Drag & Drop Icon/Tooltip settings?

[Gorshkov <listsubscriptions oghma on ca>]

I've implimented D&D from a TreeView/ListStore in one app window, to a
TreeView/TreeStore in another app window.

The D&D works properly - that's not the problem.

The problem is that the "tooltip" (that's what it looks like, anyway)
that appears under the cursor when dragging is a verbatim copy of
whatever TreeView row happened to be under the cursor when I start the
drag, regardless of how many rows are being dragged.

How do I change that "tooltip"?

I've tried using the gtk_drag_set_icon.... calls from a drag_begin
signal callback, but all that results in is having a brief flash, and
then only a normal cursor, with no 'tooltip' whatsoever, when I start to
drag.