Blitz - WPT: flexbox-column-style-change-triggers-layout-block-start.html

wpt / css / css-box / margin-trim / computed-margin-values / flexbox-column-style-change-triggers-layout-block-start.html

Data from commit:
708eb61 WPT runner: support mismatch reftests and multiple rel=match links (#665) (2026-08-09)

Subtest	Status	Message
flexbox > item 1	FAIL	assert_equals: data-offset-y expected 18 got 10
flexbox > item 2	FAIL	assert_equals: data-offset-y expected 78 got 70

Enable JavaScript in test iframe

/css/css-box/margin-trim/computed-margin-values/flexbox-column-style-change-triggers-layout-block-start.html

<!DOCTYPE html>
<html>
<head>
<link rel="author" href="mailto:sammy.gill@apple.com">
<link rel="help" href="https://drafts.csswg.org/css-box-4/#margin-trim-flex">
<meta name="assert" content="Make sure margins are no longer trimmed when margin-trim is changed to none on the flexbox">
<style>
flexbox {
    display: flex;
    flex-direction: column;
    width: min-content;
    margin-trim: block-start;
}
item {
    display: block;
    background-color: green;
    width: 50px;
    height: 50px;
    margin-block-start: 10px;
}
</style>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/check-layout-th.js"></script>
</head>
<body>
<div id="target">
<flexbox>
    <item data-expected-margin-top="10" data-offset-y="18"></item>
    <item data-expected-margin-top="10" data-offset-y="78"></item>
</flexbox>
</div>
<script>
// Force the first layout to trim margins, set margin-trim to none,
// force a second layout, and then check to see if the margins were added back
document.body.offsetHeight;
document.querySelector("flexbox").style["margin-trim"] = "none";
document.body.offsetHeight;
checkLayout("flexbox > item");
</script>
</body>
</html>