1.12 Simple Graphical User Interfaces: gui.ss

The teachpack provides operations for creating and manipulating graphical user interfaces. We recommend using the world teachpack instead.

Window A Window is a data representation of a visible window on your computer screen.

GUI-ITEM A GUI-Item is a data representation of an active component of a window on your computer screen.

(create-window g) → Window

g : (listof (listof GUI-ITEM))

Creates a window from the “matrix” of gui items g.

(window? x) → boolean?

x : any/c

Is the given value a window?

(show-window w) → true

w : Window

Shows w.

(hide-window w) → true

w : window

Hides w.

(make-button label callback) → GUI-ITEM

label : string>

callback : (-> event%  boolean)

Creates a button with label and callback function. The latter receives an argument that it may safely ignore.

(make-message msg) → GUI-ITEM

msg : string?

Creates a message item from msg.

(draw-message g m) → true

g : GUI-ITEM

m : string?

Displays m in message item g and erases the current message.

(make-text txt) → GUI-ITEM

txt : string?

Creates an text editor (with label txt) that allows users to enter text.

(text-contents g) → string?

g : GUI-ITEM

Determines the current contents of a text GUI-ITEM.

(make-choice choices) → GUI-ITEM

choices : (listof string?)

Creates a choice menu from choices that permits users to choose from some alternatives.

(choice-index g) → natural-number/c

g : GUI-ITEM

Determines the choice that is currently selected in a choice GUI-ITEM; the result is the 0-based index in the choice menu

Example 1:

> (define w

(create-window

(list (list (make-button "QUIT" (lambda (e) (hide-window w)))))))

; A button appears on the screen.

; Click on the button and it will disappear.

> (show-window w)

; The window disappears.

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

(define w

(create-window

(list

(list text1)

(list msg1)

(list (make-button "OKAY" respond)

(make-button "QUIT" (lambda (e) (hide-window w)))))))