react-native/Libraries/Experimental/Incremental.js

187 lines
5.9 KiB
JavaScript
Raw Normal View History

/**
* 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 Incremental
* @flow
*/
'use strict';
const InteractionManager = require('InteractionManager');
const React = require('React');
const infoLog = require('infoLog');
const DEBUG = false;
/**
* WARNING: EXPERIMENTAL. Breaking changes will probably happen a lot and will
* not be reliably announced. The whole thing might be deleted, who knows? Use
* at your own risk.
*
* React Native helps make apps smooth by doing all the heavy lifting off the
* main thread, in JavaScript. That works great a lot of the time, except that
* heavy operations like rendering may block the JS thread from responding
* quickly to events like taps, making the app feel sluggish.
*
* `<Incremental>` solves this by slicing up rendering into chunks that are
* spread across multiple event loops. Expensive components can be sliced up
* recursively by wrapping pieces of them and their decendents in
* `<Incremental>` components. `<IncrementalGroup>` can be used to make sure
* everything in the group is rendered recursively before calling `onDone` and
* moving on to another sibling group (e.g. render one row at a time, even if
* rendering the top level row component produces more `<Incremental>` chunks).
* `<IncrementalPresenter>` is a type of `<IncrementalGroup>` that keeps it's
* children invisible and out of the layout tree until all rendering completes
* recursively. This means the group will be presented to the user as one unit,
* rather than pieces popping in sequentially.
*
* `<Incremental>` only affects initial render - `setState` and other render
* updates are unaffected.
*
* The chunks are rendered sequentially using the `InteractionManager` queue,
* which means that rendering will pause if it's interrupted by an interaction,
* such as an animation or gesture.
*
* Note there is some overhead, so you don't want to slice things up too much.
* A target of 100-200ms of total work per event loop on old/slow devices might
* be a reasonable place to start.
*
* Below is an example that will incrementally render all the parts of `Row` one
* first, then present them together, then repeat the process for `Row` two, and
* so on:
*
* render: function() {
* return (
* <ScrollView>
* {Array(10).fill().map((rowIdx) => (
* <IncrementalPresenter key={rowIdx}>
* <Row>
* {Array(20).fill().map((widgetIdx) => (
* <Incremental key={widgetIdx}>
* <SlowWidget />
* </Incremental>
* ))}
* </Row>
* </IncrementalPresenter>
* ))}
* </ScrollView>
* );
* };
*
* If SlowWidget takes 30ms to render, then without `Incremental`, this would
* block the JS thread for at least `10 * 20 * 30ms = 6000ms`, but with
* `Incremental` it will probably not block for more than 50-100ms at a time,
* allowing user interactions to take place which might even unmount this
* component, saving us from ever doing the remaining rendering work.
*/
export type Props = {
/**
* Called when all the decendents have finished rendering and mounting
* recursively.
*/
onDone?: () => void,
/**
* Tags instances and associated tasks for easier debugging.
*/
name: string,
children?: any,
};
type DefaultProps = {
name: string,
};
type State = {
doIncrementalRender: boolean,
};
class Incremental extends React.Component<DefaultProps, Props, State> {
props: Props;
state: State;
context: Context;
_incrementId: number;
_mounted: boolean;
_rendered: boolean;
static defaultProps = {
name: '',
};
static contextTypes = {
incrementalGroup: React.PropTypes.object,
incrementalGroupEnabled: React.PropTypes.bool,
};
constructor(props: Props, context: Context) {
super(props, context);
this._mounted = false;
this.state = {
doIncrementalRender: false,
};
}
getName(): string {
const ctx = this.context.incrementalGroup || {};
return ctx.groupId + ':' + this._incrementId + '-' + this.props.name;
}
componentWillMount() {
const ctx = this.context.incrementalGroup;
if (!ctx) {
return;
}
this._incrementId = ++(ctx.incrementalCount);
InteractionManager.runAfterInteractions({
name: 'Incremental:' + this.getName(),
gen: () => new Promise(resolve => {
if (!this._mounted || this._rendered) {
resolve();
return;
}
DEBUG && infoLog('set doIncrementalRender for ' + this.getName());
this.setState({doIncrementalRender: true}, resolve);
}),
}).then(() => {
DEBUG && infoLog('call onDone for ' + this.getName());
this._mounted && this.props.onDone && this.props.onDone();
}).catch((ex) => {
ex.message = `Incremental render failed for ${this.getName()}: ${ex.message}`;
throw ex;
}).done();
}
render(): ?React.Element<any> {
if (this._rendered || // Make sure that once we render once, we stay rendered even if incrementalGroupEnabled gets flipped.
!this.context.incrementalGroupEnabled ||
this.state.doIncrementalRender) {
DEBUG && infoLog('render ' + this.getName());
this._rendered = true;
return this.props.children;
}
return null;
}
componentDidMount() {
this._mounted = true;
if (!this.context.incrementalGroup) {
this.props.onDone && this.props.onDone();
}
}
componentWillUnmount() {
this._mounted = false;
}
}
export type Context = {
incrementalGroupEnabled: boolean,
incrementalGroup: ?{
groupId: string,
incrementalCount: number,
},
};
module.exports = Incremental;