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Xgl was an X server
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

 architecture designed to take advantage of modern graphics cards via their OpenGL
OpenGL
OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...

 drivers, layered on top of OpenGL
OpenGL
OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...

 via glitz
Glitz (software)
Glitz is a software library for 2D graphics which provides hardware acceleration using OpenGL, an API for 3D graphics. Glitz is open-source software, licensed under the MIT License...

. It supported hardware acceleration
Hardware acceleration
In computing, Hardware acceleration is the use of computer hardware to perform some function faster than is possible in software running on the general-purpose CPU...

 of all X, OpenGL and XVideo applications and graphical effects by a compositing window manager
Compositing window manager
A compositing window manager is a type of window manager. A window manager is software that draws a graphical user interface on a computer display – it positions windows, draws additional elements on windows , and controls how windows interact with each other, and with the rest of the desktop...

 such as Compiz
Compiz
Compiz is one of the first compositing window managers for the X Window System that uses 3D graphics hardware to create fast compositing desktop effects for window management. The effects, such as a minimization effect and a cube workspace are implemented as loadable plugins...

 or Beryl
Beryl (window manager)
Beryl was a compositing window manager for the X Window System which forked from Compiz in September 2006 and was re-merged in 2007, under the name of Compiz Fusion.-Origin:...

. The project was started by David Reveman of Novell
Novell
Novell, Inc. is a multinational software and services company. It is a wholly owned subsidiary of The Attachmate Group. It specializes in network operating systems, such as Novell NetWare; systems management solutions, such as Novell ZENworks; and collaboration solutions, such as Novell Groupwise...

 and first released on January 2, 2006. It was removed from the X.org server in favor of AIGLX
AIGLX
Accelerated Indirect GLX is an open source project founded by Red Hat and the Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to the X.Org Server and DRI drivers...

 on June 12, 2008.

History


Xgl was originally developed on public mailing lists, but for a long time, until January 2, 2006 most development of Xgl was done behind closed doors. On that day the source to Xgl was re-opened to the public, and included in freedesktop.org
Freedesktop.org
freedesktop.org is a project to work on interoperability and shared base technology for free software desktop environments for the X Window System on Linux and other Unix-like operating systems. It was founded by Havoc Pennington from Red Hat in March 2000.The organisation focuses on the user....

, along with major restructuring to allow a wider range of supported display drivers. X server backends used by Xgl include Xglx and Xegl. In February 2006 the server gained wide publicity after a public display where the Novell
Novell
Novell, Inc. is a multinational software and services company. It is a wholly owned subsidiary of The Attachmate Group. It specializes in network operating systems, such as Novell NetWare; systems management solutions, such as Novell ZENworks; and collaboration solutions, such as Novell Groupwise...

 desktop team demonstrated a desktop using Xgl with several visual effects such as translucent
Transparency (graphic)
Transparency is possible in a number of graphics file formats. The term transparency is used in various ways by different people, but at its simplest there is "full transparency" i.e. something that is completely invisible. Of course, only part of a graphic should be fully transparent, or there...

 window
Window (computing)
In computing, a window is a visual area containing some kind of user interface. It usually has a rectangular shape that can overlap with the area of other windows...

s and a rotating 3D desktop.
The effects had first been implemented in a composite manager called glxcompmgr (not to be confused with xcompmgr), now deprecated because several effects could not be adequately implemented without tighter interaction between the window manager and the composite manager. As a solution David Reveman developed Compiz
Compiz
Compiz is one of the first compositing window managers for the X Window System that uses 3D graphics hardware to create fast compositing desktop effects for window management. The effects, such as a minimization effect and a cube workspace are implemented as loadable plugins...

