[gtkmm] TreeView custom cell renderers and create_row_drag_icon() interaction

[Pieter van Prooijen <Pieter van Prooijen daidalos nl>]

Hello,

(I'm not 100% sure if this is a gtkmm problem or a gtk+ API issue)

I'm experimenting with a custom cell renderer derived from 
CellRendererText which has its own render_vfunc() method, which works 
find when drawing normal rows.

I'm also using drag & drop with a custom cursor using the 
create_row_drag_icon() method. The problem is that render_vfunc() has a 
refptr to a Window as its first argument, where as the 
create_row_drag_icon() method invokes the cell renderer vfunc with a 
Drawable.

Because the drawable is wrapped in a RefPtr<GtkWindowObject>, the 
creation of this ref pointer fails (it tries to do a <dynamic_cast> from 
the drawable to a window object, so we get a null pointer) and an 
invalid window reference results.

Is this a problem in the gtk+ definition (which also has a Window as its 
argument, not a Drawable, but of course doesn't have the dynamic cast 
problem) or in the gtkmm wrapper of the cellrender API, or is there 
something else I'm missing ?

Let me know if I should provide more info,

Many thanks,

Pieter van Prooijen