GUI – Edit Box (Begin)

To create the new EditBox class source and header file, the new file wizard of QtCreator was again used (New File or Project... under the File menu). Under File and Classes the C++ option was selected and then C++ Class was selected to create both files and Choose... was clicked.

On the next C++ Class Wizard dialog, the Class name: was set to EditBox, Base class: was set to QTextEdit and for Type information: the Inherits QWidget option was selected.  The rest were left to the filled in defaults.  On the final Project Management dialog, git was selected to add to version control and the wizard was finished.

For now, nothing was changed in the created editbox.h and editbox.cpp files except the customary comment headers were added and the formatting was corrected to match the style of the rest of the project files.  Functionality for the EditBox class will be implemented in the commits that follow.  The sources files were also added to the CMake build file, and because the EditBox class contains QOBJECT, the editbox.h file was added to the MOC sources instead of the header files variable.

A new EditBox member pointer was added to the MainWindow class.  In the MainWindow constructor, an EditBox instance was created.  There is no need to give it a parent here because the next call to setCentralWidget() does this automatically, and makes the edit box widget the main widget of the main window.  This also means that for new there is no need to delete the EditBox instance because Qt will do this when the MainWindow instance is deleted upon the program closing.

Eventually this basic mechanism of how the single EditBox instance is maintained will change since there will be a need to have multiple edit boxes open (the plan is that subroutines and functions will be contained in their own edit boxes).  The exact interface hasn't been designed or decided yet (split windows, tabs, multiple windows, etc. are all possibilities).

[commit de0ec4eb2b]

C++ Explicit Constructors

The new EditBox class was created using QtCreator's new class wizard and I noticed that it put the explicit keyword in front of the constructor definition (it also did this with the MainWindow class).  (More about the new EditBox class in the post.)  Curious what this keyword does (which was added since I learned C++ in the early 90's), I did some research.  The explicit keyword tells the compiler not to allow implicit type conversions on constructors that take a single argument.  Consider this partial example:

class MyFloat {
    float m_value;
public:
    MyFloat(int value): m_value(value) {}
    float value(void) { return m_value; }
};

float square(MyFloat myFloat) {
    return myFloat.value() * myFloat.value();
}

MyFloat something = 47;
std::cout << square(12) << std::endl;

On the last two lines, implicit conversions occur from int to MyFloat, which are perfectly acceptable  for this simple class.  However, if the implicit conversion was not desired, the explicit keyword can be added in front of the constructor to prevent it.  The compiler will now generate errors for the last two lines above.  These lines can be rewritten to work:

MyFloat something = MyFloat(47);
std::cout << square(MyFloat(12)) << std::endl;

This is a contrived example and would probably make sense to allow the implicit conversion in this class, however, this is not the case with the classes used in this project.  Therefore, the explicit keyword was added to all the constructors that take a single argument, which included the CommandLine, Parser, Tester, Token and Translator classes.

The most glaring constructor requiring explicit was the Token constructor Token(int column = -1) that would have allowed a statement like Token token = 47;, which does not make sense (a token should not be assigned an integer).

[commit 5979939788]

GUI – Settings and Window Title

All programs should save all of their settings upon exit and restore them so that when restarted the program starts up in exactly the way it was when it exited, because otherwise it is time consuming to set all the settings again.  Very few programs do however, but this approach will be used for this project.

Fortunately, Qt has the QSettings class to perform the saving and restoring mostly automatically.  The vendor (programmer) name and program name is provided to the constructor of the QSettings instance.  For saving, the setValue() method function is used with the name of the property to save and the value to save.  When the instance goes out of scope, the settings are saved.  For restoring, the settings are automatically read when the instance is created.  The properties are accessed with the value() method function.

The settings are stored to a platform specific location.  On Windows, this is to the registry.  On Linux, this is to a text file located in the .config directory on the user's home directory within a sub-directory for the vendor name under another sub-directory for the program name.  The file name is the program name with the .conf extension.

