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JavaScript
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/
import {registrationNameDependencies} from 'events/EventPluginRegistry';
import {
TOP_BLUR,
TOP_CANCEL,
TOP_CLOSE,
TOP_FOCUS,
TOP_INVALID,
TOP_RESET,
TOP_SCROLL,
TOP_SUBMIT,
getRawEventName,
mediaEventTypes,
} from './DOMTopLevelEventTypes';
import {
setEnabled,
isEnabled,
trapBubbledEvent,
trapCapturedEvent,
} from './ReactDOMEventListener';
import isEventSupported from './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
* ReactDOMEventListener, 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
*/
const alreadyListeningTo = {};
let reactTopListenersCounter = 0;
/**
* To ensure no conflicts with other potential React instances on the page
*/
const topListenersIDKey = '_reactListenersID' + ('' + Math.random()).slice(2);
function getListeningForDocument(mountAt: any) {
// 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]];
}
/**
* 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} mountAt Container where to mount the listener
*/
export function listenTo(
registrationName: string,
mountAt: Document | Element,
) {
const isListening = getListeningForDocument(mountAt);
const dependencies = registrationNameDependencies[registrationName];
for (let i = 0; i < dependencies.length; i++) {
const dependency = dependencies[i];
if (!(isListening.hasOwnProperty(dependency) && isListening[dependency])) {
switch (dependency) {
case TOP_SCROLL:
trapCapturedEvent(TOP_SCROLL, mountAt);
break;
case TOP_FOCUS:
case TOP_BLUR:
trapCapturedEvent(TOP_FOCUS, mountAt);
trapCapturedEvent(TOP_BLUR, mountAt);
// We set the flag for a single dependency later in this function,
// but this ensures we mark both as attached rather than just one.
isListening[TOP_BLUR] = true;
isListening[TOP_FOCUS] = true;
break;
case TOP_CANCEL:
case TOP_CLOSE:
if (isEventSupported(getRawEventName(dependency))) {
trapCapturedEvent(dependency, mountAt);
}
break;
case TOP_INVALID:
case TOP_SUBMIT:
case TOP_RESET:
// We listen to them on the target DOM elements.
// Some of them bubble so we don't want them to fire twice.
break;
default:
// By default, listen on the top level to all non-media events.
// Media events don't bubble so adding the listener wouldn't do anything.
const isMediaEvent = mediaEventTypes.indexOf(dependency) !== -1;
if (!isMediaEvent) {
trapBubbledEvent(dependency, mountAt);
}
break;
}
isListening[dependency] = true;
}
}
}
export function isListeningToAllDependencies(
registrationName: string,
mountAt: Document | Element,
) {
const isListening = getListeningForDocument(mountAt);
const dependencies = registrationNameDependencies[registrationName];
for (let i = 0; i < dependencies.length; i++) {
const dependency = dependencies[i];
if (!(isListening.hasOwnProperty(dependency) && isListening[dependency])) {
return false;
}
}
return true;
}
export {setEnabled, isEnabled, trapBubbledEvent, trapCapturedEvent};