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timer update to have another correction step

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Jack 2021-11-12 01:52:10 +00:00
parent 16974cba43
commit 324b7f8570
1 changed files with 55 additions and 10 deletions
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65
src/js/test/test-timer.js
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@ -1,3 +1,6 @@
//most of the code is thanks to
//https://stackoverflow.com/questions/29971898/how-to-create-an-accurate-timer-in-javascript
import Config, * as UpdateConfig from "./config";
import * as CustomText from "./custom-text";
import * as TimerProgress from "./timer-progress";
@ -12,9 +15,13 @@ import * as Caret from "./caret";
export let slowTimer = false;
export let time = 0;
let timer = null;
const stepIntervalMS = 1000;
const interval = 1000;
let expected = 0;
let drift_history = [];
let drift_history_samples = 10;
let drift_correction = 0;
let timerDebug = false;
export function enableTimerDebug() {
timerDebug = true;
@ -159,6 +166,29 @@ function checkIfTimeIsUp() {
// ---------------------------------------
function calc_drift(arr) {
// Calculate drift correction.
/*
In this example I've used a simple median.
You can use other methods, but it's important not to use an average.
If the user switches tabs and back, an average would put far too much
weight on the outlier.
*/
var values = arr.concat(); // copy array so it isn't mutated
values.sort(function (a, b) {
return a - b;
});
if (values.length === 0) return 0;
var half = Math.floor(values.length / 2);
if (values.length % 2) return values[half];
var median = (values[half - 1] + values[half]) / 2.0;
return median;
}
async function timerStep() {
time++;
premid();
@ -173,15 +203,15 @@ async function timerStep() {
}
export function start() {
function loop() {
let dt = performance.now() - expected; //delta time
function step() {
let dt = Date.now() - expected; //delta time
if (dt > stepIntervalMS / 2) {
if (dt > interval / 2) {
//slow timer, disable animations?
slowTimer = true;
}
if (dt > stepIntervalMS) {
if (dt > interval) {
// stop timer maybe?
// Tribe.setNoAnim(true);
}
@ -193,12 +223,27 @@ export function start() {
timerStep();
expected += stepIntervalMS;
let delay = Math.max(0, stepIntervalMS - dt);
// don't update the history for exceptionally large values
if (dt <= interval) {
// sample drift amount to history after removing current correction
// (add to remove because the correction is applied by subtraction)
drift_history.push(dt + drift_correction);
// predict new drift correction
drift_correction = calc_drift(drift_history);
// cap and refresh samples
if (drift_history.length >= drift_history_samples) {
drift_history.shift();
}
}
expected += interval;
let delay = Math.max(0, interval - dt - drift_correction);
if (timerDebug) console.log(`deltatime ${dt}ms`);
if (timerDebug) console.log(`delay ${delay}ms`);
setTimeout(loop, delay);
setTimeout(step, delay);
}
expected = TestStats.start + stepIntervalMS;
setTimeout(loop, stepIntervalMS);
expected = Date.now() + interval;
setTimeout(step, interval);
}