backing store, and documentation
I just ran into something rather odd: I have an application which
requires backing store. 4.0.1 has backing store off by default.
You can turn on backing store by giving the x server the +bs option,
or by putting
in the Screen section of XF86Config.
This XF86Config option is undocumented, and the Xserver man page only
documents the -bs option -- it doesn't mention the use of the "+" sign,
nor does it mention that backing store is turned off by default.
I don't know which is right -- the documentation or the implementation.