Can you recommend a good cross-platform application development framework?

I am looking to tap into the immense wisdom and experience of the Stackoverflow community to help me choose a good cross-platform application development framework.

The target application is a desktop graphics app supporting as many existing desktop environments as reasonable (Linux, BSD, Windows, Mac). Ideally Open Source, but I do not want to limit the choice of framework so if you know of a closed source framework worth mentioning, please let us know.

The ideal framework will provide the developers with as many prefabricated building blocks as possible so that they can focus on adding this app's specific functionality on top of the framework, rather than replicate generic functionality common to many apps.

Requirements:

- Target desktop environments (Linux, BSD, Windows, Mac); not mobile
and not server.

- Programming language is a given: combination of Python and C++.

- The application itself is a graphic app that will require fast
manipulation in 3D space of images and data.

The most important building blocks I am looking for are:

- GUI Toolkit. Can be multi-platform or OS-specific, provided that the framework helps me manage OS-specific versions of the app; with a GUI editor that does not scare away the not-so-technically minded graphic designers

- 3D graphics manipulation (OpenGL)

- Efficient manipulation of large data sets (tables with 50K entries)

- An efficient build system to manage the different supported operating systems, ideally cross-compiling

Preferences:

- Preferably an Open Source Framwork

- Preferably primary development platform Linux

- Preferably IDE available as well

Although I ask the question in the context of refactoring an application which has hit a ceiling, I kindly ask you to think of this as a green field to make it relevant also to developers looking to jump start the development of a new app.

Thanks

[Qt](

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) covers just about everything:

- is proper open source, with active development and a vibrant community
- the portability aspect is covered: goes from embedded to big systems with everything (particular Windows, Mac OS X, Linux) in between; *BSD should not be an issue either,
- the GUI aspects,
- has good Open GL support
- has Python bindings (3rd party though)
- countless examples,
- very good documentation
- and much more

That said, the topic has been addressed a few times before so make sure you peruse the old questions.

Besides QT, WxWidgets is an option. Now that QT has more aggressive licensing model, it may be less important to some. The big technical difference is WxWidgets actually uses the native toolkit on a given platform where QT provides its own. To some, this makes wxWidget apps feel more native; at least on Windows, Mac, Linux/GTK, or Sun/MOTIF platforms.

I've used the C++ side of the library for successful development and it integrates nicely with many different build setups. I have never used wxPython.

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