<!DOCTYPE html>
<meta charset="utf-8">
<title>Dynamic change to paint containment</title>
<link rel="help" href="https://drafts.csswg.org/css-contain/#contain-property">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1765615">
<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<meta name="assert" content="Verify paint containment is properly updated after dynamic change to the contain property.">
<style>
/* Selectors for contain */
#none .wrapper {
contain: none;
}
#paint .wrapper {
contain: paint;
}
#none_to_paint .wrapper {
contain: none;
}
#paint_to_none .wrapper {
contain: paint;
}
/* Selectors for testing absolute/fixed positioned elements */
#top_spacer {
height: 100px;
background: lightgray;
}
.absolute_pos {
position: absolute;
top: 42px;
}
.fixed_pos {
position: fixed;
top: 42px;
}
/* Selectors for testing IFC (floats) */
.floatleft {
float: left;
}
.clearleft {
clear: left;
}
/* Selectors for testing IFC (margin collapsing) */
.blockmargin {
margin: 25px 0;
}
.wrapper.blockmargin {
background: lightgray;
}
.rect {
background: black;
width: 50px;
height: 100px;
}
</style>
<body>
<div id="log"></div>
<div id="top_spacer"></div>
<div id="none">
<div class="wrapper">
<div class="absolute_pos"></div>
<div class="fixed_pos"></div>
</div>
<div>
<div class="floatleft rect"></div>
<div class="wrapper">
<div class="clearleft rect"></div>
</div>
</div>
<div>
<div class="wrapper blockmargin">
<div class="rect blockmargin"></div>
</div>
</div>
</div>
<div id="paint">
<div class="wrapper">
<div class="absolute_pos"></div>
<div class="fixed_pos"></div>
</div>
<div>
<div class="floatleft rect"></div>
<div class="wrapper">
<div class="clearleft rect"></div>
</div>
</div>
<div>
<div class="wrapper blockmargin">
<div class="rect blockmargin"></div>
</div>
</div>
</div>
<div id="none_to_paint">
<div class="wrapper">
<div class="absolute_pos"></div>
<div class="fixed_pos"></div>
</div>
<div>
<div class="floatleft rect"></div>
<div class="wrapper">
<div class="clearleft rect"></div>
</div>
</div>
<div>
<div class="wrapper blockmargin">
<div class="rect blockmargin"></div>
</div>
</div>
</div>
<div id="paint_to_none">
<div class="wrapper">
<div class="absolute_pos"></div>
<div class="fixed_pos"></div>
</div>
<div>
<div class="floatleft rect"></div>
<div class="wrapper">
<div class="clearleft rect"></div>
</div>
</div>
<div>
<div class="wrapper blockmargin">
<div class="rect blockmargin"></div>
</div>
</div>
</div>
<script>
function verifyPaintContainment(id, applied) {
let container = document.getElementById(id);
let wrappers = container.getElementsByClassName("wrapper");
// To verify the containment box establishes an absolute positioning
// containing block and a fixed positioning containing block, we test
// positions of absolutely/fixed positioned children (a bit below the
// containment box rather than a bit below the top of the viewport).
let containingBlockTop = wrappers[0].getBoundingClientRect().top;
let absTop = container.getElementsByClassName("absolute_pos")[0]
.getBoundingClientRect().top;
assert_equals(absTop > containingBlockTop, applied, "absolute positioning containing block");
let fixedTop = container.getElementsByClassName("fixed_pos")[0]
.getBoundingClientRect().top;
assert_equals(fixedTop > containingBlockTop, applied, "fixed positioning containing block");
// To verify the containment box establishes an independent formatting
// context, we test position the clear: left div with respect to the
// float: left div.
let floatLeft = wrappers[1].previousElementSibling;
let clearLeft = wrappers[1].firstElementChild;
let clearNextToFloat = Math.abs(floatLeft.getBoundingClientRect().top - clearLeft.getBoundingClientRect().top) <= 1;
assert_equals(clearNextToFloat, applied, "independent formatting context");
// In addition, we verify that the margin inside the containment box
// are not collapsed.
let IFCWithMargin = wrappers[2];
let childWithMargin = IFCWithMargin.firstElementChild;
let marginCollapsed = Math.abs(IFCWithMargin.getBoundingClientRect().height - childWithMargin.getBoundingClientRect().height) <= 1;
assert_equals(!marginCollapsed, applied, "independent formatting context (margins collapsing)");
}
function setContain(id, value) {
let container = document.getElementById(id);
Array.from(container.getElementsByClassName("wrapper"))
.forEach(element => element.style.contain = value);
}
promise_test(async () => {
await document.fonts.ready;
verifyPaintContainment("none", /* applied=*/false);
}, "contain: none");
promise_test(async () => {
await document.fonts.ready;
verifyPaintContainment("paint", /* applied=*/true);
}, "contain: paint");
promise_test(async () => {
await document.fonts.ready;
setContain("none_to_paint", "paint");
verifyPaintContainment("none_to_paint", /* applied=*/true)
}, "switching contain from none to paint");
promise_test(async () => {
await document.fonts.ready;
setContain("paint_to_none", "none");
verifyPaintContainment("paint_to_none", /* applied=*/false);
}, "switching contain from paint to none");
</script>
</body>
Codebase Browser
chromium