XCB is a C library that is intended as a replacement for xlib.
TkGS is a graphics system that aims to replace the current Xlib emulation layer (XLEL) onto which Tk is implemented on Windows and MacOS platforms. The XLEL has shown its limits, notably in term of performance, and TkGS is an attempt to address all the issues where the XLEL fails to give satisfaction. TkGS also tries to ease the implementation of future features such as printing support.
This toolkit is not, despite some naming similarities, particularly related to Tk.
It is a FSF-supported toolkit that was developed to support the GIMP Graphics Package. The authors plan to use an object database system to "make public" the Gtk API and will use the Gtk interface in conjunction with Scheme/Guile.
Gtk can also be used with C, C++ (using Gtk--, Objective-C, Perl, and Python, which is rather more attractive than what is available for other toolkits (e.g. Qt) that are designed to work solely with C++.
Several projects have been initiated to build GUI Builders of one sort or another to assist people that are trying to build GTk applications.
Dia A gtk+ based diagram creation program
It bears striking resemblance to the OpenGL system; it cannot legally be called OpenGL as the authors of Mesa have neither run it through the official conformance tests nor paid for licensing of the OpenGL name.
Nonetheless, cases where OpenGL software cannot run using Mesa tend to be considered to represent "bugs" that need to be fixed. Cases of nonconformance are getting increasingly unusual...
Unfortunately, Amulet is no longer being actively developed at CMU.
Motif is the industry standard graphical user interface, (as defined by the IEEE 1295 specification), used on more than 200 hardware and software platforms. It provides application developers, end users, and system vendors with the industry's most widely used environment for standardizing application presentation on a wide range of platforms. Motif is the leading user interface for the Unix based operating system.
Love it or hate it (and many hate it), Motif has been the "industry standard" GUI toolkit used by commercial vendors of Unix products.
Volumes 6A and 6B of the O'Reilly Associates 'Definitive Guides to the X Window System' have been made freely available for download. They are also available from the O'Reilly Open Books Project"
... It defines a standard set of functional capabilities and supporting infrastructure, and the associated standard application programming interfaces, command line actions, data interchange formats and protocols, that must be supported by a conformant system. It provides standard forms of the facilities normally found in a graphical user interface environment, including windowing and window management, session management, file management, electronic mail, text editing, calendar and appointments management, calculator, application building and integration services, print job services, and a help service.
A freely-redistributable alternative to the Motif GUI development libraries for X. Not quite fully interoperable yet, but there are quite a number of Motif applications that work nicely with LessTif. There is a book published called [Inside LessTif. ]
Fresco - X Library - dead and gone...
This is one of the more sophisticated (failed) X GUI framework attempts; it is the outgrowth of the former InterViews X library, and builds atop CORBA. It probably should have become the "standard" X toolkit, unfortunately The Open Group chose to adopt the non-free Motif toolkit instead.
The Project formerly known as Berlin has incorporated many of Fresco's ideas, and has been renamed as Fresco.
C++ -based GUI tools for use with X. One of the most mature toolsets available.
A cross-platform C++ library usable for MacOS, Win32, BeOS, and Unix/XWindows, providing a GUI toolkit, lightweight databases, networking support...
A package oriented towards building 3D animated/graphical applications, produced by the Digital Domain group responsible for the special effects in the movie Titanic.
Digital Domain has unfortunately refused to have continued involvement with FTLK, so another company is now hosting continued development efforts.
EZWGL 1.40 is a GUI toolkit for X11. It is a C library built on top of Xlib. EZWGL includes a set of 30 or so commonly used widgets. It supports many interesting features such as Resources, Drag and Drop, Background Tiling, and Docking. EZWGL also include a 3D graphics library.
This will connect to a Display Postscript "rendering engine" to allow platform-independent graphics presentation. Work is ongoing on "Display Ghostscript," a freely available version of this. There is an extremely alpha version of Display Ghostscript available.
Display Postscript represents an "open" printing framework that is analogous to Microsoft's GDI print rendering system. It might be such, if the availability of the DGS implementation could make DPS as ubiquitous as GDI...
One of the more unambiguously useful uses of a GUI has turned out to be to build utilities to build graphical user interfaces. It tends to be a whole lot easier to "draw" GUIs than it is to "code" them.
A touch screen system deployed on Linux, AIX, and SCO, which runs as an X Window manager which assumes X terminals as touch screens on a network.
They're not selling "open source;" they are instead selling an application framework that has typically been oriented towards POS applications such as restaurant sales terminals.
They were hoping for big things when the Transmeta web slate products begin to become available.