Is GTK+-(GDK) implemented by Multi-thread method?

["刘志波" <boerliu gmail com>]

Hi forks,
   I want to know whether the GTK+- Library is implemented by Multi-thread method for itself. You know, it has been driven by event mechanism. How does GTK's main loop catch user events like key events, mouse motion,etc when other flows alway hold the CPU resource? I know, maybe the GTK lib can use the signal to receive all of the hardware events. I just want to know the GTK wheter uses the Multi-thread mechanism to program itself!
   Thanks,
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With best regards!
boer