Hooking CTRL pressed in GTK+ application

How can I hook CTRL pressed in 开发者_如何转开发"drawingarea_button_press_event_cb" function of GTK+ application?

void drawingarea_button_press_event_cb( GtkWidget *widget, GdkEventButton *event )
{
 ........
}

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Inspect the state field of the GdkEventButton structure. It will have the GDK_CONTROL_MASK bit set if Control is being held down:

if(event->state & GDK_CONTROL_MASK)
  printf("You're totally in control!\n");