The settings are restored in the MainWindow constructor.  For saving, the closeEvent() function was implemented.  This function is called when a close event occurs (for example, the File/Exit menu item, the close icon, etc.) and can decide whether to accept or reject the request.  For now, the settings are saved and the event is accepted.

For now, only the position and the size of the main window is saved and restored.  These are obtained from the geometry of the MainWindow instance.  The program will now remember where it was and how big the last time the program was closed.  Additional settings will be added as the are implemented in the program.

[commit 54a5b24f69]

GUI – Initial Actions and Menu Items

The first thing to add to the GUI are some top level File and Help menus with menu entries under them.  Menu entries are added to each top level menu using actions.  Actions can also be added to the tool bar.  For now the File menu will contain an Exit entry and the Help menu will contain the About and About Qt entries.  A separator is added before the Help menu so that Qt knows to put this menu on the right side of the menu for those styles that support this (Windows does not do this and KDE only does this for certain application appearance styles).

Actions contain information including the name of the action (an ampersand '&' is put in front of the character that is the hot key for the entry), along with an optional shortcut key, icon, and a status tip.  No icons were added to any of the entries at this time.  A connection is made from the triggered signal of each action to the function that will perform the action.

All the actions are created in the createActions() function and the menus are created in the createMenus() function, both called from the MainWindow constructor.  The about() function was moved from the private section to the private slots section of the class definition so that the connection can be made from the about action.  The temporary show() function was removed since it is no longer needed.  The size of the header for program name in the About box was reduced to match the header size in the About Qt box.

Now the GUI will start, but doesn't do much beyond the menus (see image below).  The window still has the default name given when the MainWindow class was created and there is just a generic program icon.  There is also a blank tool bar under the menu bar.  The dot or two on the left side of the tool bar allows the bar to be dragged to any side of the window and even detached from window.  Icons (via actions) will be added to the tool bar later.

[commit 16e6755c0d]

Initial GUI Design Plan

A plan is needed for what form the GUI will take for the program initially, especially considering that only the translator and parser are implemented (and only for a limited number of BASIC commands).  The basic GUI will consist of a menu bar, tool bar, status bar and the main editing window.

This menu bar will probably only consist of the File, Edit and Help menus to start.  The File menu will start with New, Open, Save, Save As, and Quit entries.  The Edit menu will start with Copy, Cut, and Paste entries.  The Help menu will have About and About Qt entries (the about Qt is customary for Qt applications and shows information about the version of Qt used to build the program).  The initial tool bar will have buttons for items in the File and Edit menus.

Most of the effort for this initial GUI will be in the main editing window and getting it to work for the requirements needed for the interactive nature of the interactive compiler.  Namely, the code will need to catch when the enter key is hit so that the current line can be read from the editing box, compiled (translated and encoded) and stored in internal memory.  Eventually the line will need to be recreated from the internal representation back to the original text (or close to it).

Since only the translator is currently implemented, each line entered into the editing window will be translated to the RPN (reverse polish notation) list.  The tokens of the  RPN list will be converted to text (as now by the test code) and displayed in a special area in the GUI known as a dock widget.  A dock widget can be moved and docked to any side of the main editing window, and can also be undocked from the application window.  This dock widget will use to validate correct operation of the program.

Qt Transition – Release

The Qt transition is now complete and the implementation of the GUI can begin.  But first this is a good point to make a development release.  Release 0.2.0 was made (branch0.2 was merged to the master branch and tagged v0.2.0).

There is one issue when running the program on Windows when starting the program from Explorer.  A console window is opened underneath the GUI (About box), which is closed upon exit.  This can be removed by adding the WIN32 option to the add_executable command in the CMake build file.  However, this causes the command line options to no longer work.  This issue will be resolved later.

Archive files containing the source files and binary files (with test files) have been uploaded to SourceForge.  For Windows, there is also the ibcp‑libs.zip file that contains all the dynamic linked libraries required to run the program if the MinGW and QtSDK packages have not been installed (extract in the ibcp directory).  Linux should already have the required libraries installed.

This concludes the 0.2 development series.  Implementation of the GUI elements will now begin with the 0.3 development series.

