[kde-linux] Testing open window

[Alain M.]

How do I detect that a certain program has an open window? Preferably 
with shell script commands.

The problem is that an application (thinderbird) closes it's window but 
stays running in memory. I just want to detect that to be able to kill 
it, I know its name and PID. I am using KDE 3.4.2 (Mandriva 2006)

Firefox has a similar problem, but it delets it's lock filejust before 
going deadlock so it is easyer to detect.

Thanks,
Alain