History

Predecessorsedit

Several bitmap display systems preceded X. From Xerox came the Alto (1973) and the Star (1981). From Apollo Computer came Display Manager (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 (1982).

Carnegie Mellon University produced a remote-access application called Alto Terminal, that displayed overlapping windows on the Xerox Alto, and made remote hosts (typically DEC VAX systems running Unix) responsible for handling window-exposure events and refreshing window contents as necessary.

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

Origin and early developmentedit

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 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 licenses 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 acquired color support to function in the DEC VAXstation-II/GPX, forming what became version 9.

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 begun asking for X. X10R2 was released in January 1986, then X10R3 in February 1986. Although MIT had licensed X6 to some outside groups for a fee, it decided at this time to license X10R3 and future versions under what became known as the MIT License, intending to popularize X further and, in return, hoping that many more applications would become available. 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 from Cognition Inc. that ran on VAXes and remotely displayed on PCs running an X server ported by Jim Fulton and Jan Hardenbergh) took place at the Autofact trade show at that time. The last version of X10, X10R4, appeared in December 1986. Attempts were made to enable X servers as real-time collaboration devices, much as Virtual Network Computing (VNC) would later allow a desktop to be shared. One such early effort was Philip J. Gust's SharedX tool.

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 with an experienced team. 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 finalized in August. Alpha testing of the software started in February 1987, beta-testing in May; the release of X11 finally occurred on 15 September 1987.

The X11 protocol design, led by Scheifler, was extensively discussed on open mailing lists on the nascent Internet that were bridged to USENET newsgroups. Gettys moved to California to help lead the X11 development work at WSL from DEC's Systems Research Center, where Phil Karlton and Susan Angebrandt led the X11 sample server design and implementation. X therefore represents one of the first very large-scale distributed free and open source software projects.

The MIT X Consortium and the X Consortium, Inc.edit

By the late 1980s X was, Simson Garfinkel wrote in 1989, "Athena's most important single achievement to date". DEC reportedly believed that its development alone had made the company's donation to MIT worthwhile. Gettys joined the design team for the VAXstation 2000 to ensure that X—which DEC called DECwindows—would run on it, and the company assigned 1,200 employees to port X to both Ultrix and VMS. 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, Chris D. Peterson, and Stephen Gildea 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. Jay Hersh joined the staff in January 1991 to work on the PEX and X113D functionality. He was followed soon after by Ralph Mor (who also worked on PEX) and Dave Sternlicht. In 1993, as the MIT X Consortium prepared to depart from MIT, the staff were joined by R. Gary Cutbill, Kaleb Keithley, and David Wiggins.

In 1993, the X Consortium, Inc. (a non-profit corporation) formed as the successor to the MIT X Consortium. It released X11R6 on 16 May 1994. In 1995 it took on the development 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, and a legacy of increasing commercial influence in the development.

The Open Groupedit

In January 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 the development of X, and specifically cited XFree86 as not significantly contributing to X. The new terms would have made X no longer free software: zero-cost for noncommercial use, but a fee otherwise. After XFree86 seemed poised to fork, the Open Group relicensed X11R6.4 under the traditional license in September 1998. The Open Group's last release came as X11R6.4 patch 3.

X.Org and XFree86edit

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 standard of X's development.

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; most technical innovation since the X Consortium had dissolved had taken place in the XFree86 project. In 1999, the XFree86 team joined X.Org as an honorary (non-paying) member, encouraged by various hardware companies 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 inactive, and active development took place largely within XFree86. However, considerable dissent developed within XFree86. The XFree86 project suffered from a perception of a far too cathedral-like development model; developers could not get CVS commit access and vendors had to maintain extensive patch sets. 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.

X.Org and XFree86 began discussing a reorganisation suited to properly nurturing the development of X. Jim Gettys had been pushing strongly for an open development model since at least 2000. 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 restrictive license which many projects relying on X found unacceptable. The added clause to the license was based on 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. Other groups saw it as against the spirit of the original X. Theo de Raadt of OpenBSD, for instance, threatened to fork XFree86 citing license concerns. The license issue, combined with the difficulties in getting changes in, left many feeling the time was ripe for a fork.

The X.Org Foundationedit

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 prior X.Org) had been vendor organizations, the Foundation was led by software developers and used community development based on the bazaar model,citation needed 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 currently support the X.Org Foundation.

The Foundation takes an oversight role over X development: technical decisions are made on their merits by achieving rough consensus among community members. Technical decisions are not made by the board of directors; in this sense, it is strongly modelled on the technically non-interventionist GNOME Foundation. The Foundation employs no developers. 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.

While X11 had received extensions such as OpenGL support during the 1990s, its architecture had remained fundamentally unchanged during the decade. In the early part of the 2000s, however, it was overhauled to resolve a number of problems that had surfaced over the years, including a "flawed" font architecture, a 2-d graphics system "which had always been intended to be augmented and/or replaced", and latency issues. X11R6.8 came out 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 window managers provide policy for the visual appearance.

On 21 December 2005, X.Org released X11R6.9, the monolithic source tree for legacy users, and X11R7.0, the same source code separated into independent modules, each maintainable in separate projects. The Foundation released X11R7.1 on 22 May 2006, about four months after 7.0, with considerable feature improvements.

XFree86 development continued for a few more years, 4.8.0 being released on 15 December 2008.