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
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
const DIRECTION_LEFT = [-1, 0]
const DIRECTION_RIGHT = [1, 0]
const DIRECTION_UP = [0, -1]
const DIRECTION_DOWN = [0, 1]
const BUTTON_LEFT = 0
const deltaCoord = (oldCoord, newCoord) => [newCoord[0] - oldCoord[0], newCoord[1] - oldCoord[1]]
const touchCoord = touch => [touch.screenX, touch.screenY]
const touchEventCoord = e => touchCoord(e.touches[0])
const pointerEventCoord = e => [e.clientX, e.clientY]
const vectorLength = v => Math.sqrt(v[0] * v[0] + v[1] * v[1])
const perpendicular = v => [v[1], -v[0]]
const dotProduct = (v1, v2) => v1[0] * v2[0] + v1[1] * v2[1]
const project = (v1, v2) => {
const scalar = (dotProduct(v1, v2) / dotProduct(v2, v2))
return [scalar * v2[0], scalar * v2[1]]
}
// direction: either use the constants above or an arbitrary 2d vector.
// threshold: how many Px to move from touch origin before checking if the
// callback should be called.
// divergentTolerance: a scalar for much of divergent direction we tolerate when
// above threshold. for example, with 1.0 we only call the callback if
// divergent component of delta is < 1.0 * direction component of delta.
const swipeGesture = (direction, onSwipe, threshold = 30, perpendicularTolerance = 1.0) => {
return {
direction,
onSwipe,
threshold,
perpendicularTolerance,
_startPos: [0, 0],
_swiping: false
}
}
const beginSwipe = (event, gesture) => {
gesture._startPos = touchEventCoord(event)
gesture._swiping = true
}
const updateSwipe = (event, gesture) => {
if (!gesture._swiping) return
// movement too small
const delta = deltaCoord(gesture._startPos, touchEventCoord(event))
if (vectorLength(delta) < gesture.threshold) return
// movement is opposite from direction
if (dotProduct(delta, gesture.direction) < 0) return
// movement perpendicular to direction is too much
const towardsDir = project(delta, gesture.direction)
const perpendicularDir = perpendicular(gesture.direction)
const towardsPerpendicular = project(delta, perpendicularDir)
if (
vectorLength(towardsDir) * gesture.perpendicularTolerance <
vectorLength(towardsPerpendicular)
) return
gesture.onSwipe()
gesture._swiping = false
}
class SwipeAndClickGesture {
// swipePreviewCallback(offsets: Array[Number])
// offsets: the offset vector which the underlying component should move, from the starting position
// swipeEndCallback(sign: 0|-1|1)
// sign: if the swipe does not meet the threshold, 0
// if the swipe meets the threshold in the positive direction, 1
// if the swipe meets the threshold in the negative direction, -1
constructor ({
direction,
// swipeStartCallback
swipePreviewCallback,
swipeEndCallback,
swipeCancelCallback,
swipelessClickCallback,
threshold = 30,
perpendicularTolerance = 1.0,
disableClickThreshold = 1
}) {
const nop = () => {}
this.direction = direction
this.swipePreviewCallback = swipePreviewCallback || nop
this.swipeEndCallback = swipeEndCallback || nop
this.swipeCancelCallback = swipeCancelCallback || nop
this.swipelessClickCallback = swipelessClickCallback || nop
this.threshold = typeof threshold === 'function' ? threshold : () => threshold
this.disableClickThreshold = typeof disableClickThreshold === 'function' ? disableClickThreshold : () => disableClickThreshold
this.perpendicularTolerance = perpendicularTolerance
this._reset()
}
_reset () {
this._startPos = [0, 0]
this._pointerId = -1
this._swiping = false
this._swiped = false
this._preventNextClick = false
}
start (event) {
// Only handle left click
if (event.button !== BUTTON_LEFT) {
return
}
this._startPos = pointerEventCoord(event)
this._pointerId = event.pointerId
this._swiping = true
this._swiped = false
}
move (event) {
if (this._swiping && this._pointerId === event.pointerId) {
this._swiped = true
const coord = pointerEventCoord(event)
const delta = deltaCoord(this._startPos, coord)
this.swipePreviewCallback(delta)
}
}
cancel (event) {
if (!this._swiping || this._pointerId !== event.pointerId) {
return
}
this.swipeCancelCallback()
}
end (event) {
if (!this._swiping) {
return
}
if (this._pointerId !== event.pointerId) {
return
}
this._swiping = false
// movement too small
const coord = pointerEventCoord(event)
const delta = deltaCoord(this._startPos, coord)
const sign = (() => {
if (vectorLength(delta) < this.threshold()) {
return 0
}
// movement is opposite from direction
const isPositive = dotProduct(delta, this.direction) > 0
// movement perpendicular to direction is too much
const towardsDir = project(delta, this.direction)
const perpendicularDir = perpendicular(this.direction)
const towardsPerpendicular = project(delta, perpendicularDir)
if (
vectorLength(towardsDir) * this.perpendicularTolerance <
vectorLength(towardsPerpendicular)
) {
return 0
}
return isPositive ? 1 : -1
})()
if (this._swiped) {
this.swipeEndCallback(sign)
}
this._reset()
// Only a mouse will fire click event when
// the end point is far from the starting point
// so for other kinds of pointers do not check
// whether we have swiped
if (vectorLength(delta) >= this.disableClickThreshold() && event.pointerType === 'mouse') {
this._preventNextClick = true
}
}
click (event) {
if (!this._preventNextClick) {
this.swipelessClickCallback()
}
this._reset()
}
}
const GestureService = {
DIRECTION_LEFT,
DIRECTION_RIGHT,
DIRECTION_UP,
DIRECTION_DOWN,
swipeGesture,
beginSwipe,
updateSwipe,
SwipeAndClickGesture
}
export default GestureService
|
