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189 lines
8.3 KiB
189 lines
8.3 KiB
14 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial.doc:580 -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Qt Tutorial - Chapter 6: Building Blocks Galore!</title>
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<style type="text/css"><!--
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fn { margin-left: 1cm; text-indent: -1cm; }
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a:link { color: #004faf; text-decoration: none }
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a:visited { color: #672967; text-decoration: none }
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body { background: #ffffff; color: black; }
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--></style>
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</head>
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<body>
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<table border="0" cellpadding="0" cellspacing="0" width="100%">
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<tr bgcolor="#E5E5E5">
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<td valign=center>
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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| <a href="classes.html">
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<font color="#004faf">All Classes</font></a>
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| <a href="mainclasses.html">
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<font color="#004faf">Main Classes</font></a>
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| <a href="annotated.html">
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<font color="#004faf">Annotated</font></a>
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| <a href="groups.html">
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<font color="#004faf">Grouped Classes</font></a>
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| <a href="functions.html">
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<font color="#004faf">Functions</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Qt Tutorial - Chapter 6: Building Blocks Galore!</h1>
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<p> <center><img src="t6.png" alt="Screenshot of tutorial six"></center>
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<p> This example shows how to encapsulate two widgets into a new component and
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how easy it is to use many widgets. For the first time, we use a custom
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widget as a child widget.
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<p> <a name="main"></a>
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<pre>/****************************************************************
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**
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** Qt tutorial 6
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**
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****************************************************************/
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#include <<a href="qapplication-h.html">qapplication.h</a>>
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#include <<a href="qpushbutton-h.html">qpushbutton.h</a>>
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#include <<a href="qslider-h.html">qslider.h</a>>
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#include <<a href="qlcdnumber-h.html">qlcdnumber.h</a>>
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#include <<a href="qfont-h.html">qfont.h</a>>
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#include <<a href="qvbox-h.html">qvbox.h</a>>
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#include <<a href="qgrid-h.html">qgrid.h</a>>
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class LCDRange : public <a href="qvbox.html">QVBox</a>
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{
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public:
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LCDRange( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
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};
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<a name="f554"></a>LCDRange::LCDRange( <a href="qwidget.html">QWidget</a> *parent, const char *name )
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: <a href="qvbox.html">QVBox</a>( parent, name )
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{
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<a href="qlcdnumber.html">QLCDNumber</a> *lcd = new <a href="qlcdnumber.html">QLCDNumber</a>( 2, this, "lcd" );
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<a href="qslider.html">QSlider</a> * slider = new <a href="qslider.html">QSlider</a>( Horizontal, this, "slider" );
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slider-><a href="qrangecontrol.html#setRange">setRange</a>( 0, 99 );
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slider-><a href="qslider.html#setValue">setValue</a>( 0 );
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<a href="qobject.html#connect">connect</a>( slider, SIGNAL(<a href="qslider.html#valueChanged">valueChanged</a>(int)), lcd, SLOT(<a href="qlcdnumber.html#display">display</a>(int)) );
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}
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class MyWidget : public <a href="qvbox.html">QVBox</a>
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{
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public:
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MyWidget( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
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};
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<a name="f555"></a>MyWidget::MyWidget( <a href="qwidget.html">QWidget</a> *parent, const char *name )
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: <a href="qvbox.html">QVBox</a>( parent, name )
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{
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<a href="qpushbutton.html">QPushButton</a> *quit = new <a href="qpushbutton.html">QPushButton</a>( "Quit", this, "quit" );
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quit-><a href="qwidget.html#setFont">setFont</a>( QFont( "Times", 18, QFont::Bold ) );
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<a href="qobject.html#connect">connect</a>( quit, SIGNAL(<a href="qbutton.html#clicked">clicked</a>()), qApp, SLOT(<a href="qapplication.html#quit">quit</a>()) );
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<a href="qgrid.html">QGrid</a> *grid = new <a href="qgrid.html">QGrid</a>( 4, this );
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for( int r = 0 ; r < 4 ; r++ )
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for( int c = 0 ; c < 4 ; c++ )
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(void)new LCDRange( grid );
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}
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int main( int argc, char **argv )
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{
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<a href="qapplication.html">QApplication</a> a( argc, argv );
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MyWidget w;
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a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &w );
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w.<a href="qwidget.html#show">show</a>();
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return a.<a href="qapplication.html#exec">exec</a>();
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}
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</pre>
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<p> <h2> Line-by-line Walkthrough
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</h2>
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<a name="1"></a><p> <pre> class LCDRange : public <a href="qvbox.html">QVBox</a>
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{
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public:
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LCDRange( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
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};
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</pre>
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<p> The LCDRange widget is a widget without any API. It just has a
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constructor. This sort of widget is not very useful, so we'll add some API later.
