From 32bbe9b0b98e1652a081ef8d7a10c7941c0985a0 Mon Sep 17 00:00:00 2001
From: gziolo <gziolo@git.wordpress.org>
Date: Mon, 25 Apr 2022 16:37:08 +0000
Subject: [PATCH] Editor: Fix styles for nested elements (link color)

This fixes an issue by which link color behaves differently in the editor and front end.

Related Gutenberg PR: https://github.com/WordPress/gutenberg/pull/37728.

Props oandregal.
See #55567.


Built from https://develop.svn.wordpress.org/trunk@53260


git-svn-id: http://core.svn.wordpress.org/trunk@52849 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/block-supports/elements.php | 84 ++++++++++++++++++++-----
 wp-includes/version.php                 |  2 +-
 2 files changed, 71 insertions(+), 15 deletions(-)

diff --git a/wp-includes/block-supports/elements.php b/wp-includes/block-supports/elements.php
index 4c813f620b..d2d707fd63 100644
--- a/wp-includes/block-supports/elements.php
+++ b/wp-includes/block-supports/elements.php
@@ -7,7 +7,20 @@
  */
 
 /**
- * Render the elements stylesheet.
+ * Get the elements class names.
+ *
+ * @since 6.0.0
+ * @access private
+ *
+ * @param array $block Block object.
+ * @return string      The unique class name.
+ */
+function wp_get_elements_class_name( $block ) {
+	return 'wp-elements-' . md5( serialize( $block ) );
+}
+
+/**
+ * Update the block content with elements class names.
  *
  * @since 5.8.0
  * @access private
@@ -43,17 +56,7 @@ function wp_render_elements_support( $block_content, $block ) {
 		return $block_content;
 	}
 
-	$class_name = wp_unique_id( 'wp-elements-' );
-
-	if ( strpos( $link_color, 'var:preset|color|' ) !== false ) {
-		// Get the name from the string and add proper styles.
-		$index_to_splice = strrpos( $link_color, '|' ) + 1;
-		$link_color_name = substr( $link_color, $index_to_splice );
-		$link_color      = "var(--wp--preset--color--$link_color_name)";
-	}
-	$link_color_declaration = esc_html( safecss_filter_attr( "color: $link_color" ) );
-
-	$style = ".$class_name a{" . $link_color_declaration . ';}';
+	$class_name = wp_get_elements_class_name( $block );
 
 	// Like the layout hook this assumes the hook only applies to blocks with a single wrapper.
 	// Retrieve the opening tag of the first HTML element.
@@ -75,9 +78,62 @@ function wp_render_elements_support( $block_content, $block ) {
 		$content              = substr_replace( $block_content, ' class="' . $class_name . '"', $first_element_offset + strlen( $first_element ) - 1, 0 );
 	}
 
-	wp_enqueue_block_support_styles( $style );
-
 	return $content;
 }
 
+/**
+ * Render the elements stylesheet.
+ *
+ * In the case of nested blocks we want the parent element styles to be rendered before their descendants.
+ * This solves the issue of an element (e.g.: link color) being styled in both the parent and a descendant:
+ * we want the descendant style to take priority, and this is done by loading it after, in DOM order.
+ *
+ * @since 6.0.0
+ * @access private
+ *
+ * @param string|null $pre_render   The pre-rendered content. Default null.
+ * @param array       $block        The block being rendered.
+ *
+ * @return null
+ */
+function wp_render_elements_support_styles( $pre_render, $block ) {
+	$block_type                    = WP_Block_Type_Registry::get_instance()->get_registered( $block['blockName'] );
+	$skip_link_color_serialization = wp_should_skip_block_supports_serialization( $block_type, 'color', 'link' );
+	if ( $skip_link_color_serialization ) {
+		return null;
+	}
+
+	$link_color = null;
+	if ( ! empty( $block['attrs'] ) ) {
+		$link_color = _wp_array_get( $block['attrs'], array( 'style', 'elements', 'link', 'color', 'text' ), null );
+	}
+
+	/*
+	* For now we only care about link color.
+	* This code in the future when we have a public API
+	* should take advantage of WP_Theme_JSON::compute_style_properties
+	* and work for any element and style.
+	*/
+	if ( null === $link_color ) {
+		return null;
+	}
+
+	$class_name = wp_get_elements_class_name( $block );
+
+	if ( strpos( $link_color, 'var:preset|color|' ) !== false ) {
+		// Get the name from the string and add proper styles.
+		$index_to_splice = strrpos( $link_color, '|' ) + 1;
+		$link_color_name = substr( $link_color, $index_to_splice );
+		$link_color      = "var(--wp--preset--color--$link_color_name)";
+	}
+	$link_color_declaration = esc_html( safecss_filter_attr( "color: $link_color" ) );
+
+	$style = ".$class_name a{" . $link_color_declaration . ';}';
+
+	wp_enqueue_block_support_styles( $style );
+
+	return null;
+}
+
 add_filter( 'render_block', 'wp_render_elements_support', 10, 2 );
+add_filter( 'pre_render_block', 'wp_render_elements_support_styles', 10, 2 );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b3e0f2a7ff..f8c87e9caa 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.0-beta2-53259';
+$wp_version = '6.0-beta2-53260';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.