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.
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.
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))))))) |