/
ReactNativeEventEmitter.js
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/
ReactNativeEventEmitter.js
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/**
* 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 {PLUGIN_EVENT_SYSTEM} from 'legacy-events/EventSystemFlags';
import {
getListener,
runExtractedPluginEventsInBatch,
} from 'legacy-events/EventPluginHub';
import {registrationNameModules} from 'legacy-events/EventPluginRegistry';
import {batchedUpdates} from 'legacy-events/ReactGenericBatching';
import warningWithoutStack from 'shared/warningWithoutStack';
import {getInstanceFromNode} from './ReactNativeComponentTree';
import type {AnyNativeEvent} from 'legacy-events/PluginModuleType';
import type {TopLevelType} from 'legacy-events/TopLevelEventTypes';
export {getListener, registrationNameModules as registrationNames};
/**
* Version of `ReactBrowserEventEmitter` that works on the receiving side of a
* serialized worker boundary.
*/
// Shared default empty native event - conserve memory.
const EMPTY_NATIVE_EVENT = (({}: any): AnyNativeEvent);
/**
* Selects a subsequence of `Touch`es, without destroying `touches`.
*
* @param {Array<Touch>} touches Deserialized touch objects.
* @param {Array<number>} indices Indices by which to pull subsequence.
* @return {Array<Touch>} Subsequence of touch objects.
*/
const touchSubsequence = function(touches, indices) {
const ret = [];
for (let i = 0; i < indices.length; i++) {
ret.push(touches[indices[i]]);
}
return ret;
};
/**
* TODO: Pool all of this.
*
* Destroys `touches` by removing touch objects at indices `indices`. This is
* to maintain compatibility with W3C touch "end" events, where the active
* touches don't include the set that has just been "ended".
*
* @param {Array<Touch>} touches Deserialized touch objects.
* @param {Array<number>} indices Indices to remove from `touches`.
* @return {Array<Touch>} Subsequence of removed touch objects.
*/
const removeTouchesAtIndices = function(
touches: Array<Object>,
indices: Array<number>,
): Array<Object> {
const rippedOut = [];
// use an unsafe downcast to alias to nullable elements,
// so we can delete and then compact.
const temp: Array<?Object> = (touches: Array<any>);
for (let i = 0; i < indices.length; i++) {
const index = indices[i];
rippedOut.push(touches[index]);
temp[index] = null;
}
let fillAt = 0;
for (let j = 0; j < temp.length; j++) {
const cur = temp[j];
if (cur !== null) {
temp[fillAt++] = cur;
}
}
temp.length = fillAt;
return rippedOut;
};
/**
* Internal version of `receiveEvent` in terms of normalized (non-tag)
* `rootNodeID`.
*
* @see receiveEvent.
*
* @param {rootNodeID} rootNodeID React root node ID that event occurred on.
* @param {TopLevelType} topLevelType Top level type of event.
* @param {?object} nativeEventParam Object passed from native.
*/
function _receiveRootNodeIDEvent(
rootNodeID: number,
topLevelType: TopLevelType,
nativeEventParam: ?AnyNativeEvent,
) {
const nativeEvent = nativeEventParam || EMPTY_NATIVE_EVENT;
const inst = getInstanceFromNode(rootNodeID);
batchedUpdates(function() {
runExtractedPluginEventsInBatch(
topLevelType,
inst,
nativeEvent,
nativeEvent.target,
PLUGIN_EVENT_SYSTEM,
);
});
// React Native doesn't use ReactControlledComponent but if it did, here's
// where it would do it.
}
/**
* Publicly exposed method on module for native objc to invoke when a top
* level event is extracted.
* @param {rootNodeID} rootNodeID React root node ID that event occurred on.
* @param {TopLevelType} topLevelType Top level type of event.
* @param {object} nativeEventParam Object passed from native.
*/
export function receiveEvent(
rootNodeID: number,
topLevelType: TopLevelType,
nativeEventParam: AnyNativeEvent,
) {
_receiveRootNodeIDEvent(rootNodeID, topLevelType, nativeEventParam);
}
/**
* Simple multi-wrapper around `receiveEvent` that is intended to receive an
* efficient representation of `Touch` objects, and other information that
* can be used to construct W3C compliant `Event` and `Touch` lists.
*
* This may create dispatch behavior that differs than web touch handling. We
* loop through each of the changed touches and receive it as a single event.
* So two `touchStart`/`touchMove`s that occur simultaneously are received as
* two separate touch event dispatches - when they arguably should be one.
*
* This implementation reuses the `Touch` objects themselves as the `Event`s
* since we dispatch an event for each touch (though that might not be spec
* compliant). The main purpose of reusing them is to save allocations.
*
* TODO: Dispatch multiple changed touches in one event. The bubble path
* could be the first common ancestor of all the `changedTouches`.
*
* One difference between this behavior and W3C spec: cancelled touches will
* not appear in `.touches`, or in any future `.touches`, though they may
* still be "actively touching the surface".
*
* Web desktop polyfills only need to construct a fake touch event with
* identifier 0, also abandoning traditional click handlers.
*/
export function receiveTouches(
eventTopLevelType: TopLevelType,
touches: Array<Object>,
changedIndices: Array<number>,
) {
const changedTouches =
eventTopLevelType === 'topTouchEnd' ||
eventTopLevelType === 'topTouchCancel'
? removeTouchesAtIndices(touches, changedIndices)
: touchSubsequence(touches, changedIndices);
for (let jj = 0; jj < changedTouches.length; jj++) {
const touch = changedTouches[jj];
// Touch objects can fulfill the role of `DOM` `Event` objects if we set
// the `changedTouches`/`touches`. This saves allocations.
touch.changedTouches = changedTouches;
touch.touches = touches;
const nativeEvent = touch;
let rootNodeID = null;
const target = nativeEvent.target;
if (target !== null && target !== undefined) {
if (target < 1) {
if (__DEV__) {
warningWithoutStack(
false,
'A view is reporting that a touch occurred on tag zero.',
);
}
} else {
rootNodeID = target;
}
}
// $FlowFixMe Shouldn't we *not* call it if rootNodeID is null?
_receiveRootNodeIDEvent(rootNodeID, eventTopLevelType, nativeEvent);
}
}