source: trunk/doc/html/forever-example.html

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[190]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/examples/forever/forever.doc:5 -->
3<html>
4<head>
5<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
6<title>A Rectangle Draw "Benchmark"</title>
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14<body>
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16<table border="0" cellpadding="0" cellspacing="0" width="100%">
17<tr bgcolor="#E5E5E5">
18<td valign=center>
19 <a href="index.html">
20<font color="#004faf">Home</font></a>
21 | <a href="classes.html">
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30<font color="#004faf">Functions</font></a>
31</td>
32<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>A Rectangle Draw "Benchmark"</h1>
33
34
35<p>
36This example continuously draws rectangles in a window and
37has another widget that counts the number of rectangles that
38are drawn per second.
39<p> <hr>
40<p> Header file:
41<p> <pre>/****************************************************************************
42** $Id: forever-example.html 2051 2007-02-21 10:04:20Z chehrlic $
43**
44** Definition of something or other
45**
46** Created : 979899
47**
48** Copyright (C) 1997-2007 Trolltech ASA. All rights reserved.
49**
50** This file is part of an example program for Qt. This example
51** program may be used, distributed and modified without limitation.
52**
53*****************************************************************************/
54
55#ifndef FOREVER_H
56#define FOREVER_H
57
58#include &lt;<a href="qwidget-h.html">qwidget.h</a>&gt;
59
60
61const int numColors = 120;
62
63
64class Forever : public <a href="qwidget.html">QWidget</a>
65{
66 <a href="metaobjects.html#Q_OBJECT">Q_OBJECT</a>
67public:
68 Forever( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
69protected:
70 void paintEvent( <a href="qpaintevent.html">QPaintEvent</a> * );
71 void timerEvent( <a href="qtimerevent.html">QTimerEvent</a> * );
72private slots:
73 void updateCaption();
74private:
75 int rectangles;
76 QColor colors[numColors];
77};
78
79
80#endif
81</pre>
82
83<p> <hr>
84<p> Implementation:
85<p> <pre>/****************************************************************************
86** $Id: forever-example.html 2051 2007-02-21 10:04:20Z chehrlic $
87**
88** Copyright (C) 1992-2007 Trolltech ASA. All rights reserved.
89**
90** This file is part of an example program for Qt. This example
91** program may be used, distributed and modified without limitation.
92**
93*****************************************************************************/
94
95#include &lt;<a href="qtimer-h.html">qtimer.h</a>&gt;
96#include &lt;<a href="qpainter-h.html">qpainter.h</a>&gt;
97#include &lt;<a href="qapplication-h.html">qapplication.h</a>&gt;
98#include &lt;stdlib.h&gt; // defines rand() function
99
100#include "forever.h"
101
102
103//
104// Forever - a widget that draws rectangles forever.
105//
106
107//
108// Constructs a Forever widget.
109//
110
111<a name="f365"></a>Forever::Forever( <a href="qwidget.html">QWidget</a> *parent, const char *name )
112 : <a href="qwidget.html">QWidget</a>( parent, name )
113{
114 for (int a=0; a&lt;numColors; a++) {
115 colors[a] = QColor( rand()&amp;255,
116 rand()&amp;255,
117 rand()&amp;255 );
118 }
119 rectangles = 0;
120 <a href="qobject.html#startTimer">startTimer</a>( 0 ); // run continuous timer
121 <a href="qtimer.html">QTimer</a> * counter = new <a href="qtimer.html">QTimer</a>( this );
122<a name="x1054"></a> <a href="qobject.html#connect">connect</a>( counter, SIGNAL(<a href="qtimer.html#timeout">timeout</a>()),
123 this, SLOT(updateCaption()) );
124<a name="x1053"></a> counter-&gt;<a href="qtimer.html#start">start</a>( 1000 );
125}
126
127
128void <a name="f366"></a>Forever::updateCaption()
129{
130 <a href="qstring.html">QString</a> s;
131<a name="x1052"></a> s.<a href="qstring.html#sprintf">sprintf</a>( "Qt Example - Forever - %d rectangles/second", rectangles );
132 rectangles = 0;
133 <a href="qwidget.html#setCaption">setCaption</a>( s );
134}
135
136
137//
138// Handles paint events for the Forever widget.
139//
140
141<a name="x1055"></a>void Forever::<a href="qwidget.html#paintEvent">paintEvent</a>( <a href="qpaintevent.html">QPaintEvent</a> * )
142{
143 <a href="qpainter.html">QPainter</a> paint( this ); // painter object
144 int w = <a href="qwidget.html#width">width</a>();
145 int h = <a href="qwidget.html#height">height</a>();
146 if(w &lt;= 0 || h &lt;= 0)
147 return;
148 paint.<a href="qpainter.html#setPen">setPen</a>( NoPen ); // do not draw outline
149 paint.<a href="qpainter.html#setBrush">setBrush</a>( colors[rand() % numColors]);// set random brush color
150
151 <a href="qpoint.html">QPoint</a> p1( rand()%w, rand()%h ); // p1 = top left
152 <a href="qpoint.html">QPoint</a> p2( rand()%w, rand()%h ); // p2 = bottom right
153
154 <a href="qrect.html">QRect</a> r( p1, p2 );
155 paint.<a href="qpainter.html#drawRect">drawRect</a>( r ); // draw filled rectangle
156}
157
158//
159// Handles timer events for the Forever widget.
160//
161
162<a name="x1048"></a>void Forever::<a href="qobject.html#timerEvent">timerEvent</a>( <a href="qtimerevent.html">QTimerEvent</a> * )
163{
164 for ( int i=0; i&lt;100; i++ ) {
165 <a href="qwidget.html#repaint">repaint</a>( FALSE ); // repaint, don't erase
166 rectangles++;
167 }
168}
169
170
171//
172// Create and display Forever widget.
173//
174
175int main( int argc, char **argv )
176{
177 <a href="qapplication.html">QApplication</a> a( argc, argv ); // create application object
178 Forever always; // create widget
179 always.<a href="qwidget.html#resize">resize</a>( 400, 250 ); // start up with size 400x250
180 a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &amp;always ); // set as main widget
181 always.<a href="qwidget.html#setCaption">setCaption</a>("Qt Example - Forever");
182 always.<a href="qwidget.html#show">show</a>(); // show widget
183 return a.<a href="qapplication.html#exec">exec</a>(); // run event loop
184}
185</pre>
186
187<p>See also <a href="examples.html">Examples</a>.
188
189<!-- eof -->
190<p><address><hr><div align=center>
191<table width=100% cellspacing=0 border=0><tr>
192<td>Copyright &copy; 2007
193<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
194<td align=right><div align=right>Qt 3.3.8</div>
195</table></div></address></body>
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