Locking Presentation Space

An application, even if specified with shared presentation space, can obtain exclusive control of a presentation space by using the Lock Presentation Space API (60) or the Lock Windows® Services API (61) functions. Requests by the other applications to use a presentation space locked by these functions are queued and processed in first-in-first-out (FIFO) order when the originating application unlocks the presentation space.

If the application that locked the presentation space does not unlock it by using the same call with an Unlock option or Reset System (21) call, the lock is removed when the application terminates or the session stops.