE;
65    virtual void OnScaleEnd(const ScaleGestureDetector&,
66                            const MotionEvent&) OVERRIDE;
67  };
68
69  ScaleGestureDetector(const Config& config, ScaleGestureListener* listener);
70  virtual ~ScaleGestureDetector();
71
72  // Accepts MotionEvents and dispatches events to a |ScaleGestureListener|
73  // when appropriate.
74  //
75  // Note: Applications should pass a complete and consistent event stream to
76  // this method. A complete and consistent event stream involves all
77  // MotionEvents from the initial ACTION_DOWN to the final ACTION_UP or
78  // ACTION_CANCEL.
79  //
80  // Returns true if the event was processed and the detector wants to receive
81  // the rest of the MotionEvents in this event stream.
82  bool OnTouchEvent(const MotionEvent& event);
83
84  // This method may be called by the owner when a a double-tap event has been
85  // detected *for the same event stream* being fed to this instance of the
86  // ScaleGestureDetector. As call order is important here, the double-tap
87  // detector should always be offered events *before* the ScaleGestureDetector.
88  bool OnDoubleTap(const MotionEvent& event);
89
90  // Set whether the associated |ScaleGestureListener| should receive
91  // OnScale callbacks when the user performs a doubletap followed by a swipe.
92  bool IsInProgress() const;
93  bool InDoubleTapMode() const;
94  float GetFocusX() const;
95  float GetFocusY() const;
96  float GetCurrentSpan() const;
97  float GetCurrentSpanX() const;
98  float GetCurrentSpanY() const;
99  float GetPreviousSpan() const;
100  float GetPreviousSpanX() const;
101  float GetPreviousSpanY() const;
102  float GetScaleFactor() const;
103  base::TimeDelta GetTimeDelta() const;
104  base::TimeTicks GetEventTime() const;
105
106 private:
107  enum DoubleTapMode { DOUBLE_TAP_MODE_NONE, DOUBLE_TAP_MODE_IN_PROGRESS };
108
109  // The TouchMajor/TouchMinor elements of a MotionEvent can flutter/jitter on
110  // some hardware/driver combos. Smooth out to get kinder, gentler behavior.
111  void AddTouchHistory(const MotionEvent& ev);
112  void ResetTouchHistory();
113
114  void ResetScaleWithSpan(float span);
115
116  ScaleGestureListener* const listener_;
117
118  float focus_x_;
119  float focus_y_;
120  float curr_span_;
121  float prev_span_;
122  float initial_span_;
123  float curr_span_x_;
124  float curr_span_y_;
125  float prev_span_x_;
126  float prev_span_y_;
127  base::TimeTicks curr_time_;
128  base::TimeTicks prev_time_;
129  bool in_progress_;
130  float span_slop_;
131  float min_span_;
132
133  // Bounds for recently seen values.
134  float touch_upper_;
135  float touch_lower_;
136  float touch_history_last_accepted_;
137  int touch_history_direction_;
138  base::TimeTicks touch_history_last_accepted_time_;
139  float touch_min_major_;
140  float touch_max_major_;
141  float double_tap_focus_x_;
142  float double_tap_focus_y_;
143  DoubleTapMode double_tap_mode_;
144
145  bool event_before_or_above_starting_gesture_event_;
146
147  DISALLOW_COPY_AND_ASSIGN(ScaleGestureDetector);
148};
149
150}  // namespace ui
151
152#endif  // UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
153