css/css-properties-values-api/register-property.html

<!DOCTYPE HTML>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api/#register-a-custom-property" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="./resources/utils.js"></script>
<div id=target></div>
<script>
// Tests for error checking during property registration

test(function() {
    assert_throws_js(TypeError, () => CSS.registerProperty());
    assert_throws_js(TypeError, () => CSS.registerProperty(undefined));
    assert_throws_js(TypeError, () => CSS.registerProperty(true));
    assert_throws_js(TypeError, () => CSS.registerProperty(2));
    assert_throws_js(TypeError, () => CSS.registerProperty("css"));
    assert_throws_js(TypeError, () => CSS.registerProperty(null));
}, "registerProperty requires a Dictionary type");

test(function() {
    // Valid property names, shouldn't throw
    CSS.registerProperty({name: '--name1', inherits: false});
    CSS.registerProperty({name: '--name2, no need for escapes', inherits: false});
    CSS.registerProperty({name: ['--name', 3], inherits: false});

    // Invalid property names
    assert_throws_js(TypeError, () => CSS.registerProperty({}));
    assert_throws_dom("SyntaxError", () => CSS.registerProperty({name: 'no-leading-dash', inherits: false}));
    assert_throws_dom("SyntaxError", () => CSS.registerProperty({name: '', inherits: false}));
    assert_throws_dom("SyntaxError", () => CSS.registerProperty({name: '\\--name', inherits: false}));
}, "registerProperty requires a name matching <custom-property-name>");

test(function() {
    CSS.registerProperty({name: '--syntax-test-1', syntax: '*', inherits: false});
    CSS.registerProperty({name: '--syntax-test-2', syntax: ' * ', inherits: false});
    assert_throws_dom("SyntaxError",
        () => CSS.registerProperty({name: '--syntax-test-3', syntax: 'length', inherits: false}));
}, "registerProperty only allows omitting initialValue if syntax is '*'");

test(function() {
    CSS.registerProperty({name: '--re-register', syntax: '<length>', initialValue: '0px', inherits: false});
    assert_throws_dom('InvalidModificationError',
        () => CSS.registerProperty({name: '--re-register', syntax: '<percentage>', initialValue: '0%', inherits: false}));
}, "registerProperty fails for an already registered property");

test(function(){
    CSS.registerProperty({name: '--inherit-test-1', syntax: '<length>', initialValue: '0px', inherits: true});
    CSS.registerProperty({name: '--inherit-test-2', syntax: '<length>', initialValue: '0px', inherits: false});
    assert_throws_js(TypeError, () => CSS.registerProperty({name: '--inherit-test-3', syntax: '<length>', initialValue: '0px'}));
}, "registerProperty requires inherits");

test(function(){
    try {
        let name = generate_name();

        target.style.setProperty(name, 'green');
        target.style.transitionProperty = name;
        target.style.transitionDuration = '1s';
        target.style.transitionTimingFunction = 'steps(1, end)';

        assert_equals(getComputedStyle(target).getPropertyValue(name), 'green');

        CSS.registerProperty({
            name: name,
            syntax: '<color>',
            initialValue: 'red',
            inherits: false
        });

        assert_equals(getComputedStyle(target).getPropertyValue(name), 'rgb(0, 128, 0)');
    } finally {
        target.style = '';
    }
}, 'Registering a property should not cause a transition');

</script>