- From: Sebastian Zartner via GitHub <sysbot+gh@w3.org>
- Date: Wed, 19 Mar 2025 22:39:44 +0000
- To: public-css-archive@w3.org
@miragecraft Please see @Loirooriol's [comment](https://github.com/w3c/csswg-drafts/issues/10455#issuecomment-2174259218)! The fallback value is checked against the property it is _applied to_, not the custom property in the `var()` construct. > In the codepen: https://codepen.io/leaverou/pen/oNRpEGO > > `<pre style="--color: red; background: var(--color, lime);">\</pre\>` is rendered as yellowgreen, even though lime is a valid syntax of the registered `--color` property. > > The WPT test mentioned also confirms this: https://github.com/web-platform-tests/wpt/blob/master/css/css-pseudo/highlight-cascade/highlight-cascade-003.html#L8-L14 > > <style> > @property --bg { > syntax: "<color>"; > inherits: false; > initial-value: green; > } > :root::selection { > background-color: var(--bg, red); > } > </style> > <main>PASS if background-color is green when selected</main> > > Why would it be green if fallback value of red is a valid `<color>`? In those two cases, the _initial value_ of the custom properties is taken, as it is a valid `<color>` value. So the fallback values are disregarded there. Put the other way round, if you have this: ```css @property --foo { syntax: "<length>"; inherits: false; initial-value: 100px; } :root { background-color: var(--foo, yellowgreen); } ``` the background should be yellowgreen because the `--foo` property is invalid at computed value time while the fallback value `yellowgreen` is a valid value for `background-color`. At least that's what was resolved on. Though browsers currently fail to apply the fallback value because they validate it against `--foo`'s `<length>` syntax. Sebastian -- GitHub Notification of comment by SebastianZ Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/10455#issuecomment-2738347180 using your GitHub account -- Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config
Received on Wednesday, 19 March 2025 22:39:45 UTC