X Window System: Encyclopedia II - X Window System - History

X Window System - History

X Window System - Predecessors

Several bitmap display systems preceded X. From Xerox came the Alto (1973) and the Star (1981). From Apple came the Lisa (1983) and the Macintosh (1984). The Unix world had the Andrew Project (1982) and Rob Pike's Blit terminal (1984).

X derives its name as a successor to a pre-1983 window system called W (the letter X directly following W in the Latin alphabet). W Window System ran under the V operating system. W used a network protocol supporting terminal and graphics windows, the server maintaining display lists.

X Window System - Origin and early development

The original idea of X emerged at MIT in 1984 as a collaboration between Jim Gettys (of Project Athena) and Bob Scheifler (of the MIT Laboratory for Computer Science). Scheifler needed a usable display environment for debugging the Argus system. Project Athena (a joint project between Digital Equipment Corporation (DEC), MIT and IBM to provide easy access to computing resources for all students) needed a platform-independent graphics system to link together its heterogeneous multiple-vendor systems; the window system then under development in Carnegie Mellon University's Andrew Project did not make licences available, and no alternatives existed.

The project solved this by creating a protocol that could both run local applications and call on remote resources. In mid-1983 an initial port of W to Unix ran at one-fifth of its speed under V; in May 1984, Scheifler replaced the synchronous protocol of W with an asynchronous protocol and the display lists with immediate mode graphics to make X version 1. X became the first windowing system environment to offer true hardware-independence and vendor-independence.

Scheifler, Gettys and Ron Newman set to work and X progressed rapidly. They released Version 6 in January 1985. DEC, then preparing to release its first Ultrix workstation, judged X the only windowing system likely to become available in time. DEC engineers ported X6 to DEC's QVSS display on MicroVAX.

In the second quarter of 1985 X aquired color support to function in the DEC VAXstation-II/GPX, forming what became version 9. Although MIT had licensed X6 to some outside groups for a fee, it decided at this time to license X9 and future versions under what became known as the MIT License. X9 appeared in September 1985.

A group at Brown University ported version 9 to the IBM RT/PC, but problems with reading unaligned data on the RT forced an incompatible protocol change, leading to version 10 in late 1985. By 1986, outside organizations had started asking for X. The release of X10R2 took place in January 1986; that of X10R3 in February 1986. X10R3 became the first version to achieve wide deployment, with both DEC and Hewlett-Packard releasing products based on it. Other groups ported X10 to Apollo and to Sun workstations and even to the IBM PC/AT. Demonstrations of the first commercial application for X (a mechanical computer-aided engineering system that ran on VAXes and displayed on PCs running an X server) took place at the Autofact trade show at that time. The last version of X10, X10R4, appeared in December 1986.

Although X10 offered interesting and powerful functionality, it had become obvious that the X protocol could use a more hardware-neutral redesign before it became too widely deployed; but MIT alone would not have the resources available for such a complete redesign. As it happened, DEC's Western Software Laboratory found itself between projects. Smokey Wallace of DEC WSL and Jim Gettys proposed that DEC WSL build X11 and make it freely available under the same terms as X9 and X10. This process started in May 1986, with the protocol finalised in August. Alpha-testing of the software started in February 1987, beta-testing in May; the release of X11 finally occurred on September 15, 1987.

The X11 protocol design, led by Scheifler, got extensively discussed on open mailing lists on the nascent Internet. X therefore represents one of the first very large-scale free software projects.

X Window System - The MIT X Consortium and the X Consortium Inc.

In 1987, with the success of X11 becoming apparent, MIT wished to relinquish the stewardship of X, but at a June 1987 meeting with nine vendors, the vendors told MIT that they believed in the need for a neutral party to keep X from fragmenting in the marketplace. In January 1988, the MIT X Consortium formed as a non-profit vendor group, with Scheifler as director, to direct the future development of X in a neutral atmosphere inclusive of commercial and educational interests. Jim Fulton joined in January 1988 and Keith Packard in March 1988 as senior developers, with Jim focusing on Xlib, fonts, window managers, and utilities; and Keith re-implementing the server. Donna Converse and Chris Peterson joined later that year, focusing on toolkits and widget sets, working closely with Ralph Swick of MIT Project Athena. The MIT X Consortium produced several significant revisions to X11, the first (Release 2 - X11R2) in February 1988.

