ReactBrowserEventEmitter.js

/**
 * 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 ReactBrowserEventEmitter
 * @typechecks static-only
 */

"use strict";

var EventConstants = require('EventConstants');
var EventPluginHub = require('EventPluginHub');
var EventPluginRegistry = require('EventPluginRegistry');
var ReactEventEmitterMixin = require('ReactEventEmitterMixin');
var ViewportMetrics = require('ViewportMetrics');

var assign = require('Object.assign');
var isEventSupported = require('isEventSupported');

/**
 * Summary of `ReactBrowserEventEmitter` event handling:
 *
 *  - Top-level delegation is used to trap most native browser events. This
 *    may only occur in the main thread and is the responsibility of
 *    ReactEventListener, which is injected and can therefore support pluggable
 *    event sources. This is the only work that occurs in the main thread.
 *
 *  - We normalize and de-duplicate events to account for browser quirks. This
 *    may be done in the worker thread.
 *
 *  - Forward these native events (with the associated top-level type used to
 *    trap it) to `EventPluginHub`, which in turn will ask plugins if they want
 *    to extract any synthetic events.
 *
 *  - The `EventPluginHub` will then process each event by annotating them with
 *    "dispatches", a sequence of listeners and IDs that care about that event.
 *
 *  - The `EventPluginHub` then dispatches the events.
 *
 * Overview of React and the event system:
 *
 * +------------+    .
 * |    DOM     |    .
 * +------------+    .
 *       |           .
 *       v           .
 * +------------+    .
 * | ReactEvent |    .
 * |  Listener  |    .
 * +------------+    .                         +-----------+
 *       |           .               +--------+|SimpleEvent|
 *       |           .               |         |Plugin     |
 * +-----|------+    .               v         +-----------+
 * |     |      |    .    +--------------+                    +------------+
 * |     +-----------.--->|EventPluginHub|                    |    Event   |
 * |            |    .    |              |     +-----------+  | Propagators|
 * | ReactEvent |    .    |              |     |TapEvent   |  |------------|
 * |  Emitter   |    .    |              |<---+|Plugin     |  |other plugin|
 * |            |    .    |              |     +-----------+  |  utilities |
 * |     +-----------.--->|              |                    +------------+
 * |     |      |    .    +--------------+
 * +-----|------+    .                ^        +-----------+
 *       |           .                |        |Enter/Leave|
 *       +           .                +-------+|Plugin     |
 * +-------------+   .                         +-----------+
 * | application |   .
 * |-------------|   .
 * |             |   .
 * |             |   .
 * +-------------+   .
 *                   .
 *    React Core     .  General Purpose Event Plugin System
 */

var alreadyListeningTo = {};
var isMonitoringScrollValue = false;
var reactTopListenersCounter = 0;

// For events like 'submit' which don't consistently bubble (which we trap at a
// lower node than `document`), binding at `document` would cause duplicate
// events so we don't include them here
var topEventMapping = {
  topBlur: 'blur',
  topChange: 'change',
  topClick: 'click',
  topCompositionEnd: 'compositionend',
  topCompositionStart: 'compositionstart',
  topCompositionUpdate: 'compositionupdate',
  topContextMenu: 'contextmenu',
  topCopy: 'copy',
  topCut: 'cut',
  topDoubleClick: 'dblclick',
  topDrag: 'drag',
  topDragEnd: 'dragend',
  topDragEnter: 'dragenter',
  topDragExit: 'dragexit',
  topDragLeave: 'dragleave',
  topDragOver: 'dragover',
  topDragStart: 'dragstart',
  topDrop: 'drop',
  topFocus: 'focus',
  topInput: 'input',
  topKeyDown: 'keydown',
  topKeyPress: 'keypress',
  topKeyUp: 'keyup',
  topMouseDown: 'mousedown',
  topMouseMove: 'mousemove',
  topMouseOut: 'mouseout',
  topMouseOver: 'mouseover',
  topMouseUp: 'mouseup',
  topPaste: 'paste',
  topScroll: 'scroll',
  topSelectionChange: 'selectionchange',
  topTextInput: 'textInput',
  topTouchCancel: 'touchcancel',
  topTouchEnd: 'touchend',
  topTouchMove: 'touchmove',
  topTouchStart: 'touchstart',
  topWheel: 'wheel'
};

/**
 * To ensure no conflicts with other potential React instances on the page
 */
var topListenersIDKey = "_reactListenersID" + String(Math.random()).slice(2);

function getListeningForDocument(mountAt) {
  // In IE8, `mountAt` is a host object and doesn't have `hasOwnProperty`
  // directly.
  if (!Object.prototype.hasOwnProperty.call(mountAt, topListenersIDKey)) {
    mountAt[topListenersIDKey] = reactTopListenersCounter++;
    alreadyListeningTo[mountAt[topListenersIDKey]] = {};
  }
  return alreadyListeningTo[mountAt[topListenersIDKey]];
}

/**
 * `ReactBrowserEventEmitter` is used to attach top-level event listeners. For
 * example:
 *
 *   ReactBrowserEventEmitter.putListener('myID', 'onClick', myFunction);
 *
 * This would allocate a "registration" of `('onClick', myFunction)` on 'myID'.
 *
 * @internal
 */
var ReactBrowserEventEmitter = assign({}, ReactEventEmitterMixin, {

