Dialogs with Call backs built in

dialog(Title,Top,Left,Depth,Width,Items,
  Buttons, Goal)

• Goal specifies a program to be run when the Ok button (or any button other than Cancel) on the dialog is pressed
• If goal succeeds - dialog terminates
• If goal fails - dialog remains displayed and control returns to the user
• Button is an integer giving the number of the button that was pressed
• Consider the example - where the integers are expected - and if not entered - a warning message is displayed

readints(I1,I2) :- 
 dialog('Integers',100,60,120,170,
 [button(65,97,26,66,'Ok'),
  button(68,10,20,60,'Cancel'),
  text(10,10,20,150,'Enter two integers:'),
  edit(34,12,20,70,'',read(I1)),
  edit(34,90,20,70,'',read(I2))],
  Response,
  are_ints(I1,I2)).

are_ints(D, B, Int1, Int2) :-
 integer(Int1),
 integer(Int2), !.

are_ints(D, B, Int1, Int2) :-
 message(['You must enter integers']),
 fail.

  
Figure 17: The integer dialog

  
Figure 18: The integer dialog with error message

 
• Modal dialog