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<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script type="text/javascript">
'use strict';
// Computes greatest common divisor of a and b using Euclid's algorithm
function computeGCD(a, b) {
if (!Number.isInteger(a) || !Number.isInteger(b)) {
throw new Error('Parameters must be integer numbers');
}
var r;
while (b != 0) {
r = a % b;
a = b;
b = r;
}
return (a < 0) ? -a : a;
}
// Finds minimum resolution Δ given a set of samples which are known to be in the form of N*Δ.
// We use GCD of all samples as a simple estimator.
function estimateMinimumResolution(samples) {
var gcd;
for (const sample of samples) {
gcd = gcd ? computeGCD(gcd, sample) : sample;
}
return gcd;
}
test(function() {
const samples = [];
for (var i = 0; i < 1e3; i++) {
var deltaInMicroSeconds = 0;
const e1 = new MouseEvent('test1');
do {
const e2 = new MouseEvent('test2');
deltaInMicroSeconds = Math.round((e2.timeStamp - e1.timeStamp) * 1000);
} while (deltaInMicroSeconds == 0) // only collect non-zero samples
samples.push(deltaInMicroSeconds);
}
const minResolution = estimateMinimumResolution(samples);
assert_greater_than_equal(minResolution, 5);
}, 'Event timestamp should not have a resolution better than 5 microseconds');
</script>
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