Allow access to display and input settings in new vector

Light refactor of existing code into reusable method to support
this.

Use Extension attributes to allow skins to provide ULS
additional configuration.

Bug: T274396
Change-Id: I7dcd49f05fae83fbc0c15768bee8ca93eab17bcc

resources/js/ext.uls.interface.js

@@ -52,6 +52,19 @@
 			.i18n();
 	}
 
+	/**
+	 * For Vector: Check whether the classic Vector or "new" vector ([[mw:Desktop_improvements]]) is enabled based
+	 * on the contents of the page.
+	 * For other skins, check if ULSDisplayInputAndDisplaySettingsInInterlanguage contains the current skin.
+	 * @return {bool}
+	 */
+	function isUsingStandaloneLanguageButton() {
+		var skin = mw.config.get( 'skin' );
+		// special handling for Vector. This can be removed when Vector is split into 2 separate skins.
+		return skin === 'vector' ? $( '#p-lang-btn' ).length > 0 :
+			mw.config.get( 'wgULSDisplaySettingsInInterlanguage' );
+	}
+
 	/**
 	 * Add display settings link to the settings bar in ULS
 	 *
@@ -233,11 +246,22 @@
 		} );
 	}
 
+	/**
+	 * Adds display and input settings to the ULS dialog after loading their code.
+	 * @param {ULS} uls instance
+	 */
+	function loadDisplayAndInputSettings( uls ) {
+		return mw.loader.using( languageSettingsModules ).then( function () {
+			addDisplaySettings( uls );
+			addInputSettings( uls );
+		} );
+	}
+
 	function initInterface() {
 		var $pLang,
 			clickHandler,
 			// T273928: No change to the heading should be made in modern Vector when the language button is present
-			changeHeadingAllowed = mw.config.get( 'skin' ) !== 'vector' || $( '#p-lang-btn' ).length > 0,
+			isButton = isUsingStandaloneLanguageButton(),
 			$ulsTrigger = $( '.uls-trigger' ),
 			anonMode = ( mw.user.isAnon() &&
 				!mw.config.get( 'wgULSAnonCanChangeLanguage' ) ),
@@ -255,7 +279,7 @@
 			// Take care of any other elements with this class.
 			$ulsTrigger = $( '.uls-settings-trigger' );
 
-			if ( !$pLang.find( 'div ul' ).children().length && changeHeadingAllowed ) {
+			if ( !$pLang.find( 'div ul' ).children().length && isButton ) {
 				// Replace the title of the interlanguage links area
 				// if there are no interlanguage links
 				$pLang.find( 'h3' )
@@ -352,11 +376,7 @@
 								return mw.uls.getFrequentLanguageList();
 							},
 							onReady: function () {
-								var uls = this;
-								mw.loader.using( languageSettingsModules, function () {
-									addDisplaySettings( uls );
-									addInputSettings( uls );
-								} );
+								loadDisplayAndInputSettings( this );
 							},
 							onSelect: function ( language ) {
 								mw.uls.changeLanguage( language );
@@ -450,7 +470,8 @@
 	 * @param {jQuery.Event} ev
 	 */
 	function clickLanguageButton( ev ) {
-		var $target = $( ev.currentTarget );
+		var uls,
+			$target = $( ev.currentTarget );
 		ev.preventDefault();
 		// Load the ULS now.
 		mw.loader.using( 'ext.uls.mediawiki' ).then( function () {
@@ -461,7 +482,13 @@
 					parent ? parent.querySelectorAll( '.interlanguage-link-target' ) : []
 				)
 			);
+			uls = $target.data( 'uls' );
 			$target.trigger( 'click' );
+			// In New Vector the settings cog is currently not shown. To provide access these are added to
+			// the footer of the ULS dialog (T274396)
+			if ( isUsingStandaloneLanguageButton() ) {
+				loadDisplayAndInputSettings( uls );
+			}
 		} );
 	}
 	/**