WIP

lib/blocks.php

@@ -203,6 +203,50 @@ function gutenberg_register_core_block_styles( $block_name ) {
 		wp_register_style( "wp-block-{$block_name}", false );
 	}
 
+	// If the current theme supports wp-block-styles, dequeue the full stylesheet
+	// and instead attach each block's theme-styles to their block styles stylesheet.
+	if ( current_theme_supports( 'wp-block-styles' ) ) {
+
+		// Dequeue the full stylesheet.
+		// Make sure this only runs once, it doesn't need to run for every block.
+		static $stylesheet_removed;
+		if ( ! $stylesheet_removed ) {
+			add_action(
+				'wp_enqueue_scripts',
+				function() {
+					wp_dequeue_style( 'wp-block-library-theme' );
+				}
+			);
+			$stylesheet_removed = true;
+		}
+
+		// Get the path to the block's stylesheet.
+		$theme_style_path = is_rtl()
+			? "build/block-library/blocks/$block_name/theme-rtl.css"
+			: "build/block-library/blocks/$block_name/theme.css";
+
+		// If the file exists, enqueue it.
+		if ( file_exists( gutenberg_dir_path() . $theme_style_path ) ) {
+
+			if ( file_exists( gutenberg_dir_path() . $style_path ) ) {
+				// If there is a main stylesheet for this block, append the theme styles to main styles.
+				wp_add_inline_style(
+					"wp-block-{$block_name}",
+					file_get_contents( gutenberg_dir_path() . $theme_style_path )
+				);
+			} else {
+				// If there is no main stylesheet for this block, register theme style.
+				wp_register_style(
+					"wp-block-{$block_name}",
+					gutenberg_url( $theme_style_path ),
+					array(),
+					filemtime( gutenberg_dir_path() . $theme_style_path )
+				);
+				wp_style_add_data( "wp-block-{$block_name}", 'path', gutenberg_dir_path() . $theme_style_path );
+			}
+		}
+	}
+
 	if ( file_exists( gutenberg_dir_path() . $editor_style_path ) ) {
 		wp_deregister_style( "wp-block-{$block_name}-editor" );
 		wp_register_style(