Dialog windows should be set transient for the main application
window they were spawned from. This allows window managers to e.g. keep the
dialog on top of the main window, or center the dialog over the
gtkDialogNewWithButtons and other convenience
functions in GTK+ will sometimes call
gtkWindowSetTransientFor on your behalf.
gtkWindowSetTransientFor(object, parent = NULL)
- parent window, or
NULL. [ allow-none ]
parent unsets the current transient window.
On Windows, this function puts the child window on top of the parent,
much as the window manager would have done on X.