how do I observe keyboard input event while the ap

Question

how do I observe keyboard input event while the applicaion is not actived.

Answer 1

You'll need to create a CGEventTap using Quartz Event Services. The user must have access for assistive devices turned on, which makes sense, because that's the only legitimate reason for you to do that.

If you want to set up a hotkey, there's an API in Carbon Event Manager for that, and a Cocoa wrapper named SGHotKeysLib. Note that the Carbon Event Manager hotkey API is still supported in current, 64-bit Mac OS X.