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/*!
    \class QDesignerPropertySheetExtension

    \brief The QDesignerPropertySheetExtension class allows you to
    manipulate a widget's properties which is displayed in Qt
    Designer's property editor.

    \sa QDesignerDynamicPropertySheetExtension

    \inmodule QtDesigner

    QDesignerPropertySheetExtension provides a collection of functions that
    are typically used to query a widget's properties, and to
    manipulate the properties' appearance in the property editor. For
    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.cpp 15

    Note that if you change the value of a property using the
    QDesignerPropertySheetExtension::setProperty() function, the undo
    stack is not updated. To ensure that a property's value can be
    reverted using the undo stack, you must use the
    QDesignerFormWindowCursorInterface::setProperty() function, or its
    buddy \l
    {QDesignerFormWindowCursorInterface::setWidgetProperty()}{setWidgetProperty()},
    instead.

    When implementing a custom widget plugin, a pointer to \QD's
    current QDesignerFormEditorInterface object (\c formEditor in the
    example above) is provided by the
    QDesignerCustomWidgetInterface::initialize() function's parameter.

    The property sheet, or any other extension, can be retrieved by
    querying \QD's extension manager using the qt_extension()
    function. When you want to release the extension, you only need to
    delete the pointer.

    All widgets have a default property sheet which populates \QD's
    property editor with the widget's properties (i.e the ones defined
    with the Q_PROPERTY() macro). But QDesignerPropertySheetExtension
    also provides an interface for creating custom property sheet
    extensions.

    \warning \QD uses the QDesignerPropertySheetExtension to feed its
    property editor. Whenever a widget is selected in its workspace,
    \QD will query for the widget's property sheet extension. If the
    selected widget has an implemented property sheet extension, this
    extension will override the default property sheet.

    To create a property sheet extension, your extension class must
    inherit from both QObject and
    QDesignerPropertySheetExtension. Then, since we are implementing
    an interface, we must ensure that it's made known to the meta
    object system using the Q_INTERFACES() macro:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.cpp 16

    This enables \QD to use qobject_cast() to query for supported
    interfaces using nothing but a QObject pointer.

    In \QD the extensions are not created until they are
    required. For that reason, when implementing a property sheet
    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}.

    When a property sheet extension is required, \QD'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 property
    sheet extension for the selected widget, is found. This factory
    will then make an instance of the extension. If no such factory
    can be found, \QD will use the default property sheet.

    There are four available types of extensions in \QD:
    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.

    The QExtensionFactory class provides a standard extension factory,
    and can also be used as an interface for custom extension
    factories. You can either create a new QExtensionFactory and
    reimplement the QExtensionFactory::createExtension() function. For
    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.cpp 17

    Or you can use an existing factory, expanding the
    QExtensionFactory::createExtension() function to make the factory
    able to create a property sheet extension extension as well. For
    example:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.cpp 18

    For a complete example using an extension 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 \QD's task menu.

    \sa QExtensionFactory, QExtensionManager, {Creating Custom Widget
    Extensions}
*/

/*!
    \fn QDesignerPropertySheetExtension::~QDesignerPropertySheetExtension()

    Destroys the property sheet extension.
*/

/*!
    \fn int QDesignerPropertySheetExtension::count() const

    Returns the selected widget's number of properties.
*/

/*!
    \fn int QDesignerPropertySheetExtension::indexOf(const QString &name) const

    Returns the index for a given property \a name.

    \sa propertyName()
*/

/*!
    \fn QString QDesignerPropertySheetExtension::propertyName(int index) const

    Returns the name of the property at the given \a index.

    \sa indexOf()
*/

/*!
    \fn QString QDesignerPropertySheetExtension::propertyGroup(int index) const

    Returns the property group for the property at the given \a index.

    \QD's property editor supports property groups, i.e. sections of
    related properties. A property can be related to a group using the
    setPropertyGroup() function. The default group of any property is
    the name of the class that defines it. For example, the
    QObject::objectName property appears within the QObject property
    group.

    \sa indexOf(), setPropertyGroup()
*/

/*!
    \fn void QDesignerPropertySheetExtension::setPropertyGroup(int index, const QString &group)

    Sets the property group for the property at the given \a index to
    \a group.

    Relating a property to a group makes it appear within that group's
    section in the property editor. The default property group of any
    property is the name of the class that defines it. For example,
    the QObject::objectName property appears within the QObject
    property group.

    \sa indexOf(), property(), propertyGroup()
*/

/*!
    \fn bool QDesignerPropertySheetExtension::hasReset(int index) const

    Returns true if the property at the given \a index has a reset
    button in \QD's property editor, otherwise false.

    \sa indexOf(), reset()
*/

/*!
    \fn bool QDesignerPropertySheetExtension::reset(int index)

    Resets the value of the property at the given \a index, to the
    default value. Returns true if a default value could be found, otherwise false.

    \sa indexOf(), hasReset(), isChanged()
*/

/*!
    \fn bool QDesignerPropertySheetExtension::isVisible(int index) const

    Returns true if the property at the given \a index is visible in
    \QD's property editor, otherwise false.

    \sa indexOf(), setVisible()
*/

/*!
    \fn void QDesignerPropertySheetExtension::setVisible(int index, bool visible)

    If \a visible is true, the property at the given \a index is
    visible in \QD's property editor; otherwise the property is
    hidden.

    \sa indexOf(), isVisible()
*/

/*!
    \fn bool QDesignerPropertySheetExtension::isAttribute(int index) const

    Returns true if the property at the given \a index is an attribute,
    which will be \e excluded from the UI file, otherwise false.

    \sa indexOf(), setAttribute()
*/

/*!
    \fn void QDesignerPropertySheetExtension::setAttribute(int index, bool attribute)

    If \a attribute is true, the property at the given \a index is
    made an attribute which will be \e excluded from the UI file;
    otherwise it will be included.

    \sa indexOf(), isAttribute()
*/

/*!
    \fn QVariant QDesignerPropertySheetExtension::property(int index) const

    Returns the value of the property at the given \a index.

    \sa indexOf(), setProperty(), propertyGroup()
*/

/*!
    \fn void QDesignerPropertySheetExtension::setProperty(int index, const QVariant &value)

    Sets the \a value of the property at the given \a index.

    \warning If you change the value of a property using this
    function, the undo stack is not updated. To ensure that a
    property's value can be reverted using the undo stack, you must
    use the QDesignerFormWindowCursorInterface::setProperty()
    function, or its buddy \l
    {QDesignerFormWindowCursorInterface::setWidgetProperty()}{setWidgetProperty()},
    instead.

    \sa indexOf(), property(), propertyGroup()
*/

/*!
    \fn bool QDesignerPropertySheetExtension::isChanged(int index) const

    Returns true if the value of the property at the given \a index
    differs from the property's default value, otherwise false.

    \sa indexOf(), setChanged(), reset()
*/

/*!
    \fn void QDesignerPropertySheetExtension::setChanged(int index, bool changed)

    Sets whether the property at the given \a index is different from
    its default value, or not, depending on the \a changed parameter.

    \sa indexOf(), isChanged()
*/