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| 31 | </td>
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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Getting Started</h1>
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| 33 |
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| 34 |
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| 35 |
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| 36 | [ <a href="motif-walkthrough.html">Home</a> ]
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| 37 | [ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
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| 38 | <p> <h2> Starting with <a href="qmotif.html">QMotif</a> and <a href="qapplication.html">QApplication</a>
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| 39 | </h2>
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| 40 | <a name="1"></a><p> To be able to use Qt, we need to create a QApplication object. The
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| 41 | QApplication class controls all the event delivery and display
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| 42 | management for all other Qt objects and widgets. We need to use the
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| 43 | QMotif class from the <em>Qt <a href="motif-extension.html#Motif">Motif</a> Extension</em> to allow QApplication
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| 44 | and the <tt>XtAppContext</tt> to coexist.
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| 45 | <p> The QApplication object must be created in the <tt>main()</tt> function.
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| 46 | We will need to modify <tt>todo.c</tt> to compile with a C++ compiler, so we
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| 47 | rename <tt>todo.c</tt> to <tt>todo.cpp</tt>.
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| 48 | <p> Next, we add the appropriate includes for the QMotif and QApplication
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| 49 | classes.
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| 50 | <p>
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| 51 |
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| 52 | <pre></pre>
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| 53 | <p> Next, we create the QMotif and QApplication objects. We create QMotif
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| 54 | with a foreign <tt>XtAppContext</tt>, and we create QApplication with a
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| 55 | foreign <tt>Display</tt>.
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| 56 | <p> <pre></pre>
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| 57 | <p> The next change is not yet necessary, but it is included to show that
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| 58 | the <em>Qt Motif Extension</em> provides a complete integration.
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| 59 | Normally, a Motif based program would use the <tt>XtAppMainLoop()</tt>
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| 60 | function to run the application's event loop. This is still possible,
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| 61 | but since we are migrating to the Qt toolkit, we prefer to use the
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| 62 | <a href="qapplication.html#exec">QApplication::exec</a>() function for running the event loop.
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| 63 | <p> <pre></pre>
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| 64 | <p> Since we renamed <tt>todo.c</tt> to <tt>todo.cpp</tt>, we must change the
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| 65 | project file and rerun <em>qmake</em> to regenerate our <tt>Makefile</tt>. When we
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| 66 | build our project, there are compile and link errors: we will fix
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| 67 | these in the following section.
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| 68 | <p> <h2> Migrating to C++
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| 69 | </h2>
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| 70 | <a name="2"></a><p> We need to convert the code in this file to proper C++ code.
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| 71 | Fortunately, the changes are not too large. Most files included from
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| 72 | existing C projects are not C++ compatible, so we make them compatible
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| 73 | by wrapping them in an <tt>extern "C"</tt> block.
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| 74 | <p>
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| 75 |
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| 76 | <p> <pre></pre>
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| 77 | <p> Global C functions that are forward declared must also be wrapped into
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| 78 | an <tt>extern "C"</tt> block.
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| 79 | <p> <pre></pre>
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| 80 | <p> The <tt>manageCB()</tt> function needs to be converted to proper C++.
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| 81 | <p> <pre></pre>
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| 82 | <p> And we need to fix two invalid casts. One is in the <tt>Save()</tt> function.
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| 83 | <p> <pre></pre>
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| 84 | <p> The other invalid cast is in the <tt>Open()</tt> function.
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| 85 | <p> <pre></pre>
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| 86 | <p> After these changes, the project compiles and links, and the
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| 87 | application runs and operates correctly.
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| 88 | <p> [ <a href="motif-walkthrough.html">Home</a> ]
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| 89 | [ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
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| 90 | <p>
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| 91 | <!-- eof -->
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| 92 | <p><address><hr><div align=center>
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| 93 | <table width=100% cellspacing=0 border=0><tr>
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| 94 | <td>Copyright © 2007
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| 95 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 96 | <td align=right><div align=right>Qt 3.3.8</div>
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| 97 | </table></div></address></body>
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