link="#009900" vlink="#007700" alink="#cc0000"> Teachpacks for How to Design Programs

GUI

gui.ss

The teachpack gui.ss provides the following operations:

show-window : -> true
to show the window

hide-window : -> true
to hide the window

create-window : (listof (listof gui-item)) -> true
to add gui-items to a window and to show the window
each list of gui-items defines one row of gui items in the window

make-button : str (event% -> boolean) -> gui-item
to create a button with label and call-back function

make-message : str -> gui-item
to create an item that displays a message

draw-message : gui-item[message%] stri -> true
to display a message in a message item
it earses the current message

make-text : str -> gui-item
to create an item (with label) that allows users to enter text

text-contents : gui-item[text%] -> str
to determine the contents of a text field

make-choice : (listof str) -> gui-item
to create a choice menu that permits users to choose from some string alternatives

choice-index : gui-item[choice%] -> num
to determine which choice is currently selected in a choice-item
the result is the 0-based index in the choice menu

Example 1:

> (create-window (list (list (make-button "QUIT" hide-window))))

A button appears on the screen. Click on the button and it will disappear.

> (show-window)

The frame reappears.

Example 2:

; text1 : GUI-ITEM
(define text1
  (make-text "Please enter your name"))

; msg1 : GUI-ITEM
(define msg1
  (make-message (string-append "Hello, World" (make-string 33 #\SPACE))))

; Event -> true
; draws the current contents of text1 into msg1, prepended with "Hello, "
(define (respond e)
  (draw-message msg1 (string-append "Hello, " (text-contents text1))))

; set up window with three "lines": a text field, a message, and two buttons
; fill in text and click OKAY
(create-window 
 (list
  (list text1)
  (list msg1)
  (list (make-button "OKAY" respond)
        (make-button "QUIT" hide-window))))