144 lines
4.0 KiB
JavaScript
144 lines
4.0 KiB
JavaScript
/**
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* Copyright 2004-present Facebook. All Rights Reserved.
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*
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* @providesModule InteractionManager
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*/
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'use strict';
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var ErrorUtils = require('ErrorUtils');
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var EventEmitter = require('EventEmitter');
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var Set = require('Set');
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var invariant = require('invariant');
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var keyMirror = require('keyMirror');
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var setImmediate = require('setImmediate');
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/**
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* InteractionManager allows long-running work to be scheduled after any
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* interactions/animations have completed. In particular, this allows JavaScript
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* animations to run smoothly.
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*
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* Applications can schedule tasks to run after interactions with the following:
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*
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* InteractionManager.runAfterInteractions(() => {
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* // ...long-running synchronous task...
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* });
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*
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* Compare this to other scheduling alternatives:
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* - requestAnimationFrame(): for code that animates a view over time.
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* - setImmediate/setTimeout(): run code later, note this may delay animations.
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* - runAfterInteractions(): run code later, without delaying active animations.
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*
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* The touch handling system considers one or more active touches to be an
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* 'interaction' and will delay `runAfterInteractions()` callbacks until all
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* touches have ended or been cancelled.
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*
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* InteractionManager also allows applications to register animations by
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* creating an interaction 'handle' on animation start, and clearing it upon
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* completion:
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*
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* var handle = InteractionManager.createInteractionHandle();
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* // run animation... (`runAfterInteractions` tasks are queued)
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* // later, on animation completion:
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* InteractionManager.clearInteractionHandle(handle);
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* // queued tasks run if all handles were cleared
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*/
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var _emitter = new EventEmitter();
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var _interactionSet = new Set();
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var _addInteractionSet = new Set();
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var _deleteInteractionSet = new Set();
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var _nextUpdateHandle = null;
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var _queue = [];
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var _inc = 0;
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var InteractionManager = {
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Events: keyMirror({
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interactionStart: true,
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interactionComplete: true,
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}),
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/**
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* Notify manager that an interaction has started.
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*/
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createInteractionHandle() {
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scheduleUpdate();
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var handle = ++_inc;
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_addInteractionSet.add(handle);
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return handle;
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},
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/**
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* Notify manager that an interaction has completed.
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*/
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clearInteractionHandle(handle) {
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invariant(
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!!handle,
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'Must provide a handle to clear.'
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);
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scheduleUpdate();
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_addInteractionSet.delete(handle);
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_deleteInteractionSet.add(handle);
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},
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/**
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* Schedule a function to run after all interactions have completed.
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*
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* @param {function} callback
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*/
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runAfterInteractions(callback) {
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invariant(
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typeof callback === 'function',
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'Must specify a function to schedule.'
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);
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scheduleUpdate();
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_queue.push(callback);
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},
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addListener: _emitter.addListener.bind(_emitter),
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};
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/**
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* Schedule an asynchronous update to the interaction state.
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*/
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function scheduleUpdate() {
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if (!_nextUpdateHandle) {
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_nextUpdateHandle = setImmediate(processUpdate);
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}
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}
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/**
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* Notify listeners, process queue, etc
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*/
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function processUpdate() {
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var interactionCount = _interactionSet.size;
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_addInteractionSet.forEach(handle =>
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_interactionSet.add(handle)
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);
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_deleteInteractionSet.forEach(handle =>
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_interactionSet.delete(handle)
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);
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var nextInteractionCount = _interactionSet.size;
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if (interactionCount !== 0 && nextInteractionCount === 0) {
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// transition from 1+ --> 0 interactions
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_emitter.emit(InteractionManager.Events.interactionComplete);
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} else if (interactionCount === 0 && nextInteractionCount !== 0) {
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// transition from 0 --> 1+ interactions
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_emitter.emit(InteractionManager.Events.interactionStart);
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}
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// process the queue regardless of a transition
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if (nextInteractionCount === 0) {
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_queue.forEach(callback => {
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ErrorUtils.applyWithGuard(callback);
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});
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_queue = [];
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}
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_nextUpdateHandle = null;
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_addInteractionSet.clear();
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_deleteInteractionSet.clear();
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}
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module.exports = InteractionManager;
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