ue the stylesheet on render.
if ( wp_should_load_block_assets_on_demand() ) {
add_filter(
'render_block',
static function ( $html, $block ) use ( $block_name, $style_properties ) {
if ( $block['blockName'] === $block_name ) {
wp_enqueue_style( $style_properties['style_handle'] );
}
return $html;
},
10,
2
);
} else {
wp_enqueue_style( $style_properties['style_handle'] );
}
}
if ( isset( $style_properties['inline_style'] ) ) {
// Default to "wp-block-library".
$handle = 'wp-block-library';
// If the site loads block styles on demand, check if the block has a stylesheet registered.
if ( wp_should_load_block_assets_on_demand() ) {
$block_stylesheet_handle = generate_block_asset_handle( $block_name, 'style' );
if ( isset( $wp_styles->registered[ $block_stylesheet_handle ] ) ) {
$handle = $block_stylesheet_handle;
}
}
// Add inline styles to the calculated handle.
wp_add_inline_style( $handle, $style_properties['inline_style'] );
}
}
}
}
/**
* Function responsible for enqueuing the assets required for block styles functionality on the editor.
*
* @since 5.3.0
*/
function enqueue_editor_block_styles_assets() {
$block_styles = WP_Block_Styles_Registry::get_instance()->get_all_registered();
$register_script_lines = array( '( function() {' );
foreach ( $block_styles as $block_name => $styles ) {
foreach ( $styles as $style_properties ) {
$block_style = array(
'name' => $style_properties['name'],
'label' => $style_properties['label'],
);
if ( isset( $style_properties['is_default'] ) ) {
$block_style['isDefault'] = $style_properties['is_default'];
}
$register_script_lines[] = sprintf(
' wp.blocks.registerBlockStyle( \'%s\', %s );',
$block_name,
wp_json_encode( $block_style, JSON_HEX_TAG | JSON_UNESCAPED_SLASHES )
);
}
}
$register_script_lines[] = '} )();';
$inline_script = implode( "\n", $register_script_lines );
wp_register_script( 'wp-block-styles', false, array( 'wp-blocks' ), true, array( 'in_footer' => true ) );
wp_add_inline_script( 'wp-block-styles', $inline_script );
wp_enqueue_script( 'wp-block-styles' );
}
/**
* Enqueues the assets required for the block directory within the block editor.
*
* @since 5.5.0
*/
function wp_enqueue_editor_block_directory_assets() {
wp_enqueue_script( 'wp-block-directory' );
wp_enqueue_style( 'wp-block-directory' );
}
/**
* Enqueues the assets required for the format library within the block editor.
*
* @since 5.8.0
*/
function wp_enqueue_editor_format_library_assets() {
wp_enqueue_script( 'wp-format-library' );
wp_enqueue_style( 'wp-format-library' );
}
/**
* Formats `' );
$processor->next_tag();
foreach ( $attributes as $name => $value ) {
/*
* Lexical variations of an attribute name may represent the
* same attribute in HTML, therefore it’s possible that the
* input array might contain duplicate attributes even though
* it’s keyed on their name. Calling code should rewrite an
* attribute’s value rather than sending a duplicate attribute.
*
* Example:
*
* array( 'id' => 'main', 'ID' => 'nav' )
*
* In this example, there are two keys both describing the `id`
* attribute. PHP array iteration is in key-insertion order so
* the 'id' value will be set in the SCRIPT tag.
*/
if ( null !== $processor->get_attribute( $name ) ) {
continue;
}
$processor->set_attribute( $name, $value ?? true );
}
return "{$processor->get_updated_html()}\n";
}
/**
* Prints formatted `" );' );
*
* // This data is unsafe and `text/plain` cannot be escaped.
* // The following will return `""` to indicate failure:
* wp_get_inline_script_tag( '', array( 'type' => 'text/plain' ) );
*
* @since 5.7.0
* @since 7.0.0 Returns an empty string if the data cannot be safely embedded in a script tag.
