Technical Q&A QA1192

Using cmpWantsRegisterMessage not recommended on Mac OS X

Q: I have a QuickTime Component which I would like to make available only under certain conditions. Is the cmpWantsRegisterMessage flag still the recommended way to do this on Mac OS X?

A: No, the behavior of the cmpWantsRegisterMessage flag as documented in IM:More Macintosh Toolbox describes the Component Manager's behavior on traditional Mac OS.

On Mac OS X, these registration calls have to happen in each process' context, so they slow down all application launches. Avoid using cmpWantsRegisterMessage on Mac OS X.

One alternative approach is to make your component fail to open by returning an error in the Component Open call if for example, your hardware is not available or your specific condition for availability has not been met.

[Mar 11, 2003]