react-dom-core/lib/ResponderTouchHistoryStore.js

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * 
 */

'use strict';

var _prodInvariant = require('./reactProdInvariant');

var EventPluginUtils = require('./EventPluginUtils');

var invariant = require('fbjs/lib/invariant');
var warning = require('fbjs/lib/warning');

var isEndish = EventPluginUtils.isEndish,
    isMoveish = EventPluginUtils.isMoveish,
    isStartish = EventPluginUtils.isStartish;

/**
 * Tracks the position and time of each active touch by `touch.identifier`. We
 * should typically only see IDs in the range of 1-20 because IDs get recycled
 * when touches end and start again.
 */

var MAX_TOUCH_BANK = 20;
var touchBank = [];
var touchHistory = {
  touchBank: 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
};

function timestampForTouch(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.
 */
function createTouchRecord(touch) {
  return {
    touchActive: true,
    startPageX: touch.pageX,
    startPageY: touch.pageY,
    startTimeStamp: timestampForTouch(touch),
    currentPageX: touch.pageX,
    currentPageY: touch.pageY,
    currentTimeStamp: timestampForTouch(touch),
    previousPageX: touch.pageX,
    previousPageY: touch.pageY,
    previousTimeStamp: timestampForTouch(touch)
  };
}

function resetTouchRecord(touchRecord, touch) {
  touchRecord.touchActive = true;
  touchRecord.startPageX = touch.pageX;
  touchRecord.startPageY = touch.pageY;
  touchRecord.startTimeStamp = timestampForTouch(touch);
  touchRecord.currentPageX = touch.pageX;
  touchRecord.currentPageY = touch.pageY;
  touchRecord.currentTimeStamp = timestampForTouch(touch);
  touchRecord.previousPageX = touch.pageX;
  touchRecord.previousPageY = touch.pageY;
  touchRecord.previousTimeStamp = timestampForTouch(touch);
}

function getTouchIdentifier(_ref) {
  var identifier = _ref.identifier;

  !(identifier != null) ? process.env.NODE_ENV !== 'production' ? invariant(false, 'Touch object is missing identifier.') : _prodInvariant('138') : void 0;
  process.env.NODE_ENV !== 'production' ? warning(identifier <= MAX_TOUCH_BANK, 'Touch identifier %s is greater than maximum supported %s which causes ' + 'performance issues backfilling array locations for all of the indices.', identifier, MAX_TOUCH_BANK) : void 0;
  return identifier;
}

function recordTouchStart(touch) {
  var identifier = getTouchIdentifier(touch);
  var touchRecord = touchBank[identifier];
  if (touchRecord) {
    resetTouchRecord(touchRecord, touch);
  } else {
    touchBank[identifier] = createTouchRecord(touch);
  }
  touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
}

function recordTouchMove(touch) {
  var touchRecord = touchBank[getTouchIdentifier(touch)];
  if (touchRecord) {
    touchRecord.touchActive = true;
    touchRecord.previousPageX = touchRecord.currentPageX;
    touchRecord.previousPageY = touchRecord.currentPageY;
    touchRecord.previousTimeStamp = touchRecord.currentTimeStamp;
    touchRecord.currentPageX = touch.pageX;
    touchRecord.currentPageY = touch.pageY;
    touchRecord.currentTimeStamp = timestampForTouch(touch);
    touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
  } else {
    console.error('Cannot record touch move without a touch start.\n' + 'Touch Move: %s\n', 'Touch Bank: %s', printTouch(touch), printTouchBank());
  }
}

function recordTouchEnd(touch) {
  var touchRecord = touchBank[getTouchIdentifier(touch)];
  if (touchRecord) {
    touchRecord.touchActive = false;
    touchRecord.previousPageX = touchRecord.currentPageX;
    touchRecord.previousPageY = touchRecord.currentPageY;
    touchRecord.previousTimeStamp = touchRecord.currentTimeStamp;
    touchRecord.currentPageX = touch.pageX;
    touchRecord.currentPageY = touch.pageY;
    touchRecord.currentTimeStamp = timestampForTouch(touch);
    touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
  } else {
    console.error('Cannot record touch end without a touch start.\n' + 'Touch End: %s\n', 'Touch Bank: %s', printTouch(touch), printTouchBank());
  }
}

function printTouch(touch) {
  return JSON.stringify({
    identifier: touch.identifier,
    pageX: touch.pageX,
    pageY: touch.pageY,
    timestamp: timestampForTouch(touch)
  });
}

function printTouchBank() {
  var printed = JSON.stringify(touchBank.slice(0, MAX_TOUCH_BANK));
  if (touchBank.length > MAX_TOUCH_BANK) {
    printed += ' (original size: ' + touchBank.length + ')';
  }
  return printed;
}

var ResponderTouchHistoryStore = {
  recordTouchTrack: function (topLevelType, nativeEvent) {
    if (isMoveish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchMove);
    } else if (isStartish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchStart);
      touchHistory.numberActiveTouches = nativeEvent.touches.length;
      if (touchHistory.numberActiveTouches === 1) {
        touchHistory.indexOfSingleActiveTouch = nativeEvent.touches[0].identifier;
      }
    } else if (isEndish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchEnd);
      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 (process.env.NODE_ENV !== 'production') {
          var activeRecord = touchBank[touchHistory.indexOfSingleActiveTouch];
          process.env.NODE_ENV !== 'production' ? warning(activeRecord != null && activeRecord.touchActive, 'Cannot find single active touch.') : void 0;
        }
      }
    }
  },


  touchHistory: touchHistory
};

module.exports = ResponderTouchHistoryStore;