react-native/Libraries/Interaction/JSEventLoopWatchdog.js
Spencer Ahrens f21da3aa31 <Incremental> for incremental rendering
Summary:Everything wrapped in `<Incremental>` is rendered sequentially via `InteractionManager`.
The `onDone` callback is called when all descendent incremental components have
finished rendering, used by `<IncrementalPresenter>` to make the story visible all at once
instead of the parts popping in randomly.

This includes an example that demonstrates streaming rendering and the use of
`<IncrementalPresenter>`.  Pressing down pauses rendering and you can see the
`TouchableOpacity` animation runs smoothly.  Video:

https://youtu.be/4UNf4-8orQ4

Ideally this will be baked into React Core at some point, but according to jordwalke that's
going to require a major refactoring and take a long time, so going with this for now.

Reviewed By: ericvicenti

Differential Revision: D2506522

fb-gh-sync-id: 5969bf248de10d38b0ac22f34d7d49bf1b3ac4b6
shipit-source-id: 5969bf248de10d38b0ac22f34d7d49bf1b3ac4b6
2016-03-10 08:14:23 -08:00

86 lines
2.6 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 JSEventLoopWatchdog
* @flow
*/
'use strict';
const performanceNow = require('performanceNow');
type Handler = {
onIterate?: () => void;
onStall: (params: {lastInterval: number}) => string;
};
/**
* A utility for tracking stalls in the JS event loop that prevent timers and
* other events from being processed in a timely manner.
*
* The "stall" time is defined as the amount of time in access of the acceptable
* threshold, which is typically around 100-200ms. So if the treshold is set to
* 100 and a timer fires 150 ms later than it was scheduled because the event
* loop was tied up, that would be considered a 50ms stall.
*
* By default, logs stall events to the console when installed. Can also be
* queried with `getStats`.
*/
const JSEventLoopWatchdog = {
getStats: function(): Object {
return {stallCount, totalStallTime, longestStall, acceptableBusyTime};
},
reset: function() {
console.log('JSEventLoopWatchdog: reset');
totalStallTime = 0;
stallCount = 0;
longestStall = 0;
},
addHandler: function(handler: Handler) {
handlers.push(handler);
},
install: function({thresholdMS}: {thresholdMS: number}) {
acceptableBusyTime = thresholdMS;
if (installed) {
return;
}
installed = true;
let lastInterval = performanceNow();
function iteration() {
const now = performanceNow();
const busyTime = now - lastInterval;
if (busyTime >= thresholdMS) {
const stallTime = busyTime - thresholdMS;
stallCount++;
totalStallTime += stallTime;
longestStall = Math.max(longestStall, stallTime);
let msg = `JSEventLoopWatchdog: JS thread busy for ${busyTime}ms. ` +
`${totalStallTime}ms in ${stallCount} stalls so far. `;
handlers.forEach((handler) => {
msg += handler.onStall({lastInterval});
});
console.log(msg);
}
handlers.forEach((handler) => {
handler.onIterate && handler.onIterate();
});
lastInterval = now;
setTimeout(iteration, thresholdMS / 5);
}
iteration();
},
};
let acceptableBusyTime = 0;
let installed = false;
let totalStallTime = 0;
let stallCount = 0;
let longestStall = 0;
const handlers: Array<Handler> = [];
module.exports = JSEventLoopWatchdog;