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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.qdoc 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.qdoc 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.qdoc 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.qdoc 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()

*/