Block Supports: Add PHP helpers for block support classes and styles

[aaronrobertshaw]

Backport of Gutenberg PRs

• Border: Add a PHP helper for block support classes and styles gutenberg#84207,
• Shadow: Add a PHP helper for block support classes and styles gutenberg#84205,
• Spacing: Add a PHP helper for block support classes and styles gutenberg#84208,
• Colour: Add a PHP helper for block support classes and styles gutenberg#84206 and
• Background: Add a PHP helper for block support classes and styles gutenberg#84209

Trac ticket: https://core.trac.wordpress.org/ticket/66269

Adds PHP helpers that turn block attributes into a block support's classes and styles, like the JS get*ClassesAndStyles() functions, and moves the block supports onto them.

This PR backports:

• wp_get_border_classes_and_styles(), wp_get_shadow_classes_and_styles(), wp_get_spacing_classes_and_styles(), wp_get_color_classes_and_styles() and wp_get_background_classes_and_styles(),
• wp_apply_border_support(), wp_apply_shadow_support(), wp_apply_spacing_support(), wp_apply_colors_support() and wp_render_background_support() built on them,
• and the accompanying block supports tests.

The block changes that call these helpers (Avatar, Post Featured Image, Icon, Post Navigation Link, Navigation Submenu, Comment Author Avatar, Calendar and Button) arrive later with the Gutenberg package update.

Dependency: #13491 (background clip). This branch is based on it, so it shows that commit until #13491 merges.

Testing instructions

The block support output should be identical to #13491 on its own. To compare, register a dynamic test block and render it on each branch:

npm run env:cli -- eval "register_block_type( 'test/helpers', array( 'api_version' => 3, 'supports' => array( 'color' => array( 'text' => true, 'background' => true ), '__experimentalBorder' => array( 'color' => true, 'radius' => true, 'style' => true, 'width' => true ), 'shadow' => true, 'spacing' => array( 'padding' => true, 'margin' => true ), 'background' => array( 'backgroundImage' => true, 'gradient' => true ) ), 'render_callback' => static function () { return '<div ' . get_block_wrapper_attributes() . '></div>'; } ) ); echo do_blocks( '<!-- wp:test/helpers {\"borderColor\":\"contrast\",\"textColor\":\"base\",\"backgroundColor\":\"accent\",\"style\":{\"border\":{\"radius\":\"8px\",\"width\":\"2px\",\"style\":\"solid\",\"top\":{\"width\":\"4px\",\"color\":\"#3858e9\",\"style\":\"dashed\"}},\"shadow\":\"6px 6px 9px #00000033\",\"spacing\":{\"padding\":{\"top\":\"20px\",\"left\":\"var:preset|spacing|40\"},\"margin\":{\"top\":\"10px\"}},\"background\":{\"backgroundImage\":{\"url\":\"https://example.com/image.jpg\"},\"backgroundSize\":\"contain\"}}} /-->' );"

Both branches output:

<div style="border-radius:8px;border-style:solid;border-width:2px;border-top-width:4px;border-top-color:#3858e9;border-top-style:dashed;padding-top:20px;padding-left:var(--wp--preset--spacing--40);margin-top:10px;box-shadow:6px 6px 9px #00000033;background-image:url(&apos;https://example.com/image.jpg&apos;);background-position:50% 50%;background-size:contain;" class="wp-block-test-helpers has-text-color has-base-color has-background has-accent-background-color has-border-color has-contrast-border-color"></div>

Use of AI

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5.5
Used for: the port from Gutenberg and the tests; I reviewed and edited them.

[github-actions]

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[aaronrobertshaw]

I've been held up on some other priorities so this one will now be aimed for WP 7.3