libreoffice/include/vcl/vclref.hxx

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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 * This file is part of the LibreOffice project.
 *
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 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you under the Apache
 *   License, Version 2.0 (the "License"); you may not use this file
 *   except in compliance with the License. You may obtain a copy of
 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 */

#ifndef INCLUDED_VCL_REFERENCE_HXX
#define INCLUDED_VCL_REFERENCE_HXX

#include <rtl/ref.hxx>

/// @cond INTERNAL
namespace vcl { namespace detail {

// A mechanism to enable up-casts, used by the VclReference conversion constructor,
// heavily borrowed from boost::is_base_and_derived
// (which manages to avoid compilation problems with ambiguous bases and cites
// comp.lang.c++.moderated mail <http://groups.google.com/groups?
// selm=df893da6.0301280859.522081f7%40posting.google.com> "SuperSubclass
// (is_base_and_derived) complete implementation!" by Rani Sharoni and cites
// Aleksey Gurtovoy for the workaround for MSVC), to avoid including Boost
// headers in URE headers (could ultimately be based on C++11 std::is_base_of):

template< typename T1, typename T2 > struct UpCast {
private:
    template< bool, typename U1, typename > struct C
    { typedef U1 t; };

    template< typename U1, typename U2 > struct C< false, U1, U2 >
    { typedef U2 t; };

    struct S { char c[2]; };

#if defined _MSC_VER
    static char f(T2 *, long);
    static S f(T1 * const &, int);
#else
    template< typename U > static char f(T2 *, U);
    static S f(T1 *, int);
#endif

    struct H {
        H(); // avoid C2514 "class has no constructors" from MSVC 2008
#if defined _MSC_VER
        operator T1 * const & () const;
#else
        operator T1 * () const;
#endif
        operator T2 * ();
    };

public:
    typedef typename C< sizeof (f(H(), 0)) == 1, void *, void >::t t;
};

}; }; // namespace detail, namespace vcl

/**
 * A thin wrapper around rtl::Reference to implement the acquire and dispose semantics we want for references to vcl::Window subclasses.
 * @param reference_type must be a subclass of vcl::Window
 */
template <class reference_type>
class VclReference
{

    ::rtl::Reference<reference_type> m_rInnerRef;

public:
    /** Constructor...
     */
    inline VclReference()
        : m_rInnerRef()
    {}


    /** Constructor...
     */
    inline VclReference (reference_type * pBody)
        : m_rInnerRef(pBody)
    {}


    /** Copy constructor...
     */
    inline VclReference (const VclReference<reference_type> & handle)
        : m_rInnerRef (handle.m_rInnerRef)
    {}

    /** Up-casting conversion constructor: Copies interface reference.

        Does not work for up-casts to ambiguous bases.  For the special case of
        up-casting to Reference< XInterface >, see the corresponding conversion
        operator.

        @param rRef another reference
    */
    template< class derived_type >
    inline VclReference(
        const VclReference< derived_type > & rRef,
        typename ::vcl::detail::UpCast< reference_type, derived_type >::t = 0 )
        : m_rInnerRef( static_cast<reference_type*>(rRef.get()) )
    {
    }

    /** Get the body. Can be used instead of operator->().
         I.e. handle->someBodyOp() and handle.get()->someBodyOp()
         are the same.
     */
    inline reference_type * SAL_CALL get() const
    {
        return m_rInnerRef.get();
    }

    /** Probably most common used: handle->someBodyOp().
     */
    inline reference_type * SAL_CALL operator->() const
    {
        return m_rInnerRef.get();
    }

    inline void disposeAndClear()
    {
        // hold it alive for the lifetime of this method
        ::rtl::Reference<reference_type> aTmp(m_rInnerRef);
        m_rInnerRef.clear(); // we should use some 'swap' method ideally ;-)
        if (aTmp.get())
            aTmp->dispose();
    }

}; // class VclReference

#endif // INCLUDED_VCL_REFERENCE_HXX

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