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/*!

    \class QDesignerCustomWidgetInterface

    \brief The QDesignerCustomWidgetInterface class enables Qt Designer

    to access and construct custom widgets.

    \inmodule QtDesigner

    QDesignerCustomWidgetInterface provides a custom widget with an

    interface. The class contains a set of functions that must be subclassed

    to return basic information about the widget, such as its class name and

    the name of its header file. Other functions must be implemented to

    initialize the plugin when it is loaded, and to construct instances of

    the custom widget for \QD to use.

    When implementing a custom widget you must subclass

    QDesignerCustomWidgetInterface to expose your widget to \QD. For

    example, this is the declaration for the plugin used in the

    \l{Custom Widget Plugin Example}{Custom Widget Plugin example} that

    enables an analog clock custom widget to be used by \QD:

    \snippet examples/designer/customwidgetplugin/customwidgetplugin.h 0

    Note that the only part of the class definition that is specific

    to this particular custom widget is the class name. In addition,

    since we are implementing an interface, we must ensure that it's

    made known to the meta object system using the Q_INTERFACES()

    macro. This enables \QD to use the qobject_cast() function to

    query for supported interfaces using nothing but a QObject

    pointer.

    After \QD loads a custom widget plugin, it calls the interface's

    initialize() function to enable it to set up any resources that it

    may need. This function is called with a QDesignerFormEditorInterface

    parameter that provides the plugin with a gateway to all of \QD's API.

    \QD constructs instances of the custom widget by calling the plugin's

    createWidget() function with a suitable parent widget. Plugins must

    construct and return an instance of a custom widget with the specified

    parent widget. 

    In the implementation of the class you must remember to export

    your custom widget plugin to \QD using the Q_EXPORT_PLUGIN2()

    macro. For example, if a library called \c libcustomwidgetplugin.so

    (on Unix) or \c libcustomwidget.dll (on Windows) contains a widget

    class called \c MyCustomWidget, we can export it by adding the

    following line to the file containing the plugin implementation:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 14

    This macro ensures that \QD can access and construct the custom widget.

    Without this macro, there is no way for \QD to use it.

    When implementing a custom widget plugin, you build it as a

    separate library. If you want to include several custom widget

    plugins in the same library, you must in addition subclass

    QDesignerCustomWidgetCollectionInterface.

    \warning If your custom widget plugin contains QVariant

    properties, be aware that only the following \l

    {QVariant::Type}{types} are supported:

    \list

    \o QVariant::ByteArray

    \o QVariant::Bool

    \o QVariant::Color

    \o QVariant::Cursor

    \o QVariant::Date

    \o QVariant::DateTime

    \o QVariant::Double

    \o QVariant::Int

    \o QVariant::Point

    \o QVariant::Rect

    \o QVariant::Size

    \o QVariant::SizePolicy

    \o QVariant::String

    \o QVariant::Time

    \o QVariant::UInt

    \endlist

    For a complete example using the QDesignerCustomWidgetInterface

    class, see the \l {designer/customwidgetplugin}{Custom Widget

    Example}. The example shows how to create a custom widget plugin

    for \QD.

    \sa QDesignerCustomWidgetCollectionInterface {Creating Custom

    Widgets for Qt Designer}

*/

/*!

    \fn QDesignerCustomWidgetInterface::~QDesignerCustomWidgetInterface()

    Destroys the custom widget interface.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::name() const

    Returns the class name of the custom widget supplied by the interface.

    The name returned \e must be identical to the class name used for the

    custom widget.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::group() const

    Returns the name of the group to which the custom widget belongs.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::toolTip() const

    Returns a short description of the widget that can be used by \QD

    in a tool tip.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::whatsThis() const

    Returns a description of the widget that can be used by \QD in

    "What's This?" help for the widget.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::includeFile() const

    Returns the path to the include file that \l uic uses when

    creating code for the custom widget.

*/

/*!

