Getting pid and details for topmost window

Question

Does anyone know how to get the PID of the top active window and then how to get the properties of the window using the PID? I mean properties like process name, program nam

Answer 1

One of things about X is that it's network transparent. It's quite possible that the actual window being displayed at the top (which has focus) is running on a machine other than your own in which case, the process id of the process running inside the window will make no sense on your machine.

Can you elaborate a little on what you want to do? I think there are some missing details here. Ideally, you should work at the X level rather than at the machine specific one.