rio (windowing system)

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rio interface
rio interface as windowing system
Developer(s)Rob Pike
Initial releaseFourth Edition / April 28, 2002; 20 years ago (2002-04-28)
Written inC
Operating systemPlan 9 from Bell Labs
TypeWindowing system Edit this on Wikidata

rio is Plan 9 from Bell Labs' windowing system. It is well known for making its window management transparent to the application. This allows running rio inside of another window manager.


rio is the latest in a long series of graphical user interfaces developed at Bell Labs, mostly developed by Rob Pike, the concurrent window system, and the Blit (which predated X).

rio was a complete rewrite of in Alef. Its main change was that it stopped parsing and rewriting graphical commands and let the client write pixels directly. This was done mainly for efficiency. As Alef disappeared due to being too difficult to maintain given the number of people working on Plan 9 at the time, rio was rewritten in C. This was done using the Plan 9 thread library which was inspired by Alef and had most of its features, such as blocking channels for interthread and interprocess communication. Another important change, due more to the environment than to rio per se, is that rio supports full colour, using alpha compositing, whereas 8½ uses bitblt operations.

Design concepts[edit]

Many of its features embody key Plan 9 design concepts:

  • Each window runs in its own private namespace.
  • It exports a file system interface to running applications. This interface is the same rio receives from the operating system, so rio can run inside a rio window without any special arrangements. Because the interface uses 9P, rio is network transparent even if it doesn't include any network-aware code.
  • Windows are treated as completely editable text.

See also[edit]

External links[edit]