Xinerama

Xinerama is an extension to the X Window System that enables X applications and window managers 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's Unix X Server Engineering Group, the software was contributed to The Open Group for X11 Release 6.4 (X11R6.4) and renamed Xinerama. It was then incorporated into the XFree86 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 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.

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.

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.

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's twinview utilize this feature to provide window managers and clients with information about the output layout relative to the framebuffer.

Xinerama requires that all of the physical screens have the same bit depth. For example, an 8-bit screen cannot be combined with a 16-bit screen.

In some implementations, OpenGL 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.

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