ICCCM

In computing, the Inter-Client Communication Conventions Manual (ICCCM or I39L short for "I", 39 letters and "L") is a standard protocol for the X Window System. It specifies communication for clients of a common . It is primarily used for communication between normal clients and the window manager.

It was designed by David S. H. Rosenthal of the MIT X Consortium in 1988.

Version 1.0 was released in July 1989 and version 2.0 in early 1994.

X deliberately specifies "mechanism, not policy". As such, an additional specification beyond the X protocol itself was needed for client interoperation.

The ICCCM specifies cut and paste buffers, window manager interaction, session management, how to manipulate shared resources and how to manage device colours. These low-level functions are generally implemented within widget toolkits or desktop environments. This isolates application programmers from working directly with the ICCCM itself, as this functionality is delegated to the implementing toolkit.

The ICCCM is notorious for being ambiguous and difficult to correctly implement. Furthermore, some parts are obsolete or no longer practical to implement.

Efforts to update and clarify the ICCCM for current needs have resulted in the Extended Window Manager Hints (EWMH), which has gained fairly broad acceptance and continues to be extended as the need arises.

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