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<html>
<head>
<title>Teachpack : GUI</title>
</head>
<body bgcolor="#ffffff" text="#000000"
link="#009900" vlink="#007700" alink="#cc0000">
<a href="index.html">Teachpacks for How to Design Programs</a>
<h1>GUI</h1>
<hr> <h3><a name="gui.ss">gui.ss</a></h3> <!-- DOCNOTE="teach=gui.ss" -->
<p>The teachpack <code>gui.ss</code> provides the following operations:
<menu>
<li> <code><a name="show-window">show-window</a> : window -> true</code>
<br>to show the window
<li> <code><a name="hide-window">hide-window</a> : window -> true</code>
<br>to hide the window
<li> <code><a name="create-window">create-window</a> : (listof (listof gui-item)) -> window</code>
<br>to add gui-items to a window and to show the window
<br>each list of gui-items defines one row of gui items in the window
<li> <code><a name="make-button">make-button</a> : str (event% -> boolean) -> gui-item</code>
<br>to create a button with label and call-back function
<li> <code><a name="make-message">make-message</a> : str -> gui-item</code>
<br>to create an item that displays a message
<li> <code><a name="draw-message">draw-message</a> : gui-item[message%] stri -> true</code>
<br>to display a message in a message item
<br>it erases the current message
<li> <code><a name="make-text">make-text</a> : str -> gui-item</code>
<br>to create an item (with label) that allows users to enter text
<li> <code><a name="text-contents">text-contents</a> : gui-item[text%] -> str</code>
<br>to determine the contents of a text field
<li> <code><a name="make-choice">make-choice</a> : (listof str) -> gui-item</code>
<br>to create a choice menu that permits users to choose from some
string alternatives
<li> <code><a name="choice-index">choice-index</a> : gui-item[choice%] -> num</code>
<br>to determine which choice is currently selected in a choice-item
<br>the result is the 0-based index in the choice menu
</menu>
<p>Example 1:
<pre>
> (define w (create-window (list (list (make-button "QUIT" (lambda (e) (hide-window w)))))))
</pre>
A button appears on the screen. Click on the button and it will disappear.
<pre>
> (show-window w)
</pre>
The frame reappears.
<p>Example 2:
<pre>
; 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)))))))
</pre>
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