Qt Toolkit - application/main.cpp example file

| Classes - Annotated - Tree - Functions - Home - Structure

# A Complete Application Window

This example program looks like a complete modern application. It has a menu bar, it has a tool bar, it has a status bar and works like a simple text editor. There is a walkthrough of this example.

Header file:

    /****************************************************************************
    ** $Id: qt/examples/application/application.h   2.3.2   edited 2001-01-26 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #ifndef APPLICATION_H
    #define APPLICATION_H

    #include <qmainwindow.h>

    class QMultiLineEdit;
    class QToolBar;
    class QPopupMenu;

    class ApplicationWindow: public QMainWindow
    {
        Q_OBJECT
    public:
        ApplicationWindow();
        ~ApplicationWindow();

    protected:
        void closeEvent( QCloseEvent* );

    private slots:
        void newDoc();
        void load();
        void load( const char *fileName );
        void save();
        void saveAs();
        void print();

        void about();
        void aboutQt();

    private:
        QPrinter *printer;
        QMultiLineEdit *e;
        QToolBar *fileTools;
        QString filename;
    };

    #endif

Implementation:

    /****************************************************************************
    ** $Id: qt/examples/application/application.cpp   2.3.2   edited 2001-06-12 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "application.h"

    #include <qimage.h>
    #include <qpixmap.h>
    #include <qtoolbar.h>
    #include <qtoolbutton.h>
    #include <qpopupmenu.h>
    #include <qmenubar.h>
    #include <qkeycode.h>
    #include <qmultilineedit.h>
    #include <qfile.h>
    #include <qfiledialog.h>
    #include <qstatusbar.h>
    #include <qmessagebox.h>
    #include <qprinter.h>
    #include <qapplication.h>
    #include <qaccel.h>
    #include <qtextstream.h>
    #include <qpainter.h>
    #include <qpaintdevicemetrics.h>
    #include <qwhatsthis.h>

    #include "filesave.xpm"
    #include "fileopen.xpm"
    #include "fileprint.xpm"

    const char * fileOpenText = "<img source=\"fileopen\"> "
    "Click this button to open a <em>new file</em>. <br><br>"
    "You can also select the <b>Open command</b> from the File menu.";
    const char * fileSaveText = "Click this button to save the file you are "
    "editing.  You will be prompted for a file name.\n\n"
    "You can also select the Save command from the File menu.\n\n"
    "Note that implementing this function is left as an exercise for the reader.";
    const char * filePrintText = "Click this button to print the file you "
    "are editing.\n\n"
    "You can also select the Print command from the File menu.";

    ApplicationWindow::ApplicationWindow()
        : QMainWindow( 0, "example application main window", WDestructiveClose )
    {
        int id;

        printer = new QPrinter;
        QPixmap openIcon, saveIcon, printIcon;

        fileTools = new QToolBar( this, "file operations" );
        fileTools->setLabel( tr( "File Operations" ) );

        openIcon = QPixmap( fileopen );
        QToolButton * fileOpen
            = new QToolButton( openIcon, "Open File", QString::null,
                               this, SLOT(load()), fileTools, "open file" );

        saveIcon = QPixmap( filesave );
        QToolButton * fileSave
            = new QToolButton( saveIcon, "Save File", QString::null,
                               this, SLOT(save()), fileTools, "save file" );

        printIcon = QPixmap( fileprint );
        QToolButton * filePrint
            = new QToolButton( printIcon, "Print File", QString::null,
                               this, SLOT(print()), fileTools, "print file" );

        (void)QWhatsThis::whatsThisButton( fileTools );

        QWhatsThis::add( fileOpen, fileOpenText );
        QMimeSourceFactory::defaultFactory()->setPixmap( "fileopen", openIcon );
        QWhatsThis::add( fileSave, fileSaveText );
        QWhatsThis::add( filePrint, filePrintText );

        QPopupMenu * file = new QPopupMenu( this );
        menuBar()->insertItem( "&File", file );

        file->insertItem( "&New", this, SLOT(newDoc()), CTRL+Key_N );

        id = file->insertItem( openIcon, "&Open",
                               this, SLOT(load()), CTRL+Key_O );
        file->setWhatsThis( id, fileOpenText );

        id = file->insertItem( saveIcon, "&Save",
                               this, SLOT(save()), CTRL+Key_S );
        file->setWhatsThis( id, fileSaveText );
        id = file->insertItem( "Save &as...", this, SLOT(saveAs()) );
        file->setWhatsThis( id, fileSaveText );
        file->insertSeparator();
        id = file->insertItem( printIcon, "&Print",
                               this, SLOT(print()), CTRL+Key_P );
        file->setWhatsThis( id, filePrintText );
        file->insertSeparator();
        file->insertItem( "&Close", this, SLOT(close()), CTRL+Key_W );
        file->insertItem( "&Quit", qApp, SLOT( closeAllWindows() ), CTRL+Key_Q );

