You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
215 lines
11 KiB
215 lines
11 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|
<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/extensions/motif/doc/walkthrough.doc:921 -->
|
|
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
|
<title>Refactoring Existing Code</title>
|
|
<style type="text/css"><!--
|
|
fn { margin-left: 1cm; text-indent: -1cm; }
|
|
a:link { color: #004faf; text-decoration: none }
|
|
a:visited { color: #672967; text-decoration: none }
|
|
body { background: #ffffff; color: black; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
|
|
<table border="0" cellpadding="0" cellspacing="0" width="100%">
|
|
<tr bgcolor="#E5E5E5">
|
|
<td valign=center>
|
|
<a href="index.html">
|
|
<font color="#004faf">Home</font></a>
|
|
| <a href="classes.html">
|
|
<font color="#004faf">All Classes</font></a>
|
|
| <a href="mainclasses.html">
|
|
<font color="#004faf">Main Classes</font></a>
|
|
| <a href="annotated.html">
|
|
<font color="#004faf">Annotated</font></a>
|
|
| <a href="groups.html">
|
|
<font color="#004faf">Grouped Classes</font></a>
|
|
| <a href="functions.html">
|
|
<font color="#004faf">Functions</font></a>
|
|
</td>
|
|
<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Refactoring Existing Code</h1>
|
|
|
|
|
|
|
|
[ <a href="motif-walkthrough-6.html">Previous: Using TQt Main Window Classes</a> ]
|
|
[ <a href="motif-walkthrough.html">Home</a> ]
|
|
[ <a href="motif-walkthrough-8.html">Next: Replacing the View Widget</a> ]
|
|
<p> In the author's view, the existing code is slightly disorganized.
|
|
Even though the code <em>does</em> work, some cleanups and reorganization
|
|
can only help with readability and maintainability. The steps
|
|
described below are not necessary during the migration process but are
|
|
included for completeness.
|
|
<p> <h2> Migrating Data Structures to C++
|
|
</h2>
|
|
<a name="1"></a><p> The <tt>Page</tt> data structure is an opaque data type. The real data
|
|
structure is called <tt>PageRec</tt>; <tt>Page</tt> defined to be a pointer to a
|
|
<tt>PageRec</tt>. In addition, we have the <tt>AllocPage()</tt> function that
|
|
allocates and initializes memory for a <tt>PageRec</tt> struct.
|
|
<p> With C++, we can do this in the constructor. We can also write a
|
|
destructor which automatically frees all resources in the <tt>PageRec</tt>,
|
|
instead of having to do it in several different places.
|
|
<p> The <tt>PageRec</tt> struct declaration is removed from <tt>page.h</tt>. We
|
|
declare a <tt>Page</tt> struct with the same data members as <tt>PageRec</tt>, a
|
|
constructor and a destructor.
|
|
<p>
|
|
|
|
<pre></pre>
|
|
<p> The existing <tt>pages</tt>, <tt>currentPage</tt> and <tt>maxpages</tt> global variables
|
|
are removed from the source files. We replace them with <tt>extern</tt>
|
|
declarations in <tt>page.h</tt>.
|
|
<p> <pre></pre>
|
|
<p> The global variable instantiations are placed in <tt>todo.cpp</tt>.
|
|
<p> Each source file contains function declarations that deal with the
|
|
global <tt>Page</tt> related variables. We remove these declarations from
|
|
the source files and declare them once in the <tt>page.h</tt> header file.
|
|
<p> <pre></pre>
|
|
<p> Now that <tt>Page</tt> has a constructor, we remove the <tt>AllocPage()</tt>
|
|
function. It is no longer needed. The calls to <tt>AllocPage()</tt> are
|
|
replaced with <tt>'new Page()'</tt> in the <tt>NewPage()</tt>, <tt>DeletePage()</tt>
|
|
and <tt>ReadDB()</tt> functions. We also replace the code to deallocate
|
|
pages with <tt>delete pages[X]</tt>, where <em>X</em> is the appropriate index
|
|
value. This is done in the <tt>ReadDB</tt> and <tt>DeletePage()</tt> functions.
|
|
<p> Code that accesses the global <tt>pages</tt> variable does not need to be
|
|
modified since the data members of the <tt>Page</tt> struct did not change.
|
|
The existing code will continue to work.
|
|
<p> The <tt>OptionsRec</tt> struct declared in <tt>page.h</tt> is also updated,
|
|
following the same pattern as the <tt>Page</tt> struct above.