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<p> <pre> LCDRange::LCDRange( <a href="qwidget.html">QWidget</a> *parent, const char *name )
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: <a href="qvbox.html">QVBox</a>( parent, name )
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{
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<a href="qlcdnumber.html">QLCDNumber</a> *lcd = new <a href="qlcdnumber.html">QLCDNumber</a>( 2, this, "lcd" );
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<a href="qslider.html">QSlider</a> * slider = new <a href="qslider.html">QSlider</a>( Horizontal, this, "slider" );
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<a name="x2325"></a> slider-><a href="qrangecontrol.html#setRange">setRange</a>( 0, 99 );
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<a name="x2326"></a> slider-><a href="qslider.html#setValue">setValue</a>( 0 );
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<a name="x2327"></a><a name="x2324"></a> <a href="qobject.html#connect">connect</a>( slider, SIGNAL(<a href="qslider.html#valueChanged">valueChanged</a>(int)), lcd, SLOT(<a href="qlcdnumber.html#display">display</a>(int)) );
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}
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</pre>
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<p> This is lifted straight from the
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<a href="tutorial1-05.html#constructor">MyWidget constructor</a> in Chapter 5.
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The only differences are that the button is left out and the class
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is renamed.
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<p> <pre> class MyWidget : public <a href="qvbox.html">QVBox</a>
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{
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public:
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MyWidget( <a href="qwidget.html">QWidget</a> *parent=0, const char *name=0 );
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};
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</pre>
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<p> MyWidget, too, contains no API except a constructor.
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<p> <pre> MyWidget::MyWidget( <a href="qwidget.html">QWidget</a> *parent, const char *name )
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: <a href="qvbox.html">QVBox</a>( parent, name )
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{
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<a href="qpushbutton.html">QPushButton</a> *quit = new <a href="qpushbutton.html">QPushButton</a>( "Quit", this, "quit" );
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<a name="x2328"></a> quit-><a href="qwidget.html#setFont">setFont</a>( QFont( "Times", 18, QFont::Bold ) );
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<a name="x2321"></a> <a href="qobject.html#connect">connect</a>( quit, SIGNAL(<a href="qbutton.html#clicked">clicked</a>()), qApp, SLOT(<a href="qapplication.html#quit">quit</a>()) );
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</pre>
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<p> The push button that used to be in what is now LCDRange has been
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separated so that we can have one "Quit" button and many LCDRange
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objects.
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<p> <pre> <a href="qgrid.html">QGrid</a> *grid = new <a href="qgrid.html">QGrid</a>( 4, this );
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</pre>
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<p> We create a <a href="qgrid.html">QGrid</a> object with four columns. The QGRid widget
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automatically arranges its children in rows and columns; you can
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specify the number of rows or of columns, and QGrid will discover its
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new children and fit them into the grid.
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<p> <pre> for( int r = 0 ; r < 4 ; r++ )
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for( int c = 0 ; c < 4 ; c++ )
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(void)new LCDRange( grid );
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</pre>
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<p> Four columns, four rows.
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<p> We create 4*4 LCDRanges, all of which are children of the grid object.
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The QGrid widget will arrange them.
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<p> <pre> }
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</pre>
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<p> That's all.
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<p> <h2> Behavior
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</h2>
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<a name="2"></a><p> This program shows how easy it is to use many widgets at a time. Each
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one behaves like the slider and LCD number in the previous
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chapter. Again, the difference lies in the implementation.
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<p> (See <a href="tutorial1-01.html#compiling">Compiling</a> for how to create a
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makefile and build the application.)
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<p> <h2> Exercises
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</h2>
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<a name="3"></a><p> Initialize each slider with a different/random value on startup.
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<p> The source contains three occurrences of "4". What happens if you
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change the one in the <a href="qgrid.html">QGrid</a> constructor call? What about the other
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two? Why is this?
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<p> You're now ready for <a href="tutorial1-07.html">Chapter 7.</a>
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<p> [<a href="tutorial1-05.html">Previous tutorial</a>]
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[<a href="tutorial1-07.html">Next tutorial</a>]
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[<a href="tutorial.html">Main tutorial page</a>]
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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</html>
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