Select language on first start based on user locale

On first client start (when `cl_show_welcome` is `1`), determine the user locale with `os_locale_str` and initially select the most fitting language for this locale.

For this the language index must also be loaded immediately on client launch, before the initial language is loaded.

src/game/client/components/menus_settings.cpp

@@ -2028,19 +2028,22 @@ void CMenus::RenderSettingsSound(CUIRect MainView)
 
 bool CMenus::RenderLanguageSelection(CUIRect MainView)
 {
-	static int s_SelectedLanguage = -1;
+	static int s_SelectedLanguage = -2; // -2 = unloaded, -1 = unset
 	static CListBox s_ListBox;
 
-	if(g_Localization.Languages().empty())
+	if(s_SelectedLanguage == -2)
 	{
-		g_Localization.LoadIndexfile(Storage(), Console());
+		s_SelectedLanguage = -1;
 		for(size_t i = 0; i < g_Localization.Languages().size(); i++)
+		{
 			if(str_comp(g_Localization.Languages()[i].m_FileName.c_str(), g_Config.m_ClLanguagefile) == 0)
 			{
 				s_SelectedLanguage = i;
+				s_ListBox.ScrollToSelected();
 				break;
 			}
 		}
+	}
 
 	const int OldSelected = s_SelectedLanguage;
 

src/game/client/gameclient.cpp

@@ -243,6 +243,9 @@ void CGameClient::OnInit()
 	}
 
 	// set the language
+	g_Localization.LoadIndexfile(Storage(), Console());
+	if(g_Config.m_ClShowWelcome)
+		g_Localization.SelectDefaultLanguage(Console(), g_Config.m_ClLanguagefile, sizeof(g_Config.m_ClLanguagefile));
 	g_Localization.Load(g_Config.m_ClLanguagefile, Storage(), Console());
 
 	// TODO: this should be different

src/game/localization.cpp

@@ -146,6 +146,59 @@ void CLocalizationDatabase::LoadIndexfile(IStorage *pStorage, IConsole *pConsole
 	std::sort(m_vLanguages.begin(), m_vLanguages.end());
 }
 
+void CLocalizationDatabase::SelectDefaultLanguage(IConsole *pConsole, char *pFilename, size_t Length) const
+{
+	char aLocaleStr[128];
+	os_locale_str(aLocaleStr, sizeof(aLocaleStr));
+
+	char aBuf[256];
+	str_format(aBuf, sizeof(aBuf), "Choosing default language based on user locale '%s'", aLocaleStr);
+	pConsole->Print(IConsole::OUTPUT_LEVEL_ADDINFO, "localization", aBuf);
+
+	while(true)
+	{
+		const CLanguage *pPrefixMatch = nullptr;
+		for(const auto &Language : Languages())
+		{
+			for(const auto &LanguageCode : Language.m_vLanguageCodes)
+			{
+				if(LanguageCode == aLocaleStr)
+				{
+					// Exact match found, use it immediately
+					str_copy(pFilename, Language.m_FileName.c_str(), Length);
+					return;
+				}
+				else if(LanguageCode.rfind(aLocaleStr, 0) == 0)
+				{
+					// Locale is prefix of language code, e.g. locale is "en" and current language is "en-US"
+					pPrefixMatch = &Language;
+				}
+			}
+		}
+		// Use prefix match if no exact match was found
+		if(pPrefixMatch)
+		{
+			str_copy(pFilename, pPrefixMatch->m_FileName.c_str(), Length);
+			return;
+		}
+
+		// Remove last segment of locale string and try again with more generic locale, e.g. "en-US" -> "en"
+		int i = str_length(aLocaleStr) - 1;
+		for(; i >= 0; --i)
+		{
+			if(aLocaleStr[i] == '-')
+			{
+				aLocaleStr[i] = '\0';
+				break;
+			}
+		}
+
+		// Stop if no more locale segments are left
+		if(i == 0)
+			break;
+	}
+}
+
 bool CLocalizationDatabase::Load(const char *pFilename, IStorage *pStorage, IConsole *pConsole)
 {
 	// empty string means unload

src/game/localization.h

@@ -56,6 +56,7 @@ public:
 
 	void LoadIndexfile(class IStorage *pStorage, class IConsole *pConsole);
 	const std::vector<CLanguage> &Languages() const { return m_vLanguages; }
+	void SelectDefaultLanguage(class IConsole *pConsole, char *pFilename, size_t Length) const;
 
 	bool Load(const char *pFilename, class IStorage *pStorage, class IConsole *pConsole);