summaryrefslogtreecommitdiffstats
path: root/doc/html/tutorial1-02.html
blob: 7b84b5ecbc84e22b09c284410daa6b8ff34718cc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial.doc:216 -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>TQt Tutorial - Chapter 2: Calling it Quits</title>
<style type="text/css"><!--
fn { margin-left: 1cm; text-indent: -1cm; }
a:link { color: #004faf; text-decoration: none }
a:visited { color: #672967; text-decoration: none }
body { background: #ffffff; color: black; }
--></style>
</head>
<body>

<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr bgcolor="#E5E5E5">
<td valign=center>
 <a href="index.html">
<font color="#004faf">Home</font></a>
 | <a href="classes.html">
<font color="#004faf">All&nbsp;Classes</font></a>
 | <a href="mainclasses.html">
<font color="#004faf">Main&nbsp;Classes</font></a>
 | <a href="annotated.html">
<font color="#004faf">Annotated</font></a>
 | <a href="groups.html">
<font color="#004faf">Grouped&nbsp;Classes</font></a>
 | <a href="functions.html">
<font color="#004faf">Functions</font></a>
</td>
<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>TQt Tutorial - Chapter 2: Calling it Quits</h1>

 
<p> <center><img src="t2.png" alt="Screenshot of tutorial two"></center> 
<p> Having created a window in <a href="tutorial1-01.html">Chapter 1,</a> we will
now go on to make the application quit properly when the user tells it to.
<p> We will also use a font that is more exciting than the default one.
<p> <pre>/****************************************************************
**
** TQt tutorial 2
**
****************************************************************/

#include &lt;<a href="qapplication-h.html">qapplication.h</a>&gt;
#include &lt;<a href="qpushbutton-h.html">qpushbutton.h</a>&gt;
#include &lt;<a href="qfont-h.html">qfont.h</a>&gt;


int main( int argc, char **argv )
{
    <a href="qapplication.html">TQApplication</a> a( argc, argv );

    <a href="qpushbutton.html">TQPushButton</a> quit( "Quit", 0 );
    quit.<a href="qwidget.html#resize">resize</a>( 75, 30 );
    quit.<a href="qwidget.html#setFont">setFont</a>( TQFont( "Times", 18, TQFont::Bold ) );

    TQObject::<a href="qobject.html#connect">connect</a>( &amp;quit, SIGNAL(<a href="qbutton.html#clicked">clicked</a>()), &amp;a, SLOT(<a href="qapplication.html#quit">quit</a>()) );

    a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &amp;quit );
    quit.<a href="qwidget.html#show">show</a>();
    return a.<a href="qapplication.html#exec">exec</a>();
}
</pre>



<p> <h2> Line-by-line Walkthrough
</h2>
<a name="1"></a><p> <pre>    #include &lt;<a href="qfont-h.html">qfont.h</a>&gt;
</pre>
<p> Since this program uses <a href="qfont.html">TQFont</a>, it needs to include qfont.h. TQt's font
abstraction is rather different from the horror provided by X, and
loading and using fonts has been highly optimized.
<p> <pre>        <a href="qpushbutton.html">TQPushButton</a> quit( "Quit", 0 );
</pre>
<p> This time, the button says "Quit" and that's exactly what the program
will do when the user clicks the button. This is not a coincidence.
We still pass 0 as the parent, since the button is a top-level window.
<p> <pre>    <a name="x2292"></a>    quit.<a href="qwidget.html#resize">resize</a>( 75, 30 );
</pre>
<p> We've chosen another size for the button since the text is a bit
shorter than "Hello world!". We could also have used <a href="qfontmetrics.html">TQFontMetrics</a>
to set right size.
<p> <pre>    <a name="x2293"></a>    quit.<a href="qwidget.html#setFont">setFont</a>( TQFont( "Times", 18, TQFont::Bold ) );
</pre>
<p> Here we choose a new font for the button, an 18-point bold font from
the Times family. Note that we create the font on the spot.
<p> It is also possible to change the default font (using <a href="qapplication.html#setFont">TQApplication::setFont</a>()) for the whole application.
<p> <pre>    <a name="x2291"></a><a name="x2290"></a><a name="x2288"></a>    TQObject::<a href="qobject.html#connect">connect</a>( &amp;quit, SIGNAL(<a href="qbutton.html#clicked">clicked</a>()), &amp;a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
</pre>
<p> connect() is perhaps <em>the</em> most central feature of TQt.
Note that connect() is a static function in <a href="qobject.html">TQObject</a>. Do not confuse it
with the connect() function in the socket library.
<p> This line establishes a one-way connection between two TQt objects (objects
that inherit TQObject, directly or indirectly). Every TQt object can have
both <tt>signals</tt> (to send messages) and <tt>slots</tt> (to receive messages). All
widgets are TQt objects. They inherit <a href="qwidget.html">TQWidget</a> which in turn inherits
TQObject.
<p> Here, the <em>clicked()</em> signal of <em>quit</em> is connected to the <em>quit()</em> slot of <em>a</em>, so that when the button is clicked, the
application quits.
<p> The <a href="signalsandslots.html">Signals and Slots</a> documentation
describes this topic in detail.
<p> <h2> Behavior
</h2>
<a name="2"></a><p> When you run this program, you will see an even smaller window than in
Chapter 1, filled with an even smaller button.
<p> (See <a href="tutorial1-01.html#compiling">Compiling</a> for how to create a
makefile and build the application.)
<p> <h2> Exercises
</h2>
<a name="3"></a><p> Try to resize the window. Press the button. Oops!  That connect()
would seem to make some difference.
<p> Are there any other signals in <a href="qpushbutton.html">TQPushButton</a> you can connect to quit?
Hint: The TQPushButton inherits most of its behavior from <a href="qbutton.html">TQButton</a>.
<p> You're now ready for <a href="tutorial1-03.html">Chapter 3.</a>
<p> [<a href="tutorial1-01.html">Previous tutorial</a>]
[<a href="tutorial1-03.html">Next tutorial</a>]
[<a href="tutorial.html">Main tutorial page</a>]
<p> 
<!-- eof -->
<p><address><hr><div align=center>
<table width=100% cellspacing=0 border=0><tr>
<td>Copyright &copy; 2007
<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
<td align=right><div align=right>TQt 3.3.8</div>
</table></div></address></body>
</html>