Detailed Description

QAbstractExtensionManager is not intended to be instantiated directly; use the QExtensionManager instead.

In Qt Designer, extension are not created until they are required. For that reason, when implementing a custom 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 Qt Designer's extension manager.

When an 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 the requested extension for the selected object, is found. This factory will then make an instance of the extension.