[commit 85d28cd9e5]

GUI Preparation – About Box

Qt contains a static library function for displaying an about box, QMessageBox::about().  All that is needed is the title for the dialog and a string with the contents for the dialog window.  This string supports a limited set of HTML tags for formatting the text.  There is an OK button to close the dialog.  The creation of the about string and call to the Qt about function was put into the about() function in the MainWindow class.

The about string contains the full name of the program using the HTML header tag for emphasis.  As done in the Tester run function, the lines of GPL statement are added next.  Instead of putting the program name as the first part of the copyright line, the version string will be used instead with the string "Version" in front of it.  For the about box, the tr() function is used to translate the strings.  Since this is a preliminary about box, a placeholder for the full GUI, an italicized message stating such is added next.  This is followed by the command line usage string (modified to show all the options are optional).  An image of the about box running on Windows 7 is shown below.

So that the new about function has access to the GPL statement, version string, copyright year and usage string, the CommandLine instance was made a member variable as a pointer to the MainWindow class instead of being temporary in the constructor.  The instance is created in the constructor and deleted in the destructor.

The show() function for the QMainWindow class was temporarily reimplemented in the MainWindow class to prevent the full GUI from appearing (which is currently empty).  The reimplemented function calls the about() function and then does a single shot timer connected to the application quit function to end the program once the event process loop is entered.  Finally, a check for no command line options was added towards the beginning of the constructor to exit the constructor (which will start the GUI in the main function).

[commit 6eab34398c]

GUI Preparation – Usage String

Since for now the GUI is only going to pop up the About box and then exit, it would be nice if it included some information about how to use the program from the command line, specifically displaying the usage string that was previously output when no arguments were given (which will start the GUI).  The CommandLine class was modified to generate the usage string at the beginning of the constructor and save it in a new member variable, with a new function to access it.

Previously, the test options were obtained from the Tester instance, but this isn't created until later in the constructor and won't be created if there are no command line options (the constructor will return).  The Tester options access function didn't actually use any instance variables, so this function was made a static member function so that now an instance isn't necessary to access the test options.

[commit 3b93360cff]

GUI Preparation – Version String

One of the items needed in the About box is the version string.  Two minor changes were made to the CommandLine class so that it can provide the version string.  The previous version() function was renamed to isVersionOption() to mirror the name of the isHelpOption() function.

A new version() function was added to access the version string.  The version string is accessed from the ibcp_RELEASE_STRING definition contained in the CMake generated ibcp_config.h header file (from ibcp_config.h.in).  CMake gets the release string from either git (if the repository is present) or from variables set in the CMakeLists.txt file.  The actual version string starts at the seventh character of release string, which skips over the "release" part of the string.

An include statement could be added to whichever source file needs the release string, but keeping the include in a single source file and providing access functions to its values allows this to be updated in the future without having to change a bunch of other source files.  This also applies to the copyright year value.  The CommandLine class also provides access to the program name.

[commit 5431b8f9b4]

GUI Preparation – GPL Statement

The lines of the GPL statement was implemented as a QStringList in the CommandLine class.  The intention was to use this string untranslated for the test output (so the output matches the expected output files).  The QT_TR_NOOP() macro was used on the strings, so that the strings could be found by the Qt translation utilities.  The tr() function would be used later (by the GUI's About box), to translate strings (given the program was set up to do translations and the appropriate translation file was available).

However, this is not how the tr() function works.  The tr() function takes a constant char pointer and translates the string.  It does not accept a QString, so the scheme described above will not work.  Therefore, the GPL statement was changed from a QStringList to a const char * array, and also changed from a regular member to a static member.  The initialization of which was moved outside of the CommandLine constructor.  The variable was also appropriately prefixed with a 's_' to represent a static member.

The first line of the GPL statement requires special handling:

"%1  Copyright (c) 2010-%2  Thunder422"

Where the %1 and %2 are place holders for the program name and the current copyright year.  These were previously filled in by the CommandLine constructor when the QStringList was created.  This can only be done after the string is in a QString, in other words, after it has been translated (if it is going to be translated).

