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<!DOCTYPE HTML>
<html>
<head>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<script src="/tests/SimpleTest/EventUtils.js"></script>
<link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
</head>
<body>
<style>
.box {
background: linear-gradient(90deg, rgba(256,0,0,1), rgba(256,0,0,1));
background-attachment: fixed;
width: 25%;
height: 450px;
}
</style>
<div style="height: 1000vh;"></div>
<div class="box"></div>
<script>
SimpleTest.waitForExplicitFinish();
add_task(async function() {
let utils = SpecialPowers.DOMWindowUtils;
let sc = document.getElementById("sc");
let boundingClientRect = document.documentElement.getBoundingClientRect();
let canvas = document.createElement("canvas");
canvas.setAttribute("width", boundingClientRect.width);
canvas.setAttribute("height", boundingClientRect.height);
let ctx = canvas.getContext("2d");
let rect = new window.DOMRect(boundingClientRect.x, boundingClientRect.y,
boundingClientRect.width,
boundingClientRect.height);
let image = await SpecialPowers.snapshotContext(window, rect, "rgb(255,255,255)");
SpecialPowers.wrap(ctx).drawImage(image, 0, 0);
var data = ctx.getImageData(0, 0, boundingClientRect.width, boundingClientRect.height).data;
var foundRed = false;
for (var i = 0; i < data.length; i+=4) {
if (data[i] == 255 && data[i+1] == 0 && data[i+2] == 0 && data[i+3] == 255) {
foundRed = true;
break;
}
}
ok(foundRed, "found some red pixels");
});
</script>
</body>
</html>
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