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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>Getting Started</h1>
[ <a href="motif-walkthrough.html">Home</a> ]
[ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
<p> <h2> Starting with <a href="qmotif.html">QMotif</a> and <a href="qapplication.html">QApplication</a>
</h2>
<a name="1"></a><p> To be able to use Qt, we need to create a QApplication object. The
QApplication class controls all the event delivery and display
management for all other Qt objects and widgets. We need to use the
QMotif class from the <em>Qt <a href="motif-extension.html#Motif">Motif</a> Extension</em> to allow QApplication
and the <tt>XtAppContext</tt> to coexist.
<p> The QApplication object must be created in the <tt>main()</tt> function.
We will need to modify <tt>todo.c</tt> to compile with a C++ compiler, so we
rename <tt>todo.c</tt> to <tt>todo.cpp</tt>.
<p> Next, we add the appropriate includes for the QMotif and QApplication
classes.
<p>
<pre></pre>
<p> Next, we create the QMotif and QApplication objects. We create QMotif
with a foreign <tt>XtAppContext</tt>, and we create QApplication with a
foreign <tt>Display</tt>.
<p> <pre></pre>
<p> The next change is not yet necessary, but it is included to show that
the <em>Qt Motif Extension</em> provides a complete integration.
Normally, a Motif based program would use the <tt>XtAppMainLoop()</tt>
function to run the application's event loop. This is still possible,
but since we are migrating to the Qt toolkit, we prefer to use the
<a href="qapplication.html#exec">QApplication::exec</a>() function for running the event loop.
<p> <pre></pre>
<p> Since we renamed <tt>todo.c</tt> to <tt>todo.cpp</tt>, we must change the
project file and rerun <em>qmake</em> to regenerate our <tt>Makefile</tt>. When we
build our project, there are compile and link errors: we will fix
these in the following section.
<p> <h2> Migrating to C++
</h2>
<a name="2"></a><p> We need to convert the code in this file to proper C++ code.
Fortunately, the changes are not too large. Most files included from
existing C projects are not C++ compatible, so we make them compatible
by wrapping them in an <tt>extern "C"</tt> block.
<p>
<p> <pre></pre>
<p> Global C functions that are forward declared must also be wrapped into
an <tt>extern "C"</tt> block.
<p> <pre></pre>
<p> The <tt>manageCB()</tt> function needs to be converted to proper C++.
<p> <pre></pre>
<p> And we need to fix two invalid casts. One is in the <tt>Save()</tt> function.
<p> <pre></pre>
<p> The other invalid cast is in the <tt>Open()</tt> function.
<p> <pre></pre>
<p> After these changes, the project compiles and links, and the
application runs and operates correctly.
<p> [ <a href="motif-walkthrough.html">Home</a> ]
[ <a href="motif-walkthrough-2.html">Next: Preparing to Migrate the User Interface</a> ]
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