[Xcb] Is XCB's asynchronous mode necessary for a Window Manager?

[Chengqi Song]

Hi,

After digging into xcb's documents and Awesome window manager's source code, I
have a strong doubt about the necessity of asynchronous operation for a window
manager.

According to XCB's document (http://xcb.freedesktop.org/tutorial/), the main
improvement of XCB is to reduce the time spent in multiple round trip time into
one. But for a window manager:

1. the number of sequential operations is not large, so the number of RTT is not
large,

2. RTT in a local machine is very short, it's only larger when connecting a
remote X client,

so I think RTT is not a critical bottleneck for a window manager. On the other
side, XLib provides more higher level operations than XCB, so it's easier to
build a window manager basing on xlib than xcb, less lines of source code at
least.

Is my doubt true? Please point out my misunderstanding and clarify it, thanks
very much.

Regards
Lars