stacking-context-transform-lose-to-animation.html
<!DOCTYPE html>
<html class="reftest-wait">
<title>
Transform transition and animation overridden by !important rule create
a stacking context
</title>
<style>
span {
height: 100px;
width: 100px;
position: fixed;
background: green;
top: 50px;
}
@keyframes Transform100px {
from, to { transform: translateX(100px); }
}
#test {
width: 100px; height: 100px;
background: blue;
transform: translateX(200px) ! important;
transition: transform 100s steps(1, start);
animation: Transform100px 100s;
}
</style>
<span></span>
<div id="test"></div>
<script>
window.addEventListener("load", () => {
var target = document.getElementById("test");
getComputedStyle(target).transform;
// Change the transform style to 'none'.
target.style.setProperty("transform", "none", "important");
// Important style is changed but there is a CSS animation,
// so transition won't be visible and the CSS animation is overridden by
// the !important rule. As a result transform style here should be 'none'
// specified by the important rule, but we should create a stacking
// context for it because there are animations.
getComputedStyle(target).transform;
document.documentElement.classList.remove("reftest-wait");
});
</script>
