gtk:dialog-set-default-response (dialog response)

dialog -- a gtk:dialog widget
response -- a response ID, which is a positive integer or a value of the gtk:response-type enumeration

Sets the last widget in the action area of the dialog with the given response value as the default widget for the dialog. Pressing the Enter key normally activates the default widget. The gtk:dialog implementation is deprecated since 4.10. Use the gtk:window widget instead.