, the first proper OpenGL compositing window manager
Compositing window manager
A compositing window manager is a type of window manager. A window manager is software that draws a graphical user interface on a computer display – it positions windows, draws additional elements on windows , and controls how windows interact with each other, and with the rest of the desktop...

 for the X Window System. Later, in September 2006, the Beryl
Beryl (window manager)
Beryl was a compositing window manager for the X Window System which forked from Compiz in September 2006 and was re-merged in 2007, under the name of Compiz Fusion.-Origin:...

 compositing window manager
Compositing window manager
A compositing window manager is a type of window manager. A window manager is software that draws a graphical user interface on a computer display – it positions windows, draws additional elements on windows , and controls how windows interact with each other, and with the rest of the desktop...

 was released as a fork of the original Compiz. Compiz and Beryl have merged back in April 2007, which resulted in the development of Compiz Fusion.

Backends


OpenGL does not specify how to initialize a display and manipulate drawing contexts. Instead these operations are handled by an API specific to the native windowing system. So far there are two different backend approaches to solving this initialization problem. Most likely the majority of each backend will contain the same code and the differences will primarily be in the initialization portions of the servers.

Xglx


Xglx was the first backend implemented for this architecture. It requires an already existing X server to run on top of and uses GLX
GLX
GLX provides the interface connecting OpenGL and the X Window System: it enables programs wishing to use OpenGL to do so within a window provided by the X Window System.-History:...

 to create an OpenGL window which Xgl then uses, similar to Xnest
Xnest
Xnest is an X Window System server that shows its output in a window. In other words, Xnest opens a window that works like another screen in which the user can open windows, etc....

. This mode is only intended to be used for development in the future, as it is redundant to require an X server to run Xgl on top of.

At XDevConf 2006 (the 2006 X development conference), NVIDIA
NVIDIA
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...

 made a presentation arguing that this is the wrong direction to take because the layered server abstracts features of the cards away. This makes driver specific capabilities like support for 3D glasses and dual monitor support much more difficult.

However, delegating initialization to an existing X server allows the developers to immediately focus on server functionality rather than dedicating substantial time to specifics of interfacing with numerous video hardware.
At the moment, Xglx does not officially support multiple monitors, although it has been achieved on Ubuntu Dapper / ATI / NVIDIA (twinview).

Xegl


Xegl was said to be the future of Xgl and a long term goal of X server development. It shares much of the drawing code with the Xglx server, but the initialization of the OpenGL drawable and context management is handled by the EGL API developed by Khronos (EGL is a window system-independent equivalent to the GLX and WGL APIs, which respectively enable OpenGL support in X and Microsoft Windows). The current implementation uses Mesa-solo
Mesa 3D
Mesa 3D is an open source 3D computer graphics library that provides a generic OpenGL implementation for rendering three-dimensional graphics on multiple platforms. It was initially developed by Brian Paul in August 1993, and is still maintained by him today...

 to provide OpenGL rendering directly to the Linux framebuffer
Linux framebuffer
The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console...

 or DRI
Direct Rendering Infrastructure
In computing, the Direct Rendering Infrastructure is an interface and a free software implementation used in the X Window System to securely allow user applications to access the video hardware without requiring data to be passed through the X server. Its primary application is to provide...

 to the graphics hardware. Xegl can only be run using Radeon R200
Radeon R200
The Radeon R200 is the second generation of Radeon graphics chips from ATI Technologies. The architecture features 3D acceleration based upon Microsoft Direct3D 8.1 and OpenGL 1.3, a major improvement in features and performance compared to the preceding Radeon R100 design. The GPU also includes 2D...

 graphics hardware and development is currently stalled. It is likely that it will remain so until the Xglx server has proven itself and the closed source drivers add support for the EGL API, when it should be a transparent replacement for the nested Xglx server.

Rationale


Structuring all rendering on top of OpenGL could potentially simplify video driver development. It removes the artificial separation of 2D
2D computer graphics
2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them...

 and 3D
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...

 acceleration
Hardware acceleration
In computing, Hardware acceleration is the use of computer hardware to perform some function faster than is possible in software running on the general-purpose CPU...

. This is advantageous as 2D operations are frequently unaccelerated (which is counterintuitive, since 2D is a subset of 3D).

