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<!DOCTYPE HTML>
<html>
<head>
<title>Test for High Resolution Timer</title>
<script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
<script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
</head>
<body>
<script>
ok(window.performance, "Performance object should exist.");
ok(typeof window.performance.now == 'function', "Performance object should have a 'now' method.");
var n = window.performance.now(), d = Date.now();
ok(n >= 0, "The value of now() should be equal to or greater than 0.");
ok(window.performance.now() >= n, "The value of now() should monotonically increase.");
SimpleTest.waitForExplicitFinish();
SimpleTest.requestFlakyTimeout("untriaged");
// The spec says performance.now() should have micro-second resolution, but allows 1ms if the platform doesn't support it.
// Our implementation does provide micro-second resolution, except for windows XP combined with some HW properties
// where we can't use QueryPerformanceCounters (see comments at mozilla-central/xpcom/ds/TimeStamp_windows.cpp).
// This XP-low-res case results in about 15ms resolutions, and can be identified when perf.now() returns only integers.
//
// Since setTimeout might return too early/late, our goal is that perf.now() changed within 2ms
// (or 25ms for XP-low-res), rather than specific number of setTimeout(N) invocations.
// See bug 749894 (intermittent failures of this test)
var platformPossiblyLowRes = navigator.oscpu.indexOf("Windows NT 5.1") == 0; // XP only
var allInts = (n % 1) == 0; // Indicator of limited HW resolution.
var checks = 0;
function checkAfterTimeout() {
checks++;
var d2 = Date.now();
var n2 = window.performance.now();
allInts = allInts && (n2 % 1) == 0;
var lowResCounter = platformPossiblyLowRes && allInts;
if ( n2 == n && checks < 50 && // 50 is just a failsafe. Our real goals are 2ms or 25ms.
( (d2 - d) < 2 // The spec allows 1ms resolution. We allow up to measured 2ms to ellapse.
||
lowResCounter &&
(d2 - d) < 25
)
) {
setTimeout(checkAfterTimeout, 1);
return;
}
// Loose spec: 1ms resolution, or 15ms resolution for the XP-low-res case.
// We shouldn't test that dt is actually within 2/25ms since the iterations break if it isn't, and timeout could be late.
ok(n2 > n, "Loose - the value of now() should increase within 2ms (or 25ms if low-res counter) (delta now(): " + (n2 - n) + " ms).");
// Strict spec: if it's not the XP-low-res case, while the spec allows 1ms resolution, it prefers microseconds, which we provide.
// Since the fastest setTimeout return which I observed was ~500 microseconds, a microseconds counter should change in 1 iteretion.
ok(n2 > n && (lowResCounter || checks == 1),
"Strict - [if high-res counter] the value of now() should increase after one setTimeout (hi-res: " + (!lowResCounter) +
", iters: " + checks +
", dt: " + (d2 - d) +
", now(): " + n2 + ").");
SimpleTest.finish();
};
setTimeout(checkAfterTimeout, 1);
</script>
</body>
</html>
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