What's the different in gtk_widget_realize , gtk_widget_map ,and gtk_widget_show

[hzeng]

Hello,
    I just begin to learn gtk. I want to know what happen inside these founctions when 
they are called.
It seems like that they all do something to create the widget but I can not know what 
they do clearly.
Thanks for your help!
Hzeng  
    
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