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<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#space {
height: 4000px;
}
#header {
background-color: #F5B335;
height: 50px;
width: 100%;
}
#content {
background-color: #D3D3D3;
height: 400px;
}
.scroller {
overflow: scroll;
position: relative;
width: 600px;
height: 600px;
}
</style>
<div id="maybeScroller">
<div id="space">
<div id="header"></div>
<div id="before"></div>
<div id="content"></div>
</div>
</div>
<script>
// Tests that scroll anchoring is suppressed when an element in the scroller
// changes its in-flow state.
var scroller;
function runCase(oldPos, newPos, expectSuppression, skipInverse) {
var header = document.querySelector("#header");
var before = document.querySelector("#before");
header.style.position = oldPos;
before.style.height = "0";
scroller.scrollTop = 200;
header.style.position = newPos;
before.style.height = "25px";
var expectedTop = expectSuppression ? 200 : 225;
assert_equals(scroller.scrollTop, expectedTop);
if (!skipInverse)
runCase(newPos, oldPos, expectSuppression, true);
}
test(() => {
scroller = document.scrollingElement;
document.querySelector("#maybeScroller").className = "";
runCase("static", "fixed", true);
runCase("static", "absolute", true);
runCase("static", "relative", false);
runCase("fixed", "absolute", false);
runCase("fixed", "relative", true);
runCase("absolute", "relative", true);
}, "Position changes in document scroller.");
test(() => {
scroller = document.querySelector("#maybeScroller");
scroller.className = "scroller";
runCase("static", "fixed", true);
runCase("static", "absolute", true);
runCase("static", "relative", false);
runCase("fixed", "absolute", false);
runCase("fixed", "relative", true);
runCase("absolute", "relative", true);
}, "Position changes in scrollable <div>.");
</script>
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