Mac Forum / Programming / Mac Programming / October 2005

Hi, I have a simple single-window Cocoa app (not document-based). When
the app starts I would like bring up a sheet asking for a password.
Once the password is valid, the sheet should disappear and the
application can be used by the user.

Attempt 1:   using NSApplication's
beginSheet:modalForWindow:modalDelegate:didEndSelector:contextInfo:

This is what I'm currently using. The problem is that once the sheet is
displayed on screen, program flow immediately proceeds. In other words,
it doesn't wait for the password to be entered and the sheet to be
closed.

Attempt 2:
Searching through the docs I found that I could use this for tighter
control over the event loop:

NSModalSession session = [NSApp beginModalSessionForWindow:theWindow];
for (;;) {
   if ([NSApp runModalSession:session] != NSRunContinuesResponse)
       break;
   }
[NSApp endModalSession:session];

This code does work, and can be used to wait for the sheet to be closed
but unfortunately it uses 80% of CPU (as I expected it would).

Attempt 3:
Trying to reduce the amount of CPU used, I did the same thing as
Attempt 1, but added locking (using NSLock) to wait on sheet closing.
That was dumb because it would put the same thread to sleep that was
supposed to clear the lock at some point.

Attempt 4:
Finally, I gave up on sheets and used a Panel instead with
NSApplication's runModalForWindow:. This does wait for the panel to be
closed (actually waits for stopModal) without any contortions on my
part. But damnit, I really want a sheet :-)

So how do I get a sheet to behave like a panel with runModalForWindow:
in terms of only returning when the sheet is closed?

Thanks for any insight.

Chris