I'm looking for a good way to program multi-document, multi-window (gui) applications to run on a free OS --- such as ubuntu.
So i'm looking for the right tools --- not necessarily an IDE, but an IDE for designing the gui would be useful.
The quickly ubuntu application looks very good, although it's not clear to me whether it can easily accommodate compiled C code (which is probably necessary for any serious programming due to all the C libraries, and the need for occasional intensive or deeply nested and looped routines).
Something based on vala would also be interesting.
Something that is tuned to be multi-platform is not necessarily good: anything called engineering involves trade-offs, and portability to non-free systems will come at the expense of something else (e.g., a natural feel on the hosts one is concerned with).