[wp-trac] [WordPress Trac] #52623: Proposal: Add CSS variable for admin-bar height to core.

[WordPress Trac]

#52623: Proposal: Add CSS variable for admin-bar height to core.
-------------------------+-----------------------
 Reporter:  nico23       |       Owner:  ryelle
     Type:  enhancement  |      Status:  assigned
 Priority:  normal       |   Milestone:  5.8
Component:  Themes       |     Version:  trunk
 Severity:  minor        |  Resolution:
 Keywords:  has-patch    |     Focuses:  ui, css
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Changes (by ryelle):

 * owner:  (none) => ryelle
 * status:  new => assigned
 * milestone:  Awaiting Review => 5.8


Comment:

 Thanks for kicking this off with your PR @nico23!

 There's some ongoing [https://make.wordpress.org/core/2021/01/29
 /introducing-css-custom-properties/ custom property discussion] regarding
 colors, but I think this would be a good, self-contained use case to get
 support for custom properties into core.

 We do support IE11, so in addition to adding the variable, we'll want to
 add a **PostCSS plugin for fallbacks**. There are two I know of, and both
 have drawbacks.

 - `postcss-custom-properties` is one option, but it doesn't support
 properties that are updated in media queries.
 - `postcss-css-variables` is another - this one does support media
 queries, but it also has a bug where it generates duplicate styles, so
 we'd need to also add `postcss-discard-duplicates`. This is the approached
 [https://core.trac.wordpress.org/browser/trunk/src/wp-
 content/themes/twentytwentyone/postcss.config.js that was used in Twenty
 Twenty-One].
 - Another suggestion?

 It's possible we'll drop support for IE11 (see #49696), but the timeline
 there is up in the air, so it's best to proceed assuming we need to
 support it.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/52623#comment:3>
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