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129 lines
6.2 KiB
129 lines
6.2 KiB
<!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:216 -->
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<html>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>TQt Tutorial - Chapter 2: Calling it Quits</title>
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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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>TQt Tutorial - Chapter 2: Calling it Quits</h1>
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<p> <center><img src="t2.png" alt="Screenshot of tutorial two"></center>
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<p> Having created a window in <a href="tutorial1-01.html">Chapter 1,</a> we will
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now go on to make the application quit properly when the user tells it to.
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<p> We will also use a font that is more exciting than the default one.
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<p> <pre>/****************************************************************
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**
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** TQt tutorial 2
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**
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****************************************************************/
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#include <<a href="qapplication-h.html">ntqapplication.h</a>>
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#include <<a href="qpushbutton-h.html">ntqpushbutton.h</a>>
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#include <<a href="qfont-h.html">ntqfont.h</a>>
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int main( int argc, char **argv )
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{
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<a href="ntqapplication.html">TQApplication</a> a( argc, argv );
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<a href="ntqpushbutton.html">TQPushButton</a> quit( "Quit", 0 );
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quit.<a href="ntqwidget.html#resize">resize</a>( 75, 30 );
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quit.<a href="ntqwidget.html#setFont">setFont</a>( TQFont( "Times", 18, TQFont::Bold ) );
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TQObject::<a href="ntqobject.html#connect">connect</a>( &quit, TQ_SIGNAL(<a href="ntqbutton.html#clicked">clicked</a>()), &a, TQ_SLOT(<a href="ntqapplication.html#quit">quit</a>()) );
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a.<a href="ntqapplication.html#setMainWidget">setMainWidget</a>( &quit );
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quit.<a href="ntqwidget.html#show">show</a>();
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return a.<a href="ntqapplication.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> #include <<a href="qfont-h.html">ntqfont.h</a>>
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</pre>
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<p> Since this program uses <a href="ntqfont.html">TQFont</a>, it needs to include ntqfont.h. TQt's font
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abstraction is rather different from the horror provided by X, and
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loading and using fonts has been highly optimized.
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<p> <pre> <a href="ntqpushbutton.html">TQPushButton</a> quit( "Quit", 0 );
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</pre>
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<p> This time, the button says "Quit" and that's exactly what the program
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will do when the user clicks the button. This is not a coincidence.
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We still pass 0 as the parent, since the button is a top-level window.
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<p> <pre> <a name="x2292"></a> quit.<a href="ntqwidget.html#resize">resize</a>( 75, 30 );
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</pre>
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<p> We've chosen another size for the button since the text is a bit
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shorter than "Hello world!". We could also have used <a href="ntqfontmetrics.html">TQFontMetrics</a>
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to set right size.
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<p> <pre> <a name="x2293"></a> quit.<a href="ntqwidget.html#setFont">setFont</a>( TQFont( "Times", 18, TQFont::Bold ) );
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</pre>
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<p> Here we choose a new font for the button, an 18-point bold font from
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the Times family. Note that we create the font on the spot.
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<p> It is also possible to change the default font (using <a href="ntqapplication.html#setFont">TQApplication::setFont</a>()) for the whole application.
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<p> <pre> <a name="x2291"></a><a name="x2290"></a><a name="x2288"></a> TQObject::<a href="ntqobject.html#connect">connect</a>( &quit, TQ_SIGNAL(<a href="ntqbutton.html#clicked">clicked</a>()), &a, TQ_SLOT(<a href="ntqapplication.html#quit">quit</a>()) );
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</pre>
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<p> connect() is perhaps <em>the</em> most central feature of TQt.
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Note that connect() is a static function in <a href="ntqobject.html">TQObject</a>. Do not confuse it
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with the connect() function in the socket library.
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<p> This line establishes a one-way connection between two TQt objects (objects
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that inherit TQObject, directly or indirectly). Every TQt object can have
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both <tt>signals</tt> (to send messages) and <tt>slots</tt> (to receive messages). All
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widgets are TQt objects. They inherit <a href="ntqwidget.html">TQWidget</a> which in turn inherits
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TQObject.
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<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
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application quits.
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<p> The <a href="signalsandslots.html">Signals and Slots</a> documentation
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describes this topic in detail.
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<p> <h2> Behavior
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</h2>
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<a name="2"></a><p> When you run this program, you will see an even smaller window than in
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Chapter 1, filled with an even smaller button.
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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> Try to resize the window. Press the button. Oops! That connect()
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would seem to make some difference.
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<p> Are there any other signals in <a href="ntqpushbutton.html">TQPushButton</a> you can connect to quit?
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Hint: The TQPushButton inherits most of its behavior from <a href="ntqbutton.html">TQButton</a>.
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<p> You're now ready for <a href="tutorial1-03.html">Chapter 3.</a>
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<p> [<a href="tutorial1-01.html">Previous tutorial</a>]
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[<a href="tutorial1-03.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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<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>TQt 3.3.8</div>
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