wp-includes/class-wp-duotone.php:1246Outputs all necessary SVG for duotone filters, CSS for classic themes.
public static function output_footer_assets() { if ( ! empty( self::$used_svg_filter_data ) ) { echo self::get_svg_definitions( self::$used_svg_filter_data ); } // In block themes, the CSS is added in the head via wp_add_inline_style in the wp_enqueue_scripts action. if ( ! wp_is_block_theme() ) { $style_tag_id = 'core-block-supports-duotone'; wp_register_style( $style_tag_id, false ); if ( ! empty( self::$used_global_styles_presets ) ) { wp_add_inline_style( $style_tag_id, self::get_global_styles_presets( self::$used_global_styles_presets ) ); } if ( ! empty( self::$block_css_declarations ) ) { wp_add_inline_style( $style_tag_id, wp_style_engine_get_stylesheet_from_css_rules( self::$block_css_declarations ) ); } wp_enqueue_style( $style_tag_id ); } }Introduced in 6.3.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-duotone.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.