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<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Test: scroll tracking for ::scroll-marker </title>
<link rel="help" href="https://drafts.csswg.org/css-overflow-5/#scroll-container-scroll">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/css-transitions/support/helper.js"></script>
<script src="/dom/events/scrolling/scroll_support.js"></script>
<style>
#scroller {
overflow: scroll;
scroll-marker-group: before;
height: 100px;
scroll-behavior: smooth;
background-color: purple;
border: solid 1px black;
}
#scroller::scroll-marker-group {
border: 3px solid black;
display: flex;
width: 100px;
height: 20px;
}
#scroller div {
width: 100px;
height: 100px;
}
#scroller div::scroll-marker {
content: '';
background-color: red;
display: inline-flex;
width: 10px;
height: 10px;
border-radius: 50%;
}
#scroller div::scroll-marker:target-current {
background-color: green;
}
</style>
<div id='scroller'>
<div id="initial"></div>
<div class="inbetween"></div>
<div class="inbetween"></div>
<div class="inbetween"></div>
<div id='target'></div>
</div>
<script>
const inbetweens = scroller.querySelectorAll(".inbetween");
const GREEN = "rgb(0, 128, 0)";
const RED = "rgb(255, 0, 0)";
function assertPseudoElementProperty(originatingElement, pseudoType, backgroundColor) {
const pseudoStyle = getComputedStyle(originatingElement, pseudoType);
const pseudoBackgroundColor = pseudoStyle.getPropertyValue('background-color');
assert_equals(pseudoBackgroundColor, backgroundColor, pseudoType +
" background-color should be " + backgroundColor.toString() +
" but was " + pseudoBackgroundColor.toString());
}
let marker_change_observed = false;
function watchFrames() {
const initialPseudoStyle = getComputedStyle(initial, "::scroll-marker");
const initialPseudoBackgroundColor =
initialPseudoStyle.getPropertyValue('background-color');
if (initialPseudoBackgroundColor === RED) {
marker_change_observed = true;
} else {
assert_false(marker_change_observed);
assert_equals(initialPseudoBackgroundColor, GREEN,
"initial scroll-marker is initially green");
}
// All the markers in between should always be red.
for (const inbetween of inbetweens) {
assertPseudoElementProperty(inbetween, "::scroll-marker", RED);
}
// target should become and stay the selected scroll-marker.
assertPseudoElementProperty(target, "::scroll-marker",
marker_change_observed ? GREEN : RED);
requestAnimationFrame(watchFrames);
}
function scrollPromise() {
return new Promise((resolve) => {
// For browsers that don't support the scrollend event, just wait till
// at least half the expected scroll is done.
if (document.scrollingElement.onscrollend === undefined) {
function scrollListener() {
const max_scroll_offset =
scroller.scrollHeight - scroller.ClientHeight;
if (scroller.scrollTop >= max_scroll_offset / 2) {
scroller.removeEventListener(scrollListener);
resolve();
}
}
scroller.addEventListener("scroll", scrollListener);
} else {
function scrollEndListener() {
scroller.removeEventListener("scrollend", scrollEndListener);
resolve();
}
scroller.addEventListener("scrollend", scrollEndListener);
}
});
};
promise_test(async (t) => {
await waitForAnimationFrames(2);
assertPseudoElementProperty(initial, "::scroll-marker", GREEN);
assertPseudoElementProperty(target, "::scroll-marker", RED);
function changeDivWidths() {
const WIDTH1 = "100px";
const WIDTH2 = "200px";
const divs = scroller.querySelectorAll("div");
const current_width = divs[0].style.width;
const target_width = current_width === WIDTH1 ? WIDTH2 : WIDTH1;
divs.forEach(div => { div.style.width = target_width; });
}
// Add a scroll listener which will trigger a layout change.
// Despite the layout change, the user agent should only select
// the eventual scroll position of the ongoing smooth scrollIntoView.
scroller.addEventListener("scroll", changeDivWidths);
const scroll_promise = scrollPromise();
watchFrames();
target.scrollIntoView({ behavior: "smooth" });
await scroll_promise;
assertPseudoElementProperty(initial, "::scroll-marker", RED);
assertPseudoElementProperty(target, "::scroll-marker", GREEN);
}, "The selected ::scroll-marker is updated using the eventual scroll " +
"position for a programmatic scroll");
</script>
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