cannot set tooltips over a picker widget?

[Francesco Montorsi <f18m_cpp217828 yahoo it>]

GTK+ 2.10.3


Hi,
   I'm trying to set a tooltip on a GtkFileChooserButton widget without 
success... maybe it's simply not possible?

I've done a minimal change to the attached pickers.c file of the 
"gtk-demo" app in order to show it... just drop it over your original 
one and recompile the gtk-demo: I can't see any tooltip...

Thanks for any hint,
Francesco

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