  /**
   * Injectable event backend
   */
  ReactEventListener: null,

  injection: {
    /**
     * @param {object} ReactEventListener
     */
    injectReactEventListener: function(ReactEventListener) {
      ReactEventListener.setHandleTopLevel(
        ReactBrowserEventEmitter.handleTopLevel
      );
      ReactBrowserEventEmitter.ReactEventListener = ReactEventListener;
    }
  },

  /**
   * Sets whether or not any created callbacks should be enabled.
   *
   * @param {boolean} enabled True if callbacks should be enabled.
   */
  setEnabled: function(enabled) {
    if (ReactBrowserEventEmitter.ReactEventListener) {
      ReactBrowserEventEmitter.ReactEventListener.setEnabled(enabled);
    }
  },

  /**
   * @return {boolean} True if callbacks are enabled.
   */
  isEnabled: function() {
    return !!(
      ReactBrowserEventEmitter.ReactEventListener &&
      ReactBrowserEventEmitter.ReactEventListener.isEnabled()
    );
  },

  /**
   * We listen for bubbled touch events on the document object.
   *
   * Firefox v8.01 (and possibly others) exhibited strange behavior when
   * mounting `onmousemove` events at some node that was not the document
   * element. The symptoms were that if your mouse is not moving over something
   * contained within that mount point (for example on the background) the
   * top-level listeners for `onmousemove` won't be called. However, if you
   * register the `mousemove` on the document object, then it will of course
   * catch all `mousemove`s. This along with iOS quirks, justifies restricting
   * top-level listeners to the document object only, at least for these
   * movement types of events and possibly all events.
   *
   * @see http://www.quirksmode.org/blog/archives/2010/09/click_event_del.html
   *
   * Also, `keyup`/`keypress`/`keydown` do not bubble to the window on IE, but
   * they bubble to document.
   *
   * @param {string} registrationName Name of listener (e.g. `onClick`).
   * @param {object} contentDocumentHandle Document which owns the container
   */
  listenTo: function(registrationName, contentDocumentHandle) {
    var mountAt = contentDocumentHandle;
    var isListening = getListeningForDocument(mountAt);
    var dependencies = EventPluginRegistry.
      registrationNameDependencies[registrationName];

    var topLevelTypes = EventConstants.topLevelTypes;
    for (var i = 0, l = dependencies.length; i < l; i++) {
      var dependency = dependencies[i];
      if (!(
            isListening.hasOwnProperty(dependency) &&
            isListening[dependency]
          )) {
        if (dependency === topLevelTypes.topWheel) {
          if (isEventSupported('wheel')) {
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topWheel,
              'wheel',
              mountAt
            );
          } else if (isEventSupported('mousewheel')) {
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topWheel,
              'mousewheel',
              mountAt
            );
          } else {
            // Firefox needs to capture a different mouse scroll event.
            // @see http://www.quirksmode.org/dom/events/tests/scroll.html
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topWheel,
              'DOMMouseScroll',
              mountAt
            );
          }
        } else if (dependency === topLevelTypes.topScroll) {

          if (isEventSupported('scroll', true)) {
            ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
              topLevelTypes.topScroll,
              'scroll',
              mountAt
            );
          } else {
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topScroll,
              'scroll',
              ReactBrowserEventEmitter.ReactEventListener.WINDOW_HANDLE
            );
          }
        } else if (dependency === topLevelTypes.topFocus ||
            dependency === topLevelTypes.topBlur) {

          if (isEventSupported('focus', true)) {
            ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
              topLevelTypes.topFocus,
              'focus',
              mountAt
            );
            ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
              topLevelTypes.topBlur,
              'blur',
              mountAt
            );
          } else if (isEventSupported('focusin')) {
            // IE has `focusin` and `focusout` events which bubble.
            // @see http://www.quirksmode.org/blog/archives/2008/04/delegating_the.html
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topFocus,
              'focusin',
              mountAt
            );
            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
              topLevelTypes.topBlur,
              'focusout',
              mountAt
            );
          }

          // to make sure blur and focus event listeners are only attached once
          isListening[topLevelTypes.topBlur] = true;
          isListening[topLevelTypes.topFocus] = true;
        } else if (topEventMapping.hasOwnProperty(dependency)) {
          ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
            dependency,
            topEventMapping[dependency],
            mountAt
          );
        }

        isListening[dependency] = true;
      }
    }
  },

  trapBubbledEvent: function(topLevelType, handlerBaseName, handle) {
    return ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
      topLevelType,
      handlerBaseName,
      handle
    );
  },

  trapCapturedEvent: function(topLevelType, handlerBaseName, handle) {
    return ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
      topLevelType,
      handlerBaseName,
      handle
    );
  },

  /**
   * Listens to window scroll and resize events. We cache scroll values so that
   * application code can access them without triggering reflows.
   *
   * NOTE: Scroll events do not bubble.
   *
   * @see http://www.quirksmode.org/dom/events/scroll.html
   */
  ensureScrollValueMonitoring: function(){
    if (!isMonitoringScrollValue) {
      var refresh = ViewportMetrics.refreshScrollValues;
      ReactBrowserEventEmitter.ReactEventListener.monitorScrollValue(refresh);
      isMonitoringScrollValue = true;
    }
  },

  eventNameDispatchConfigs: EventPluginHub.eventNameDispatchConfigs,

  registrationNameModules: EventPluginHub.registrationNameModules,

  putListener: EventPluginHub.putListener,

  getListener: EventPluginHub.getListener,

  deleteListener: EventPluginHub.deleteListener,

  deleteAllListeners: EventPluginHub.deleteAllListeners

});

module.exports = ReactBrowserEventEmitter;