Q:  How many windows can the handle WindowServer simultaneously?

A:  This is unlikely to be a problem!  The WindowServer should be able to handle any number up to the limit of 64K simultaneous windows.  Working from a client, you probably are restricted to one-half or one-quarter of that figure, due to client library issues.

QA25

Valid for 1.0, 2.0, 3.0, 3.1