I find the comment:
gtk_object_set_user_data is deprecated and should not be used in newly-written code.
Use g_object_set_data() instead.
However, the official nim gtk2 module does not seem to define g_object_set_data
I don't see an official gtk3 module yet and it doesn't seem standard with the Linux distros yet anyway.
Please advise: Either:
proc new_set_data*(anObject: PObject, key: cstring, data: gpointer){.cdecl,
importc: "g_object_set_data", dynlib: lib.}
OOPS - - - my bad.
Found g_object_set_data in glib2.nim I'm clearly not very familiar with Gtk
Sorry!