Display server

A display server or window server is a program whose primary task is to coordinate the input and output of its clients to and from the rest of the operating system, the hardware, and each other. The display server communicates with its clients over the display server protocol, a , which can be network-transparent or simply network-capable.

The display server is a key component in any graphical user interface, specifically the windowing system.

One example of a display server is the X.Org Server, which runs on top of the kernel (usually a Unix-based kernel, such as Linux or BSD). It receives data from evdev and passes it to one of its clients. The display server also receives data from its clients; it processes the data, it does the compositing and passes the data to one of three kernel components – DRM, gem or KMS driver. The component writes the data into the framebuffer and content of the framebuffer is transmitted to the connected screen and displayed. X relies on GLX.

One of the implementations of display server concept is X Window System, in particular its actually used version – X.Org Server and Xlib and XCB client libraries. The X.Org Server is a display server, but in its current implementation it relies on a second program, the compositing window manager, to do the compositing. Examples are Mutter or KWin.

Notable examples of display servers implementing the X11 display server protocol are X.Org Server, XFree86, XQuartz and Cygwin/X, while client libraries implementing the X11 display server protocol are Xlib and XCB.

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