*
* @param string $data Data for script tag: JavaScript, importmap, speculationrules, etc.
* @param array $attributes Optional. Key-value pairs representing `' );
$processor->next_tag();
foreach ( $attributes as $name => $value ) {
/*
* Lexical variations of an attribute name may represent the
* same attribute in HTML, therefore it’s possible that the
* input array might contain duplicate attributes even though
* it’s keyed on their name. Calling code should rewrite an
* attribute’s value rather than sending a duplicate attribute.
*
* Example:
*
* array( 'id' => 'main', 'ID' => 'nav' )
*
* In this example, there are two keys both describing the `id`
* attribute. PHP array iteration is in key-insertion order so
* the 'id' value will be set in the SCRIPT tag.
*/
if ( null !== $processor->get_attribute( $name ) ) {
continue;
}
$processor->set_attribute( $name, $value ?? true );
}
if ( ! $processor->set_modifiable_text( $data ) ) {
_doing_it_wrong(
__FUNCTION__,
__( 'Unable to set inline script data.' ),
'7.0.0'
);
return '';
}
return "{$processor->get_updated_html()}\n";
}
/**
* Prints an inline script tag.
*
* It is possible to inject attributes in the `" from
* around an inline script after trimming whitespace. Typically this
* is used in conjunction with output buffering, where `ob_get_clean()`
* is passed as the `$contents` argument.
*
* Example:
*
* // Strips exact literal empty SCRIPT tags.
* $js = ';
* 'sayHello();' === wp_remove_surrounding_empty_script_tags( $js );
*
* // Otherwise if anything is different it warns in the JS console.
* $js = '';
* 'console.error( ... )' === wp_remove_surrounding_empty_script_tags( $js );
*
* @since 6.4.0
* @access private
*
* @see wp_print_inline_script_tag()
* @see wp_get_inline_script_tag()
*
* @param string $contents Script body with manually created SCRIPT tag literals.
* @return string Script body without surrounding script tag literals, or
* original contents if both exact literals aren't present.
*/
function wp_remove_surrounding_empty_script_tags( $contents ) {
$contents = trim( $contents );
$opener = '';
if (
strlen( $contents ) > strlen( $opener ) + strlen( $closer ) &&
strtoupper( substr( $contents, 0, strlen( $opener ) ) ) === $opener &&
strtoupper( substr( $contents, -strlen( $closer ) ) ) === $closer
) {
return substr( $contents, strlen( $opener ), -strlen( $closer ) );
} else {
$error_message = __( 'Expected string to start with script tag (without attributes) and end with script tag, with optional whitespace.' );
_doing_it_wrong( __FUNCTION__, $error_message, '6.4' );
return sprintf(
'console.error(%s)',
wp_json_encode(
sprintf(
/* translators: %s: wp_remove_surrounding_empty_script_tags() */
__( 'Function %s used incorrectly in PHP.' ),
'wp_remove_surrounding_empty_script_tags()'
) . ' ' . $error_message
)
);
}
}
/**
* Adds hooks to load block styles on demand in classic themes.
*
* This function must be called before {@see wp_default_styles()} and {@see register_core_block_style_handles()} so that
* the filters are added to cause {@see wp_should_load_separate_core_block_assets()} to return true.
*
* @since 6.9.0
* @since 7.0.0 This is now invoked at the `wp_default_styles` action with priority 0 instead of at `init` with priority 8.
*
* @see _add_default_theme_supports()
*/
function wp_load_classic_theme_block_styles_on_demand(): void {
// This is not relevant to block themes, as they are opted in to loading separate styles on demand via _add_default_theme_supports().
if ( wp_is_block_theme() ) {
return;
}
/*
* Make sure that wp_should_output_buffer_template_for_enhancement() returns true even if there aren't any
* `wp_template_enhancement_output_buffer` filters added, but do so at priority zero so that applications which
* wish to stream responses can more easily turn this off.
