Tips to deploy applications to multiple Mac OS X versions

if I don't use it, will my application perform worse on Leopard? - Is there a way to differentiate part of code by platform? I remember I saw in some files lines like this #if MACOSX_DEPLOYMENT_TARGET == MAC_OS_X_VERSION_10_4 #endif is this correct? Thanks, Lor

Sheet window as firstResponder

Hi, I'm trying to get keyDown events from the contentView of a sheet window. I overrided the acceptsFirstResponder method to return YES, and added a - (void) keyDown: (NSEvent *) event. The problem is that when the sheet becomes visible and I press a key I hear a system alert and the keyDow