Global Styles: Switching styles takes a while on the frontend

[jasmussen]

Switching to an alternate style variation, inside the editor, is instant. Click one of the tiles and the visual is shown immediately:

If you then save the changes and preview the site frontend, however, the styles take a while to settle in. The following GIF shows changing a style, opening the frontend in a new tab, and then reloading the page over and over to see what takes:

Note that the typography and a few of the style changes are immediately shown. But things like background colors take a while, up to several minutes. Clearing the cache doesn't make any difference.

Steps to reproduce:

• Use a block theme, such as TT3 or TT2
• Go to the site editor
• Switch to a different style variation (Click global styles > Browse styles > Pick one). Save the changes.
• Click view > View site. Note that the new styles aren't applied immediately. Wait up to several minutes to reload. Eventually the whole style is applied.

Tested in Chrome on Mac.

[jasmussen]

Just to confirm, this is running latest trunk Gutenberg and TT3.

[Mamaduka]

Probably a duplicate of #43395, or the cause might be the same.

[jasmussen]

Excellent, thank you!

Closing in favor of #43395.

[jasmussen]

Reopening as this issue does appear to be separate from #43395 after all.

[Mamaduka]

The improvements proposed by @spacedmonkey in #56910 will also fix this issue.

The missing cache invalidation for wp_get_global_stylesheet is the cause of this problem.

[Mamaduka]

@jasmussen, I'm thinking of bumping this issue to WP 6.2.

The problem has been around since WP 6.0, and I think we both prefer to solve it with better cache invalidation proposed in #56910.

[jasmussen]

No objections from my part. It's a good one to fix, but definitely let's do it right.

[oandregal]

@mmtr has a PR that fixes this at #45679

There's an issue with the test but we're looking at fixing that the next week (not in time for 6.1.1).