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Processes messages in MediaMonkey's internal message queue.
MediaMonkey runs scripts in the same thread as its graphical user interface. When you're doing heavy work in an internal script (e.g. using lengthy, processor-heavy loops), be sure to call ProcessMessages once in a while to keep the MediaMonkey gui responsive.
Note however, that using this method without any limits can be a little dangerous and result in deadlocks. Definitely try to work without this method, if you can. There are other options of how to do lengthy work on background (e.g. OnIdle event). Definitely try to avoid calling it while you have some SQL open (i.e. some SELECT command) without starting an SQL transaction.