About xcb-proto

The xcb-proto package provides the XML-XCB (X C Bindings) protocol descriptions that libxcb uses to generate the majority of its code and API. We provide them separately from libxcb to allow reuse by other projects, such as additional language bindings, protocol dissectors, or documentation generators.

Separation of XCB's transport and protocol layers simplifies both writing extensions and client-side support for extensions. By contrast, with the xlib infrastructure, client-side support for new extensions requires significant duplication of effort. With XCB and the XML-XCB protocol descriptions, client-side support for a new extension requires only an XML description of the extension--and not a single line of code.

Python libraries: xcb-proto also contains language-independent Python libraries that are used to parse an XML description and create objects used by Python code generators in individual language bindings.