Question

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/application.h   3.0.5   edited May 7 17:30 $
**
** 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 QTextEdit;

class ApplicationWindow: public QMainWindow
{
    Q_OBJECT

public:
    ApplicationWindow();
    ~ApplicationWindow();

protected:
    void closeEvent( QCloseEvent* );

private slots:
    void newDoc();
    void choose();
    void load( const QString &fileName );
    void save();
    void saveAs();
    void print();

    void about();
    void aboutQt();

private:
    QPrinter *printer;
    QTextEdit *e;
    QString filename;
};


#endif

---

Implementation:

/****************************************************************************
** $Id$
**
** Copyright (C) 1992-2002 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 <qtextedit.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"

ApplicationWindow::ApplicationWindow()
    : QMainWindow( 0, "example application main window", WDestructiveClose )
{
    printer = new QPrinter;
    QPixmap openIcon, saveIcon, printIcon;

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

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

    const char * fileOpenText = "<p><img source=\"fileopen\"> "
                 "Click this button to open a <em>new file</em>. <br>"
                 "You can also select the <b>Open</b> command "
                 "from the <b>File</b> menu.</p>";

    QWhatsThis::add( fileOpen, fileOpenText );

    QMimeSourceFactory::defaultFactory()->setPixmap( "fileopen", openIcon );

    const char * fileSaveText = "<p>Click this button to save the file you "
                 "are editing. You will be prompted for a file name.\n"
                 "You can also select the <b>Save</b> command "
                 "from the <b>File</b> menu.</p>";

    QWhatsThis::add( fileSave, fileSaveText );

    const char * filePrintText = "Click this button to print the file you "
                 "are editing.\n You can also select the Print "
                 "command from the File menu.";

    QWhatsThis::add( filePrint, filePrintText );


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


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

    int id;
    id = file->insertItem( openIcon, "&Open...",
                           this, SLOT(choose()), 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 );

    menuBar()->insertSeparator();

    QPopupMenu * help = new QPopupMenu( this );
    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 QTextEdit( 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::choose()
{
    QString fn = QFileDialog::getOpenFileName( QString::null, QString::null,
                                               this);
    if ( !fn.isEmpty() )
        load( fn );
    else
        statusBar()->message( "Loading aborted", 2000 );
}


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

    QTextStream ts( &f );
    e->setText( ts.read() );
    e->setModified( FALSE );
    setCaption( fileName );
    statusBar()->message( "Loaded document " + fileName, 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->setModified( 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()
{
    // ###### Rewrite to use QSimpleRichText to print here as well
    const int Margin = 10;
    int pageNo = 1;

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

        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->lines() ; 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->text( 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->isModified() ) {
        ce->accept();
        return;
    }

    switch( QMessageBox::information( this, "Qt Application Example",
                                      "Do you want to save the changes"
                                      " to the document?",
                                      "Yes", "No", "Cancel",
                                      0, 1 ) ) {
    case 0:
        save();
        ce->accept();
        break;
    case 1:
        ce->accept();
        break;
    case 2:
    default: // just for sanity
        ce->ignore();
        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/main.cpp   3.0.5   edited Oct 12 2001 $
**
** 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();
}

See also Examples.