How can make it on focus?

["Ji kai,liu" <archiver db geocrawler com>]

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Hi,I am new programmer of GTK,now I have a stupid 
question,here it is:
when I click a button in a window,it pops up one
window or dialog,I want to make the window or 
dialog be on focus one it pops up,I know there is
must a function does this work,can anyone give me
a hand?thank u in advance. 

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