react-native/Libraries/vendor/react/browser/eventPlugins/ResponderTouchHistoryStore.js

179 lines
6.1 KiB
JavaScript

/**
* @providesModule ResponderTouchHistoryStore
*/
"use strict";
var EventPluginUtils = require('EventPluginUtils');
var invariant = require('invariant');
var isMoveish = EventPluginUtils.isMoveish;
var isStartish = EventPluginUtils.isStartish;
var isEndish = EventPluginUtils.isEndish;
var MAX_TOUCH_BANK = 20;
/**
* Touch position/time tracking information by touchID. Typically, we'll only
* see IDs with a range of 1-20 (they are recycled when touches end and then
* start again). This data is commonly needed by many different interaction
* logic modules so precomputing it is very helpful to do once.
* Each touch object in `touchBank` is of the following form:
* { touchActive: boolean,
* startTimeStamp: number,
* startPageX: number,
* startPageY: number,
* currentPageX: number,
* currentPageY: number,
* currentTimeStamp: number
* }
*/
var touchHistory = {
touchBank: [ ],
numberActiveTouches: 0,
// If there is only one active touch, we remember its location. This prevents
// us having to loop through all of the touches all the time in the most
// common case.
indexOfSingleActiveTouch: -1,
mostRecentTimeStamp: 0,
};
var timestampForTouch = function(touch) {
// The legacy internal implementation provides "timeStamp", which has been
// renamed to "timestamp". Let both work for now while we iron it out
// TODO (evv): rename timeStamp to timestamp in internal code
return touch.timeStamp || touch.timestamp;
};
/**
* TODO: Instead of making gestures recompute filtered velocity, we could
* include a built in velocity computation that can be reused globally.
* @param {Touch} touch Native touch object.
*/
var initializeTouchData = function(touch) {
return {
touchActive: true,
startTimeStamp: timestampForTouch(touch),
startPageX: touch.pageX,
startPageY: touch.pageY,
currentPageX: touch.pageX,
currentPageY: touch.pageY,
currentTimeStamp: timestampForTouch(touch),
previousPageX: touch.pageX,
previousPageY: touch.pageY,
previousTimeStamp: timestampForTouch(touch),
};
};
var reinitializeTouchTrack = function(touchTrack, touch) {
touchTrack.touchActive = true;
touchTrack.startTimeStamp = timestampForTouch(touch);
touchTrack.startPageX = touch.pageX;
touchTrack.startPageY = touch.pageY;
touchTrack.currentPageX = touch.pageX;
touchTrack.currentPageY = touch.pageY;
touchTrack.currentTimeStamp = timestampForTouch(touch);
touchTrack.previousPageX = touch.pageX;
touchTrack.previousPageY = touch.pageY;
touchTrack.previousTimeStamp = timestampForTouch(touch);
};
var validateTouch = function(touch) {
var identifier = touch.identifier;
invariant(identifier != null, 'Touch object is missing identifier');
if (identifier > MAX_TOUCH_BANK) {
console.warn(
'Touch identifier ' + identifier + ' is greater than maximum ' +
'supported ' + MAX_TOUCH_BANK + ' which causes performance issues ' +
'backfilling array locations for all of the indices.'
);
}
};
var recordStartTouchData = function(touch) {
var touchBank = touchHistory.touchBank;
var identifier = touch.identifier;
var touchTrack = touchBank[identifier];
if (__DEV__) {
validateTouch(touch);
}
if (!touchTrack) {
touchBank[touch.identifier] = initializeTouchData(touch);
} else {
reinitializeTouchTrack(touchTrack, touch);
}
touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
};
var recordMoveTouchData = function(touch) {
var touchBank = touchHistory.touchBank;
var touchTrack = touchBank[touch.identifier];
if (__DEV__) {
validateTouch(touch);
invariant(touchTrack, 'Touch data should have been recorded on start');
}
touchTrack.touchActive = true;
touchTrack.previousPageX = touchTrack.currentPageX;
touchTrack.previousPageY = touchTrack.currentPageY;
touchTrack.previousTimeStamp = touchTrack.currentTimeStamp;
touchTrack.currentPageX = touch.pageX;
touchTrack.currentPageY = touch.pageY;
touchTrack.currentTimeStamp = timestampForTouch(touch);
touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
};
var recordEndTouchData = function(touch) {
var touchBank = touchHistory.touchBank;
var touchTrack = touchBank[touch.identifier];
if (__DEV__) {
validateTouch(touch);
invariant(touchTrack, 'Touch data should have been recorded on start');
}
touchTrack.previousPageX = touchTrack.currentPageX;
touchTrack.previousPageY = touchTrack.currentPageY;
touchTrack.previousTimeStamp = touchTrack.currentTimeStamp;
touchTrack.currentPageX = touch.pageX;
touchTrack.currentPageY = touch.pageY;
touchTrack.currentTimeStamp = timestampForTouch(touch);
touchTrack.touchActive = false;
touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
};
var ResponderTouchHistoryStore = {
recordTouchTrack: function(topLevelType, nativeEvent) {
var touchBank = touchHistory.touchBank;
if (isMoveish(topLevelType)) {
nativeEvent.changedTouches.forEach(recordMoveTouchData);
} else if (isStartish(topLevelType)) {
nativeEvent.changedTouches.forEach(recordStartTouchData);
touchHistory.numberActiveTouches = nativeEvent.touches.length;
if (touchHistory.numberActiveTouches === 1) {
touchHistory.indexOfSingleActiveTouch = nativeEvent.touches[0].identifier;
}
} else if (isEndish(topLevelType)) {
nativeEvent.changedTouches.forEach(recordEndTouchData);
touchHistory.numberActiveTouches = nativeEvent.touches.length;
if (touchHistory.numberActiveTouches === 1) {
for (var i = 0; i < touchBank.length; i++) {
var touchTrackToCheck = touchBank[i];
if (touchTrackToCheck != null && touchTrackToCheck.touchActive) {
touchHistory.indexOfSingleActiveTouch = i;
break;
}
}
if (__DEV__) {
var activeTouchData = touchBank[touchHistory.indexOfSingleActiveTouch];
var foundActive = activeTouchData != null && !!activeTouchData.touchActive;
invariant(foundActive, 'Cannot find single active touch');
}
}
}
},
touchHistory: touchHistory,
};
module.exports = ResponderTouchHistoryStore;