Layout Support appears to be incomplete

Thanks for submitting. I tried to recreate with DG 3 and Drupal 10 with the Gutenberg starter theme and I cannot recreate it.

Maybe I just miss out on the part of the UI you're thinking about?

Hi Thor,

I also couldn't replicate the issue in the latest version, and on doing some further investigation, a fix for the missing styles was added in this commit.

I think my tests at the time of writing were based off 3.0.0-beta5 which didn't have the fix, and was only added in 3.0.0-beta6.

The LayoutProcessor::isSupported() review part was added for a reason though, I haven't worked on the 3.x branch in a while, but I'll be sure to update the issue summary accordingly if I run into any specific issues when I attempt an upgrade.

Upon upgrading to the latest 3.0.5 version, I was finally able to replicate what my original issue was.

And can be replicated by creating the attached piece of content → on a WordPress installation running Gutenberg 10.7.0 (equivalent of Drupal's v2.14) and WP 5.9, then later viewing the same content after updating to Gutenberg 16.7.0 (equivalent of Drupal's 3.0.5).

The frontend styles and HTML has changed enough that it no longer uses margins for the spacing, however, those same classes are currently missing in the current Drupal implementation and messes up the layout:

The expected layout should be something along the lines of this:

Work done so far in the MR provides a way to provide theme.json support in Drupal (it can be added as a theme.json file or the <theme>.gutenberg.theme.yml file.

But requires pulling in a bunch of WordPress code in in order to properly render and manipulate the blocks as WordPress does.
This provides the side effect of us essentially needing to reimplement a lightweight version of the wordpress filter system in order to get things to function as they should.