I think, the duty of flext would be just to provide that handle to the object's box (along with some means to control it) and let the user use whatever GUI generating interface he likes (if portable or not).
i don't think so, the principle is that the external sends messages to a graphic server which is embedded in the application's GUI, that's TCL/TK for PD, don't know of MAX's.
I see, my simple approach is much like the one Max uses, where there is no client/server architecture. It's all self-consistent and bound to one machine. Maybe there is some cross-platform GUI library which support the client/server approach? (there are some indications that wxWindows does) I honestly admit that i don't like TCL/TK at all.
greetings, Thomas