TVirtualStringTree.OnGetUserClipboardFormats Event

Drag'n drop and clipboard support event.

property OnGetUserClipboardFormats: TVTGetUserClipboardFormatsEvent;

Whenever the tree needs to specify the available clipboard formats for a clipboard or drag'n drop operation it calls this event too, to allow the application or descentants (which would override DoGetUserClipboardFormats) to specify own formats which can be rendered. Since the build-in data object does not know how to render formats which are specified here you have to supply a handler for the OnRenderOLEData event or an own IDataObject implementation to fully support your own formats. 

Use the Formats parameter which is an open array and add the identifiers of your formats (which you got when you registered the format).

TVirtualStringTree Class