Drag & Drop Shell items / stream format with VB's DataObject

Problem: Setting up an stream format with VB's DataObject.

Scenario:
Drag & Drop of shell items in SysTree32, wrapped in an usercontrol,
using IShellFolder,IDataObject,IDropTarget COM interfaces.

Operation (acting as drop target):

In the UC_OLEDragOver event (state = vbEnter) I get the IDataObject of
dragged items from VB's DataObject by Edanmo's black magic:
(http://www.mvps.org/emorcillo/en/code/vb6/getidataobject.shtml)
CopyMemory ido, ByVal ObjPtr(Data) + 16, 4&

In sucessive _OLEDragOver, OLEDragDrop I retrieve the IDropTarget of
the drop node and call IDropTarget.DragEnter etc methods passing the
IDataObject.

This works flawless , including the drag image provided by
IDropTargetHelper.


Operation (acting as drop source):

Normally you would implement an IDropSource as a public class with
QueryContinueDrag() and GiveFeedback() and call the DoDragDrop API.
This I want to avoid, since it would limit using the usercontrol in a
compiled ocx or ActiveExe project.

So I get the IDataObject of dragged items by ISF.GetUIObjectOf(),
enumerate it's contents with IEnumFORMATETC, copy content of a format
to a bytearray and populate VB's DataObject with it. So the shell
provides me with all needed formats,
especially the difficult CFSTR_SHELLIDLIST.

Sucessive _OLEDragOver, OLEDragDrop events like above.

I create the drag image by IDragSourceHelper.InitializeFromBitmap().

Dragging in- or outside is fine, but drag image only shows up in my
tree, not in other (explorer) app.

IDragSourceHelper,IDropTargetHelper use two internal (thus
undocumented) formats:
CFSTR_DRAGBITS uses global memory (TYMED_HGLOBAL) and is copied to my
VB.DataObject.
CFSTR_DRAGCONTEXT is a simple 16 bytes stream (TYMED_ISTREAM) and I
don't know how to copy it.

Possible solutions:
I suspect the missing CFSTR_DRAGCONTEXT format causes the missing
image, so
- Can VB.DataObject handle somehow stream formats?

VB's DataObject wraps an IDataObject, so I tried to exchange the
original with a pointer to the IDataObject, obtained from shell.
-> no luck. Any clues, hints or documentation, how VB's DataObject
works internally?

The UserControl must have an IDropSource implementation.
- Does anyone posess black magic, howto obtain a reference ?

All the ones, I can't think of:
- Your turn, please!

PS:
I published the treeview usercontrol on PSC:
http://www.planet-source-code.com/vb/scripts/ShowCode.asp?
txtCodeId=59769&lngWId=1

A set of helper classes & modules turning it into an
Explorer alike tree, i will publish too,
when you hopefully solved my last problem.

.

Relevant Pages