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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>Using Existing Dialogs with QMotifDialog</h1>
[ <a href="motif-walkthrough-4.html">Previous: Using Custom QDialogs</a> ]
[ <a href="motif-walkthrough.html">Home</a> ]
[ <a href="motif-walkthrough-6.html">Next: Using Qt Main Window Classes</a> ]
<p> As mentioned earlier, the <em>Print</em> dialog cannot be replaced until we
have converted the <em>View</em> widget. The <em>Print</em> dialog will be
removed once we have finished our migration, since we will use
<a href="qprinter.html">QPrinter</a> instead. Based on this information, we decide that it is not
worth replacing the <em>Print</em> dialog with a custom <a href="qdialog.html">QDialog</a> replacement.
Instead, we will keep the <a href="motif-extension.html#Motif">Motif</a> based dialog and use <a href="qmotifdialog.html">QMotifDialog</a> to
integrate the dialog with the application.
<p> <h2> Modality Requirements
</h2>
<a name="1"></a><p> Modality with QDialog is different from Motif. The <a href="qdialog.html#exec">QDialog::exec</a>()
function does not return until the dialog is finished. In Motif,
modality is simply a property of the shell, and the application
programmer must write QDialog::exec() style functionality if they
want that behavior.
<p> Since we will be using QMotifDialog (which is a QDialog subclass), we
will need to have an <em>accept</em> and a <em>reject</em> callback for each
dialog we integrate with QMotifDialog. The predefined Motif dialogs
have these already: the <tt>XmNokCallback</tt> and <tt>XmNcancelCallback</tt>
callbacks. However, the <em>Print</em> dialog only has an <em>accept</em> callback
(the <tt>XmdNprintCallback</tt>), but it does not have a <em>reject</em> callback.
We need to add this.
<p> This is easily done. We add an <tt>XtCallbackList</tt> for the <tt>XmNcancelCallback</tt> callback in <tt>Xmd/PrintP.h</tt>:
<p>
<pre></pre>
<p> We add the <tt>XmNcancelCallback</tt> callback to the list of resources for
the <tt>XmdPrint</tt> widget class in <tt>Xmd/Print.c</tt>:
<p>
<pre></pre>
<p> We need to activate this callback whenever we unmanage the widget and
do not activate the <em>print</em> callback, which is in the <tt>do_help_cb()</tt>
function:
<p> <pre></pre>
<p> ... and in the unmanage_cb() function:
<p> <pre></pre>
<p> <h2> Integrating the <em>Print</em> Dialog
</h2>
<a name="2"></a><p> Now that the <em>Print</em> dialog has the appropriate <em>accept</em> and <em>reject</em> callbacks, we can use <a href="qmotifdialog.html">QMotifDialog</a>. First we need to include
the QMotifDialog header in <tt>todo.cpp</tt>.
<p>
<p> <pre></pre>
<p> We add a <tt>ShowPrintDialog()</tt> function which will create and execute the
print dialog.
<p> <pre></pre>
<p> We change the <em>Print</em> menu item callback to call the new <tt>ShowPrintDialog()</tt> function. We pass the top-level <a href="qmotifwidget.html">QMotifWidget</a>, which
we will use as the parent for the dialog.
<p> <pre></pre>
<p> The <tt>ShowPrintDialog()</tt> function creates the <em>Print</em> dialog and
executes it. We use the <tt>XmdNprintCallback</tt> callback to accept the
dialog and the <tt>XmNcancelCallback</tt> callback to reject the dialog. We
can do this easily by using the <a href="qmotifdialog.html#acceptCallback">QMotifDialog::acceptCallback</a>() and
<a href="qmotifdialog.html#rejectCallback">QMotifDialog::rejectCallback</a>() functions, respectively. We also
ensure that the <em>print</em> callback continues to call the <tt>Print()</tt> function as before.
<p> <pre></pre>
<p> After we build the project, the application runs and operates as
expected. There is no visual or behavioral difference, even though
the <em>Print</em> dialog is using <a href="qmotifdialog.html">QMotifDialog</a>.
<p> [ <a href="motif-walkthrough-4.html">Previous: Using Custom QDialogs</a> ]
[ <a href="motif-walkthrough.html">Home</a> ]
[ <a href="motif-walkthrough-6.html">Next: Using Qt Main Window Classes</a> ]
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