How to debug a buggy running GUI application?

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http://unix.stackexchange.com – Suppose the GUI applications are not given names in its GUI, so you don't know what to check in 'ps -A', i.e. the nameless applications in the task bar. How do I know which GUI application belong to what process and start debugging its errors (i.e. GUI frozen, program crash...)? With CLI applications, I can use attach the process to GDB and start investigating it. (HowTos)