Cocoa - Get window ID on click, as used in Grab

Hey everyone, I have been searching for this answer and I realized that I don't even really know what to search for. Here's what I'm trying to do, and maybe someone can give me at least what to search for, if not the answer itself!

I'm building a Cocoa app right now in which I want to be able to click any window that is open and get the process serial or any kind of window ID number that I can compare to other windows. This is similar to the functionality of the Grab screen-shot utility that comes with OS X.

If you open Grab, then select Capture->Window, it comes up with a message box and you click "Choose Window", and the cursor becomes a camera, and any window you click while it is a camera is what Grab takes the screenshot of. I want to be able to click a window and return its ID. Any thoughts??

Any and all help is greatly appreciated!

 

@kainjow, thanks alot! I will check that out and see if it can do exactly what I need. Just reading glancing over that header file makes me think it will do nicely.

@lee1210, I'll definitely keep that in mind, and that's where I'm going if CGWindow doesn't exactly cut it. Thanks again for the speedy help!