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# Simple editor that can load encodings

Header file:

    /****************************************************************************
    ** $Id: qt/qwerty.h   3.3.8   edited Jan 11 14:37 $
    **
    ** Copyright (C) 1992-2007 Trolltech ASA.  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 QWERTY_H
    #define QWERTY_H

    #include <qwidget.h>
    #include <qmenubar.h>
    #include <qmultilineedit.h>
    #include <qprinter.h>

    class Editor : public QWidget
    {
        Q_OBJECT
    public:
        Editor( QWidget *parent=0, const char *name="qwerty" );
       ~Editor();

        void load( const QString& fileName, int code=-1 );

    public slots:
        void newDoc();
        void load();
        bool save();
        void print();
        void addEncoding();
        void toUpper();
        void toLower();
        void font();
    protected:
        void resizeEvent( QResizeEvent * );
        void closeEvent( QCloseEvent * );

    private slots:
        void saveAsEncoding( int );
        void openAsEncoding( int );
        void textChanged();

    private:
        bool saveAs( const QString& fileName, int code=-1 );
        void rebuildCodecList();
        QMenuBar       *m;
        QMultiLineEdit *e;
    #ifndef QT_NO_PRINTER
        QPrinter        printer;
    #endif
        QPopupMenu     *save_as;
        QPopupMenu     *open_as;
        bool changed;
    };

    #endif // QWERTY_H

Implementation:

    /****************************************************************************
    ** $Id: qt/qwerty.cpp   3.3.8   edited Jan 11 14:37 $
    **
    ** Copyright (C) 1992-2007 Trolltech ASA.  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 "qwerty.h"
    #include <qapplication.h>
    #include <qfile.h>
    #include <qfiledialog.h>
    #include <qpopupmenu.h>
    #include <qtextstream.h>
    #include <qpainter.h>
    #include <qmessagebox.h>
    #include <qpaintdevicemetrics.h>
    #include <qptrlist.h>
    #include <qfontdialog.h>

    #include <qtextcodec.h>

    const bool no_writing = FALSE;

    static QPtrList<QTextCodec> *codecList = 0;

    enum { Uni = 0, MBug = 1, Lat1 = 2, Local = 3, Guess = 4, Codec = 5 };

    Editor::Editor( QWidget * parent , const char * name )
        : QWidget( parent, name, WDestructiveClose )
    {
        m = new QMenuBar( this, "menu" );

        QPopupMenu * file = new QPopupMenu();
        Q_CHECK_PTR( file );
        m->insertItem( "&File", file );

        file->insertItem( "&New",   this, SLOT(newDoc()),   ALT+Key_N );
        file->insertItem( "&Open...",  this, SLOT(load()),     ALT+Key_O );
        file->insertItem( "&Save...",  this, SLOT(save()),     ALT+Key_S );
        file->insertSeparator();
        open_as = new QPopupMenu();
        file->insertItem( "Open &As",  open_as );
        save_as = new QPopupMenu();
        file->insertItem( "Sa&ve As",  save_as );
        file->insertItem( "Add &Encoding", this, SLOT(addEncoding()) );
    #ifndef QT_NO_PRINTER
        file->insertSeparator();
        file->insertItem( "&Print...", this, SLOT(print()),    ALT+Key_P );
    #endif
        file->insertSeparator();
        file->insertItem( "&Close", this, SLOT(close()),ALT+Key_W );
        file->insertItem( "&Quit",  qApp, SLOT(closeAllWindows()),     ALT+Key_Q );

        connect( save_as, SIGNAL(activated(int)), this, SLOT(saveAsEncoding(int)) );
        connect( open_as, SIGNAL(activated(int)), this, SLOT(openAsEncoding(int)) );
        rebuildCodecList();

        QPopupMenu * edit = new QPopupMenu();
        Q_CHECK_PTR( edit );
        m->insertItem( "&Edit", edit );

        edit->insertItem( "To &Uppercase",   this, SLOT(toUpper()),   ALT+Key_U );
        edit->insertItem( "To &Lowercase",   this, SLOT(toLower()),   ALT+Key_L );
    #ifndef QT_NO_FONTDIALOG
        edit->insertSeparator();
        edit->insertItem( "&Select Font" ,   this, SLOT(font()),     ALT+Key_T );
    #endif
        changed = FALSE;
        e = new QMultiLineEdit( this, "editor" );
        connect( e, SIGNAL( textChanged() ), this, SLOT( textChanged() ) );

