I never used TCL, sorry.
It works with template system, when in GUI/CUI mode. I use language like XSLT, but better fits with my needs. Application request to activate action /action/ok and it activate templates /action/ _. Inside one of /action/_ (or /action/ok) template we generate button, attaching callback given by app to button in this template and set text to ok (last-part-of-path). When app request to change text of ok button, it can do this by special API of course. Very positive aspect is, libgreattao can generate gui in many ways. Another style (style could be selected by user), we generate dropdown list with options like /actions/ok, /action/cancel, etc. and two buttons: (1) process button to process event related to selected option and (2) cancel, with will be generated only if /actions/cancel is requested. We could also set template priority, so /actions/cancel wouldn't be provided in dropdown list, but only near process button.