*/
add_filter( 'wp_should_output_buffer_template_for_enhancement', '__return_true', 0 );
// If a site has opted out of the template enhancement output buffer, then bail.
if ( ! wp_should_output_buffer_template_for_enhancement() ) {
return;
}
// The following two filters are added by default for block themes in _add_default_theme_supports().
/*
* Load separate block styles so that the large block-library stylesheet is not enqueued unconditionally, and so
* that block-specific styles will only be enqueued when they are used on the page. A priority of zero allows for
* this to be easily overridden by themes which wish to opt out. If a site has explicitly opted out of loading
* separate block styles, then abort.
*/
add_filter( 'should_load_separate_core_block_assets', '__return_true', 0 );
if ( ! wp_should_load_separate_core_block_assets() ) {
return;
}
/*
* Also ensure that block assets are loaded on demand (although the default value is from should_load_separate_core_block_assets).
* As above, a priority of zero allows for this to be easily overridden by themes which wish to opt out. If a site
* has explicitly opted out of loading block styles on demand, then abort.
*/
add_filter( 'should_load_block_assets_on_demand', '__return_true', 0 );
if ( ! wp_should_load_block_assets_on_demand() ) {
return;
}
// Add hooks which require the presence of the output buffer. Ideally the above two filters could be added here, but they run too early.
add_action( 'wp_template_enhancement_output_buffer_started', 'wp_hoist_late_printed_styles' );
}
/**
* Adds the hooks needed for CSS output to be delayed until after the content of the page has been established.
*
* @since 6.9.0
*
* @see wp_load_classic_theme_block_styles_on_demand()
* @see _wp_footer_scripts()
*/
function wp_hoist_late_printed_styles(): void {
// Skip the embed template on-demand styles aren't relevant, and there is no wp_head action.
if ( is_embed() ) {
return;
}
/*
* Add a placeholder comment into the inline styles for wp-block-library, after which the late block styles
* can be hoisted from the footer to be printed in the header by means of a filter below on the template enhancement
* output buffer.
*
* Note that wp_maybe_inline_styles() prepends the inlined style to the extra 'after' array, which happens after
* this code runs. This ensures that the placeholder appears right after any inlined wp-block-library styles,
* which would be common.css.
*/
$placeholder = sprintf( '/*%s*/', uniqid( 'wp_block_styles_on_demand_placeholder:' ) );
$dependency = wp_styles()->query( 'wp-block-library', 'registered' );
if ( $dependency ) {
if ( ! isset( $dependency->extra['after'] ) ) {
wp_add_inline_style( 'wp-block-library', $placeholder );
} else {
array_unshift( $dependency->extra['after'], $placeholder );
}
}
/*
* Create a substitute for `print_late_styles()` which is aware of block styles. This substitute does not print
* the styles, but it captures what would be printed for block styles and non-block styles so that they can be
* later hoisted to the HEAD in the template enhancement output buffer. This will run at `wp_print_footer_scripts`
* before `print_footer_scripts()` is called.
*/
$printed_core_block_styles = '';
$printed_other_block_styles = '';
$printed_global_styles = '';
$printed_late_styles = '';
$capture_late_styles = static function () use ( &$printed_core_block_styles, &$printed_other_block_styles, &$printed_global_styles, &$printed_late_styles ) {
// Gather the styles related to on-demand block enqueues.
$all_core_block_style_handles = array();
$all_other_block_style_handles = array();
foreach ( WP_Block_Type_Registry::get_instance()->get_all_registered() as $block_type ) {
if ( str_starts_with( $block_type->name, 'core/' ) ) {
foreach ( $block_type->style_handles as $style_handle ) {
$all_core_block_style_handles[] = $style_handle;
}
} else {
foreach ( $block_type->style_handles as $style_handle ) {
$all_other_block_style_handles[] = $style_handle;
}
}
}
/*
* First print all styles related to core blocks which should be inserted right after the wp-block-library stylesheet
* to preserve the CSS cascade. The logic in this `if` statement is derived from `wp_print_styles()`.
