forked from mirrors/gecko-dev
3f226f1b33
As per the CSS Animations spec [1], animations must behave as if 'will-change' is specified, and as per the Will Change spec [2] the element having 'will-change' property other than 'auto' behaves as a containing block for fixed-pos descendants. This reftest tests that behavior. The reason we also specified visibility:hidden there is that we are going to optimize transform animations on/inside visibility:hidden element, so this reftest also tests it. In this reftest, if the containing block is correctly generated, the fixed-pos element is rendered inside the parent element, thus the scrollable element overflows, then the vertial scroll bar appears. [1] https://drafts.csswg.org/css-animations-1/#animations > While an animation is applied but has not finished, or has finished but has > an animation-fill-mode of forwards or both, the user agent must act as if > the will-change property ([css-will-change-1]) on the element additionally > includes all the properties animated by the animation. [2] https://drafts.csswg.org/css-will-change/#will-change > If any non-initial value of a property would cause the element to generate > a containing block for fixed positioned elements, specifying that property > in will-change must cause the element to generate a containing block for > fixed positioned elements. MozReview-Commit-ID: Kx5Fdx8FJUG --HG-- extra : rebase_source : 926f10590e90a10876339ccbea331a981f9f4773
26 lines
354 B
HTML
26 lines
354 B
HTML
<!DOCTYPE html>
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<style>
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#parent {
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visibility: hidden;
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will-change: transform;
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}
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#fixed {
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position: fixed;
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background-color: green;
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height: 100px;
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width: 100px;
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}
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#scroll {
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overflow-y: scroll;
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overflow-x: hidden;
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height: 80px;
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width: 100px;
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}
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</style>
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<div id="scroll">
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<div id="parent">
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<div id="fixed"></div>
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</div>
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</div>
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