WordPress/wp-includes/theme-templates.php

<?php

/**
 * Generates a unique slug for templates.
 *
 * @access private
 * @since 5.8.0
 *
 * @param string $override_slug The filtered value of the slug (starts as `null` from apply_filter).
 * @param string $slug          The original/un-filtered slug (post_name).
 * @param int    $post_ID       Post ID.
 * @param string $post_status   No uniqueness checks are made if the post is still draft or pending.
 * @param string $post_type     Post type.
 * @return string The original, desired slug.
 */
function wp_filter_wp_template_unique_post_slug( $override_slug, $slug, $post_ID, $post_status, $post_type ) {
	if ( 'wp_template' !== $post_type ) {
		return $override_slug;
	}

	if ( ! $override_slug ) {
		$override_slug = $slug;
	}

	// Template slugs must be unique within the same theme.
	// TODO - Figure out how to update this to work for a multi-theme
	// environment.  Unfortunately using `get_the_terms` for the 'wp-theme'
	// term does not work in the case of new entities since is too early in
	// the process to have been saved to the entity.  So for now we use the
	// currently activated theme for creation.
	$theme = wp_get_theme()->get_stylesheet();
	$terms = get_the_terms( $post_ID, 'wp_theme' );
	if ( $terms && ! is_wp_error( $terms ) ) {
		$theme = $terms[0]->name;
	}

	$check_query_args = array(
		'post_name__in'  => array( $override_slug ),
		'post_type'      => $post_type,
		'posts_per_page' => 1,
		'no_found_rows'  => true,
		'post__not_in'   => array( $post_ID ),
		'tax_query'      => array(
			array(
				'taxonomy' => 'wp_theme',
				'field'    => 'name',
				'terms'    => $theme,
			),
		),
	);
	$check_query      = new WP_Query( $check_query_args );
	$posts            = $check_query->get_posts();

	if ( count( $posts ) > 0 ) {
		$suffix = 2;
		do {
			$query_args                  = $check_query_args;
			$alt_post_name               = _truncate_post_slug( $override_slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
			$query_args['post_name__in'] = array( $alt_post_name );
			$query                       = new WP_Query( $query_args );
			$suffix++;
		} while ( count( $query->get_posts() ) > 0 );
		$override_slug = $alt_post_name;
	}

	return $override_slug;
}

/**
 * Print the skip-link script & styles.
 *
 * @access private
 * @since 5.8.0
 *
 * @return void
 */
function the_block_template_skip_link() {

	// Early exit if not an FSE theme.
	if ( ! current_theme_supports( 'block-templates' ) ) {
		return;
	}
	?>

	<?php
	/**
	 * Print the skip-link styles.
	 */
	?>
	<style id="skip-link-styles">
		.skip-link.screen-reader-text {
			border: 0;
			clip: rect(1px,1px,1px,1px);
			clip-path: inset(50%);
			height: 1px;
			margin: -1px;
			overflow: hidden;
			padding: 0;
			position: absolute !important;
			width: 1px;
			word-wrap: normal !important;
		}

		.skip-link.screen-reader-text:focus {
			background-color: #eee;
			clip: auto !important;
			clip-path: none;
			color: #444;
			display: block;
			font-size: 1em;
			height: auto;
			left: 5px;
			line-height: normal;
			padding: 15px 23px 14px;
			text-decoration: none;
			top: 5px;
			width: auto;
			z-index: 100000;
		}
	</style>
	<?php
	/**
	 * Print the skip-link script.
	 */
	?>
	<script>
	( function() {
		var skipLinkTarget = document.querySelector( 'main' ),
			parentEl,
			skipLinkTargetID,
			skipLink;

		// Early exit if a skip-link target can't be located.
		if ( ! skipLinkTarget ) {
			return;
		}

		// Get the site wrapper.
		// The skip-link will be injected in the beginning of it.
		parentEl = document.querySelector( '.wp-site-blocks' ) || document.body,

		// Get the skip-link target's ID, and generate one if it doesn't exist.
		skipLinkTargetID = skipLinkTarget.id;
		if ( ! skipLinkTargetID ) {
			skipLinkTargetID = 'wp--skip-link--target';
			skipLinkTarget.id = skipLinkTargetID;
		}

		// Create the skip link.
		skipLink = document.createElement( 'a' );
		skipLink.classList.add( 'skip-link', 'screen-reader-text' );
		skipLink.href = '#' + skipLinkTargetID;
		skipLink.innerHTML = '<?php esc_html_e( 'Skip to content' ); ?>';

		// Inject the skip link.
		parentEl.insertAdjacentElement( 'afterbegin', skipLink );
	}() );
	</script>
	<?php
}

// By default, themes support block templates.
add_theme_support( 'block-templates' );