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<!DOCTYPE HTML>
<html>
<meta charset="utf-8">
<title>Test for Bug 1774135</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
<style>
.split {
width: 299px;
display: flex;
background: red; /* so we can see if it's visible. It should NOT be visible */
}
.split>* {
flex: 1 1 auto;
height: 50px;
}
.left {
background: pink;
}
.middle {
background: lightgreen;
}
.right {
background: lightblue;
}
</style>
<script>
function WidthTracker(observed) {
this._observer = new ResizeObserver(this._handleNotification.bind(this));
this._observed = observed;
}
WidthTracker.prototype = {
_handleNotification(entries) {
for (let entry of entries) {
this._elemToWidth.set(
entry.target,
entry.devicePixelContentBoxSize[0].inlineSize
);
}
for (let elem of this._observed) {
if (!this._elemToWidth.has(elem)) {
return;
}
}
// Note(dshin): Wait a tick - we need to let the resize observer loop exit
// and avoid resize loop error.
const resolve = this._resolve;
const result = new Map(this._elemToWidth);
this._observer.disconnect();
delete this._resolve;
delete this._elemToWidth;
window.requestAnimationFrame(function() {
resolve(result);
});
},
start() {
this._elemToWidth = new Map();
for (const elem of this._observed) {
this._observer.observe(elem);
}
return new Promise(res => { this._resolve = res; });
},
};
async function run_test(tracker, container, children, relativeZoom) {
SpecialPowers.setFullZoom(window, relativeZoom);
let result = await tracker.start(Array.from(children).concat([container]));
let observedChildrenWidths = 0;
for (const child of children) {
observedChildrenWidths += result.get(child);
}
let containerWidth = result.get(container);
is(observedChildrenWidths, containerWidth, "Combined widths of children == container width");
}
const originalZoom = SpecialPowers.getFullZoom(window);
let tracker;
let container;
let children;
const zoomsToTest = [
300,
240,
200,
170,
150,
133,
120,
110,
100,
90,
80,
67,
50,
30,
];
add_task(async () => {
container = document.querySelector('.split');
children = document.querySelectorAll('.split>*');
tracker = new WidthTracker(Array.from(children).concat([container]));
});
for (let i = 0; i < zoomsToTest.length; ++i) {
let relativeZoom = originalZoom * zoomsToTest[i] / 100;
add_task(async () => { await run_test(tracker, container, children, relativeZoom); });
}
add_task(async () => { SpecialPowers.setFullZoom(window, originalZoom); });
</script>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1774135">Mozilla Bug 1774135</a>
<div class="split">
<div class="left"></div>
<div class="middle"></div>
<div class="right"></div>
</div>
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