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diff --git a/doc/html/motif-walkthrough-7.html b/doc/html/motif-walkthrough-7.html new file mode 100644 index 0000000..11ffb48 --- /dev/null +++ b/doc/html/motif-walkthrough-7.html @@ -0,0 +1,214 @@ +<!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 Qt 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="qcstring.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="qcstring.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. Qt +provides the <tt>QMIN()</tt> and <tt>QMAX()</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">QMotif</a>. To prepare for this, we remove the +<tt>resources</tt> and <tt>optionDesc</tt> arrays and create the QMotif 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 Qt 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>Qt 3.3.8</div> +</table></div></address></body> +</html> |