Fix align support in block themes

[tomusborne]

Closes #87

Previously we were checking get_theme_support( 'align-wide' ) to see if we should include the wide/full alignment options in the Container block.

However, block-based themes don't use add_theme_support() (https://fullsiteediting.com/lessons/global-styles/#h-layout-and-content-width), so this check was failing for them.

This PR ditches the get_theme_support() check and uses getBlockSupport() (https://github.com/WordPress/gutenberg/blob/1da217e8a57803e2c9183316cdef3d09c618ffcb/packages/blocks/src/store/selectors.js#L264) with an empty block name and true as the default value. This seems to allow us to artificially set support for align to true only when we need it.

It should:

1. Show the alignment option in the toolbar for "classic" themes using add_theme_support() (GeneratePress)
2. Show the alignment option in the toolbar for block-based themes (https://wordpress.org/themes/tt1-blocks/)
3. Not show the alignment option for "classic" themes if add_theme_support( 'align-wide' ) is not set
4. Not show the alignment option for block-based themes if the layout options aren't set in theme.json: https://github.com/WordPress/theme-experiments/blob/master/tt1-blocks/theme.json#L111-L114

It would obviously be easier if we could set the align supports option to true in block registration, but then we would:

1. Have wide/full alignment for grid items which isn't possible
2. Not have control over where in the toolbar the option appears

[JeanPaiva]

All good.

[bradhogan]

What was the solution to this? I'm also running into an issue when I have theme.json and add_theme_support( 'align-wide' ); with the align wide and full options not appearing in the editor.

[markdavies]

I'm still seeing this issue as well. add_theme_support( 'align-wide' ); has no effect for image blocks

[flmuel]

The theme.json overrides features added via add_theme_support(). This is known and ok. But strangely the theme.json overwrites also the function "align-wide" although this is not defined in the schema or can't be configured there at all.

The problem lies in the merging of the settings. The error is in the function "get_theme_data()" in the "WP_Theme_JSON_Resolver" class -> https://github.com/WordPress/WordPress/blob/master/wp-includes/class-wp-theme-json-resolver.php#L195 where "Theme Support" settings are mapped to the SCHEMA. So "align-wide" and possibly other features are simply removed here.
Obviously, only these (false) merged settings from get_merged_data() are then used for the editor.

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Long story short -> you have to define minimum "contentSize" child attribute of "layout" in theme.json to display the "Full width" button in Align...
Then you also don't have to add theme support for "align-wide".

[Zsolt-R]

This problem reappeared in Gutenberg version 15.1.0
With a clean installation, created a test child theme containing:

• style.css
• index.php
• functions.php with add_theme_support( 'align-wide' );

Create a new page and insert a cover block and you have the align wide/full controls, then add a basic theme.json with only this content:
{ "$schema": "https://schemas.wp.org/trunk/theme.json", "version": 2, "settings": { "layout": { "contentSize": "650px", "wideSize": "1200px" } } }
the align wide/full disappears from all the blocks that had alignments.

[strarsis]

@Zsolt-R: +1, same issue again with latest Gutenberg!