The framework provides the following classes to implement default features for ActiveX designer interfaces:
The IDesignerDropTargetImpl class provides default Drag&Drop target support for toolbox items. The IDesignerToolboxImpl class provides default toolbox support by implementing the IDesignerToolbox interface. TThe other two classes also implement the ActiveX designer interface of the corresponding name; for example, IActiveDesignerImpl implements the IActiveDesigner interface.
When your designer requires default features for any one of the ActiveX Designer interfaces, it should inherit from the corresponding IxxImpl class. However, you can override the defaults by overriding the public implementation methods provided in each class. This approach is similar to that used by ATL's CComControl class for ActiveX controls.