From d796c9dd933ab96ec83b9a634feedd5d32e1ba3f Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Tue, 8 Nov 2011 12:31:36 -0600 Subject: Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731 --- doc/html/motif-walkthrough-7.html | 214 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 214 insertions(+) create mode 100644 doc/html/motif-walkthrough-7.html (limited to 'doc/html/motif-walkthrough-7.html') diff --git a/doc/html/motif-walkthrough-7.html b/doc/html/motif-walkthrough-7.html new file mode 100644 index 000000000..018258ae2 --- /dev/null +++ b/doc/html/motif-walkthrough-7.html @@ -0,0 +1,214 @@ + + + + + +Refactoring Existing Code + + + + + + + +

Refactoring Existing Code

+ + + +[ Previous: Using TQt Main Window Classes ] +[ Home ] +[ Next: Replacing the View Widget ] +

In the author's view, the existing code is slightly disorganized. +Even though the code does 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. +

Migrating Data Structures to C++ +

The Page data structure is an opaque data type. The real data +structure is called PageRec; Page defined to be a pointer to a +PageRec. In addition, we have the AllocPage() function that +allocates and initializes memory for a PageRec struct. +

With C++, we can do this in the constructor. We can also write a +destructor which automatically frees all resources in the PageRec, +instead of having to do it in several different places. +

The PageRec struct declaration is removed from page.h. We +declare a Page struct with the same data members as PageRec, a +constructor and a destructor. +

+ +

The existing pages, currentPage and maxpages global variables +are removed from the source files. We replace them with extern +declarations in page.h. +

The global variable instantiations are placed in todo.cpp. +

Each source file contains function declarations that deal with the +global Page related variables. We remove these declarations from +the source files and declare them once in the page.h header file. +

Now that Page has a constructor, we remove the AllocPage() +function. It is no longer needed. The calls to AllocPage() are +replaced with 'new Page()' in the NewPage(), DeletePage() +and ReadDB() functions. We also replace the code to deallocate +pages with delete pages[X], where X is the appropriate index +value. This is done in the ReadDB and DeletePage() functions. +

Code that accesses the global pages variable does not need to be +modified since the data members of the Page struct did not change. +The existing code will continue to work. +

The OptionsRec struct declared in page.h is also updated, +following the same pattern as the Page struct above. +

The global variable instantiation is also placed in todo.cpp. +

Code that accesses the global options variable does not need to be +modified since the data members of the Options struct did not +change. The existing code will continue to work. +

Using new and delete +

The destructors of the Page and Options structs use delete +instead of XtFree() to deallocate all char* members. This is a +necessary change since we are migrating away from Xt/Motif. We need +to fix existing code that modifies the Page struct members to use +new and delete ( instead of XtMalloc(), XtNewString() and +XtFree() ). +

The PageChange() function in todo.cpp simply saves the contents +and cursor position of current page before calling SetPage(). We +use new and delete when modifying members of the Page struct. +

+ +

When storing the context of the XmText widget, we use qstrdup() +to make a copy of the string returned by the XmTextGetString() +function. +

The ReadDB() function in io.cpp needs similar changes. We +replace all use of XtMalloc() and XtNewString() with new and +qstrdup(), respectively. +

This needs to be done just after opening the file. +

+ +

... when starting a new page ... +

+    ...
+

+ +

... and when reading in the label and tab texts/ +

+    ...
+

+ +

+    ...
+

+ +

+    ...
+

+ +

The ReadDB() function uses XtRealloc() 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. +

There is also one occurence in ReadDB() where we call XtMalloc() +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 new. +

The SaveDB() function in io.cpp also needs these changes. We +change one occurence of XtFree() to delete. +

Finally, We need to replace two occurences of XtNewString() in the main() function in todo.cpp. +

+ +

Moving Existing Code +

The rest of the refactoring process involves moving existing code into +new places. Currently, each function in the mainwindow.ui.h file +simply calls the old callback handlers present in the other files. +Instead of calling the old callback functions, the implementations are +moved accordingly. +

Function	Original File	Moved to Function +
`New()`	`todo.cpp`	`MainWindow::fileNew()` +
`Open()`	`todo.cpp`	`MainWindow::fileOpen()` +
`SaveIt()`	`actions.cpp`	`MainWindow::fileSave()` +
`Save()`	`todo.cpp`	`MainWindow::fileSaveAs()` +
`ShowPrintDialog()`	`todo.cpp`	`MainWindow::filePrint()` +
`EditPage()`	`actions.cpp`	`MainWindow::selProperties()` +
`NewPage()`	`actions.cpp`	`MainWindow::selNewPage()` +
`DeletePage()`	`actions.cpp`	`MainWindow::selDeletePage()` +

The Print() callback function is still used by the Print +dialog, so we move it into mainwindow.ui.h and make it static. +

Previously, the Open(), Save(), EditPage() and DeletePage() +functions created dialogs with client_data as the parent argument. +Since we have moved the code directly into the Main Window +implementation, we create these dialogs with this as the parent +argument. +

The PageChange() callback function is moved from actions.cpp +to todo.cpp and made static since it is not used anywhere else. +

Earlier modifications to actions.cpp caused the Trim() function +to become redundant, so we remove it. +

The MIN() and MAX() macros in todo.cpp are redundant. TQt +provides the TQMIN() and TQMAX() macros which we will use. +

Earlier modifications caused the fallback_resources array to become +redundant, so we remove it. +

In the near future, our program will not use Motif any more, and we +will no longer need to use TQMotif. To prepare for this, we remove the +resources and optionDesc arrays and create the TQMotif instance +with just the APP_CLASS argument. +

The #include statements in the source files are mostly incorrect +due to the refactoring changes. Many of the #include statements +are no longer needed. The #include statements from each file are +listed below, instead of describing which includes are removed and +added to each file. +

Includes for actions.cpp: +

+ +

Includes for io.cpp: +

+ +

Includes for todo.cpp: +

+ +

Includes for mainwindow.ui.h: +

+ +

[ Previous: Using TQt Main Window Classes ] +[ Home ] +[ Next: Replacing the View Widget ] +

+ +

Trademarks +

TQt 3.3.8

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