rrwood asks: "I'm starting work on what is more or less an open-source 3D modeling application, and I'd like to make it as cross-platform as possible (Linux, FreeBSD, Windows, MacOS, etc.). OpenGL takes care of the 3D rendering I'm going to need, but I also need some sort of widget set, and I'm looking for advice as to what to use in that regard. I've done my Google homework and have come up with the following, but would like feedback from anyone who has already used any of these, or has recommendations about anything I may have missed. Yes, I know about Blender, and be reassured I am not planning on reinventing that wheel, okay? :-) So, here's what I've found so far. As I said, if anyone can add to this list or share his/her experiences actually working with any of these, that would be greatly appreciated."
"GLUI provides a flexible windowing system and a rich selection of widgets (buttons, checkboxes, radio button sets, spinners, text boxes, arcballs, dividers, packing panels, packing columns, etc.). GLUI's design is very straightforward, and the docs and examples are extremely well done. GLUI is highly portable, since it depends only on OpenGL and Glut.
GLOW is 'a cross-platform object-oriented framework for building interactive applications using OpenGL or similar APIs such as Mesa.' GLOW is basically an elegant C++ wrapper around Glut, providing push buttons, check boxes, radio buttons, scroll bars, sliders, text fields, menus, etc. This is a really nice description of GLOW, including comparisons to GLUI and MUI.
Speaking of MUI, Steve Baker's advice is basically 'just don't.' Instead, Steve recommends PUI, which he wrote. :) Actually, he speaks very highly of GLUI, and does a nice job of pointing out the subtle differences between GLUI and PUI.
PUI is part of PLIB, a rich and vibrant set of libraries for cross-platform game development. This is a wonderful intro to PUI. Go read it right now. Really. PUI itself does all the sorts of stuff I'm looking for, and perhaps more. It looks to be very stable and mature, too.
LibUFO is a C++ widget set for OpenGL, currently in alpha. Features include pluggable look and feel, theme support, and layout manager support. LibUFO can be used with GLUT, SDL or any native GL context, so it is highly portable, too. Except for the fact that this is only alpha code at this point, it looks quite nice.
FOX is a C++ toolkit for developing cross-platform GUI apps. It seems like a fairly standard C++ framework, with built-in OpenGL widgets, too. By all accounts, FOX is quite mature and stable, with a fairly active developer base. FOX supports many OSes, but not, unfortunately, the Mac. And yes, I could easily hack out Mac support myself, but I don't want to do that-- I want to write my app.
FLTK is another cross-platform C++ GUI toolkit with OpenGL support. The advantage of FLTK over FOX is that FLTK supports MacOS X (not 9.x and earlier-- too bad).
DirectFB is a library built on top of a framebuffer device such as the Linux framebuffer or SDL. There seems to be some 3D support in there via DirectFBGL, though the docs say that there is no hardware acceleration support (i.e. Mesa vs OpenGL). The thing that makes DirectFB particularly attractive is the fact that Gtk/Gdk has been ported to it.
SDL and ParaGUI are also an attractive option. SDL is insanely portable, and ParaGUI is a wonderful GUI/widget toolkit that runs on top of SDL. You really need to see the ParaGUI demos running to appreciate how slick it is. The screenshots are nice and all, but they don't do it justice. As well, ParaGUI is really slick in its support for themes, XML, and Python.
PicoGUI was a recent SlashDotting victim. As mentioned at that time, PicoGUI is actually a sophisticated client-server framework, capable of running in a wide variety of environments, including on top of OpenGL. There is plenty of info at the PicoGUI FAQ, including a few comments that suggest it would be a perfectly reasonable choice for what I'm looking at doing. Given the scope of what PicoGUI is trying to achieve, I'm a little nervous that it might be overkill for what I want to do.
Fresco is another client-server framework which some may have previously known as Berlin. Fresco seems very cool, but again, I suspect it is overkill for what I'm doing.
The GUI Toolkit/Framework Page is also an excellent resource for cross-platform development of all stripes.
And the OpenGL Toolkit FAQ is also an excellent resource with special emphasis on OpenGL."