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default_extensionfactory.cpp

/****************************************************************************
**
** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
**
** This file is part of the Qt Designer of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
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** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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****************************************************************************/

#include <QtDesigner/default_extensionfactory.h>
#include "qextensionmanager.h"
#include <qpointer.h>
#include <QtCore/qdebug.h>

/*!
    \class QExtensionFactory

    \brief The QExtensionFactory class allows you to create a factory
    that is able to make instances of custom extensions in Qt
    Designer.

    \inmodule QtDesigner

    In \QD the extensions are not created until they are required. For
    that reason, when implementing a custom extension, you must also
    create a QExtensionFactory, i.e. a class that is able to make an
    instance of your extension, and register it using \QD's \l
    {QExtensionManager}{extension manager}.

    The QExtensionManager class provides extension management
    facilities for Qt Designer. When an extension is required, Qt
    Designer's \l {QExtensionManager}{extension manager} will run
    through all its registered factories calling
    QExtensionFactory::createExtension() for each until the first one
    that is able to create a requested extension for the selected
    object, is found. This factory will then make an instance of the
    extension.

    There are four available types of extensions in Qt Designer:
    QDesignerContainerExtension , QDesignerMemberSheetExtension,
    QDesignerPropertySheetExtension and QDesignerTaskMenuExtension. Qt
    Designer's behavior is the same whether the requested extension is
    associated with a multi page container, a member sheet, a property
    sheet or a task menu.

    You can either create a new QExtensionFactory and reimplement the
    QExtensionFactory::createExtension() function. For example:

    \code
        QObject *ANewExtensionFactory::createExtension(QObject *object,
                const QString &iid, QObject *parent) const
        {
            if (iid != Q_TYPEID(QDesignerContainerExtension))
                return 0;

            if (MyCustomWidget *widget = qobject_cast<MyCustomWidget*>
                   (object))
                return new MyContainerExtension(widget, parent);

            return 0;
        }
    \endcode

    Or you can use an existing factory, expanding the
    QExtensionFactory::createExtension() function to make the factory
    able to create your extension as well. For example:

    \code
        QObject *AGeneralExtensionFactory::createExtension(QObject *object,
                const QString &iid, QObject *parent) const
        {
            MyCustomWidget *widget = qobject_cast<MyCustomWidget*>(object);

            if (widget && (iid == Q_TYPEID(QDesignerTaskMenuExtension))) {
                return new MyTaskMenuExtension(widget, parent);

            } else if (widget && (iid == Q_TYPEID(QDesignerContainerExtension))) {
                return new MyContainerExtension(widget, parent);

            } else {
                return 0;
            }
        }
    \endcode

    For a complete example using the QExtensionFactory class, see the
    \l {designer/taskmenuextension}{Task Menu Extension example}. The
    example shows how to create a custom widget plugin for Qt
    Designer, and how to to use the QDesignerTaskMenuExtension class
    to add custom items to Qt Designer's task menu.

    \sa QExtensionManager, QAbstractExtensionFactory
*/

/*!
    Constructs an extension factory with the given \a parent.
*/
00112 QExtensionFactory::QExtensionFactory(QExtensionManager *parent)
    : QObject(parent)
{
}

/*!
    Returns the extension specified by \a iid for the given \a object.

    \sa createExtension()
*/

00123 QObject *QExtensionFactory::extension(QObject *object, const QString &iid) const
{
    if (!object)
        return 0;

    QPair<QString, QObject*> key = qMakePair(iid, object);
    if (!m_extensions.contains(key)) {
        if (QObject *ext = createExtension(object, iid, const_cast<QExtensionFactory*>(this))) {
            connect(ext, SIGNAL(destroyed(QObject*)), this, SLOT(objectDestroyed(QObject*)));
            m_extensions.insert(key, ext);
        }
    }

    if (!m_extended.contains(object)) {
        connect(object, SIGNAL(destroyed(QObject*)), this, SLOT(objectDestroyed(QObject*)));
        m_extended.insert(object, true);
    }

    return m_extensions.value(key);
}

void QExtensionFactory::objectDestroyed(QObject *object)
{
    QMutableMapIterator< QPair<QString,QObject*>, QObject*> it(m_extensions);
    while (it.hasNext()) {
        it.next();

        QObject *o = it.key().second;
        if (o == object || object == it.value()) {
            it.remove();
        }
    }

    m_extended.remove(object);
}

/*!
    Creates an extension specified by \a iid for the given \a object.
    The extension object is created as a child of the specified \a
    parent.

    \sa extension()
*/
00166 QObject *QExtensionFactory::createExtension(QObject *object, const QString &iid, QObject *parent) const
{
    Q_UNUSED(object);
    Q_UNUSED(iid);
    Q_UNUSED(parent);

    return 0;
}

/*!
    Returns the extension manager for the extension factory.
*/
00178 QExtensionManager *QExtensionFactory::extensionManager() const
{
    return static_cast<QExtensionManager *>(parent());
}

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