    \fn QIcon QDesignerCustomWidgetInterface::icon() const

    Returns the icon used to represent the custom widget in \QD's

    widget box.

*/

/*!

    \fn bool QDesignerCustomWidgetInterface::isContainer() const

    Returns true if the custom widget is intended to be used as a

    container; otherwise returns false.

    Most custom widgets are not used to hold other widgets, so their

    implementations of this function will return false, but custom

    containers will return true to ensure that they behave correctly

    in \QD.

*/

/*!

    \fn QWidget *QDesignerCustomWidgetInterface::createWidget(QWidget *parent)

    Returns a new instance of the custom widget, with the given \a

    parent.

*/

/*!

    \fn bool QDesignerCustomWidgetInterface::isInitialized() const

    Returns true if the widget has been initialized; otherwise returns

    false.

    \sa initialize()

*/

/*!

    \fn void QDesignerCustomWidgetInterface::initialize(QDesignerFormEditorInterface *formEditor)

    Initializes the widget for use with the specified \a formEditor

    interface.

    \sa isInitialized()

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::domXml() const

    Returns the XML that is used to describe the custom widget's

    properties to \QD.

*/

/*!

    \fn QString QDesignerCustomWidgetInterface::codeTemplate() const

    This function is reserved for future use by \QD.

    \omit

    Returns the code template that \QD includes in forms that contain

    the custom widget when they are saved.

    \endomit

*/

/*!

    \macro QDESIGNER_WIDGET_EXPORT

    \relates QDesignerCustomWidgetInterface

    \since 4.1

    This macro is used when defining custom widgets to ensure that they are

    correctly exported from plugins for use with \QD.

    On some platforms, the symbols required by \QD to create new widgets

    are removed from plugins by the build system, making them unusable.

    Using this macro ensures that the symbols are retained on those platforms,

    and has no side effects on other platforms.

    For example, the \l{designer/worldtimeclockplugin}{World Time Clock Plugin}

    example exports a custom widget class with the following declaration:

    \snippet examples/designer/worldtimeclockplugin/worldtimeclock.h 0

    \dots

    \snippet examples/designer/worldtimeclockplugin/worldtimeclock.h 2

    \sa {Creating Custom Widgets for Qt Designer}

*/

/*!

    \class QDesignerCustomWidgetCollectionInterface

    \brief The QDesignerCustomWidgetCollectionInterface class allows

    you to include several custom widgets in one single library.

    \inmodule QtDesigner

    When implementing a custom widget plugin, you build it as a

    separate library. If you want to include several custom widget

    plugins in the same library, you must in addition subclass

    QDesignerCustomWidgetCollectionInterface.

    QDesignerCustomWidgetCollectionInterface contains one single

    function returning a list of the collection's

    QDesignerCustomWidgetInterface objects. For example, if you have

    several custom widgets \c CustomWidgetOne, \c CustomWidgetTwo and

    \c CustomWidgetThree, the class definition may look like this:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 12

    In the class constructor you add the interfaces to your custom

    widgets to the list which you return in the customWidgets()

    function:

    \snippet doc/src/snippets/code/doc_src_qtdesigner.qdoc 13

    Note that instead of exporting each custom widget plugin using the

    Q_EXPORT_PLUGIN2() macro, you export the entire collection. The

    Q_EXPORT_PLUGIN2() macro ensures that \QD can access and construct

    the custom widgets. Without this macro, there is no way for \QD to

    use them.

    \sa QDesignerCustomWidgetInterface, {Creating Custom Widgets for

    Qt Designer}

*/

/*!

    \fn QDesignerCustomWidgetCollectionInterface::~QDesignerCustomWidgetCollectionInterface() {

    Destroys the custom widget collection interface.

*/

/*!

    \fn QList<QDesignerCustomWidgetInterface*> QDesignerCustomWidgetCollectionInterface::customWidgets() const

    Returns a list of interfaces to the collection's custom widgets.

*/