How to verify user input to GtkEntry fields

[Neoklis Kyriazis <neoklis users sourceforge net>]

Hi all,

I am trying to incorporate some basic verification of user input to
GtkEntry type fields. I have used the focus_out_event to run some code
that reads and checks user input but moving the mouse out of my apps
window, for example, triggers off this process since the first field
already has focus. What is the right way to do this?

I also need to return focus to the erroneous field and select the
bad entry but I am a beginner and couldn't get both actions to happen
simultaneously! 

My thanks in advance.

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