Implement language-selection-method event

Change-Id: If2d207f8a221c8f2a560b1399ad69a3032b2064b

resources/js/ext.uls.init.js

@@ -39,6 +39,39 @@
 	mw.uls.previousLanguagesCookie = 'uls-previous-languages';
 	mw.uls.languageSettingsModules = ['ext.uls.inputsettings', 'ext.uls.displaysettings'];
 
+	// What was the last thing that the user did to select the language:
+	// * 'map' - clicked the map
+	// * 'search' - typed in the search box
+	// * 'common' - clicked a link in the "Common languages" section
+	// If the user just clicked in some other section, it remains undefined.
+	// This is useful for logging.
+	mw.uls.languageSelectionMethod = undefined;
+
+	/**
+	 * Add event logging triggers, which are common to different
+	 * ULS instances
+	 */
+	mw.uls.addEventLoggingTriggers = function () {
+		// Remove previous values when reinitializing
+		mw.uls.languageSelectionMethod = undefined;
+
+		$( '#map-block' ).on( 'click', function () {
+			mw.uls.languageSelectionMethod = 'map';
+		} );
+
+		$( '#languagefilter' ).on( 'keydown', function () {
+			// If it's the first letter,
+			// log the usage of the search box
+			if ( $( this ).val() === '' ) {
+				mw.uls.languageSelectionMethod = 'search';
+			}
+		} );
+
+		$( '#uls-lcd-quicklist a' ).on( 'click', function () {
+			mw.uls.languageSelectionMethod = 'common';
+		} );
+	};
+
 	/**
 	 * Change the language of wiki using setlang URL parameter
 	 * @param {string} language Language code.