        QPopupMenu * help = new QPopupMenu( this );
        menuBar()->insertSeparator();
        menuBar()->insertItem( "&Help", help );

        help->insertItem( "&About", this, SLOT(about()), Key_F1 );
        help->insertItem( "About &Qt", this, SLOT(aboutQt()) );
        help->insertSeparator();
        help->insertItem( "What's &This", this, SLOT(whatsThis()), SHIFT+Key_F1 );

        e = new QMultiLineEdit( this, "editor" );
        e->setFocus();
        setCentralWidget( e );
        statusBar()->message( "Ready", 2000 );
        resize( 450, 600 );
    }

    ApplicationWindow::~ApplicationWindow()
    {
        delete printer;
    }

    void ApplicationWindow::newDoc()
    {
        ApplicationWindow *ed = new ApplicationWindow;
        ed->setCaption("Qt Example - Application");
        ed->show();
    }

    void ApplicationWindow::load()
    {
        QString fn = QFileDialog::getOpenFileName( QString::null, QString::null,
                                                   this);
        if ( !fn.isEmpty() )
            load( fn );
        else
            statusBar()->message( "Loading aborted", 2000 );
    }

    void ApplicationWindow::load( const char *fileName )
    {
        QFile f( fileName );
        if ( !f.open( IO_ReadOnly ) )
            return;

        e->setAutoUpdate( FALSE );
        e->clear();

        QTextStream t(&f);
        while ( !t.eof() ) {
            QString s = t.readLine();
            e->append( s );
        }
        f.close();

        e->setAutoUpdate( TRUE );
        e->repaint();
        e->setEdited( FALSE );
        setCaption( fileName );
        QString s;
        s.sprintf( "Loaded document %s", fileName );
        statusBar()->message( s, 2000 );
    }

    void ApplicationWindow::save()
    {
        if ( filename.isEmpty() ) {
            saveAs();
            return;
        }

        QString text = e->text();
        QFile f( filename );
        if ( !f.open( IO_WriteOnly ) ) {
            statusBar()->message( QString("Could not write to %1").arg(filename),
                                  2000 );
            return;
        }

        QTextStream t( &f );
        t << text;
        f.close();

        e->setEdited( FALSE );

        setCaption( filename );

        statusBar()->message( QString( "File %1 saved" ).arg( filename ), 2000 );
    }

    void ApplicationWindow::saveAs()
    {
        QString fn = QFileDialog::getSaveFileName( QString::null, QString::null,
                                                   this );
        if ( !fn.isEmpty() ) {
            filename = fn;
            save();
        } else {
            statusBar()->message( "Saving aborted", 2000 );
        }
    }

    void ApplicationWindow::print()
    {
        const int Margin = 10;
        int pageNo = 1;

        if ( printer->setup(this) ) {               // printer dialog
            statusBar()->message( "Printing..." );
            QPainter p;
            if( !p.begin( printer ) )
                return;                             // paint on printer

            p.setFont( e->font() );
            int yPos        = 0;                    // y position for each line
            QFontMetrics fm = p.fontMetrics();
            QPaintDeviceMetrics metrics( printer ); // need width/height
                                                    // of printer surface
            for( int i = 0 ; i < e->numLines() ; i++ ) {
                if ( Margin + yPos > metrics.height() - Margin ) {
                    QString msg( "Printing (page " );
                    msg += QString::number( ++pageNo );
                    msg += ")...";
                    statusBar()->message( msg );
                    printer->newPage();             // no more room on this page
                    yPos = 0;                       // back to top of page
                }
                p.drawText( Margin, Margin + yPos,
                            metrics.width(), fm.lineSpacing(),
                            ExpandTabs | DontClip,
                            e->textLine( i ) );
                yPos = yPos + fm.lineSpacing();
            }
            p.end();                                // send job to printer
            statusBar()->message( "Printing completed", 2000 );
        } else {
            statusBar()->message( "Printing aborted", 2000 );
        }
    }

    void ApplicationWindow::closeEvent( QCloseEvent* ce )
    {
        if ( !e->edited() ) {
            ce->accept();
            return;
        }

        switch( QMessageBox::information( this, "Qt Application Example",
                                          "The document has been changed since "
                                          "the last save.",
                                          "Save Now", "Cancel", "Leave Anyway",
                                          0, 1 ) ) {
        case 0:
            save();
            ce->accept();
            break;
        case 1:
        default: // just for sanity
            ce->ignore();
            break;
        case 2:
            ce->accept();
            break;
        }
    }

    void ApplicationWindow::about()
    {
        QMessageBox::about( this, "Qt Application Example",
                            "This example demonstrates simple use of "
                            "QMainWindow,\nQMenuBar and QToolBar.");
    }

    void ApplicationWindow::aboutQt()
    {
        QMessageBox::aboutQt( this, "Qt Application Example" );
    }

Main:

    /****************************************************************************
    ** $Id: qt/examples/application/main.cpp   2.3.2   edited 2001-06-12 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include <qapplication.h>
    #include "application.h"

    int main( int argc, char ** argv ) {
        QApplication a( argc, argv );
        ApplicationWindow * mw = new ApplicationWindow();
        mw->setCaption( "Qt Example - Application" );
        mw->show();
        a.connect( &a, SIGNAL(lastWindowClosed()), &a, SLOT(quit()) );
        return a.exec();
    }