From bd0f3345a938b35ce6a12f6150373b0955b8dd12 Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Sun, 10 Jul 2011 15:24:15 -0500 Subject: Add Qt3 development HEAD version --- doc/html/motif-walkthrough-8.html | 212 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 212 insertions(+) create mode 100644 doc/html/motif-walkthrough-8.html (limited to 'doc/html/motif-walkthrough-8.html') diff --git a/doc/html/motif-walkthrough-8.html b/doc/html/motif-walkthrough-8.html new file mode 100644 index 0000000..f461b88 --- /dev/null +++ b/doc/html/motif-walkthrough-8.html @@ -0,0 +1,212 @@ + + + + + +Replacing the View Widget + + + + + + + +

Replacing the View Widget

+ + + +[ Previous: Refactoring Existing Code ] +[ Home ] +[ Next: Replacing the Print Dialog ] +

We are ready to start replacing the View widget. However, our +example program uses the XmNotebook widget class. Qt does not +provide a direct equivalent of this class, so we are faced with three +possibilities, each with several advantages and disadvantages. +

We can continue the conversion using existing Qt widgets. +
- Advantages - The widgets provided by Qt are well designed and +tested, allowing us to quickly redesign the user interface. +
- Disadvantages - Most, if not all, of the existing data structures +and code will need to be modified or rewritten. New code must be +written in a way that maintains compatibility with previous versions +of our application. +
+
We can write a new QWidget subclass that is identical to the XmNotebook widget class. +
- Advantages - The existing data structures will not change, allowing +compatibility with previous and future versions. +
- Disadvantages - The new widget will need to be written and +regression tested. Existing code in our application will need to be +changed in order to deal with the new widget's API. +
+
We can leave the XmNotebook widget untouched. +
- Advantages - The existing data structures and code remain +unchanged, allowing us to continue development on other projects, +new features, etc. +
- Disadvantages - This is the simplest solution, but the application +will still be dependent upon X11; we will not be able to deploy our +application on all platforms supported by Qt. +
+

We will use the first approach to complete the migration of the +example project used in this walkthrough, using QTextEdit, QLabel and +QSpinBox to provide a similar look. The only difference is that we +will not have tabs. +

We use Qt Designer to add the +QTextEdit, QLabel and QSpinBox widgets to the Main Window widget. +

Data Structure Modifications +

The Page struct contains majorPB and minorPB members which +need to be removed. These members correspond to the tabs displayed in +the existing version. The new version will not have any tabs, so we +remove them. +

+ +

Code Modifications +

Most of the existing functions in our application need to be modified +to work with the new View widget. The MainWindow class has five +new functions that correspond to existing functions. +

Existing Function	New Function +
`void SetPage( int )`	`void MainWindow::setPage( int )` +
`void PageChange( ... )`	`void MainWnidow::pageChange( int )` +
`void TextChanged( ... )`	`void MainWnidow::textChanged()` +
`void ReadDB( char * )`	`void MainWindow::readDB( char * )` +
`void SaveDB( char * )`	`void MainWindow::saveDB( char * )` +

The SetPage() function implementation is moved to the MainWindow::setPage() function in mainwindow.ui.h. We remove the +SetPage() function declaration and implementation from page.h +and actions.cpp, respectively. In order to make MainWindow::setPage() work correctly, we need to modify the code to +use the new widgets in our Main Window widget. +

+ +

First, we set the current value of the spinbox to the current page +number. +

Next, we set the current text and cursor position of the textedit +to the contents of the current page. +

If the current page has a custom label, we set it as the current text +of the textlabel; otherwise we set the textlabel contents to +"Page X" (where X is the current page number). +

If the current page has major and/or minor tab text, we append these +to the labeltext. This ensures that all information entered by the +user remains visible. +

We should continue to handle the possibility that the current page +does not exist. In this case, we clear the contents of the textedit widget and set the textlabel contents to the current page +number (with an indication that the page is invalid). +

The PageChange() function is moved from todo.cpp to the MainWindow::pageChange() function in mainwindow.ui.h. As with the +MainWindow::setPae() function, we need to modify the code to use +the new widgets in our Main Window widget. +

Note: QTextEdit::text() returns a QString, which needs to be converted +into a normal char* array. To do this we create a copy of the +string in the local encoding. We need to make the copy using qstrdup() because the data contained in the QCString returned by +QString::local8Bit() is deallocated when the QCString is destroyed. +

The TextChanged() function does nothing more than set the modified variable to 1. Our new MainWindow::textChanged() function +does exactly the same. +

Since both the MainWindow::pageChange() and MainWindow::textChanged() functions access the modified global +variable, we add a forward declaration at the top of mainwindow.ui.h. +

The ReadDB() and \s SaveDB() implementations in io.cpp are +renamed to MainWindow::readDB() and MainWindow::saveDB(), +respectively. We need to modify the code in order to make the code +work properly. +

First, We add #include statements for the MainWindow, QSpinBox +and QTextEdit classes. +

+ +

The new MainWindow::readDB() and MainWindow::saveDB() functions +will not use any Xt/Motif functions, so we remove the Xt/Motif #include statements and the global variables notebook and textw. +These functions remain largely unchanged, maintaining compatibility +with previous versions. Also, the ReadDB() and SaveDB() +functions have been converted into MainWindow member functions, so +we can pass this as the parent argument to the QMessageBox +functions. +

After reading the file in the MainWindow::readDB() function, we set +the current and maximum values of the spinbox to the appropriate +values. +

+ +

In the MainWindow::saveDB() function, we need to store the text +currently displayed, so we use QTextEdit::text() instead of XmTextGetString(). Note: QTextEdit::text() returns a QString, which +needs to be converted into a normal char* array. To do this we +create a copy of the string in the local encoding. We need to make +the copy using qstrdup() because the data contained in the QCString +returned by QString::local8Bit() is deallocated when the QCString is +destroyed. +

Due to the removal of the majorPB and minorPB members from the +Page struct, the FixPages() function in actions.cpp is no +longer needed. We remove the implementation and forward declaration +of FixPages() from actions.cpp and page.h, respectively. +Calls to FixPages() are removed from the MainWindow::selNewPage() and MainWindow::selDeletePage(), both of +which are in mainwindow.ui.h. +

We move AdjustPages() to mainwindow.ui.h and make it static, +since it is only used in this file. We remove the forward declaration +from page.h as well. +

After our modifications, the actions.cpp file is empty. We remove +it from our project file and regenerate our Makefile. +

Now that we have implemented our new View widget, we need to remove +the old Motif based view widget from todo.cpp. +

Since we will not be using any Motif widgets, we remove all Motif #include statements, including qmotifwidget.h. +

+ +

We also remove the forward declarations of the ReadDB() function +and the notebook, textw and labelw global variables. +

Next, we remove the center widget, which uses QMotifWidget. The Main Window widget and View widget are contained entirely in our +MainWindow class, so no extra initialization is needed after +creating the mainwindow widget. +

Since the ReadDB() and SetPage() functions have been changed into +MainWindow member functions, we need to call them using our mainwindow instance. +

The View widget has now been replaced. After building our project, +we confirm that the application works correctly. +

[ Previous: Refactoring Existing Code ] +[ Home ] +[ Next: Replacing the Print Dialog ] +

+ +

Trademarks +

Qt 3.3.8

+ -- cgit v1.2.1