[csswg-drafts] [css-conditional] testing support of properties and values with partial implementations (#3559)

rachelandrew has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-conditional] testing support of properties and values with partial implementations ==
There are a few places where `@supports` is unable to help authors as the property and value they want to test for is supported by the user agent, but not in the context they want to use it.

The obvious one (and where it keeps coming up at the moment) is testing support of any of the gap properties `column-gap`, `row-gap` or `gap`. I can test for support of `column-gap` and every browser will tell me it has support, however if I then try to use it in flexbox, I will only get a gap in Firefox, as that is the only user agent to have an implementation right now.

This means authors can't create a nice fallback with margins, then removing the margin on testing for support. It is likely that other box alignment properties - perhaps as browsers start to implement them for block layout, will have the same issue.

Other places this might be an issue are for fragmentation, I might want to test if fragmentation properties are available in a certain context.

It feels as if we need a way to ask for support of, for example, `column: gap` in `display: flex`. I don't know if that is even feasible in implementations, but it seems that this is likely to continue to be an issue as specs become more modular. 

I found an older issue which also refers to partial implementations not being testable: https://github.com/w3c/csswg-drafts/issues/1167 


Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3559 using your GitHub account

Received on Saturday, 26 January 2019 08:50:16 UTC