| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | * |
| 7 | * @flow |
| 8 | */ |
| 9 | |
| 10 | import {isStartish, isMoveish, isEndish} from './ResponderTopLevelEventTypes'; |
| 11 | |
| 12 | /** |
| 13 | * Tracks the position and time of each active touch by `touch.identifier`. We |
| 14 | * should typically only see IDs in the range of 1-20 because IDs get recycled |
| 15 | * when touches end and start again. |
| 16 | */ |
| 17 | type TouchRecord = { |
| 18 | touchActive: boolean, |
| 19 | startPageX: number, |
| 20 | startPageY: number, |
| 21 | startTimeStamp: number, |
| 22 | currentPageX: number, |
| 23 | currentPageY: number, |
| 24 | currentTimeStamp: number, |
| 25 | previousPageX: number, |
| 26 | previousPageY: number, |
| 27 | previousTimeStamp: number, |
| 28 | }; |
| 29 | |
| 30 | const MAX_TOUCH_BANK = 20; |
| 31 | const touchBank: Array<TouchRecord> = []; |
| 32 | const touchHistory = { |
| 33 | touchBank, |
| 34 | numberActiveTouches: 0, |
| 35 | // If there is only one active touch, we remember its location. This prevents |
| 36 | // us having to loop through all of the touches all the time in the most |
| 37 | // common case. |
| 38 | indexOfSingleActiveTouch: -1, |
| 39 | mostRecentTimeStamp: 0, |
| 40 | }; |
| 41 | |
| 42 | type Touch = { |
| 43 | identifier: ?number, |
| 44 | pageX: number, |
| 45 | pageY: number, |
| 46 | timestamp: number, |
| 47 | ... |
| 48 | }; |
| 49 | type TouchEvent = { |
| 50 | changedTouches: Array<Touch>, |
| 51 | touches: Array<Touch>, |
| 52 | ... |
| 53 | }; |
| 54 | |
| 55 | function timestampForTouch(touch: Touch): number { |
| 56 | // The legacy internal implementation provides "timeStamp", which has been |
| 57 | // renamed to "timestamp". Let both work for now while we iron it out |
| 58 | // TODO (evv): rename timeStamp to timestamp in internal code |
| 59 | return (touch as any).timeStamp || touch.timestamp; |
| 60 | } |
| 61 | |
| 62 | /** |
| 63 | * TODO: Instead of making gestures recompute filtered velocity, we could |
| 64 | * include a built in velocity computation that can be reused globally. |
| 65 | */ |
| 66 | function createTouchRecord(touch: Touch): TouchRecord { |
| 67 | return { |
| 68 | touchActive: true, |
| 69 | startPageX: touch.pageX, |
| 70 | startPageY: touch.pageY, |
| 71 | startTimeStamp: timestampForTouch(touch), |
| 72 | currentPageX: touch.pageX, |
| 73 | currentPageY: touch.pageY, |
| 74 | currentTimeStamp: timestampForTouch(touch), |
| 75 | previousPageX: touch.pageX, |
| 76 | previousPageY: touch.pageY, |
| 77 | previousTimeStamp: timestampForTouch(touch), |
| 78 | }; |
| 79 | } |
| 80 | |
| 81 | function resetTouchRecord(touchRecord: TouchRecord, touch: Touch): void { |
| 82 | touchRecord.touchActive = true; |
| 83 | touchRecord.startPageX = touch.pageX; |
| 84 | touchRecord.startPageY = touch.pageY; |
| 85 | touchRecord.startTimeStamp = timestampForTouch(touch); |
| 86 | touchRecord.currentPageX = touch.pageX; |
| 87 | touchRecord.currentPageY = touch.pageY; |
| 88 | touchRecord.currentTimeStamp = timestampForTouch(touch); |
| 89 | touchRecord.previousPageX = touch.pageX; |
| 90 | touchRecord.previousPageY = touch.pageY; |
| 91 | touchRecord.previousTimeStamp = timestampForTouch(touch); |
| 92 | } |
| 93 | |
| 94 | function getTouchIdentifier({identifier}: Touch): number { |
| 95 | if (identifier == null) { |
| 96 | throw new Error('Touch object is missing identifier.'); |
| 97 | } |
| 98 | |
| 99 | if (__DEV__) { |
| 100 | if (identifier > MAX_TOUCH_BANK) { |
| 101 | console.error( |
| 102 | 'Touch identifier %s is greater than maximum supported %s which causes ' + |
| 103 | 'performance issues backfilling array locations for all of the indices.', |
| 104 | identifier, |
| 105 | MAX_TOUCH_BANK, |
| 106 | ); |
| 107 | } |
| 108 | } |
| 109 | return identifier; |
| 110 | } |
| 111 | |
| 112 | function recordTouchStart(touch: Touch): void { |
| 113 | const identifier = getTouchIdentifier(touch); |
| 114 | const touchRecord = touchBank[identifier]; |
| 115 | if (touchRecord) { |
| 116 | resetTouchRecord(touchRecord, touch); |
| 117 | } else { |
| 118 | touchBank[identifier] = createTouchRecord(touch); |
| 119 | } |
| 120 | touchHistory.mostRecentTimeStamp = timestampForTouch(touch); |
| 121 | } |
| 122 | |
| 123 | function recordTouchMove(touch: Touch): void { |
| 124 | const touchRecord = touchBank[getTouchIdentifier(touch)]; |
