1.14 Simple Graphical User Interfaces: "gui.rkt"
| (require htdp/gui) | package: htdp-lib |
The teachpack provides functions for creating and manipulating graphical user interfaces. We recommend using 2htdp/universe 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.
procedure
(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?
procedure
(show-window w) → true
w : Window
Shows w.
procedure
(hide-window w) → true
w : window
Hides w.
procedure
(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.
procedure
(make-message msg) → GUI-ITEM
msg : string?
Creates a message item from msg.
procedure
(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.
procedure
(text-contents g) → string?
g : GUI-ITEM
Determines the current contents of a text GUI-ITEM.
procedure
(make-choice choices) → GUI-ITEM
choices : (listof string?)
Creates a choice menu from choices that permits users to choose
from some alternatives.
procedure
(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)))))))