[wp-trac] [WordPress Trac] #58550: Update layout block support definitions to be handled by a function, stabilise the block support

[WordPress Trac]

#58550: Update layout block support definitions to be handled by a function,
stabilise the block support
--------------------------+--------------------
 Reporter:  andrewserong  |      Owner:  (none)
     Type:  enhancement   |     Status:  new
 Priority:  normal        |  Milestone:  6.3
Component:  General       |    Version:  trunk
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Backport changes from the Gutenberg repo relating to stabilising the
 layout block support.

 Two changes that would be good to group together include moving the layout
 definitions from being stored in `theme.json` to being output by a PHP
 function, and stabilising the block support by looking layout support via
 the `layout` key with a fallback to `__experimentalLayout`.

 These changes landed in the Gutenberg plugin in the following PRs:

 * Move layout definitions:
 https://github.com/WordPress/gutenberg/pull/50621
 * Stabilise layout block support:
 https://github.com/WordPress/gutenberg/pull/51434

 Due to the relationship between the PHP and JS changes for moving layout
 definitions, backporting the above changes should likely land just after
 or at the same time as landing the JS packages update for WordPress 6.3.

 A note: moving the layout definitions is technically a breaking change in
 case there were any themes or plugins attempting to override the layout
 definitions in `theme.json`. This is unlikely to be common, as overriding
 layout definitions was both discouraged and the ability to do so was
 undocumented and would likely have broken block themes that attempted to
 do it.

 Assuming the backports are approved and land for 6.3, I'll write up a dev
 note covering the change.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/58550>
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