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<!DOCTYPE html>
<title>
Moving the current snap target should make the scroller resnap to it.
</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#re-snap" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
position: relative;
margin: 0;
}
#block {
height: 100px;
width: 100px;
}
#scroller {
height: 500px;
width: 500px;
overflow: hidden;
scroll-snap-type: both mandatory;
}
#initial-target {
width: 300px;
height: 300px;
left: 100px;
top: 0;
transform: none;
background-color: green;
scroll-snap-align: start;
}
#other-target {
width: 300px;
height: 300px;
left: 300px;
background-color: red;
scroll-snap-align: start;
}
.area {
width: 2000px;
height: 2000px;
}
</style>
<div id="scroller">
<div id="block"></div>
<div id="initial-target"></div>
<div id="other-target"></div>
<div class="area"></div>
</div>
<script>
const initial_target = document.getElementById("initial-target");
const other_target = document.getElementById("other-target");
const block = document.getElementById("block");
const scroller = document.getElementById("scroller");
function cleanup() {
initial_target.style.setProperty("transform", "none");
initial_target.style.setProperty("top", "0");
block.style.setProperty("height", "100px");
}
test(t => {
t.add_cleanup(cleanup);
scroller.scrollTo(0,0);
assert_equals(scroller.scrollTop, 100);
assert_equals(scroller.scrollLeft, 100);
initial_target.style.setProperty("top", "300px");
assert_equals(scroller.scrollTop, 400);
assert_equals(scroller.scrollLeft, 100);
}, "Moving the current snap target should make the scroller resnap to it.");
test(t => {
t.add_cleanup(cleanup);
scroller.scrollTo(0,0);
assert_equals(scroller.scrollTop, 100);
assert_equals(scroller.scrollLeft, 100);
block.style.setProperty("height", "200px");
assert_equals(scroller.scrollTop, 200);
assert_equals(scroller.scrollLeft, 100);
}, "Changing the layout of other elements should be able to cause resnapping to \
the target.");
test(t => {
t.add_cleanup(cleanup);
scroller.scrollTo(0,0);
assert_equals(scroller.scrollTop, 100);
assert_equals(scroller.scrollLeft, 100);
initial_target.style.setProperty("transform", "translate(0,100px)");
assert_equals(scroller.scrollTop, 200);
assert_equals(scroller.scrollLeft, 100);
}, "Transforming the current snap target should make the scroller resnap to it.");
test(t => {
t.add_cleanup(cleanup);
initial_target.style.setProperty("top", "100px");
scroller.scrollTo(0,0);
assert_equals(scroller.scrollTop, 200);
assert_equals(scroller.scrollLeft, 100);
initial_target.style.setProperty("transform", "translate(0,100px)");
initial_target.style.setProperty("top", "0");
assert_equals(scroller.scrollTop, 200);
assert_equals(scroller.scrollLeft, 100);
}, "Applying two property changes that do not change the visual offset of the \
target should not change the scroll offset.");
</script>
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