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TapEventPlugin.js
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TapEventPlugin.js
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/**
* Copyright 2013-2014, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* @providesModule TapEventPlugin
* @typechecks static-only
*/
"use strict";
var EventConstants = require('EventConstants');
var EventPluginUtils = require('EventPluginUtils');
var EventPropagators = require('EventPropagators');
var SyntheticUIEvent = require('SyntheticUIEvent');
var TouchEventUtils = require('TouchEventUtils');
var ViewportMetrics = require('ViewportMetrics');
var keyOf = require('keyOf');
var topLevelTypes = EventConstants.topLevelTypes;
var isStartish = EventPluginUtils.isStartish;
var isEndish = EventPluginUtils.isEndish;
/**
* Number of pixels that are tolerated in between a `touchStart` and `touchEnd`
* in order to still be considered a 'tap' event.
*/
var tapMoveThreshold = 10;
var startCoords = {x: null, y: null};
var Axis = {
x: {page: 'pageX', client: 'clientX', envScroll: 'currentPageScrollLeft'},
y: {page: 'pageY', client: 'clientY', envScroll: 'currentPageScrollTop'}
};
function getAxisCoordOfEvent(axis, nativeEvent) {
var singleTouch = TouchEventUtils.extractSingleTouch(nativeEvent);
if (singleTouch) {
return singleTouch[axis.page];
}
return axis.page in nativeEvent ?
nativeEvent[axis.page] :
nativeEvent[axis.client] + ViewportMetrics[axis.envScroll];
}
function getDistance(coords, nativeEvent) {
var pageX = getAxisCoordOfEvent(Axis.x, nativeEvent);
var pageY = getAxisCoordOfEvent(Axis.y, nativeEvent);
return Math.pow(
Math.pow(pageX - coords.x, 2) + Math.pow(pageY - coords.y, 2),
0.5
);
}
var dependencies = [
topLevelTypes.topMouseDown,
topLevelTypes.topMouseMove,
topLevelTypes.topMouseUp
];
var touchDependencies = [
topLevelTypes.topTouchStart,
topLevelTypes.topTouchCancel,
topLevelTypes.topTouchEnd,
topLevelTypes.topTouchMove
];
if (EventPluginUtils.useTouchEvents) {
dependencies = dependencies.concat(touchDependencies);
}
var eventTypes = {
touchTap: {
phasedRegistrationNames: {
bubbled: keyOf({onTouchTap: null}),
captured: keyOf({onTouchTapCapture: null})
},
dependencies: dependencies
}
};
var usedTouch = false;
var usedTouchTime = 0;
var TOUCH_DELAY = 500;
var TapEventPlugin = {
tapMoveThreshold: tapMoveThreshold,
eventTypes: eventTypes,
/**
* @param {string} topLevelType Record from `EventConstants`.
* @param {DOMEventTarget} topLevelTarget The listening component root node.
* @param {string} topLevelTargetID ID of `topLevelTarget`.
* @param {object} nativeEvent Native browser event.
* @return {*} An accumulation of synthetic events.
* @see {EventPluginHub.extractEvents}
*/
extractEvents: function(
topLevelType,
topLevelTarget,
topLevelTargetID,
nativeEvent) {
if (!isStartish(topLevelType) && !isEndish(topLevelType)) {
return null;
}
// on ios, there is a delay after touch event and synthetic
// mouse events, so that user can perform double tap
// solution: ignore mouse events following touchevent within small timeframe
if (touchDependencies.indexOf(topLevelType) !== -1) {
usedTouch = true;
usedTouchTime = Date.now();
} else {
if (usedTouch && (Date.now() - usedTouchTime < TOUCH_DELAY)) {
return;
}
}
var event = null;
var distance = getDistance(startCoords, nativeEvent);
if (isEndish(topLevelType) && distance < tapMoveThreshold) {
event = SyntheticUIEvent.getPooled(
eventTypes.touchTap,
topLevelTargetID,
nativeEvent
);
}
if (isStartish(topLevelType)) {
startCoords.x = getAxisCoordOfEvent(Axis.x, nativeEvent);
startCoords.y = getAxisCoordOfEvent(Axis.y, nativeEvent);
} else if (isEndish(topLevelType)) {
startCoords.x = 0;
startCoords.y = 0;
}
EventPropagators.accumulateTwoPhaseDispatches(event);
return event;
}
};
module.exports = TapEventPlugin;