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<!DOCTYPE html>
<html>
<head>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap"/>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/dom/events/scrolling/scroll_support.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-actions.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="resources/common.js"></script>
</head>
<body>
<style>
.large-space {
position: absolute;
height: 300vh;
width: 300vw;
z-index: -1;
}
.target {
width: 100px;
height: 100px;
background-color: green;
scroll-snap-align: start;
}
.snapcontainer {
border:solid 1px black;
overflow: scroll;
scroll-snap-type: y mandatory;
}
.outer {
height: 315px;
width: 1200px;
position: relative;
}
.inner {
height: 115px;
width: 120px;
}
.positioned {
position: absolute;
top: 150px;
}
.outer .target1 {
left: 0px;
}
.outer .target2 {
left: 110px;
}
.outer .target3 {
left: 220px;
}
.outer .target4 {
left: 330px;
}
.outer .target5 {
left: 440px;
}
.inner .target1 {
left: 550px;
}
.inner .target2 {
left: 660px;
}
.inner .target3 {
left: 770px;
}
.inner .target4 {
left: 880px;
}
.inner .target5 {
left: 990px;
}
.placeholder {
background-color: purple;
top: 0px;
}
.outer > .placeholder {
position: absolute;
top: 0px;
left: 200px;
}
</style>
<!--
Placeholder snap areas are used to make it necessary for the scroller to
scroll in order to reach its snap targets. This forces the scroller to
invoke the snap point selection algorithm. Otherwise (i.e. if no scroll
happens) a layout change (inserting and removing children) may not be enough
to cause the scroller to select the intended snap targets.
-->
<div id="outerscroller" class="outer snapcontainer">
<div id="outerplaceholder1" class="placeholder target">Outer placeholder
</div>
<div id="outertarget1" class="positioned target target1">Outer 1</div>
<div id="outertarget2" class="positioned target target2">Outer 2</div>
<div id="outertarget3" class="positioned target target3">Outer 3</div>
<div id="outertarget4" class="positioned target target4">Outer 4</div>
<div id="outertarget5" class="positioned target target5">Outer 5</div>
<div id="innerscroller" class="inner snapcontainer">
<div id="innerplaceholder1" class="placeholder target">Inner Placeholder
</div>
<div id="innertarget1" class="positioned target target1">Inner 1</div>
<div id="innertarget2" class="positioned target target2">Inner 2</div>
<div id="innertarget3" class="positioned target target3">Inner 3</div>
<div id="innertarget4" class="positioned target target4">Inner 4</div>
<div id="innertarget5" class="positioned target target5">Inner 5</div>
</div>
<div class="large-space"></div>
</div>
<script>
window.onload = async () => {
const outerscroller = document.getElementById("outerscroller");
const innerscroller = document.getElementById("innerscroller");
const outertargets = Array.from(
document.querySelectorAll(".outer > .positioned.target"));
const innertargets = Array.from(
document.querySelectorAll(".inner > .positioned.target"));
promise_test(async (t) => {
for (const target of outertargets) {
await waitForScrollReset(t, outerscroller);
await waitForCompositorCommit();
// Make target first in tree order.
outerscroller.removeChild(target);
outerscroller.prepend(target);
await runScrollSnapSelectionVerificationTest(t, outerscroller,
/*aligned_elements_x=*/[],
/*aligned_elements_y=*/outertargets,
/*axis=*/"y",
/*expected_target_x*/null,
/*expected_target_y*/target);
}
// The next for-loop tests outerscroller's selection of
// out-of-positioned targets that are children of innerscroller. For
// outerscroller to consider them first in tree order relative to its
// own children, innerscroller must be the first child of outer
// scroller.
outerscroller.removeChild(innerscroller);
outerscroller.prepend(innerscroller);
for (const target of innertargets) {
await waitForScrollReset(t, outerscroller);
await waitForCompositorCommit();
// Make target first in tree order.
innerscroller.removeChild(target);
innerscroller.prepend(target);
await runScrollSnapSelectionVerificationTest(t, outerscroller,
/*aligned_elements_x=*/[],
/*aligned_elements_y=*/innertargets,
/*axis=*/"y",
/*expected_target_x*/null,
/*expected_target_y*/target);
}
}, "first in tree-order is selected as snap target.");
}
</script>
</body>
</html>
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