libxcb provides an interface to the X Window System protocol, slated to
replace the current Xlib interface. It has several advantages over
Xlib, including:
  - size: small library and lower memory footprint
  - latency hiding: batch several requests and wait for the replies later
  - direct protocol access: one-to-one mapping between interface and protocol
  - proven thread support: transparently access XCB from multiple threads
  - easy extension implementation: interfaces auto-generated from XML-XCB

Xlib can also use XCB as a transport layer, allowing software to make
requests and receive responses with both, which eases porting to XCB.
However, client programs, libraries, and toolkits will gain the most
benefit from a native XCB port.

1. build dependencies:
   1. libXau-devel
   2. libselinux-devel
   3. libXdmcp-devel
   4. doxygen
   5. python2.7(distutils)
   6. fonts-ttf-freefont
   7. pkgconfig(xcb-proto) >= 1.13
   8. xorg-util-macros
   9. xsltproc
   10. graphviz