*/
$enqueued_core_block_styles = array_values( array_intersect( $all_core_block_style_handles, wp_styles()->queue ) );
if ( count( $enqueued_core_block_styles ) > 0 ) {
ob_start();
wp_styles()->do_items( $enqueued_core_block_styles );
$printed_core_block_styles = (string) ob_get_clean();
}
// Capture non-core block styles so they can get printed at the point where wp_enqueue_registered_block_scripts_and_styles() runs.
$enqueued_other_block_styles = array_values( array_intersect( $all_other_block_style_handles, wp_styles()->queue ) );
if ( count( $enqueued_other_block_styles ) > 0 ) {
ob_start();
wp_styles()->do_items( $enqueued_other_block_styles );
$printed_other_block_styles = (string) ob_get_clean();
}
// Capture the global-styles so that it can be printed at the point where wp_enqueue_global_styles() runs.
if ( wp_style_is( 'global-styles' ) ) {
ob_start();
wp_styles()->do_items( array( 'global-styles' ) );
$printed_global_styles = (string) ob_get_clean();
}
/*
* Print all remaining styles not related to blocks. This contains a subset of the logic from
* `print_late_styles()`, without admin-specific logic and the `print_late_styles` filter to control whether
* late styles are printed (since they are being hoisted anyway).
*/
ob_start();
wp_styles()->do_footer_items();
$printed_late_styles = (string) ob_get_clean();
};
/*
* If `_wp_footer_scripts()` was unhooked from the `wp_print_footer_scripts` action, or if `wp_print_footer_scripts()`
* was unhooked from running at the `wp_footer` action, then only add a callback to `wp_footer` which will capture the
* late-printed styles.
*
* Otherwise, in the normal case where `_wp_footer_scripts()` will run at the `wp_print_footer_scripts` action, then
* swap out `_wp_footer_scripts()` with an alternative which captures the printed styles (for hoisting to HEAD) before
* proceeding with printing the footer scripts.
*/
$wp_print_footer_scripts_priority = has_action( 'wp_print_footer_scripts', '_wp_footer_scripts' );
if ( false === $wp_print_footer_scripts_priority || false === has_action( 'wp_footer', 'wp_print_footer_scripts' ) ) {
// The normal priority for wp_print_footer_scripts() is to run at 20.
add_action( 'wp_footer', $capture_late_styles, 20 );
} else {
remove_action( 'wp_print_footer_scripts', '_wp_footer_scripts', $wp_print_footer_scripts_priority );
add_action(
'wp_print_footer_scripts',
static function () use ( $capture_late_styles ) {
$capture_late_styles();
print_footer_scripts();
},
$wp_print_footer_scripts_priority
);
}
// Replace placeholder with the captured late styles.
add_filter(
'wp_template_enhancement_output_buffer',
static function ( $buffer ) use ( $placeholder, &$printed_core_block_styles, &$printed_other_block_styles, &$printed_global_styles, &$printed_late_styles ) {
// Anonymous subclass of WP_HTML_Tag_Processor which exposes underlying bookmark spans.
$processor = new class( $buffer ) extends WP_HTML_Tag_Processor {
/**
* Gets the span for the current token.
*
* @return WP_HTML_Span Current token span.
*/
private function get_span(): WP_HTML_Span {
// Note: This call will never fail according to the usage of this class, given it is always called after ::next_tag() is true.
$this->set_bookmark( 'here' );
return $this->bookmarks['here'];
}
/**
* Inserts text before the current token.
*
* @param string $text Text to insert.
