Helu, I have often found myself in need of an option menu or combo box in LTK.
However at present LTK supports only one type of (cascade) menu. Although ltk.lisp (0.90 at the time of writing) defines unused *class-args* via defargs for menubutton and menu, the classes menubutton and menu do not support the various interactions that Tk allows between its (Tk's) "menubuttons" and "menus". It is not clear what the thinking of the author is on supporting other interactions in the future. Code adding such functionality depends on LTK's internals and is therefore liable to break.
I am attaching a file which adds support for the tk_optionsMenu command via a new function TK-OPTION-MENU and a new LTK widget called OPTIONSMENU. This turns out to fit (nicely) with the LTK model of menus and I would request considering it for inclusion in an appropriate form into LTK. Especially as it depends on LTK's clos protocols.
Most of the file is comments and example code, I took the liberty of copying the licensing from ltk-mw and hope it is suitable. Feedback welcome.
-- Best Regards Madhu