It also removes all driver-dependent code from the X server itself, and allows for accelerated Composite
Compositing
Compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously called "chroma key", "blue screen", "green screen" and other names. Today,...

 and Render
XRender
The X Rendering Extension is an X Window System extension to implement Porter-Duff image compositing in the X server, to allow efficient display of transparent images.- History :...

 operations independent of the graphics driver.

Competitors


Hardware acceleration of 2D drawing operations has been a common feature of many window systems (including X11) for many years. The novelty of Xgl and similar systems is the use of APIs specifically developed for 3D rendering for accelerating 2D desktop operations. Prior to the adoption of anti-aliased drawing by X11, the use of 3D rendering APIs for 2D desktop rendering was undesirable because such APIs did not make the pixel accurate rendering guarantees that are part of the original X11 protocol definition.

Hardware-accelerated OpenGL window and desktop rendering, limited to using OpenGL for texture composition, has been in use in Mac OS X, in a technology called Quartz Extreme
Quartz Compositor
Quartz Compositor is the windowing system in Mac OS X. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other renderers in the Quartz technologies family...

, since Mac OS X v10.2
Mac OS X v10.2
Mac OS X version 10.2 "Jaguar" is the third major release of Mac OS X, Apple's desktop and server operating system. It superseded Mac OS X v10.1 code name Puma and preceded Mac OS X Panther...

. Quartz 2D Extreme
Quartz 2D
Quartz 2D is the primary two-dimensional graphics rendering API for Mac OS X, part of the Core Graphics framework.-Overview:Quartz 2D is available to all Mac OS X application environments, and provides resolution-independent and device-independent rendering of bitmap graphics, text, and vectors...

 is an enhancement of this feature and more directly comparable to Xgl. Like Xgl, Quartz 2D Extreme brings OpenGL acceleration to all 2D drawing operations (not just desktop compositing) and ships with Mac OS X v10.4
Mac OS X v10.4
Mac OS X v10.4 Tiger is the fifth major release of Mac OS X, Apple's desktop and server operating system for Macintosh computers. Tiger was released to the public on 29 April 2005 for US$129.95 as the successor to Mac OS X Panther , which had been released 18 months earlier...

, but is disabled by default pending a formal declaration of production-readiness. Core Animation is the extension of this effort for Leopard (Mac OS X v10.5
Mac OS X v10.5
Mac OS X Leopard is the sixth major release of Mac OS X, Apple's desktop and server operating system for Macintosh computers. Leopard was released on 26 October 2007 as the successor of Tiger , and is available in two variants: a desktop version suitable for personal computers, and a...

).

Several desktop interfaces based on 3D APIs have been developed, more recently OpenCroquet and Sun Microsystems' Project Looking Glass
Project Looking Glass
Project Looking Glass is a now inactive free software project under the GPL to create an innovative 3D desktop environment for Linux, Solaris, and Windows. It was sponsored by Sun Microsystems....

 http://www.sun.com/software/looking_glass/details.xml; these take advantage of 3D acceleration for software built within their own framework, but do not appear to accelerate existing 2D desktop applications rendered within their environment (often via mechanisms like VNC).

Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 developed a similar technology based on DirectX
DirectX
Microsoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay,...

, named the DWM
Desktop Window Manager
Desktop Window Manager is the window manager in Windows Vista and Windows 7 that enables the Windows Aero graphical user interface and visual theme. The Desktop Window Manager requires video cards supporting DirectX 9.0 and Shader Model 2.0. DWM is not included with Windows Vista Starter edition...

, as part of its Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...

 operating system. This technology was first shown publicly at Microsoft's October 2003 PDC.

Availability


, the Xgl X Server
X Window System protocols and architecture
In computing, the X Window System is a network-transparent windowing system for bitmap displays. This article details the protocols and technical structure of X11.-Client–server model and network transparency:...

