Add wxUILocale::GetSystemLocaleId()

This function replaces the existing GetSystemLocale() as it can
represent the locales that don't have any corresponding wxLanguage
values and for which GetSystemLocale() has no choice but to return
wxLANGUAGE_UNKNOWN.

include/wx/uilocale.h

@@ -158,12 +158,18 @@ public:
     // its dtor is not virtual.
     ~wxUILocale();
 
+    // Return the locale ID representing the default system locale, which would
+    // be set is UseDefault() is called.
+    static wxLocaleIdent GetSystemLocaleId();
+
     // Try to get user's (or OS's) preferred language setting.
     // Return wxLANGUAGE_UNKNOWN if the language-guessing algorithm failed
+    // Prefer using GetSystemLocaleId() above.
     static int GetSystemLanguage();
 
     // Try to get user's (or OS's) default locale setting.
     // Return wxLANGUAGE_UNKNOWN if the locale-guessing algorithm failed
+    // Prefer using GetSystemLocaleId() above.
     static int GetSystemLocale();
 
     // Try to retrieve a list of user's (or OS's) preferred UI languages.

interface/wx/uilocale.h

@@ -289,7 +289,7 @@ public:
               by the operating system (for example, Windows 7 and below), the user's
               default @em locale will be used.
 
-        @see wxTranslations::GetBestTranslation().
+        @see wxTranslations::GetBestTranslation(), GetSystemLocaleId().
     */
     static int GetSystemLanguage();
 
@@ -297,7 +297,8 @@ public:
         Tries to detect the user's default locale setting.
 
         Returns the ::wxLanguage value or @c wxLANGUAGE_UNKNOWN if the locale-guessing
-        algorithm failed.
+        algorithm failed or if the locale can't be described using solely a
+        language constant. Consider using GetSystemLocaleId() in this case.
 
         @note This function works with @em locales and returns the user's default
               locale. This may be, and usually is, the same as their preferred UI
@@ -308,7 +309,19 @@ public:
 
         @see wxTranslations::GetBestTranslation().
     */
-    static int GetSystemLocale();};
+    static int GetSystemLocale();
+
+    /**
+        Return the description of the default system locale.
+
+        This function can always represent the system locale, even when using
+        a language and region pair that doesn't correspond to any of the
+        predefined ::wxLanguage constants, such as e.g. "fr-DE", which means
+        French language used with German locale settings.
+
+        @since 3.3.0
+     */
+};
 
 /**
     Return the format to use for formatting user-visible dates.

src/common/uilocale.cpp

@@ -632,6 +632,13 @@ wxUILocale::~wxUILocale()
 }
 
 
+/* static */
+wxLocaleIdent wxUILocale::GetSystemLocaleId()
+{
+    wxUILocale defaultLocale(wxUILocaleImpl::CreateUserDefault());
+    return defaultLocale.GetLocaleId();
+}
+
 /*static*/
 int wxUILocale::GetSystemLanguage()
 {
@@ -677,11 +684,9 @@ int wxUILocale::GetSystemLanguage()
 /*static*/
 int wxUILocale::GetSystemLocale()
 {
-    // Create default wxUILocale
-    wxUILocale defaultLocale(wxUILocaleImpl::CreateUserDefault());
-    const wxLocaleIdent locId = defaultLocale.GetLocaleId();
+    const wxLocaleIdent locId = GetSystemLocaleId();
 
-    // Find corresponding wxLanguageInfo
+    // Find wxLanguageInfo corresponding to the default locale.
     const wxLanguageInfo* defaultLanguage = wxUILocale::FindLanguageInfo(locId);
 
     // Check if it really corresponds to this locale: we could find it via the

tests/intl/intltest.cpp

@@ -480,9 +480,11 @@ wxString GetLocaleDesc(const char* when)
 // ways to change the current locale.
 TEST_CASE("wxUILocale::ShowSystem", "[.]")
 {
-    WARN("System locale:\t"
+    WARN("System locale identifier:\t"
+            << wxUILocale::GetSystemLocaleId().GetTag() << "\n"
+         "System locale as language:\t"
             << GetLangName(wxUILocale::GetSystemLocale()) << "\n"
-         "System language:\t"
+         "System language identifier:\t"
             << GetLangName(wxUILocale::GetSystemLanguage()));
 
     WARN(GetLocaleDesc("Before calling any locale functions"));