Polish duotone rendering code (#49706)

* Rename gutenberg_get_slug_from_attr for clarity

* Use double quotes for string concatination

* Correct WP_Duotone_Gutenberg class comment

* Match example filter slugs used throughout the file

* Update comments to clarify methods and variables

* Fix @SInCE declarations on public methods

* Reorder methods for better readablity

* Add existance check for core versions of actions/filters

lib/block-supports/duotone.php

@@ -5,7 +5,7 @@
  * @package gutenberg
  */
 
-// Register duotone block supports.
+// Register the block support. (overrides core one).
 WP_Block_Supports::get_instance()->register(
 	'duotone',
 	array(
@@ -14,26 +14,49 @@
 );
 
 // Set up metadata prior to rendering any blocks.
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_action( 'wp_loaded', array( 'WP_Duotone', 'set_global_styles_presets' ) );
+	remove_action( 'wp_loaded', array( 'WP_Duotone', 'set_global_style_block_names' ) );
+}
 add_action( 'wp_loaded', array( 'WP_Duotone_Gutenberg', 'set_global_styles_presets' ), 10 );
 add_action( 'wp_loaded', array( 'WP_Duotone_Gutenberg', 'set_global_style_block_names' ), 10 );
 
-// Remove WordPress core filter to avoid rendering duplicate support elements.
-remove_filter( 'render_block', 'wp_render_duotone_support', 10, 2 );
+// Add classnames to blocks using duotone support.
+if ( function_exists( 'wp_render_duotone_support' ) ) {
+	// Deprecated render function.
+	remove_filter( 'render_block', 'wp_render_duotone_support' );
+}
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_filter( 'render_block', array( 'WP_Duotone', 'render_duotone_support' ) );
+}
 add_filter( 'render_block', array( 'WP_Duotone_Gutenberg', 'render_duotone_support' ), 10, 2 );
 
 // Enqueue styles.
 // Block styles (core-block-supports-inline-css) before the style engine (gutenberg_enqueue_stored_styles).
 // Global styles (global-styles-inline-css) after the other global styles (gutenberg_enqueue_global_styles).
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_action( 'wp_enqueue_scripts', array( 'WP_Duotone', 'output_block_styles' ) );
+	remove_action( 'wp_enqueue_scripts', array( 'WP_Duotone', 'output_global_styles' ) );
+}
 add_action( 'wp_enqueue_scripts', array( 'WP_Duotone_Gutenberg', 'output_block_styles' ), 9 );
 add_action( 'wp_enqueue_scripts', array( 'WP_Duotone_Gutenberg', 'output_global_styles' ), 11 );
 
 // Add SVG filters to the footer. Also, for classic themes, output block styles (core-block-supports-inline-css).
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_action( 'wp_footer', array( 'WP_Duotone', 'output_footer_assets' ) );
+}
 add_action( 'wp_footer', array( 'WP_Duotone_Gutenberg', 'output_footer_assets' ), 10 );
 
 // Add styles and SVGs for use in the editor via the EditorStyles component.
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_filter( 'block_editor_settings_all', array( 'WP_Duotone', 'add_editor_settings' ) );
+}
 add_filter( 'block_editor_settings_all', array( 'WP_Duotone_Gutenberg', 'add_editor_settings' ), 10 );
 
 // Migrate the old experimental duotone support flag.
+if ( class_exists( 'WP_Duotone' ) ) {
+	remove_filter( 'block_type_metadata_settings', array( 'WP_Duotone', 'migrate_experimental_duotone_support_flag' ) );
+}
 add_filter( 'block_type_metadata_settings', array( 'WP_Duotone_Gutenberg', 'migrate_experimental_duotone_support_flag' ), 10, 2 );
 
 /*