 (and related components including the Compiz compositing manager and associated graphical config tools) ships as a non-default in one major Linux distribution, SUSE
SUSE Linux distributions
SUSE Linux is a computer operating system. It is built on top of the open source Linux kernel and is distributed with system and application software from other open source projects. SUSE Linux is of German origin and mainly developed in Europe. The first version appeared in early 1994, making...

 10.1, and is included in Frugalware Linux
Frugalware
Frugalware Linux is a general-purpose Linux distribution designed for intermediate users who are familiar with command-line operations. Early versions were based on Slackware, but it is now an independently-developed distribution...

 or SUSE Linux Enterprise Desktop
SUSE Linux Enterprise Desktop
SUSE Linux Enterprise Desktop , formerly introduced as Novell Linux Desktop, is a Linux distribution supplied by Novell and targeted at the business market. It is targeted for desktops. New major versions are released at an interval of 24–36 months, while minor versions are released every 9–12...

 10. Xgl can be set up fairly easily for Ubuntu
Ubuntu (operating system)
Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...

 6.06 LTS (Dapper Drake) and 6.10 (Edgy Eft) and for Freespire
Freespire
Freespire was a community-driven Linux distribution which was composed mostly of free, open source software, while providing users the choice of including proprietary software including multimedia codecs, device drivers and application software....

 with binary packages from unofficial repositories
Software repository
A software repository is a storage location from which software packages may be retrieved and installed on a computer.- Discussion :Many software publishers and other organizations maintain servers on the Internet for this purpose, either free of charge or for a subscription fee...

. Xgl is also available as an overlayed package in Gentoo Linux
Gentoo Linux
Gentoo Linux is a computer operating system built on top of the Linux kernel and based on the Portage package management system. It is distributed as free and open source software. Unlike a conventional software distribution, the user compiles the source code locally according to their chosen...

, and as a PKGBUILD for Arch Linux
Arch Linux
Arch Linux is an independently developed, Linux-based operating system for i686 and x86-64 computers. It is composed predominantly of free and open source software, and supports community involvement....

.

The latest Mandriva Linux
Mandriva Linux
Mandriva Linux is a Linux distribution distributed by Mandriva. It uses the RPM Package Manager...

 2007 includes official packages to run Compiz
Compiz
Compiz is one of the first compositing window managers for the X Window System that uses 3D graphics hardware to create fast compositing desktop effects for window management. The effects, such as a minimization effect and a cube workspace are implemented as loadable plugins...

, using Xgl and AIGLX
AIGLX
Accelerated Indirect GLX is an open source project founded by Red Hat and the Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to the X.Org Server and DRI drivers...

. Mandriva provides drak3d, a tool to configure a 3D Desktop in two clicks.

Ubuntu
Ubuntu (operating system)
Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...

 6.10 "Edgy Eft" and later use AIGLX
AIGLX
Accelerated Indirect GLX is an open source project founded by Red Hat and the Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to the X.Org Server and DRI drivers...

, not Xgl, by default.

Xgl was removed from X11R7.5 in 2009 due to its being an unmaintained server variant.

See also

  • X Window System
    X Window System
    The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

  • AIGLX
    AIGLX
    Accelerated Indirect GLX is an open source project founded by Red Hat and the Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to the X.Org Server and DRI drivers...

  • VirtualGL
    VirtualGL
    VirtualGL is an open source program which redirects the 3D rendering commands from Unix and Linux OpenGL applications to 3D accelerator hardware in a dedicated server and displays the rendered output interactively to a thin client located elsewhere on the network.- The problem :Normally, VNC and...

  • OpenGL
    OpenGL
    OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...

  • Compiz
    Compiz
    Compiz is one of the first compositing window managers for the X Window System that uses 3D graphics hardware to create fast compositing desktop effects for window management. The effects, such as a minimization effect and a cube workspace are implemented as loadable plugins...

  • Beryl
    Beryl (window manager)
    Beryl was a compositing window manager for the X Window System which forked from Compiz in September 2006 and was re-merged in 2007, under the name of Compiz Fusion.-Origin:...


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