The Tester run function previously received the GPL statement (as a QStringList argument), which it simply output.  However, since the statement is now raw character strings, it will need to fill in the first line with the program name and copyright, neither of which it had access to.  These could have been added as additional arguments, but instead, the argument was changed to a CommandLine instance pointer, which has new access functions for these values.  After converting the GPL line to a QString, if at the first line, the program name and copyright year are filled in.

One other minor problem in the Tester run function was discovered and corrected with the interactive testing mode.  The "Testing Xxx..." string was being output before the GPL statement and it should have been after the statement and the "Table initialization successful" message.

[commit c25848a1829] [commit e27358a938]

GUI Preparation

The 0.2 development series is going to conclude with the program displaying its about box and then exiting.  The GUI elements will be added in the 0.3 development series.  Before adding the about box, some modifications to existing classes are needed, which will occur over the next set of commits.  But first, this is probably a good time to create the v0.2-6 tag as there have been 11 commits since the last development tag.

The base GUI is already present in the program, which was added by default when the main window class was created by new class wizard in QtCreator.  This GUI only contains a blank menu bar, tool bar and status bar.  If it was activated, the only thing present beside the window title (with the normal minimize, maximum, close, etc. icons) would a blank window with an empty tool bar that can be docked (more on this later) on any of the four sides of the window.

However, the program is not currently activating this window because it exits with a usage message if no options were present on the command line.  The command line and tester classes need some minor modifications before the about box can be implemented, which will contain information that will be obtained from the command line class (version, GPL statement, etc.).

[commit 6f55c2ffae]

Table Initialization – Revisited

The Table class was modified to be singleton class (see November 14).  This implementation was modified.  To be consistent with the Token class, which is initialized with a static initialize() function, the Table class create() function was renamed to initialize() and changed to return nothing instead of a list of errors.

The old initialize() function, a normal private member function, was renamed to setupAndCheck() and still returns a list of errors.  Two new static functions were added to access the error list: hasErrors() to report if there were any errors detected and errorList() to return the list of errors.  Both fatally abort the program if the initialize function was not called.  The initialize function stores the error list returned by setupAndCheck() into a new static error list member variable.

The two static members, one for the pointer to the single instance and the other for the error list are now prefixed with 's_' instead of 'm_' to denote a static member as opposed to a regular member variable.  The static member variables to the Token class were also renamed with the 's_' prefix.

The new initialize function also checks if either the instance pointer is not null or if the error list is not empty to determine if the table instance was previously created or at least attempted.  When an error is found, the instance is deleted, so the instance pointer alone can't be used to determine if the instance creation was attempted.  Similarly, the new error list access functions also check if both the instance pointer is null and error list is empty to determine if there was a creation attempt.  The check for a non-empty error list was also added to the instance() access function.

The Token and Table initialize function calls were moved from the Tester run function to the main function.  This keeps the initialization in a single location.  The Tester run function still contains the check for table errors.  The error check was not moved to main because when the GUI is started, any table errors need to be reported in an error dialog box, not to the console output.  When the program is started from say an OS start menu or file browser, there is no console for these errors and the program will inexplicably fail to start.  Now work on the GUI can begin...

[commit 5c5da1f069]  [commit e0474f5144]

Standard Error Output - Oops

My job took me away from this project the past week.  In making the next set of changes, I discovered that the last commit did not compile.  During the development of the standard error output changes, the coutClose() function (which closes the current channel if open) was originally named cclose().  At the last moment, this was renamed to the more appropriate coutClose(), but in the haste to get the code committed, the code was not compiled and retested.

It has been recent policy recently make sure every commit pushed to the repository compile and test successfully, at least on the development platform (Linux).  Any problems with testing would be noted in the commit message.  The last commit failed this policy and I apologize (and worst, it went for a week in this state).

When a development tag is added, it is validated to compile and test successfully on both the Linux and Windows platform (specifically XP, though it should work on 7 also).  Again any problems are noted in the commit message.  For an actual release however, it will also be tested on the Windows 7 platform (and there should be no test issues).

