<!DOCTYPE HTML>
<html>
<head>
<title>Test that we don't get unnecessary repaints due to subpixel shifts</title>
<script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
<script type="text/javascript" src="chrome://mochikit/content/tests/SimpleTest/paint_listener.js"></script>
<link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
</head>
<!-- Need a timeout here to allow paint unsuppression before we start the test -->
<body onload="setTimeout(startTest,0)">
<div id="t" style="width:400px; height:100px; background:yellow; overflow:hidden">
<div style="height:40px;"></div>
<div id="e" style="height:30px; background:lime"></div>
<div style="height:60.4px; background:pink"></div>
</div>
<pre id="test">
<script type="application/javascript">
SimpleTest.waitForExplicitFinish();
var t = document.getElementById("t");
var e = document.getElementById("e");
var utils = window.QueryInterface(Components.interfaces.nsIInterfaceRequestor).
getInterface(Components.interfaces.nsIDOMWindowUtils);
function startTest() {
// Do a scroll to ensure we trigger activity heuristics.
waitForAllPaintsFlushed(function () {
t.scrollTop = 5;
// Scroll down as far as we can, to put our rendering layer at a subpixel offset within the layer
waitForAllPaintsFlushed(function () {
t.scrollTop = 1000;
waitForAllPaintsFlushed(function () {
// Clear paint state now and scroll again.
utils.checkAndClearPaintedState(e);
// scroll up a little bit. This should not cause anything to be repainted.
t.scrollTop = t.scrollTop - 10;
waitForAllPaintsFlushed(function () {
var painted = utils.checkAndClearPaintedState(e);
is(painted, false, "Fully-visible scrolled element should not have been painted");
SimpleTest.finish();
});
});
});
});
}
</script>
</pre>
</body>
</html>