It's interesting but disappointing that there's no standout "winner" among desktop GUI toolkits. Among other things, devs want to write software that runs on their favorite GNU/Linux distribution, but that also runs nicely and is easily installed on MS Windows and Mac OS X. Here are the arguments I hear against some current popular toolkits:

* GTK+ -- Has lots of moving parts. Difficult to build/install on MS Windows. Some say it's too closely tied to X11. Doesn't look enough like MS Windows on MS Windows. The LGPL licensing is very successful though, as demonstrated by the fairly large developer community and by its use in Gnome.

* Qt -- Either GPL your software or pay the licensing fees. Also some don't like having to deal with C++ if you're required to ever look under the hood. Nice that it comes in one big piece though.

* Tk -- Some have referred to Tk as a vistigial GUI appendage from a bygone era. Also it depends upon Tk. This one would be a hard sell to get everyone to agree on.

* wxWidgets -- Complaints are that it looks too much like the MS Windows API, and also that it's too big (being a wrapper around lower-level GUI toolkits).

It would seem that we (the free software community) should just bite the bullet, list out the basic requirements for a successful GUI toolkit, and go ahead and create it. I'd dare say that the requirements might look like this:

* Written in C. C is fast, portable, and everyone knows it. Corollary: keep it simple (like Tk) and packaged in one piece (like Qt). Having a half dozen different pieces all bolted together (like GTK+) in the name of modularity only makes it harder to create easily-distributable cross-platform apps. 2nd corollary: be careful not to tie it too closely to X11.

* Keep it simple so it's easy to port to Windows and Mac OS X (Cocoa). Corollary: simple and easy to build too.

* LGPL licensed. Most camps can probably (at least grudgingly) come to agreement on this, and it's worked pretty well for GTK+. Works for free software and for commercial apps, and tends to build nice communities.

* Can easily be made to look like MS Windows on MS Windows, and Aqua on Mac OS X. I really don't care if it's themable or not, but for wide adoption, it had at least better be able to easily make itself look like MS Windows and Aqua.

* Easy to make bindings for Python, Ruby, Perl, etc. I really do not want to write GUI apps in C, but I don't want it so fancy that you have to do acrobatics to mate, say, Python, to it.

* Simple and easy to use (like Tk).

Anyone working on or know of that cross-platform GUI toolkit? Because that's the one I want to use, and I bet it's the one a lot of devs would also want to use.