conversion_check.h

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/*
   This file is part of the KDE libraries
   Copyright (c) 2006 Thomas Braxton <brax108@cox.net>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public License
   along with this library; see the file COPYING.LIB.  If not, write to
   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
   Boston, MA 02110-1301, USA.
*/


#ifndef CONVERSION_CHECK_H
#define CONVERSION_CHECK_H

#include <QtCore/QString>
#include <QtGui/QColor>
#include <QtGui/QFont>
#include <QtCore/QDate>
#include <QtCore/QPoint>
#include <QtCore/QSize>
#include <QtCore/QRect>
#include <kurl.h>
#include <QtCore/QVariant>

namespace ConversionCheck {

// used to distinguish between supported/unsupported types
struct supported { };
struct unsupported { };

// traits type class to define support for constraints
template <typename T>
struct QVconvertible
{
  typedef unsupported toQString;
  typedef unsupported toQVariant;
};

// constraint classes
template <typename T>
struct type_toQString
{
  void constraint() { supported x = y; Q_UNUSED(x); }
  typename QVconvertible<T>::toQString y;
};

template <typename T>
struct type_toQVariant
{
  void constraint() { supported x = y; Q_UNUSED(x); }
  typename QVconvertible<T>::toQVariant y;
};


// check if T is convertible to QString thru QVariant
// if not supported can't be used in QList<T> functions
template <typename T>
inline void to_QString()
{
  void (type_toQString<T>::*x)() = &type_toQString<T>::constraint;
  Q_UNUSED(x);
}

// check if T is convertible to QVariant & supported in readEntry/writeEntry
template <typename T>
inline void to_QVariant()
{
  void (type_toQVariant<T>::*x)() = &type_toQVariant<T>::constraint;
  Q_UNUSED(x);
}

// define for all types handled in readEntry/writeEntry
// string_support - is supported by QVariant(type).toString(),
//                  can be used in QList<T> functions
// variant_support - has a QVariant constructor
#define QVConversions(type, string_support, variant_support) \
template <> struct QVconvertible<type> {\
 typedef string_support toQString;\
 typedef variant_support toQVariant;\
}

// The only types needed here are the types handled in readEntry/writeEntry
// the default QVconvertible will take care of the rest.
QVConversions(bool, supported, supported);
QVConversions(int, supported, supported);
QVConversions(unsigned int, supported, supported);
QVConversions(long long, supported, supported);
QVConversions(unsigned long long, supported, supported);
QVConversions(float, supported, supported);
QVConversions(double, supported, supported);
QVConversions(QString, supported, supported);
QVConversions(QColor, unsupported, supported);
QVConversions(QFont, supported, supported);
QVConversions(QDateTime, unsupported, supported);
QVConversions(QDate, unsupported, supported);
QVConversions(QSize, unsupported, supported);
QVConversions(QRect, unsupported, supported);
QVConversions(QPoint, unsupported, supported);
QVConversions(QSizeF, unsupported, supported);
QVConversions(QRectF, unsupported, supported);
QVConversions(QPointF, unsupported, supported);
QVConversions(QByteArray, supported, supported);
QVConversions(QStringList, unsupported, supported);
QVConversions(QVariantList, unsupported, supported);
QVConversions(KUrl, supported, supported);
QVConversions(KUrl::List, unsupported, supported);
}

#endif