| 125 | if (touchRecord) { |
| 126 | touchRecord.touchActive = true; |
| 127 | touchRecord.previousPageX = touchRecord.currentPageX; |
| 128 | touchRecord.previousPageY = touchRecord.currentPageY; |
| 129 | touchRecord.previousTimeStamp = touchRecord.currentTimeStamp; |
| 130 | touchRecord.currentPageX = touch.pageX; |
| 131 | touchRecord.currentPageY = touch.pageY; |
| 132 | touchRecord.currentTimeStamp = timestampForTouch(touch); |
| 133 | touchHistory.mostRecentTimeStamp = timestampForTouch(touch); |
| 134 | } else { |
| 135 | if (__DEV__) { |
| 136 | console.warn( |
| 137 | 'Cannot record touch move without a touch start.\n' + |
| 138 | 'Touch Move: %s\n' + |
| 139 | 'Touch Bank: %s', |
| 140 | printTouch(touch), |
| 141 | printTouchBank(), |
| 142 | ); |
| 143 | } |
| 144 | } |
| 145 | } |
| 146 | |
| 147 | function recordTouchEnd(touch: Touch): void { |
| 148 | const touchRecord = touchBank[getTouchIdentifier(touch)]; |
| 149 | if (touchRecord) { |
| 150 | touchRecord.touchActive = false; |
| 151 | touchRecord.previousPageX = touchRecord.currentPageX; |
| 152 | touchRecord.previousPageY = touchRecord.currentPageY; |
| 153 | touchRecord.previousTimeStamp = touchRecord.currentTimeStamp; |
| 154 | touchRecord.currentPageX = touch.pageX; |
| 155 | touchRecord.currentPageY = touch.pageY; |
| 156 | touchRecord.currentTimeStamp = timestampForTouch(touch); |
| 157 | touchHistory.mostRecentTimeStamp = timestampForTouch(touch); |
| 158 | } else { |
| 159 | if (__DEV__) { |
| 160 | console.warn( |
| 161 | 'Cannot record touch end without a touch start.\n' + |
| 162 | 'Touch End: %s\n' + |
| 163 | 'Touch Bank: %s', |
| 164 | printTouch(touch), |
| 165 | printTouchBank(), |
| 166 | ); |
| 167 | } |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | function printTouch(touch: Touch): string { |
| 172 | return JSON.stringify({ |
| 173 | identifier: touch.identifier, |
| 174 | pageX: touch.pageX, |
| 175 | pageY: touch.pageY, |
| 176 | timestamp: timestampForTouch(touch), |
| 177 | }); |
| 178 | } |
| 179 | |
| 180 | function printTouchBank(): string { |
| 181 | let printed = JSON.stringify(touchBank.slice(0, MAX_TOUCH_BANK)); |
| 182 | if (touchBank.length > MAX_TOUCH_BANK) { |
| 183 | printed += ' (original size: ' + touchBank.length + ')'; |
| 184 | } |
| 185 | return printed; |
| 186 | } |
| 187 | |
| 188 | let instrumentationCallback: ?(string, TouchEvent) => void; |
| 189 | |
| 190 | const ResponderTouchHistoryStore = { |
| 191 | /** |
| 192 | * Registers a listener which can be used to instrument every touch event. |
| 193 | */ |
| 194 | instrument(callback: (string, TouchEvent) => void): void { |
| 195 | instrumentationCallback = callback; |
| 196 | }, |
| 197 | |
| 198 | recordTouchTrack(topLevelType: string, nativeEvent: TouchEvent): void { |
| 199 | if (instrumentationCallback != null) { |
| 200 | instrumentationCallback(topLevelType, nativeEvent); |
| 201 | } |
| 202 | |
| 203 | if (isMoveish(topLevelType)) { |
| 204 | nativeEvent.changedTouches.forEach(recordTouchMove); |
| 205 | } else if (isStartish(topLevelType)) { |
| 206 | nativeEvent.changedTouches.forEach(recordTouchStart); |
| 207 | touchHistory.numberActiveTouches = nativeEvent.touches.length; |
| 208 | if (touchHistory.numberActiveTouches === 1) { |
| 209 | touchHistory.indexOfSingleActiveTouch = |
| 210 | // $FlowFixMe[incompatible-type] might be null according to type |
| 211 | nativeEvent.touches[0].identifier; |
| 212 | } |
| 213 | } else if (isEndish(topLevelType)) { |
| 214 | nativeEvent.changedTouches.forEach(recordTouchEnd); |
| 215 | touchHistory.numberActiveTouches = nativeEvent.touches.length; |
| 216 | if (touchHistory.numberActiveTouches === 1) { |
| 217 | for (let i = 0; i < touchBank.length; i++) { |
| 218 | const touchTrackToCheck = touchBank[i]; |
| 219 | if (touchTrackToCheck != null && touchTrackToCheck.touchActive) { |
| 220 | touchHistory.indexOfSingleActiveTouch = i; |
| 221 | break; |
| 222 | } |
| 223 | } |
| 224 | if (__DEV__) { |
| 225 | const activeRecord = touchBank[touchHistory.indexOfSingleActiveTouch]; |
| 226 | if (activeRecord == null || !activeRecord.touchActive) { |
| 227 | console.error('Cannot find single active touch.'); |
| 228 | } |
| 229 | } |
| 230 | } |
| 231 | } |
| 232 | }, |
| 233 | |
| 234 | touchHistory, |
| 235 | }; |
| 236 | |
| 237 | export default ResponderTouchHistoryStore; |