2011/11/3 Marc Feeley feeley@iro.umontreal.ca:
The actual C callback needs to pass the "callback data" (the wrapped closure) to scheme-callback by calling scheme_callback.
Thanks for the information. It was very useful to understand the Scheme-C interaction.
But the problem is much bigger than I thought, because only simple Gtk callbacks require no parameters. There are many signals which want to pass arguments to the callback function. The delete-from-cursor of the entry widget is such a signal:
http://developer.gnome.org/gtk3/stable/GtkEntry.html#GtkEntry-delete-from-cu...
And because of that it would not help much to be able to call a Scheme function without arguments. It is necessary to convert all arguments to Scheme values and call a Scheme function from C. I think I have to follow the link Alex has posted. The problem can not be solved without the Gtk marshal functions.