In 1993, the X Consortium, Inc. (a non-profit corporation) formed as the successor to the MIT X Consortium. It released X11R6 on May 16, 1994. In 1995 it took over stewardship of the Motif toolkit and of the Common Desktop Environment for Unix systems. The X Consortium dissolved at the end of 1996, producing a final revision, X11R6.3.

X Window System - The Open Group

In mid-1997 the X Consortium passed stewardship of X to The Open Group, a vendor group formed in early 1996 by the merger of the Open Software Foundation and X/Open.

The Open Group released X11R6.4 in early 1998. Controversially, X11R6.4 departed from the traditional liberal licensing terms, as the Open Group sought to assure funding for X's development [6]. The new terms would have prevented its adoption by many projects (such as XFree86) and even by some commercial vendors. After XFree86 threatened a fork [7], the Open Group relicensed X11R6.4 under the traditional license in September 1998. [8] The Open Group's last release came as X11R6.4 patch 3.

X Window System - X.Org and XFree86

XFree86 originated in 1992 from the X386 server for IBM PC compatibles included with X11R5 in 1991, written by Thomas Roell and Mark W. Snitily and donated to the MIT X Consortium by Snitily Graphics Consulting Services (SGCS). XFree86 evolved over time from just one port of X to the leading and most popular implementation and the de facto steward of X's development [9].

In May 1999, the Open Group formed X.Org. X.Org supervised the release of versions X11R6.5.1 onward. X development at this time had become moribund [10]; most technical innovation since the X Consortium had dissolved had taken place in the XFree86 project [11]. In 1999, the XFree86 team joined X.Org as an honorary (non-paying) member [12], encouraged by various hardware companies [13] interested in using XFree86 with Linux and in its status as the most popular version of X.

By 2003, while the popularity of Linux (and hence the installed base of X) surged, X.Org remained all but inactive [14], and active development took place largely within XFree86. However, considerable dissent developed within XFree86. The XFree86 project sufferred from a perception of a far too cathedral-like development model; developers could not get CVS commit access [15] [16] and vendors had to maintain extensive patch sets [17]. In March 2003 the XFree86 organization expelled Keith Packard, who had joined XFree86 after the end of the original MIT X Consortium, with considerable ill-feeling [18] [19] [20].

X.Org and XFree86 began discussing a reorganisation suited to properly nurturing the development of X [21] [22] [23]. Jim Gettys had been pushing strongly for an open development model since at least 2000 [24]. Gettys, Packard and several others began discussing in detail the requirements for the effective governance of X with open development.

Finally, in an echo of the X11R6.4 licensing dispute, XFree86 released version 4.4 in February 2004 under a more restricted license which many projects relying on X found unacceptable [25]. The added clause to the license was based upon the original BSD license's advertising clause, which was viewed by the Free Software Foundation and Debian as incompatible with the GNU General Public License [26]. Other groups saw further restrictions as being against the spirit of the original X (OpenBSD threatening a fork, for example). The GPL issue, combined with the difficulties in getting changes in, left many feeling the time was ripe for a fork [27].

X Window System - The X.Org Foundation

In early 2004 various people from X.Org and freedesktop.org formed the X.Org Foundation, and the Open Group gave it control of the x.org domain name. This marked a radical change in the governance of X. Whereas the stewards of X since 1988 (including the previous X.Org) had been vendor organizations, the Foundation was led by software developers and used community development based on the bazaar model, which relies on outside involvement. Membership was opened to individuals, with corporate membership being in the form of sponsorship. Several major corporations such as Hewlett-Packard and Sun Microsystems currently support the X.Org Foundation.

The Foundation released X11R6.7, the X.Org Server, in April 2004, based on XFree86 4.4RC2 with X11R6.6 changes merged. Gettys and Packard had taken the last version of XFree86 under the old license and, by making a point of an open development model and retaining GPL compatibility, brought many of the old XFree86 developers on board [28].

X11R6.8 was released in September 2004. It added significant new features, including preliminary support for translucent windows and other sophisticated visual effects, screen magnifiers and thumbnailers, and facilities to integrate with 3D immersive display systems such as Sun's Project Looking Glass and the Croquet project. External applications called compositing managers provide policy for the visual appearance.

Adapted from the Wikipedia article "History", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki