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Once you have a custom widget plugin for Qt Designer, you can provide it with the expected behavior and functionality within Qt Designer's workspace, using custom widget extensions. QDesignerContainerExtension is necessary when implementing a custom multi-page container. Extension Types
There are several available types of extensions in Qt Designer. You can use all of these extensions in the same pattern, only replacing the respective extension base class.
![]() | QDesignerTaskMenuExtension QDesignerTaskMenuExtension is useful for custom widgets. It provides an extension that allows you to add custom menu entries to Qt Designer's task menu. The Task Menu Extension example illustrates how to use this class. |
![]() | QDesignerContainerExtension QDesignerContainerExtension is necessary when implementing a custom multi-page container. It provides an extension that allows you to add and delete pages for a multi-page container plugin in Qt Designer. The Container Extension example further explains how to use this class. Note: It is not possible to add custom per-page properties for some widgets (e.g., QTabWidget) due to the way they are implemented. |
![]() | QDesignerMemberSheetExtension The QDesignerMemberSheetExtension class allows you to manipulate a widget's member functions displayed when connecting signals and slots. |
![]() | QDesignerPropertySheetExtension, QDesignerDynamicPropertySheetExtension These extension classes allow you to control how a widget's properties are displayed in Qt Designer's property editor. |
Warning: All widgets have default property and member sheets. If you implement custom property sheet or member sheet extensions, your custom extensions will override the default sheets.Creating an Extension
To create an extension you must inherit both QObject and the appropriate base class, and reimplement its functions. Since we are implementing an interface, we must ensure that it is made known to the meta object system using the Q_INTERFACES() macro in the extension class's definition. For example:
class MyExtension: public QObject, public QdesignerContainerExtension { Q_OBJECT Q_INTERFACE(QDesignerContainerExtension) ... }This enables Qt Designer to use the qobject_cast() function to query for supported interfaces using a QObject pointer only.
When an extension is requested, Qt Designer's extension manager will run through its registered factories calling QExtensionFactory::createExtension() for each of them until it finds one that is able to create the requested extension for the selected widget. This factory will then make an instance of the extension.
The purpose is to reimplement the QExtensionFactory::createExtension() function, making it able to create your extension, such as a MultiPageWidget container extension.
You can either create a new QExtensionFactory and reimplement the QExtensionFactory::createExtension() function:
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 enable the factory to create your custom extension as well:
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; } }
void MyPlugin::initialize(QDesignerFormEditorInterface *formEditor) { if (initialized) return; QExtensionManager *manager = formEditor->extensionManager(); Q_ASSERT(manager != 0); manager->registerExtensions(new MyExtensionFactory(manager), Q_TYPEID(QDesignerTaskMenuExtension)); initialized = true; }The formEditor parameter in the QDesignerCustomWidgetInterface::initialize() function is a pointer to Qt Designer's current QDesignerFormEditorInterface object. You must use the QDesignerFormEditorInterface::extensionManager() function to retrieve an interface to Qt Designer's extension manager. Then you use the QExtensionManager::registerExtensions() function to register your custom extension factory.
Copyright © 2009 Nokia Corporation and/or its subsidiary(-ies) | Trademarks | Qt Jambi 4.5.2_01 |