*/
public function insert_before( string $text ): void {
$this->lexical_updates[] = new WP_HTML_Text_Replacement( $this->get_span()->start, 0, $text );
}
/**
* Inserts text after the current token.
*
* @param string $text Text to insert.
*/
public function insert_after( string $text ): void {
$span = $this->get_span();
$this->lexical_updates[] = new WP_HTML_Text_Replacement( $span->start + $span->length, 0, $text );
}
/**
* Removes the current token.
*/
public function remove(): void {
$span = $this->get_span();
$this->lexical_updates[] = new WP_HTML_Text_Replacement( $span->start, $span->length, '' );
}
/**
* Replaces the current token.
*
* @param string $text Text to replace with.
*/
public function replace( string $text ): void {
$span = $this->get_span();
$this->lexical_updates[] = new WP_HTML_Text_Replacement( $span->start, $span->length, $text );
}
};
// Locate the insertion points in the HEAD.
while ( $processor->next_tag( array( 'tag_closers' => 'visit' ) ) ) {
if (
'STYLE' === $processor->get_tag() &&
'wp-global-styles-placeholder-inline-css' === $processor->get_attribute( 'id' )
) {
/** This is added in {@see wp_enqueue_global_styles()} */
$processor->set_bookmark( 'wp_global_styles_placeholder' );
} elseif (
'STYLE' === $processor->get_tag() &&
'wp-block-styles-placeholder-inline-css' === $processor->get_attribute( 'id' )
) {
/** This is added in {@see wp_enqueue_registered_block_scripts_and_styles()} */
$processor->set_bookmark( 'wp_block_styles_placeholder' );
} elseif (
'STYLE' === $processor->get_tag() &&
'wp-block-library-inline-css' === $processor->get_attribute( 'id' )
) {
/** This is added here in {@see wp_hoist_late_printed_styles()} */
$processor->set_bookmark( 'wp_block_library' );
} elseif ( 'HEAD' === $processor->get_tag() && $processor->is_tag_closer() ) {
$processor->set_bookmark( 'head_end' );
break;
}
}
/**
* Replace the placeholder for global styles enqueued during {@see wp_enqueue_global_styles()}. This is done
* even if $printed_global_styles is empty.
*/
if ( $processor->has_bookmark( 'wp_global_styles_placeholder' ) ) {
$processor->seek( 'wp_global_styles_placeholder' );
$processor->replace( $printed_global_styles );
$printed_global_styles = '';
}
/*
* Insert block styles right after wp-block-library (if it is present). The placeholder CSS comment will
* always be added to the wp-block-library inline style since it gets printed at `wp_head` before the blocks
* are rendered. This means that there may not actually be any block styles to hoist from the footer to
* insert after this inline style. The placeholder CSS comment needs to be added so that the inline style
* gets printed, but if the resulting inline style is empty after the placeholder is removed, then the
* inline style is removed.
*/
if ( $processor->has_bookmark( 'wp_block_library' ) ) {
$processor->seek( 'wp_block_library' );
$css_text = $processor->get_modifiable_text();
/*
* Split the block library inline style by the placeholder to identify the original inlined CSS, which
* likely would be common.css, followed by any inline styles which had been added by the theme or
* plugins via `wp_add_inline_style( 'wp-block-library', '...' )`. The separate block styles loaded on
* demand will get inserted after the inlined common.css and before the extra inline styles added by the
* user.
*/
$css_text_around_placeholder = explode( $placeholder, $css_text, 2 );
$extra_inline_styles = '';
if ( count( $css_text_around_placeholder ) === 2 ) {
$css_text = $css_text_around_placeholder[0];
if ( '' !== trim( $css_text ) ) {
$inlined_src = wp_styles()->get_data( 'wp-block-library', 'inlined_src' );
if ( $inlined_src ) {
$css_text .= sprintf(
"\n/*# sourceURL=%s */\n",
esc_url_raw( $inlined_src )
);
}
}
$extra_inline_styles = $css_text_around_placeholder[1];
}
/*
* The placeholder CSS comment was added to the inline style in order to force an inline STYLE tag to
* be printed. Now that the inline style has been located and the placeholder comment has been removed, if
* there is no CSS left in the STYLE tag after removal, then remove the STYLE tag entirely.
