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<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Properties and Values API: optional initial-value descriptor</title>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api/#initial-value-descriptor">
<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/9078">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
@property --registered {
syntax: '*';
initial-value: ;
inherits: false;
}
#target {
--test-bg: var(--registered) green;
--test-fallback: var(--registered, red);
background-color: var(--test-bg, var(--test-fallback));
}
</style>
<div id="target"></div>
<script>
test(function() {
const target = document.getElementById('target');
const style = getComputedStyle(target);
// When initial-value is omitted (empty space), the property should be registered
// with a space character as the initial value, making var(--registered) green
// evaluate to " green" which is a valid color value.
assert_equals(style.backgroundColor, 'rgb(0, 128, 0)',
'background-color should be green when @property has empty initial-value');
}, '@property with empty initial-value should use space character');
</script>
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