react-native/Libraries/Interaction/InteractionManager.js

198 lines
6.1 KiB
JavaScript

/**
* Copyright (c) 2015-present, 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 InteractionManager
* @flow
*/
'use strict';
const BatchedBridge = require('BatchedBridge');
const EventEmitter = require('EventEmitter');
const Set = require('Set');
const TaskQueue = require('TaskQueue');
const invariant = require('fbjs/lib/invariant');
const keyMirror = require('fbjs/lib/keyMirror');
const setImmediate = require('setImmediate');
type Handle = number;
import type {Task} from 'TaskQueue';
const _emitter = new EventEmitter();
const DEBUG_DELAY = 0;
const DEBUG = false;
/**
* InteractionManager allows long-running work to be scheduled after any
* interactions/animations have completed. In particular, this allows JavaScript
* animations to run smoothly.
*
* Applications can schedule tasks to run after interactions with the following:
*
* ```
* InteractionManager.runAfterInteractions(() => {
* // ...long-running synchronous task...
* });
* ```
*
* Compare this to other scheduling alternatives:
*
* - requestAnimationFrame(): for code that animates a view over time.
* - setImmediate/setTimeout(): run code later, note this may delay animations.
* - runAfterInteractions(): run code later, without delaying active animations.
*
* The touch handling system considers one or more active touches to be an
* 'interaction' and will delay `runAfterInteractions()` callbacks until all
* touches have ended or been cancelled.
*
* InteractionManager also allows applications to register animations by
* creating an interaction 'handle' on animation start, and clearing it upon
* completion:
*
* ```
* var handle = InteractionManager.createInteractionHandle();
* // run animation... (`runAfterInteractions` tasks are queued)
* // later, on animation completion:
* InteractionManager.clearInteractionHandle(handle);
* // queued tasks run if all handles were cleared
* ```
*
* `runAfterInteractions` takes either a plain callback function, or a
* `PromiseTask` object with a `gen` method that returns a `Promise`. If a
* `PromiseTask` is supplied, then it is fully resolved (including asynchronous
* dependencies that also schedule more tasks via `runAfterInteractions`) before
* starting on the next task that might have been queued up synchronously
* earlier.
*
* By default, queued tasks are executed together in a loop in one
* `setImmediate` batch. If `setDeadline` is called with a positive number, then
* tasks will only be executed until the deadline (in terms of js event loop run
* time) approaches, at which point execution will yield via setTimeout,
* allowing events such as touches to start interactions and block queued tasks
* from executing, making apps more responsive.
*/
var InteractionManager = {
Events: keyMirror({
interactionStart: true,
interactionComplete: true,
}),
/**
* Schedule a function to run after all interactions have completed.
*/
runAfterInteractions(task: ?Task): Promise<any> {
return new Promise(resolve => {
_scheduleUpdate();
if (task) {
_taskQueue.enqueue(task);
}
const name = task && task.name || '?';
_taskQueue.enqueue({run: resolve, name: 'resolve ' + name});
});
},
/**
* Notify manager that an interaction has started.
*/
createInteractionHandle(): Handle {
DEBUG && console.log('create interaction handle');
_scheduleUpdate();
var handle = ++_inc;
_addInteractionSet.add(handle);
return handle;
},
/**
* Notify manager that an interaction has completed.
*/
clearInteractionHandle(handle: Handle) {
DEBUG && console.log('clear interaction handle');
invariant(
!!handle,
'Must provide a handle to clear.'
);
_scheduleUpdate();
_addInteractionSet.delete(handle);
_deleteInteractionSet.add(handle);
},
addListener: _emitter.addListener.bind(_emitter),
/**
* A positive number will use setTimeout to schedule any tasks after the
* eventLoopRunningTime hits the deadline value, otherwise all tasks will be
* executed in one setImmediate batch (default).
*/
setDeadline(deadline: number) {
_deadline = deadline;
},
};
const _interactionSet = new Set();
const _addInteractionSet = new Set();
const _deleteInteractionSet = new Set();
const _taskQueue = new TaskQueue({onMoreTasks: _scheduleUpdate});
let _nextUpdateHandle = 0;
let _inc = 0;
let _deadline = -1;
/**
* Schedule an asynchronous update to the interaction state.
*/
function _scheduleUpdate() {
if (!_nextUpdateHandle) {
if (_deadline > 0) {
_nextUpdateHandle = setTimeout(_processUpdate, 0 + DEBUG_DELAY);
} else {
_nextUpdateHandle = setImmediate(_processUpdate);
}
}
}
/**
* Notify listeners, process queue, etc
*/
function _processUpdate() {
_nextUpdateHandle = 0;
var interactionCount = _interactionSet.size;
_addInteractionSet.forEach(handle =>
_interactionSet.add(handle)
);
_deleteInteractionSet.forEach(handle =>
_interactionSet.delete(handle)
);
var nextInteractionCount = _interactionSet.size;
if (interactionCount !== 0 && nextInteractionCount === 0) {
// transition from 1+ --> 0 interactions
_emitter.emit(InteractionManager.Events.interactionComplete);
} else if (interactionCount === 0 && nextInteractionCount !== 0) {
// transition from 0 --> 1+ interactions
_emitter.emit(InteractionManager.Events.interactionStart);
}
// process the queue regardless of a transition
if (nextInteractionCount === 0) {
while (_taskQueue.hasTasksToProcess()) {
_taskQueue.processNext();
if (_deadline > 0 &&
BatchedBridge.getEventLoopRunningTime() >= _deadline) {
// Hit deadline before processing all tasks, so process more later.
_scheduleUpdate();
break;
}
}
}
_addInteractionSet.clear();
_deleteInteractionSet.clear();
}
module.exports = InteractionManager;