Q. When in my XFCN, I'm given a handle to the parameter string. Is the
handle locked? Should I lock it if I de-reference it? Is it OK to unlock
it? Can I operate on the string in memory and just pass back the handle
that was given to me?
A. Never assume a handle to be in a certain state -- locked, unlocked,
purgable, unpurgable, etc. If you wish to ensure the handle is in a
known state, call HGetState to retrieve the current state of the handle.
The HLock and HUnlock procedures allow you to set the flag as you like.
At the end of your routine, reset the flag as it was, by passing back
the original flag.
This technique should be used if you wish to modify the state bits of
any handle not created by your program.
Q. How do I treat a handle that really belongs to another process?
A. If a handle belongs to another process, don't call HUnlock if locked,
or HPurge if unpurgable flag is set -- HyperCard has set those flags
that way for a reason, and they shouldn't be tampered with.
Q. When I set the return handle, does HyperCard dispose of it for me?
A. HyperCard disposes of the handle when you're through with it.