Unless I missed completely missed something about OSX, you would preferably code it in Objective-C (which is a fantastic language for creating GUI's). In which case, GUI's for most other platforms are coded in C, C++, Delphi, VB, etc. wouldn't have a place on OSX.
Apple has two first-class APIs to the OS. One is C, one is Objective-C. The C APIs can (obviously) be directly called from C++.
Is the prefered language to program GUI's on OSX, C++?
No. C or Objective-C. The C APIs and the Objective-C APIs are approximately equipotent.
Most moder GUI development for Unicies, uses C++; for Win32 it is either C, C++, VB, or Delphi. So the question then... would a Boost GUI library (which is C++) be unlikely to be used on OSX?
The quality of the user interface of all of those applications is something that I, as a professional Mac developer, would be ashamed to ship. (They are not all equally bad, though.)
you highlighted my point exactly - they are bad, compared to native applications, because it is _really hard_ to make a cross-platform GUI library. They are good, particularily considering this fact.
Really hard, yes. Really important, too, if you want to ship a product that doesn't suck.
I firmly believe that the problem of producing a cross-platform framework that is able to accommodate the user experience demands of several platforms is difficult and tractable.
tractable => "Easily managed or controlled; governable" (dictionary.com)
is the problem "difficult" or "easy"? (my guess that you have miss-type the last bit of the sentence - although I'm not sure which way it was meant...)
Ah, it would appear that I was not using "tractable" properly. Thanks for the correction. What I meant it "possible to solve given a sufficiently capable and motivated group of engineers". I believe the problem is hard, but not without a solution. I also think that there's a partial solution that is considerably simpler, and that's what people seem to be shipping today.
I agree completely - and is why this "Java style GUI..." is a good discussion topic. Mathew