With the DK.Delphi edition a user defined layer can be created via the Delphi source code. Refer to the DK.Delphi sample TGIS_LayerMIF for guidance on how to create a custom layer. That sample shows both reading and writing the custom layer to disk. Also, the OpenGIS SQL vector support is an example of a user defined layer which was, of course, developed by TatukGIS.
There are constraints on the creation of a fully user defined layer with the DK.ActiveX, because customizing via Delphi source code is out of scope for the ActiveX developer. But a custom Layer can be created with the DK.ActiveX by overriding. The easiest way is to create a XGIS_LayerVector and fill it with data using the custom adaptor. This involves adding shapes and adding points to that shape. The result is not a real native format but, depending on the situation, it can be enough. Superclassing in ActiveX is not possible. Latter we might possibly add a generic DLL to the DK.ActiveX which can be compiled to support custom formats.
Another option for the ActiveX developer is to hire TatukGIS to custom develop the required user defined layer.