Re: [csswg-drafts] Proposal: grid-guideline property for visualizing grid lines in development (#12921)

I totally forgot about [`document.designMode`](https://html.spec.whatwg.org/multipage/interaction.html#making-entire-documents-editable:-the-designmode-idl-attribute), but discovering this author-controlled state from CSS/Selectors – e.g. `:root:read-write`? – would be different from discovering the user-controlled state of Developer Tools being active. 

Perhaps – and I’m not sure this is a good idea at all – a viable approach for some related use cases would be a couple of new system color keywords that would always compute to `transparent`. Only in “design mode”, ”debug mode ”, “edit mode” or “user input mode”, they would become a visible, implementation-dependent color:

- `Invisible` or `InvisibleBackground`
- `InvisibleText` or `InvisibleCharacters` for 8874
- `InvisibleRule`, `InvisibleBorder` or `InvisibleFrame` to solve this issue when used within `rule`

Optionally, new properties similar to [`accent-color`](https://drafts.csswg.org/css-ui-4/#widget-accent) could influence the looks at the behest of authors, cf. #11199.

Alas, I assume some authors would also want to have lengths that come to `0px` unless in that special mode, and I don’t feel good alt handling that by special values. 

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Received on Sunday, 12 October 2025 14:03:40 UTC