MU WPCOM: Port font-smoothing-antialiased feature from ETK (#38195)

* MU WPCOM: Port font-smoothing-antialiased feature from ETK

* changelog

projects/packages/jetpack-mu-wpcom/changelog/mu-wpcom-font-smoothing

@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+MU WPCOM: Port font-smoothing-antialiased feature from ETK

projects/packages/jetpack-mu-wpcom/src/class-jetpack-mu-wpcom.php

@@ -90,6 +90,7 @@ public static function load_features() {
 		require_once __DIR__ . '/features/cloudflare-analytics/cloudflare-analytics.php';
 		require_once __DIR__ . '/features/error-reporting/error-reporting.php';
 		require_once __DIR__ . '/features/first-posts-stream/first-posts-stream-helpers.php';
+		require_once __DIR__ . '/features/font-smoothing-antialiased/font-smoothing-antialiased.php';
 		// To avoid potential collisions with ETK.
 		if ( ! class_exists( 'A8C\FSE\Help_Center' ) ) {
 			require_once __DIR__ . '/features/help-center/class-help-center.php';

projects/packages/jetpack-mu-wpcom/src/features/font-smoothing-antialiased/font-smoothing-antialiased.css

@@ -0,0 +1,10 @@
+@media (-webkit-min-device-pixel-ratio: 1.25), (min-resolution: 120dpi) {
+	body.font-smoothing-antialiased,
+	/** Overriding an existing core WP rule so the ID selector is necessary */
+	body.font-smoothing-antialiased #wpwrap,
+	body.font-smoothing-antialiased #wpadminbar * {
+		text-rendering: optimizeLegibility;
+		-moz-osx-font-smoothing: grayscale;
+		-webkit-font-smoothing: antialiased;
+	}
+}

projects/packages/jetpack-mu-wpcom/src/features/font-smoothing-antialiased/font-smoothing-antialiased.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * Apply the new font-smoothing styles.
+ *
+ * @package automattic/jetpack-mu-wpcom
+ */
+
+use Automattic\Jetpack\Jetpack_Mu_Wpcom;
+
+// Turn off the feature on ETK plugin.
+define( 'A8C_USE_FONT_SMOOTHING_ANTIALIASED', false );
+
+/**
+ * Adds custom classes to the admin body classes.
+ *
+ * @param string $classes Classes for the body element.
+ * @return string
+ */
+function wpcom_add_font_smoothing_antialiased_class( $classes ) {
+	$classes .= ' font-smoothing-antialiased ';
+	return $classes;
+}
+add_filter( 'admin_body_class', 'wpcom_add_font_smoothing_antialiased_class' );
+
+/**
+ * Enqueue assets
+ */
+function wpcom_enqueue_font_smoothing_antialiased_assets() {
+	wp_enqueue_style(
+		'wpcom-font-smoothing-antialiased',
+		plugins_url( 'font-smoothing-antialiased.css', __FILE__ ),
+		array(),
+		Jetpack_Mu_Wpcom::PACKAGE_VERSION
+	);
+}
+add_action( 'admin_enqueue_scripts', 'wpcom_enqueue_font_smoothing_antialiased_assets' );