Fix decimal separator handling (#4547)

Makes LMMS can handle both periods and commas properly when loading real numbers.

include/DataFile.h

@@ -84,25 +84,6 @@ public:
 		return m_type;
 	}
 
-	// small helper class for adjusting application's locale settings
-	// when loading or saving floating point values rendered to strings
-	class LocaleHelper
-	{
-	public:
-		enum Modes
-		{
-			ModeLoad,
-			ModeSave,
-			ModeCount
-		};
-		typedef Modes Mode;
-
-		LocaleHelper( Mode mode );
-		~LocaleHelper();
-
-	};
-
-
 private:
 	static Type type( const QString& typeName );
 	static QString typeName( Type type );

include/LocaleHelper.h

@@ -0,0 +1,67 @@
+/*
+ * LocaleHelper.h - compatibility functions for handling decimal separators
+ * Providing helper functions which handle both periods and commas
+ * for decimal separators to load old projects correctly
+ *
+ * Copyright (c) 2014 Tobias Doerffel <tobydox/at/users.sourceforge.net>
+ * Copyright (c) 2018 Hyunjin Song <tteu.ingog/at/gmail.com>
+ *
+ * This file is part of LMMS - https://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef LOCALEHELPER_H
+#define LOCALEHELPER_H
+
+#include <QLocale>
+
+#include <limits>
+#include <cmath>
+
+namespace LocaleHelper
+{
+inline double toDouble(QString str, bool* ok = nullptr)
+{
+	bool isOkay;
+	double value;
+	QLocale c(QLocale::C);
+	c.setNumberOptions(QLocale::RejectGroupSeparator);
+	value = c.toDouble(str, &isOkay);
+	if (!isOkay)
+	{
+		QLocale german(QLocale::German);
+		german.setNumberOptions(QLocale::RejectGroupSeparator);
+		value = german.toDouble(str, &isOkay);
+	}
+	if (ok != nullptr) {*ok = isOkay;}
+	return value;
+}
+
+inline float toFloat(QString str, bool* ok = nullptr)
+{
+	double d = toDouble(str, ok);
+	if (!std::isinf(d) && std::fabs(d) > std::numeric_limits<float>::max())
+	{
+		if (ok != nullptr) {*ok = false;}
+		return 0.0f;
+	}
+	return static_cast<float>(d);
+}
+}
+
+#endif // LOCALEHELPER_H