[commit 4ffed94ea2]

Standard Error Output

Command line error messages should be sent to the standard error channel; the Qt qWarning() function should not be used because these messages can be disabled.  The cout() function was modified to accept a FILE stream (channel) pointer, either stdout or stderr, with stdout the default.  The qWarning() calls were changed to cout(stderr), which made these lines cleaner because the qPrintable() function is not longer needed to output QString values.

There was also a qWarning() call in the Tester run function when table errors are detected.  These only occur when there are problems in the table entries and are followed by a qFatal() call (which terminates the program).  This qWarning() call was changed to a qCritical() call, whose messages can not be disabled.

Previously, to get the usage message, invalid arguments had to be specified.  To get the usage message without returning an error, new help options were added (either '-?' or '-h').  The usage message will be output to standard output channel when using these options, but to the standard error channel for invalid arguments.

When an error occurs in the Tester run function, like when the test file can't be opened, the standard output channel needs to be closed and the standard error channel opened to output the error message.  The new function coutClose() was added to the CommandLine class, which closes the current channel (if open), which is called before outputting the error message from the Tester instance.  The code for this function was pulled from the destructor, which was replaced with a call to the new function.

[commit e64eadee4a]

Returning Command Line Errors

When the starting of the single shot time to force the application to quit upon entering the event loop was replaced by a simple return (of 0), I realized that it should really be returning an error code if there is an error in the command line options.

To accomplish this, the processed flag in the CommandLine class was replaced with return code variable, which has three values: 0 for successfully processed command line only option, 1 for error occurred with the command line options, and -1 for no command line only options (in other words, start the GUI).  An access function was added for the return code.

The processed access function remains (so callers don't need to be modified), but now returns true if the return code variable is not negative.  A return code variable was also added to the MainWindow class along with an access function.  In the constructor, the return code is obtained from the command line instance when the GUI active flag is set to false (when the command line was processed).  The main function was modified to return this code.

By convention, a command returns a code of 0 to indicate success and any other value to indicate an error.  Some commands return a specific error code value, but here just a general error occurred code (1) is returned.  To test if this new functionality was working correctly, this command was used:

ibcp -v && echo no error

This command will output the version number followed by the "no error" message.  If the -v is replaced with an invalid option, the "no error" message will not be output.

[commit 164fb19fe8]

Qt GUI Files and CMake

Previously, new header or source files were added to the list of header and source files in the CMake build file CMakeLists.txt.  Qt form files (with the .ui extension) and header files containing the Q_OBJECT macro are handled differently.

The Q_OBJECT macro is added to any class definition that contains Qt's C++ extensions for defining signals and slots, which are class sections in additional to the normal private, public and protected sections.  These are handled by Qt's Meta-Object Compiler (moc), which produces a special MOC source file from the header file.  For mainwindow.h, the special source file produced is moc_mainwindow.cxx, which then gets compiled and linked into the program.

In the CMake build file, this is handled by the qt4_wrap_cpp command that is added as part of the Qt4 CMake module.  It is given a list of MOC source files and produces a list of MOC output source files.  This output list is then specified as a dependency to the output executable.  When a header file is included in the MOC sources list, it does not also need to be specified in the list of [normal] header files.

Qt form files are generated as an XML like language.  This file needs to be converted into a class definition (within a header file) so that it can be used by the C++ code.  These conversions are handled by Qt's User Interface Compiler (uic), which produces a special header file from the form file.  For mainwindow.ui, the special header file produced is ui_mainwindow.h, which contains the Ui_MainWindow class.  This source file is then included by the mainwinow.h header file.

In the CMake build file, this is handled by the qt4_wrap_ui command.  It is given a list of form UI files and produces a list of user interface header files.  This output list is then specified as a dependency to the output executive.

All of the generated files are placed in the CMake build directory, the same directory where the auto-generated header files (from the awk scripts) are placed.  This directory (the project binary directory) is specified in the include_directories command, so that the C++ compiler can find all of these generated files.  It is also no longer necessary to specifically check for an in-source build to not add this directory because the conflict no long exists between the system string.h header file (not used) and project string.h header file (removed).

[commit f4a35bbab6] [commit 266022803b]