Mono is probably the best choice if you're primarily a .NET developer and don't care about creating a well-integrated Mac app (which behaves like the Mac app in many cases that Mac users expect), Given your problem space, it sounds like you are. In doing so, pay particular attention to this limitation from the WebBrowser page if it relates to your problem:
Mono Webbrowser currently lacks support for window.external, a bridge that allows Javascript code to be built into the browser to communicate with the managed world using ObjectForScripting.
QT has worked very well and is a great platform if you want to develop this in C ++. Remember that there are licensing fees if this is a commercial application.
I played a little with wxWidgets. The big advantage here is that it will probably be the smallest distribution since you only need to include what you need. If all you need is a web browser, I would look at it, but in my experience it is difficult to make wxWidgets programs look good or act correctly on a Mac (or Windows, for that matter).
Rob napier
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