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Xinerama is an extension to the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at ...
that enables X applications and
window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...
s to use two or more physical displays as one large virtual display. Developed under the name ''PanoramiX'' by Madeline T. Asmus of the
Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...
's Unix X Server Engineering Group, the software was contributed to
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for X11 Release 6.4 (X11R6.4) and renamed Xinerama. It was then incorporated into the
XFree86 XFree86 is an implementation of the X Window System. It was originally written for Unix-like operating systems on IBM PC compatibles and was available for many other operating systems and platforms. It is free software, free and Open-source softw ...
4.0 release in 1998 and the Solaris 7 11/99 release. According to X Server project lead Rob Lembree, the name was inspired by the
Cinerama Cinerama is a widescreen process that originally projected images simultaneously from three synchronized 35 mm movie film, 35mm projectors onto a huge, deeply curved screen, Subtended angle, subtending 146-degrees of arc. The trademarked pr ...
widescreen theatre process. "We were frustrated by having big Alpha machines with multiple displays, and being unable to move applications from one to another. It was developed as much out of frustration as out of competitive advantage." Xinerama advantages include the ability to only maximize windows to the dimensions of the active physical display, and to allow new pop-up windows on the active physical display.


General theory of operation

When Xinerama is enabled in the X server, multiple X screens can be unified into a single workspace. This unified work area allows windows to be transferred across X screens.


XINERAMA extension

The Xinerama extension provides clients with information about the layout of viewports within the unified workspace. Its information regarding offset and size information allows clients to make intelligent decisions about window placement, window maximization and other user interaction events.


Use in non-XINERAMA environments

The X server's client/server architecture allows the server to expose Xinerama information to the client regardless of whether the Xinerama infrastructure is active. RandR and
NVidia Nvidia Corporation ( ) is an American multinational corporation and technology company headquartered in Santa Clara, California, and incorporated in Delaware. Founded in 1993 by Jensen Huang (president and CEO), Chris Malachowsky, and Curti ...
's twinview utilize this feature to provide window managers and clients with information about the output layout relative to the framebuffer.


Known problems


Common color depth

Xinerama requires that all of the physical screens have the same
bit The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as ...
depth. For example, an
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data bu ...
screen cannot be combined with a
16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...
screen.


Hardware rendering

In some implementations,
OpenGL OpenGL (Open Graphics Library) is a Language-independent specification, cross-language, cross-platform application programming interface (API) for rendering 2D computer graphics, 2D and 3D computer graphics, 3D vector graphics. The API is typic ...
direct-rendering only works on one screen. Windows that should show 3D graphics on other screens tend to appear black, a problem most commonly seen with 3D screen savers. The Solaris SPARC OpenGL implementation and ATI and nVidia proprietary Linux drivers support hardware-accelerated rendering of all screens in Xinerama mode.


Static configuration

Physical screens cannot be added or removed dynamically, and there is no way to change the resolution of a screen. This is particularly difficult for mobile computer users, who may use an external physical display in addition to the computer's built-in screen, but only at certain locations. It is recommended that RandR or ATI's or nVidia's single GPU method be used in these cases. Xinerama's lack of support for adding or removing screens causes several problems: * Windows may be drawn to a screen that is not connected to the computer. The user is required to drag these windows to the main screen, but is unable to see them. * Video signals sent to disconnected displays use unnecessary power and may reduce battery life. * It becomes difficult to use a device in multiple locations, where available external screens are likely to be configured differently. These problems are related to Xinerama's implementation rather than its design, and can be corrected with further development.


Window manager support

Some
window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...
s and
desktop environment In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphi ...
s have limited awareness of the separate physical screens in Xinerama, so that the desktop is simply stretched over the physical screens instead of arranged as a single large desktop. The window manager may place a new window on an unexpected screen, which can be confusing and annoying. Xinerama nevertheless offers the advantage that windows can be moved between screens.


Dead space

The physical displays do not need to be the same resolution, and the virtual display area is not necessarily rectangular if the component physical displays are not the same size. Some window managers assume a rectangular display area, and enforce this by creating excess "dead space" at the edges of a display. The window manager needs awareness of Xinerama to avoid placing new windows in this dead space.


See also

*
Multi-monitor Multi-monitor, also called multi-display and multi-head, is the use of multiple physical display devices, such as Computer monitor, monitors, Television set, televisions, and Video projector, projectors, in order to increase the area available fo ...


Resource

Asmus, Madeline T. (December 1995) "''The PanoramiX Extension''" THE X RESOURCE 16: A Practical Journal of the X Window System. pp. 59–73 .


Notes


References


Overview of X11R6.8
(X.Org)


External links



-
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from
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.
Using multiple monitors with XFree86
- Simple configuration examples. {{XWinSys Freedesktop.org Multi-monitor X Window extensions