Toolbar: add CSS from admin color scheme on front end

src/wp-includes/admin-bar.php

@@ -1399,3 +1399,49 @@ function _get_admin_bar_pref( $context = 'front', $user = 0 ) {
 
 	return 'true' === $pref;
 }
+
+/**
+ * Adds CSS from the administration color scheme stylesheet on the front end.
+ *
+ * @since 7.0.0
+ *
+ * @global array $_wp_admin_css_colors Registered administration color schemes.
+ */
+function wp_admin_bar_add_color_scheme_to_front_end() {
+	if ( is_admin() ) {
+		return;
+	}
+
+	global $_wp_admin_css_colors;
+
+	if ( empty( $_wp_admin_css_colors ) ) {
+		register_admin_color_schemes();
+	}
+
+	$color_scheme = get_user_option( 'admin_color' );
+
+	if ( empty( $color_scheme ) || ! isset( $_wp_admin_css_colors[ $color_scheme ] ) ) {
+		$color_scheme = 'modern';
+	}
+
+	$color = $_wp_admin_css_colors[ $color_scheme ] ?? null;
+	$url   = $color->url ?? '';
+
+	if ( $url ) {
+		$response = wp_remote_get( $url );
+		if ( ! is_wp_error( $response ) ) {
+			$css = $response['body'];
+			if ( is_string( $css ) && str_contains( $css, '#wpadminbar' ) ) {
+				$start_position = strpos( $css, '#wpadminbar' );
+				$end_position   = strpos( $css, '.wp-pointer' );
+				if ( false !== $end_position && $end_position > $start_position ) {
+					$css = substr( $css, $start_position, $end_position - $start_position );
+					if ( SCRIPT_DEBUG ) {
+						$css = str_replace( '/* Pointers */', '', $css );
+					}
+				}
+				wp_add_inline_style( 'admin-bar', $css );
+			}
+		}
+	}
+}

src/wp-includes/default-filters.php

@@ -705,6 +705,7 @@
 add_action( 'wp_body_open', 'wp_admin_bar_render', 0 );
 add_action( 'wp_footer', 'wp_admin_bar_render', 1000 ); // Back-compat for themes not using `wp_body_open`.
 add_action( 'in_admin_header', 'wp_admin_bar_render', 0 );
+add_action( 'admin_bar_init', 'wp_admin_bar_add_color_scheme_to_front_end', 0 );
 
 // Former admin filters that can also be hooked on the front end.
 add_action( 'media_buttons', 'media_buttons' );

tests/phpunit/tests/dependencies/wpStyleLoaderSrc.php

@@ -12,15 +12,20 @@ class Tests_Dependencies_wpStyleLoaderSrc extends WP_UnitTestCase {
 
 	/**
 	 * Tests that PHP warnings are not thrown when wp_style_loader_src() is called
-	 * before the `$_wp_admin_css_colors` global is set.
+	 * before the `$_wp_admin_css_colors` global is set within the admin.
 	 *
 	 * The warnings that we should not see:
 	 * `Warning: Trying to access array offset on null`.
 	 * `Warning: Attempt to read property "url" on null`.
 	 *
 	 * @ticket 61302
+	 * @ticket 64762
 	 */
 	public function test_without_wp_admin_css_colors_global() {
-		$this->assertFalse( wp_style_loader_src( '', 'colors' ) );
+		if ( is_admin() ) {
+			$this->assertFalse( wp_style_loader_src( '', 'colors' ) );
+		} else {
+			$this->assertStringContainsString( '/colors.css', wp_style_loader_src( '', 'colors' ) );
+		}
 	}
 }