Clarified documentation for SystemStats::getDisplayLanguage(), to make clear that it may return a multi-part region name. Updated the win32 implementation of this method to include the region code.

modules/juce_core/native/juce_win32_SystemStats.cpp

@@ -428,8 +428,16 @@ String SystemStats::getDisplayLanguage()
     DynamicLibrary dll ("kernel32.dll");
     JUCE_LOAD_WINAPI_FUNCTION (dll, GetUserDefaultUILanguage, getUserDefaultUILanguage, LANGID, (void))
 
-    if (getUserDefaultUILanguage != nullptr)
-        return getLocaleValue (MAKELCID (getUserDefaultUILanguage(), SORT_DEFAULT), LOCALE_SISO639LANGNAME, "en");
+    if (getUserDefaultUILanguage == nullptr)
+        return "en";
 
-    return "en";
+    const DWORD langID = MAKELCID (getUserDefaultUILanguage(), SORT_DEFAULT);
+
+    String mainLang (getLocaleValue (langID, LOCALE_SISO639LANGNAME, "en"));
+    String region   (getLocaleValue (langID, LOCALE_SISO3166CTRYNAME, nullptr));
+
+    if (region.isNotEmpty())
+        mainLang << '-' << region;
+
+    return mainLang;
 }

modules/juce_core/system/juce_SystemStats.h

@@ -118,7 +118,9 @@ public:
     static String getUserRegion();
 
     /** Returns the user's display language.
-        The return value is a 2 or 3 letter language code (ISO 639-1 or ISO 639-2)
+        The return value is a 2 or 3 letter language code (ISO 639-1 or ISO 639-2).
+        Note that depending on the OS and region, this may also be followed by a dash
+        and a sub-region code, e.g "en-GB"
     */
     static String getDisplayLanguage();