Combining TreeView and DrawingArea (i.e. drawing on top of TreeView)

[Nickolai Dobrynin <dobrynin cs uwm edu>]

I would like to use a TreeView-generated table and be able to do some
customary drawing on top of it, the way it is done in DrawingArea.
Thus, I am inheriting from both TreeView and DrawingArea and override
the on_expose_event method.

Unfortunately, this doesn't compile:

error: no unique final overrider for `virtual void
   Glib::ObjectBase::destroy_notify_()' in `TreeViewWithDrawings'

error: no unique final overrider for `virtual void
   Glib::ObjectBase::set_manage()' in `TreeViewWithDrawings'

error: no unique final overrider for `virtual void
   Glib::ObjectBase::destroy_notify_()' in `TreeViewWithDrawings'

error: no unique final overrider for `virtual void
   Glib::ObjectBase::set_manage()' in `TreeViewWithDrawings'

Is there any way I could safely combine these two?  Any examples?

I do realize that what I'm doing is somewhat scary because the two classes
share the same base, so there must be some inheritance issues to deal with.

If, finally, the two widgets are not combinable, then maybe there is a different
way to draw a few straight lines on top of TreeView?  All I'm trying to do
is put a frame around several cells in a table, all within the same row.


Thanks very much,

Nickolai Dobrynin