It should also be noted that in general, Xlib can do a lot more than XCB with a /lot/ less effort and bugs, and has an actual documentation, tutorials, books.

It should also be noted that in general, Xlib can do a lot more than XCB with a /lot/ less effort and bugs, and has an actual documentation, tutorials, books. Xlib certainly is quirky, in particular around error handling, though.