Try fixing responsive layout in Nav block

[tellthemachines]

What?

Part of #77817.

Viewport-specific layout styles in the Navigation block don't work due to the complex nest of custom properties that enables the inner container to receive the layout attributes. It also doesn't help that both root block class and layout attribute classes for justification etc.. are output on the inner as well as the outer containers.

This PR tries to fix the issue by outputting viewport-specific custom properties and adding the generated wp-block-navigation-x classname to the inner container on the front end.

This is similar to the approach in #79984 where we make Gallery responsible for outputting responsive versions of its custom styles.

I briefly looked into upgrading Nav to a more default layout logic by allowing the layout support to target the correct wrapper for layout classnames, but this isn't straightforward to do because Nav is a sort of reusable block, so its markup isn't fully available to layout. Also, we'd likely have to preserve the duplicate classnames and custom properties for back compat reasons, which means viewport states would still require custom logic to work properly.

Testing Instructions

1. Add a Nav block to a post, enable responsive styles and try changing the layout styles in Tablet or Mobile viewport.
2. Save and check the viewport-specific changes apply correctly in both editor and front end.

Testing Instructions for Keyboard

Screenshots or screencast

responsive-nav.mp4

Use of AI Tools

used codex/gpt 5.6

[github-actions]

Size Change: +498 B (+0.01%)

Total Size: 7.72 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-library/index.min.js	351 kB	+498 B (+0.14%)

_{compressed-size-action}

[github-actions]

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Co-authored-by: tellthemachines <isabel_brison@git.wordpress.org>
Co-authored-by: talldan <talldanwp@git.wordpress.org>

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[talldan]

Works well for me. This is seems like a really useful fix, as it essentially gives users 'stack on mobile' if they don't want to use the overlay menu (maybe they have a really small menu).

A couple of optional code style comments, I leave those up to you, nothing blocking.

[talldan]

It's really minor, but #79072 uses a filter for a similar situation (block_core_navigation_add_state_class_to_container).

I wonder if we could consolidate the two together (just one block_core_navigation_process_style_state function). Or alternatively keep it seperate, but make the two work similarly, both use filters or both called as part of the render.

[tellthemachines]

I tried consolidating both functions. There's a fair bit of custom logic in each so it's not a huge economy in terms of lines of code but it means everything state-related is now in the same function and the same filter.

[talldan]

Nit: I see what it's doing here, but it seems like a harder to read way of doing it vs. something like:

if ( method_exists( 'WP_Theme_JSON_Gutenberg', 'get_viewport_media_queries' ) ) {
    $responsive_media_queries = WP_Theme_JSON_Gutenberg::get_viewport_media_queries( $viewport_settings );
} elseif ( method_exists( 'WP_Theme_JSON', 'get_viewport_media_queries' ) ) {
  $responsive_media_queries = WP_Theme_JSON::get_viewport_media_queries( $viewport_settings );
}

Also more lines of code.

[github-actions]

Flaky tests detected in 5f60fb0.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/29477134195
📝 Reported issues:

• [Flaky Test] should update the HTML only for the latest navigation #78835 in /test/e2e/specs/interactivity/router-navigate.spec.ts

[github-actions]

I just cherry-picked this PR to the wp/7.1 branch to get it included in the next release: 291e373

[t-hamano]

I just cherry-picked this PR to the release/23.6 branch to get it included in the next release: c8ed1ac