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QDesignerContainerExtension Class Reference
[QtDesigner module]

The QDesignerContainerExtension class allows you to add pages to a custom multi-page container in Qt Designer's workspace. More...

#include <QDesignerContainerExtension>

Public Functions


Detailed Description

The QDesignerContainerExtension class allows you to add pages to a custom multi-page container in Qt Designer's workspace.

QDesignerContainerExtension provide an interface for creating custom container extensions. A container extension consists of a collection of functions that Qt Designer needs to manage a multi-page container plugin, and a list of the container's pages.

Warning: This is not an extension for container plugins in general, only custom multi-page containers.

To create a container extension, your extension class must inherit from both QObject and QDesignerContainerExtension. For example:

    class MyContainerExtension : public QObject,
           public QDesignerContainerExtension
    {
        Q_OBJECT
        Q_INTERFACES(QDesignerContainerExtension)

    public:
        MyContainerExtension(MyCustomWidget *widget,
                             QObject *parent = 0);
        int count() const;
        QWidget *widget(int index) const;
        int currentIndex() const;
        void setCurrentIndex(int index);
        void addWidget(QWidget *widget);
        void insertWidget(int index, QWidget *widget);
        void remove(int index);

    private:
        MyCustomWidget *myWidget;
    };

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.

You must reimplement several functions to enable Qt Designer to manage a custom multi-page container widget: Qt Designer uses count() to keep track of the number pages in your container, widget() to return the page at a given index in the list of the container's pages, and currentIndex() to return the list index of the selected page. Qt Designer uses the addWidget() function to add a given page to the container, expecting it to be appended to the list of pages, while it expects the insertWidget() function to add a given page to the container by inserting it at a given index.

In Qt Designer the extensions are not created until they are required. For that reason you must also create a QExtensionFactory, i.e a class that is able to make an instance of your extension, and register it using Qt Designer's extension manager.

When a container extension is required, Qt Designer's extension manager will run through all its registered factories calling QExtensionFactory::createExtension() for each until the first one that is able to create a container extension, is found. This factory will then create the extension for the plugin.

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.

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:

    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;
    }

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

    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;
        }
    }

For a complete example using the QDesignerContainerExtension class, see the Container Extension example. The example shows how to create a custom multi-page plugin for Qt Designer.

See also QExtensionFactory, QExtensionManager, and Creating Custom Widget Extensions.


Member Function Documentation

QDesignerContainerExtension::~QDesignerContainerExtension ()   [virtual]

Destroys the extension.

void QDesignerContainerExtension::addWidget ( QWidget * page )   [pure virtual]

Adds the given page to the container by appending it to the extension's list of pages.

See also insertWidget(), remove(), and widget().

int QDesignerContainerExtension::count () const   [pure virtual]

Returns the number of pages in the container.

int QDesignerContainerExtension::currentIndex () const   [pure virtual]

Returns the index of the currently selected page in the container.

See also setCurrentIndex().

void QDesignerContainerExtension::insertWidget ( int index, QWidget * page )   [pure virtual]

Adds the given page to the container by inserting it at the given index in the extension's list of pages.

See also addWidget(), remove(), and widget().

void QDesignerContainerExtension::remove ( int index )   [pure virtual]

Removes the page at the given index from the extension's list of pages.

See also addWidget() and insertWidget().

void QDesignerContainerExtension::setCurrentIndex ( int index )   [pure virtual]

Sets the the currently selected page in the container to be the page at the given index in the extension's list of pages.

See also currentIndex().

QWidget * QDesignerContainerExtension::widget ( int index ) const   [pure virtual]

Returns the page at the given index in the extension's list of pages.

See also addWidget() and insertWidget().


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