Editor: Apply duotone presets with slugs that are not kebab-case on the front end

[maheshbohara]

A duotone preset whose slug is not already kebab-case (for example blueOrange or duotone1) works in the block editor but is not applied on the front end.

WP_Duotone::get_all_global_styles_presets() registers presets under a kebab-cased filter ID, but two other places use the raw slug:

• get_slug_from_attribute() returns the slug exactly as written in the block attribute, so the lookup in is_preset() fails.
• get_global_styles_presets() names the CSS custom property after the raw slug.

This PR converts the slug to kebab-case in both, so the class name, SVG filter ID, CSS custom property and block CSS all use the same form. Slugs that are already kebab-case are unchanged.

Before

Preset blueOrange applied to an Image block (var:preset|duotone|blueOrange): the preset is not recognised, the attribute is treated as a raw CSS value, and no SVG filter is printed.

<figure class="wp-block-image wp-duotone-varpresetduotoneblueorange-1">

.wp-duotone-varpresetduotoneblueorange-1.wp-block-image img { filter: var:preset|duotone|blueOrange; }

The same preset applied through global styles: since [63641] the reference is kebab-cased, but the custom property is still defined with the raw slug, so it never resolves.

:root { --wp--preset--duotone--blueOrange: url(#wp-duotone-blue-orange); }
.wp-duotone-blue-orange.wp-block-image img { filter: var(--wp--preset--duotone--blue-orange); }

After

<figure class="wp-block-image wp-duotone-blue-orange">

:root { --wp--preset--duotone--blue-orange: url(#wp-duotone-blue-orange); }
.wp-duotone-blue-orange.wp-block-image img { filter: var(--wp--preset--duotone--blue-orange); }

and <filter id="wp-duotone-blue-orange"> is printed in the footer.

Testing

1. In a block theme's theme.json, add a duotone preset with a camelCase slug:

   "settings": { "color": { "duotone": [
   	{ "slug": "blueOrange", "name": "Blue Orange", "colors": [ "#0000ff", "#ffa500" ] }
   ] } }

2. Add an Image block to a post, apply the "Blue Orange" duotone filter and save.
3. View the post on the front end. Before this change the image has no filter; after it the filter is applied.

Unit tests:

npm run test:php -- tests/phpunit/tests/block-supports/duotone.php

The new test_render_duotone_support_preset_with_non_kebab_case_slug covers a camelCase slug referenced both ways, a slug with a trailing number, and a kebab-case slug as a control. New cases were also added to the get_slug_from_attribute and is_preset data providers.

One existing expectation changed: a reference whose slug is only . now yields an empty slug instead of ., because kebab-casing removes it. It was not a valid preset before either.

Note

lib/class-wp-duotone-gutenberg.php in the Gutenberg plugin has the same two lines and would need the same change.

Trac ticket: https://core.trac.wordpress.org/ticket/66285

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus
Used for: Investigating and reproducing the bug, and drafting the patch, unit tests and this description. I reviewed the changes and ran the tests locally.

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