|
|
<p> <pre></pre>
|
|
<p> The global variable instantiation is also placed in <tt>todo.cpp</tt>.
|
|
<p> Code that accesses the global <tt>options</tt> variable does not need to be
|
|
modified since the data members of the <tt>Options</tt> struct did not
|
|
change. The existing code will continue to work.
|
|
<p> <h2> Using <em>new</em> and <em>delete</em>
|
|
</h2>
|
|
<a name="2"></a><p> The destructors of the <tt>Page</tt> and <tt>Options</tt> structs use <em>delete</em>
|
|
instead of <tt>XtFree()</tt> to deallocate all <tt>char*</tt> members. This is a
|
|
necessary change since we are migrating away from Xt/Motif. We need
|
|
to fix existing code that modifies the <tt>Page</tt> struct members to use
|
|
<em>new</em> and <em>delete</em> ( instead of <tt>XtMalloc()</tt>, <tt>XtNewString()</tt> and
|
|
<tt>XtFree()</tt> ).
|
|
<p> The <tt>PageChange()</tt> function in <tt>todo.cpp</tt> simply saves the contents
|
|
and cursor position of current page before calling <tt>SetPage()</tt>. We
|
|
use <em>new</em> and <em>delete</em> when modifying members of the <tt>Page</tt> struct.
|
|
<p>
|
|
|
|
<pre></pre>
|
|
<p> When storing the context of the <tt>XmText</tt> widget, we use <a href="ntqcstring.html#qstrdup">qstrdup</a>()
|
|
to make a copy of the string returned by the <tt>XmTextGetString()</tt>
|
|
function.
|
|
<p> <pre></pre>
|
|
<p> The <tt>ReadDB()</tt> function in <tt>io.cpp</tt> needs similar changes. We
|
|
replace all use of <tt>XtMalloc()</tt> and <tt>XtNewString()</tt> with <em>new</em> and
|
|
<a href="ntqcstring.html#qstrdup">qstrdup</a>(), respectively.
|
|
<p> This needs to be done just after opening the file.
|
|
<p>
|
|
|
|
<pre></pre>
|
|
<p> ... when starting a new page ...
|
|
<p> <pre>
|
|
...
|
|
</pre>
|
|
|
|
<pre></pre>
|
|
<p> ... and when reading in the label and tab texts/
|
|
<p> <pre>
|
|
...
|
|
</pre>
|
|
|
|
<pre></pre><pre>
|
|
...
|
|
</pre>
|
|
|
|
<pre></pre><pre>
|
|
...
|
|
</pre>
|
|
|
|
<pre></pre>
|
|
<p> The <tt>ReadDB()</tt> function uses <tt>XtRealloc()</tt> to expand the data
|
|
storage buffer. Unfortunately, C++ does not provide a way to
|
|
reallocate an existing block of data, so we have to do this ourselves.
|
|
<p> <pre></pre>
|
|
<p> There is also one occurence in <tt>ReadDB()</tt> where we call <tt>XtMalloc()</tt>
|
|
with an argument of 2. This was done when a file could not be read.
|
|
Creating an empty string is not necessary, so we remove this code
|
|
instead of using <em>new</em>.
|
|
<p> <pre></pre>
|
|
<p> The <tt>SaveDB()</tt> function in <tt>io.cpp</tt> also needs these changes. We
|
|
change one occurence of <tt>XtFree()</tt> to <em>delete</em>.
|
|
<p> <pre></pre>
|
|
<p> Finally, We need to replace two occurences of <tt>XtNewString()</tt> in the <tt>main()</tt> function in <tt>todo.cpp</tt>.
|
|
<p>
|
|
|
|
<pre></pre>
|
|
<p> <h2> Moving Existing Code
|
|
</h2>
|
|
<a name="3"></a><p> The rest of the refactoring process involves moving existing code into
|
|
new places. Currently, each function in the <tt>mainwindow.ui.h</tt> file
|
|
simply calls the old callback handlers present in the other files.
|
|
Instead of calling the old callback functions, the implementations are
|
|
moved accordingly.
