Brandon Allbery [2012.04.17 1344 -0400]:
Well, they are somewhat related, but I think the issue I'm talking about here
has a much more straightforward fix than trying to generate pure approximations
of layouts that can generate their exact answer only impurely.
My idea was to keep a Map that associates a rectangle with each window ID
(actually a list + offline sorting is enough and may be faster). After
Caching previous computations is a pretty necessary part of the full solution to that issue, which is why I pointed to it.