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# QDesignerCustomWidgetInterface Class Reference
[QtDesigner module]

The QDesignerCustomWidgetInterface class enables Qt Designer to access and construct a custom widget. More...

    #include <QDesignerCustomWidgetInterface>

- List of all members, including inherited members

### Public Functions

- virtual ~QDesignerCustomWidgetInterface ()
- virtual QString codeTemplate () const
- virtual QWidget * createWidget ( QWidget * parent ) = 0
- virtual QString domXml () const
- virtual QString group () const = 0
- virtual QIcon icon () const = 0
- virtual QString includeFile () const = 0
- virtual void initialize ( QDesignerFormEditorInterface * formEditor )
- virtual bool isContainer () const = 0
- virtual bool isInitialized () const
- virtual QString name () const = 0
- virtual QString toolTip () const = 0
- virtual QString whatsThis () const = 0

## Detailed Description

The QDesignerCustomWidgetInterface class enables Qt Designer to access and construct a custom widget.

QDesignerCustomWidgetInterface provides a custom widget with an interface. The class contains a set of functions that gives Qt Designer the basic information about the widget, such as its class name and its include file. Furthermore the interface is able to create instances of the custom widget, and it defines the initialize() function which is called after the custom widget plugin is loaded into Qt Designer. This latter function's QDesignerFormEditorInterface parameter provides the plugin with a gateway to all of Qt Designer's API.

When implementing a custom widget you must subclass QDesignerCustomWidgetInterface to expose your widget to Qt Designer. For example:

        class MyCustomWidgetPlugin : public QObject, public QDesignerCustomWidgetInterface
        {
            Q_OBJECT
            Q_INTERFACES(QDesignerCustomWidgetInterface)

        public:
            MyCustomWidgetPlugin(QObject *parent = 0);

            bool isContainer() const;
            bool isInitialized() const;
            QIcon icon() const;
            QString domXml() const;
            QString group() const;
            QString includeFile() const;
            QString name() const;
            QString toolTip() const;
            QString whatsThis() const;
            QWidget *createWidget(QWidget *parent);
            void initialize(QDesignerFormEditorInterface *core);

        private:
            bool initialized;
        };

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 Qt Designer to use the qobject_cast() function to query for supported interfaces using nothing but a QObject pointer.

In the implementation of the class you must remember to export your custom widget plugin to Qt Designer using the Q_EXPORT_PLUGIN2() macro:

            Q_EXPORT_PLUGIN2(MyCustomWidget)

This macro ensures that Qt Designer can access and construct the custom widget. Without this macro, there is no way for Qt Designer 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 types are supported:

- QVariant::ByteArray
- QVariant::Bool
- QVariant::Color
- QVariant::Cursor
- QVariant::Date
- QVariant::DateTime
- QVariant::Double
- QVariant::Int
- QVariant::Point
- QVariant::Rect
- QVariant::Size
- QVariant::SizePolicy
- QVariant::String
- QVariant::Time
- QVariant::UInt

For a complete example using the QDesignerCustomWidgetInterface class, see the Custom Widget Example. The example shows how to create a custom widget plugin for Qt Designer.

See also QDesignerCustomWidgetCollectionInterface and Creating Custom Widgets for Qt Designer.

## Member Function Documentation

### QDesignerCustomWidgetInterface::~QDesignerCustomWidgetInterface () `[virtual]`

Destroys the custom widget interface.

### QString QDesignerCustomWidgetInterface::codeTemplate () const `[virtual]`

This function is reserved for future use by Qt Designer.

### QWidget * QDesignerCustomWidgetInterface::createWidget ( QWidget * parent ) `[pure virtual]`

Returns a new instance of the custom widget, with the given parent.

### QString QDesignerCustomWidgetInterface::domXml () const `[virtual]`

Returns the XML that is used to describe the custom widget's properties to Qt Designer.

### QString QDesignerCustomWidgetInterface::group () const `[pure virtual]`

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

### QIcon QDesignerCustomWidgetInterface::icon () const `[pure virtual]`

Returns the icon used to represent the custom widget in Qt Designer's widget box.

### QString QDesignerCustomWidgetInterface::includeFile () const `[pure virtual]`

Returns the path to the include file that uic uses when creating code for the custom widget.

### void QDesignerCustomWidgetInterface::initialize ( QDesignerFormEditorInterface * formEditor ) `[virtual]`

Initializes the widget for use with the specified formEditor interface.

See also isInitialized().

### bool QDesignerCustomWidgetInterface::isContainer () const `[pure virtual]`

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 Qt Designer.

### bool QDesignerCustomWidgetInterface::isInitialized () const `[virtual]`

Returns true if the widget has been initialized; otherwise returns false.

See also initialize().

### QString QDesignerCustomWidgetInterface::name () const `[pure virtual]`

Returns the name of the class that implements the custom widget.

### QString QDesignerCustomWidgetInterface::toolTip () const `[pure virtual]`

Returns a short description of the widget that can be used by Qt Designer in a tool tip.

### QString QDesignerCustomWidgetInterface::whatsThis () const `[pure virtual]`

Returns a description of the widget that can be used by Qt Designer in "What's This?" help for the widget.