Bug 240653
| Summary: | [iOS] opacity animation changes computed font-size | ||
|---|---|---|---|
| Product: | WebKit | Reporter: | Mauricio <mauricio> |
| Component: | Animations | Assignee: | Nobody <webkit-unassigned> |
| Status: | NEW | ||
| Severity: | Critical | CC: | dino, graouts, graouts, mmaxfield, webkit-bug-importer, zalan |
| Priority: | P2 | Keywords: | HTML5, InRadar |
| Version: | Safari 15 | ||
| Hardware: | iPhone / iPad | ||
| OS: | iOS 15 | ||
Mauricio
Safari iOS has a bug that will make a `font-size` property scale up consistently in the presence of an opacity animation. The computed value diverges from the set CSS value. But even without a set CSS value, you can see how the text jumps, speak the `font-size` grows at the end of the animation.
To reproduce the bug, you need a parent DOM element containing a unit width or height + `overflow: hidden. At the same time, you require at least two `<p>`. And last a DOM element with `opacity: 0` will be set to 1 through JavaScript (See the HTML example below).
You can see a live demo in this CodeSandbox. https://8d838r.csb.app/
This is a minimal representation of the bug.
<!DOCTYPE html>
<head>
<style>
.container {
overflow: hidden;
width: 100%;
height: 2000px;
background: yellow;
}
.transition {
opacity: 0;
background: red;
width: 9px;
height: 9px;
will-change: transform;
z-index: 2;
}
</style>
</head>
<body>
<div class="container">
<p>XXX</p>
<p>XXX</p>
<p>XXX</p>
<p>XXX</p>
<div id="ani" class="transition"></div>
</div>
<script>
setTimeout(() => {
document.getElementById("ani").style.opacity = 1;
}, 2000);
</script>
</body>
| Attachments | ||
|---|---|---|
| Add attachment proposed patch, testcase, etc. |
Sam Sneddon [:gsnedders]
I feel like I've seen this bug recently, but I can't find any duplicate, Antoine?
Antoine Quint
Does not ring a bell!
Radar WebKit Bug Importer
<rdar://problem/93970773>