Respect languages preferences on login page

Fixes #4169

UI/MainUI/SOGoRootPage.h

@@ -31,6 +31,8 @@
   NSString *cookieLogin;
 }
 
+- (NSArray *) languages;
+
 @end
 
 #endif /* SOGOROOTPAGE_H */

UI/MainUI/SOGoRootPage.m

@@ -521,6 +521,16 @@
   return item;
 }
 
+- (BOOL) hasManyLanguages
+{
+  return [[self languages] count] > 1;
+}
+
+- (NSString *) language
+{
+  return [[context resourceLookupLanguages] objectAtIndex: 0];
+}
+
 - (NSArray *) languages
 {
   return [[SOGoSystemDefaults sharedSystemDefaults] supportedLanguages];

UI/Templates/MainUI/SOGoRootPage.wox

@@ -42,20 +42,22 @@
 	    <label><var:string label:value="Password"/><br/>
 	    <input class="textField" id="password"
 		   name="password" type="password" var:value="password" /></label>
+            <var:if condition="hasManyLanguages">
 	    <label><var:string label:value="Language"/><br/>
 	    <var:popup const:id="language" const:name="language"
 		       list="languages"
 		       item="item"
 		       var:value="item"
+		       var:selection="language"
 		       string="languageText"
 		       label:noSelectionString="choose"
 		       /></label>
+            </var:if>
             <var:if condition="hasLoginDomains">
 	    <label><var:string label:value="Domain"/><br/>
 	    <var:popup const:id="domain" const:name="domain"
 		       list="loginDomains"
 		       item="item"
-		       var:selection="item"
 		       var:value="item"
 		       string="item"
 		       /></label>

UI/WebServerResources/SOGoRootPage.js

@@ -24,6 +24,15 @@ function initLogin() {
                 event.stop() });
     }
 
+    var language = $("language");
+    if (language)
+        language.on("change", function(event) {
+                var value = $("language").value;
+                if (value != "WONoSelectionString")
+                    // Reload page
+                    window.location.href = ApplicationBaseURL + '/login?language=' + value;
+            });
+
     var submit = $("submit");
     submit.observe("click", onLoginClick);