frontend: Use system locale on Windows instead of 'C'

Sets runtime locale to system locale with UTF-8 codepage. This is already default behavior on unix, but Windows defaults to minimal 'C' locale.

OBS Studio language settings no longer change QLocale default locale, instead system locale is used for conformity. It is likely this is what user wants as well. Ie. sorting and formatting functions should follow OS locale instead of OBS Studio language (which also lacks country information).

Author: Dankirk

frontend/OBSApp.cpp

@@ -693,10 +693,6 @@ bool OBSApp::InitLocale()
 
 	locale = lang;
 
-	// set basic default application locale
-	if (!locale.empty())
-		QLocale::setDefault(QLocale(QString::fromStdString(locale).replace('-', '_')));
-
 	string englishPath;
 	if (!GetDataFilePath("locale/" DEFAULT_LANG ".ini", englishPath)) {
 		OBSErrorBox(NULL, "Failed to find locale/" DEFAULT_LANG ".ini");
@@ -732,10 +728,6 @@ bool OBSApp::InitLocale()
 			blog(LOG_INFO, "Using preferred locale '%s'", locale_.c_str());
 			locale = locale_;
 
-			// set application default locale to the new choosen one
-			if (!locale.empty())
-				QLocale::setDefault(QLocale(QString::fromStdString(locale).replace('-', '_')));
-
 			return true;
 		}
 
@@ -868,11 +860,49 @@ OBSApp::OBSApp(int &argc, char **argv, profiler_name_store_t *store)
 	  profilerNameStore(store),
 	  appLaunchUUID_(QUuid::createUuid())
 {
+
+	bool usingUTF8 = true;
+#ifdef _WIN32
+	/*
+	 Appropriate setlocale() calls are already performed for unix platforms in QCoreApplicationPrivate::initLocale()
+	 We are just following suit for win32
+	*/
+
+	// Use system locale with UTF-8 codepage (available from Windows 10 version 1803)
+	// Qt calls setlocale(LC_ALL, "") for unix system defaults, but it is likely unix defaults to UTF-8 ccodepage
+	if (!setlocale(LC_ALL, ".UTF-8")) {
+
+		// Fallback to minimal C locale
+		// Could use "" for system defaults, but the Windows default ANSI codepages (.125x or .9xx)
+		// mismatch with UTF-8 that is assumed by many parts of the codebase
+		setlocale(LC_ALL, "C");
+		usingUTF8 = false;
+	}
+#else
+	// Extend Qt default locale calls for unix by enforcing UTF-8 LC_COLLATE (string comparisons, sorting, regex)
+	{
+		QByteArray collationLocale = setlocale(LC_COLLATE, nullptr);
+		if (qsizetype dot = collationLocale.indexOf('.'); dot != -1)
+			collationLocale.truncate(dot); // remove encoding, if any
+
+		if (qsizetype at = collationLocale.indexOf('@'); at != -1)
+			collationLocale.truncate(at); // remove variant, as the old de_DE@euro
+
+		collationLocale += ".UTF-8";
+		if (!setlocale(LC_COLLATE, collationLocale))
+			usingUTF8 = false;
+	}
+#endif
+
 	/* fix float handling */
-#if defined(Q_OS_UNIX)
 	if (!setlocale(LC_NUMERIC, "C"))
 		blog(LOG_WARNING, "Failed to set LC_NUMERIC to C locale");
-#endif
+
+	if (!usingUTF8)
+		blog(LOG_WARNING, "Failed to set UTF-8 codepage for locales");
+
+	const char *localeStr = setlocale(LC_ALL, nullptr);
+	blog(LOG_INFO, "Set locale to: %s", localeStr);
 
 #ifndef _WIN32
 	/* Handle SIGINT properly */