|
|
<p> <center><table cellpadding="4" cellspacing="2" border="0">
|
|
<tr bgcolor="#a2c511"> <th valign="top">Function <th valign="top">Original File <th valign="top">Moved to Function
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><tt>New()</tt> <td valign="top"><tt>todo.cpp</tt> <td valign="top"><tt>MainWindow::fileNew()</tt>
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><tt>Open()</tt> <td valign="top"><tt>todo.cpp</tt> <td valign="top"><tt>MainWindow::fileOpen()</tt>
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><tt>SaveIt()</tt> <td valign="top"><tt>actions.cpp</tt> <td valign="top"><tt>MainWindow::fileSave()</tt>
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><tt>Save()</tt> <td valign="top"><tt>todo.cpp</tt> <td valign="top"><tt>MainWindow::fileSaveAs()</tt>
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><tt>ShowPrintDialog()</tt> <td valign="top"><tt>todo.cpp</tt> <td valign="top"><tt>MainWindow::filePrint()</tt>
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><tt>EditPage()</tt> <td valign="top"><tt>actions.cpp</tt> <td valign="top"><tt>MainWindow::selProperties()</tt>
|
|
<tr bgcolor="#f0f0f0"> <td valign="top"><tt>NewPage()</tt> <td valign="top"><tt>actions.cpp</tt> <td valign="top"><tt>MainWindow::selNewPage()</tt>
|
|
<tr bgcolor="#d0d0d0"> <td valign="top"><tt>DeletePage()</tt> <td valign="top"><tt>actions.cpp</tt> <td valign="top"><tt>MainWindow::selDeletePage()</tt>
|
|
</table></center>
|
|
<p> The <tt>Print()</tt> callback function is still used by the <em>Print</em>
|
|
dialog, so we move it into <tt>mainwindow.ui.h</tt> and make it <tt>static</tt>.
|
|
<p> Previously, the <tt>Open()</tt>, <tt>Save()</tt>, <tt>EditPage()</tt> and <tt>DeletePage()</tt>
|
|
functions created dialogs with <em>client_data</em> as the parent argument.
|
|
Since we have moved the code directly into the <em>Main Window</em>
|
|
implementation, we create these dialogs with <em>this</em> as the parent
|
|
argument.
|
|
<p> The <tt>PageChange()</tt> callback function is moved from <tt>actions.cpp</tt>
|
|
to <tt>todo.cpp</tt> and made <tt>static</tt> since it is not used anywhere else.
|
|
<p> Earlier modifications to <tt>actions.cpp</tt> caused the <tt>Trim()</tt> function
|
|
to become redundant, so we remove it.
|
|
<p> The <tt>MIN()</tt> and <tt>MAX()</tt> macros in <tt>todo.cpp</tt> are redundant. TQt
|
|
provides the <tt>TQMIN()</tt> and <tt>TQMAX()</tt> macros which we will use.
|
|
<p> Earlier modifications caused the <tt>fallback_resources</tt> array to become
|
|
redundant, so we remove it.
|
|
<p> In the near future, our program will not use <a href="motif-extension.html#Motif">Motif</a> any more, and we
|
|
will no longer need to use <a href="qmotif.html">TQMotif</a>. To prepare for this, we remove the
|
|
<tt>resources</tt> and <tt>optionDesc</tt> arrays and create the TQMotif instance
|
|
with just the <em>APP_CLASS</em> argument.
|
|
<p> The <tt>#include</tt> statements in the source files are mostly incorrect
|
|
due to the refactoring changes. Many of the <tt>#include</tt> statements
|
|
are no longer needed. The <tt>#include</tt> statements from each file are
|
|
listed below, instead of describing which includes are removed and
|
|
added to each file.
|
|
<p> Includes for <tt>actions.cpp</tt>:
|
|
<p>
|
|
|
|
<pre></pre>
|
|
<p> Includes for <tt>io.cpp</tt>:
|
|
<p>
|
|
|
|
<pre></pre><pre></pre><pre></pre>
|
|
<p> Includes for <tt>todo.cpp</tt>:
|
|
<p>
|
|
|
|
<pre></pre><pre></pre><pre></pre>
|
|
<p> Includes for <tt>mainwindow.ui.h</tt>:
|
|
<p>
|
|
|
|
<pre></pre><pre></pre><pre></pre><pre></pre><pre></pre>
|
|
<p> [ <a href="motif-walkthrough-6.html">Previous: Using TQt Main Window Classes</a> ]
|
|
[ <a href="motif-walkthrough.html">Home</a> ]
|
|
[ <a href="motif-walkthrough-8.html">Next: Replacing the View Widget</a> ]
|
|
<p>
|
|
<!-- eof -->
|
|
<p><address><hr><div align=center>
|
|
<table width=100% cellspacing=0 border=0><tr>
|
|
<td>Copyright © 2007
|
|
<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
|
|
<td align=right><div align=right>TQt 3.3.8</div>
|
|
</table></div></address></body>
|
|
</html>
|