From e65186c443a5887024da50b66fe92bcf267a0752 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Bartosz=20Dziewo=C5=84ski?= <matma.rex@gmail.com>
Date: Mon, 1 Feb 2016 23:38:37 +0100
Subject: [PATCH] Work around T87871 to avoid double-loading OOjs UI PHP styles

Use a <meta> tag added when enabling OOUI, and a skipFunction that
looks for it, to avoid double-loading the modules: oojs-ui.styles,
oojs-ui.styles.icons, oojs-ui.styles.indicators, oojs-ui.styles.textures.

This saves us loading of around 200K of CSS (20K when gzipped) on pages
that both use OOjs UI PHP server-side and load OOjs UI client-side.
(For example, all MediaWiki special pages using OOUIHTMLForm.)

Interesting caveat: this causes the aforementioned modules to no
longer appear in the output of `mw.loader.inspect()` on such pages.

Bug: T125292
Change-Id: Ia7e2256cd239841e1f78c4a6bf666dd939c0d2c7
---
 includes/OutputPage.php              |  3 +++
 resources/ResourcesOOUI.php          | 11 ++++++++---
 resources/src/oojs-ui-styles-skip.js |  9 +++++++++
 3 files changed, 20 insertions(+), 3 deletions(-)
 create mode 100644 resources/src/oojs-ui-styles-skip.js

diff --git a/includes/OutputPage.php b/includes/OutputPage.php
index 3b8d741595..494e857852 100644
--- a/includes/OutputPage.php
+++ b/includes/OutputPage.php
@@ -4051,5 +4051,8 @@ class OutputPage extends ContextSource {
 			'oojs-ui.styles.textures',
 			'mediawiki.widgets.styles',
 		) );
+		// Used by 'skipFunction' of the four 'oojs-ui.styles.*' modules. Please don't treat this as a
+		// public API or you'll be severely disappointed when T87871 is fixed and it disappears.
+		$this->addMeta( 'X-OOUI-PHP', '1' );
 	}
 }
diff --git a/resources/ResourcesOOUI.php b/resources/ResourcesOOUI.php
index 647efa23e4..851b1c73dc 100644
--- a/resources/ResourcesOOUI.php
+++ b/resources/ResourcesOOUI.php
@@ -68,9 +68,6 @@ return call_user_func( function () {
 			'es5-shim',
 			'oojs',
 			'oojs-ui.styles',
-			'oojs-ui.styles.icons',
-			'oojs-ui.styles.indicators',
-			'oojs-ui.styles.textures',
 			'mediawiki.language',
 		),
 		'targets' => array( 'desktop', 'mobile' ),
@@ -81,6 +78,14 @@ return call_user_func( function () {
 		'styles' => 'resources/src/oojs-ui-local.css', // HACK, see inside the file
 		'skinStyles' => $getSkinSpecific( 'core' ),
 		'targets' => array( 'desktop', 'mobile' ),
+		// ResourceLoaderImageModule doesn't support 'skipFunction', so instead we set this up so that
+		// this module is skipped together with its dependencies. Nothing else depends on these modules.
+		'dependencies' => array(
+			'oojs-ui.styles.icons',
+			'oojs-ui.styles.indicators',
+			'oojs-ui.styles.textures',
+		),
+		'skipFunction' => 'resources/src/oojs-ui-styles-skip.js',
 	);
 
 	// Deprecated old name for the module 'oojs-ui-core.styles'.
diff --git a/resources/src/oojs-ui-styles-skip.js b/resources/src/oojs-ui-styles-skip.js
new file mode 100644
index 0000000000..57c905a345
--- /dev/null
+++ b/resources/src/oojs-ui-styles-skip.js
@@ -0,0 +1,9 @@
+/*!
+ * Skip function for OOjs UI PHP style modules.
+ *
+ * The `<meta name="X-OOUI-PHP" />` is added to pages by OutputPage::enableOOUI().
+ *
+ * Looking for elements in the DOM might be expensive, but it's probably better than double-loading
+ * 200 KB of CSS with embedded images because of bug T87871.
+ */
+return !!jQuery( 'meta[name="X-OOUI-PHP"]' ).length;
-- 
2.20.1