I think the reason the please wait dialogs don't cause a problem is that nothing can ever come up on top of them. The key is that no event loop is running while you're doing your computation, so there is no way the OS can present any dialogs. The assumption here is that the OS has only one thread that can write to the screen. I think that's a safe assumption for the time being, but it probably will be something you'll need to mess around with in the future.
As to when to use a please wait dialog, I think you're quite right that if you've done what you can to make an operation fast, but it's still too slow, it is probably better to show such a dialog than not to. If you can come up with a way to break your computation up, or to determine how much of the computation is left to go (either stages or percent complete), I suggest you use the progress manager to present a more friendly and detailed description of the progress made so far. This is only appropriate if the operation is quite slow. If it just takes a few seconds, a please wait dialog is probably your best bet. -- Peter Epstein Palm, Inc. -- For information on using the Palm Developer Forums, or to unsubscribe, please see http://www.palmos.com/dev/support/forums/