*/
if ( '' === trim( $css_text ) ) {
$processor->remove();
} else {
$processor->set_modifiable_text( $css_text );
}
$inserted_after = $printed_core_block_styles;
$printed_core_block_styles = '';
/*
* Add a new inline style for any user styles added via wp_add_inline_style( 'wp-block-library', '...' ).
* This must be added here after $printed_core_block_styles to preserve the original CSS cascade when
* the combined block library stylesheet was used. The pattern here is checking to see if it is not just
* a sourceURL comment after the placeholder above is removed.
*/
if ( ! preg_match( ':^\s*(/\*# sourceURL=\S+? \*/\s*)?$:s', $extra_inline_styles ) ) {
$style_processor = new WP_HTML_Tag_Processor( '' );
$style_processor->next_tag();
$style_processor->set_attribute( 'id', 'wp-block-library-inline-css-extra' );
$style_processor->set_modifiable_text( $extra_inline_styles );
$inserted_after .= "{$style_processor->get_updated_html()}\n";
}
if ( '' !== $inserted_after ) {
$processor->insert_after( "\n" . $inserted_after );
}
}
// Insert block styles at the point where wp_enqueue_registered_block_scripts_and_styles() normally enqueues styles.
if ( $processor->has_bookmark( 'wp_block_styles_placeholder' ) ) {
$processor->seek( 'wp_block_styles_placeholder' );
if ( '' !== $printed_other_block_styles ) {
$processor->replace( "\n" . $printed_other_block_styles );
} else {
$processor->remove();
}
$printed_other_block_styles = '';
}
// Print all remaining styles.
$remaining_styles = $printed_core_block_styles . $printed_other_block_styles . $printed_global_styles . $printed_late_styles;
if ( $remaining_styles && $processor->has_bookmark( 'head_end' ) ) {
$processor->seek( 'head_end' );
$processor->insert_before( $remaining_styles . "\n" );
}
return $processor->get_updated_html();
}
);
}
/**
* Return the corresponding JavaScript `dataset` name for an attribute
* if it represents a custom data attribute, or `null` if not.
*
* Custom data attributes appear in an element's `dataset` property in a
* browser, but there's a specific way the names are translated from HTML
* into JavaScript. This function indicates how the name would appear in
* JavaScript if a browser would recognize it as a custom data attribute.
*
* Example:
*
* // Dash-letter pairs turn into capital letters.
* 'postId' === wp_js_dataset_name( 'data-post-id' );
* 'Before' === wp_js_dataset_name( 'data--before' );
* '-One--Two---' === wp_js_dataset_name( 'data---one---two---' );
*
* // Not every attribute name will be interpreted as a custom data attribute.
* null === wp_js_dataset_name( 'post-id' );
* null === wp_js_dataset_name( 'data' );
*
* // Some very surprising names will; for example, a property whose name is the empty string.
* '' === wp_js_dataset_name( 'data-' );
* 0 === strlen( wp_js_dataset_name( 'data-' ) );
*
* @since 6.9.0
*
* @see https://html.spec.whatwg.org/#concept-domstringmap-pairs
* @see \wp_html_custom_data_attribute_name()
*
* @param string $html_attribute_name Raw attribute name as found in the source HTML.
* @return string|null Transformed `dataset` name, if interpretable as a custom data attribute, else `null`.
*/
function wp_js_dataset_name( string $html_attribute_name ): ?string {
if ( 0 !== substr_compare( $html_attribute_name, 'data-', 0, 5, true ) ) {
return null;
}
$end = strlen( $html_attribute_name );
/*
* If it contains characters which would end the attribute name parsing then
* something else is wrong and this contains more than just an attribute name.
