var function inside attribute selectors

[bertdida]

I propose to allow var function inside attribute selectors, something like [attribute=var(--variable)].

[tabatkins]

Unfortunately, this isn't possible. Variables draw their values from custom properties, and so you need to have some element to get those from. But selectors obviously don't have an element associated with them; they select the elements! So, you can't use a var() like this.

That said, env() will allow this once custom environment variables are defined; they aren't associated with any element (they're global values instead).