X.Org's C Bindings library
libxcb-1.13.1-2-x86_64
XCB provides application binary interface compatibility with both Xlib and XCB, providing an incremental porting path. XCB uses the protocol layer of Xlib, but replaces the Xlib transport layer with XCB, and provides access to the underlying XCB connection for direct use of XCB.
XCB allows an application to open a single connection to the Xdisplay server and use both XCB and Xlib, possibly through a mixture of libraries designed for one or the other.