*/
if ( ( $end - 5 ) !== strcspn( $html_attribute_name, "=/> \t\f\r\n", 5 ) ) {
return null;
}
/**
* > For each name in list, for each U+002D HYPHEN-MINUS character (-)
* > in the name that is followed by an ASCII lower alpha, remove the
* > U+002D HYPHEN-MINUS character (-) and replace the character that
* > followed it by the same character converted to ASCII uppercase.
*
* @see https://html.spec.whatwg.org/#concept-domstringmap-pairs
*/
$custom_name = '';
$at = 5;
$was_at = $at;
while ( $at < $end ) {
$next_dash_at = strpos( $html_attribute_name, '-', $at );
if ( false === $next_dash_at || $next_dash_at === $end - 1 ) {
break;
}
// Transform `-a` to `A`, for example.
$c = $html_attribute_name[ $next_dash_at + 1 ];
if ( ( $c >= 'A' && $c <= 'Z' ) || ( $c >= 'a' && $c <= 'z' ) ) {
$prefix = substr( $html_attribute_name, $was_at, $next_dash_at - $was_at );
$custom_name .= strtolower( $prefix );
$custom_name .= strtoupper( $c );
$at = $next_dash_at + 2;
$was_at = $at;
continue;
}
$at = $next_dash_at + 1;
}
// If nothing has been added it means there are no dash-letter pairs; return the name as-is.
return '' === $custom_name
? strtolower( substr( $html_attribute_name, 5 ) )
: ( $custom_name . strtolower( substr( $html_attribute_name, $was_at ) ) );
}
/**
* Returns a corresponding HTML attribute name for the given name,
* if that name were found in a JS element’s `dataset` property.
*
* Example:
*
* 'data-post-id' === wp_html_custom_data_attribute_name( 'postId' );
* 'data--before' === wp_html_custom_data_attribute_name( 'Before' );
* 'data---one---two---' === wp_html_custom_data_attribute_name( '-One--Two---' );
*
* // Not every attribute name will be interpreted as a custom data attribute.
* null === wp_html_custom_data_attribute_name( '/not-an-attribute/' );
* null === wp_html_custom_data_attribute_name( 'no spaces' );
*
* // Some very surprising names will; for example, a property whose name is the empty string.
* 'data-' === wp_html_custom_data_attribute_name( '' );
*
* @since 6.9.0
*
* @see https://html.spec.whatwg.org/#concept-domstringmap-pairs
* @see \wp_js_dataset_name()
*
* @param string $js_dataset_name Name of JS `dataset` property to transform.
* @return string|null Corresponding name of an HTML custom data attribute for the given dataset name,
* if possible to represent in HTML, otherwise `null`.
*/
function wp_html_custom_data_attribute_name( string $js_dataset_name ): ?string {
$end = strlen( $js_dataset_name );
if ( 0 === $end ) {
return 'data-';
}
/*
* If it contains characters which would end the attribute name parsing then
* something it’s not possible to represent this in HTML.
*/
if ( strcspn( $js_dataset_name, "=/> \t\f\r\n" ) !== $end ) {
return null;
}
$html_name = 'data-';
$at = 0;
$was_at = $at;
while ( $at < $end ) {
$next_upper_after = strcspn( $js_dataset_name, 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', $at );
$next_upper_at = $at + $next_upper_after;
if ( $next_upper_at >= $end ) {
break;
}
$prefix = substr( $js_dataset_name, $was_at, $next_upper_at - $was_at );
$html_name .= strtolower( $prefix );
$html_name .= '-' . strtolower( $js_dataset_name[ $next_upper_at ] );
$at = $next_upper_at + 1;
$was_at = $at;
}
if ( $was_at < $end ) {
$html_name .= strtolower( substr( $js_dataset_name, $was_at ) );
}
return $html_name;
}