        // We use Unifont - if you have it installed you'll see all
        // Unicode character glyphs.
        //
        // Unifont only comes in one pixel size, so we cannot let
        // it change pixel size as the display DPI changes.
        //
        QFont unifont("unifont",16,50); unifont.setPixelSize(16);
        e->setFont( unifont );

        e->setFocus();
    }

    Editor::~Editor()
    {
    }

    void Editor::font()
    {
    #ifndef QT_NO_FONTDIALOG
        bool ok;
        QFont f = QFontDialog::getFont( &ok, e->font() );
        if ( ok ) {
            e->setFont( f );
        }
    #endif
    }

    void Editor::rebuildCodecList()
    {
        delete codecList;
        codecList = new QPtrList<QTextCodec>;
        QTextCodec *codec;
        int i;
        for (i = 0; (codec = QTextCodec::codecForIndex(i)); i++)
            codecList->append( codec );
        int n = codecList->count();
        for (int pm=0; pm<2; pm++) {
            QPopupMenu* menu = pm ? open_as : save_as;
            menu->clear();
            QString local = "Local (";
            local += QTextCodec::codecForLocale()->name();
            local += ")";
            menu->insertItem( local, Local );
            menu->insertItem( "Unicode", Uni );
            menu->insertItem( "Latin1", Lat1 );
            menu->insertItem( "Microsoft Unicode", MBug );
            if ( pm )
                menu->insertItem( "[guess]", Guess );
            for ( i = 0; i < n; i++ )
                menu->insertItem( codecList->at(i)->name(), Codec + i );
        }
    }

    void Editor::newDoc()
    {
        Editor *ed = new Editor;
        if ( qApp->desktop()->size().width() < 450
             || qApp->desktop()->size().height() < 450 ) {
            ed->showMaximized();
        } else {
            ed->resize( 400, 400 );
            ed->show();
        }
    }

    void Editor::load()
    {
    #ifndef QT_NO_FILEDIALOG
        QString fn = QFileDialog::getOpenFileName( QString::null, QString::null, this );
        if ( !fn.isEmpty() )
            load( fn, -1 );
    #endif
    }

    void Editor::load( const QString& fileName, int code )
    {
        QFile f( fileName );
        if ( !f.open( IO_ReadOnly ) )
            return;

        e->setAutoUpdate( FALSE );

        QTextStream t(&f);
        if ( code >= Codec )
            t.setCodec( codecList->at(code-Codec) );
        else if ( code == Uni )
            t.setEncoding( QTextStream::Unicode );
        else if ( code == MBug )
            t.setEncoding( QTextStream::UnicodeReverse );
        else if ( code == Lat1 )
            t.setEncoding( QTextStream::Latin1 );
        else if ( code == Guess ) {
            QFile f(fileName);
            f.open(IO_ReadOnly);
            char buffer[256];
            int l = 256;
            l=f.readBlock(buffer,l);
            QTextCodec* codec = QTextCodec::codecForContent(buffer, l);
            if ( codec ) {
                QMessageBox::information(this,"Encoding",QString("Codec: ")+codec->name());
                t.setCodec( codec );
            }
        }
        e->setText( t.read() );
        f.close();

        e->setAutoUpdate( TRUE );
        e->repaint();
        setCaption( fileName );

        changed = FALSE;
    }

    void Editor::openAsEncoding( int code )
    {
    #ifndef QT_NO_FILEDIALOG
        //storing filename (proper save) is left as an exercise...
        QString fn = QFileDialog::getOpenFileName( QString::null, QString::null, this );
        if ( !fn.isEmpty() )
            (void) load( fn, code );
    #endif
    }

    bool Editor::save()
    {
    #ifndef QT_NO_FILEDIALOG
        //storing filename (proper save) is left as an exercise...
        QString fn = QFileDialog::getSaveFileName( QString::null, QString::null, this );
        if ( !fn.isEmpty() )
            return saveAs( fn );
        return FALSE;
    #endif
    }

    void Editor::saveAsEncoding( int code )
    {
    #ifndef QT_NO_FILEDIALOG
        //storing filename (proper save) is left as an exercise...
        QString fn = QFileDialog::getSaveFileName( QString::null, QString::null, this );
        if ( !fn.isEmpty() )
            (void) saveAs( fn, code );
    #endif
    }

    void Editor::addEncoding()
    {
    #ifndef QT_NO_FILEDIALOG
        QString fn = QFileDialog::getOpenFileName( QString::null, "*.map", this );
        if ( !fn.isEmpty() ) {
            QFile f(fn);
            if (f.open(IO_ReadOnly)) {
                if (QTextCodec::loadCharmap(&f)) {
                    rebuildCodecList();
                } else {
                    QMessageBox::warning(0,"Charmap error",
                        "The file did not contain a valid charmap.\n\n"
                        "A charmap file should look like this:\n"
                           "  <code_set_name> thename\n"
                           "  <escape_char> /\n"
                           "  % alias thealias\n"
                           "  CHARMAP\n"
                           "  <tokenname> /x12 <U3456>\n"
                           "  <tokenname> /xAB/x12 <U0023>\n"
                           "  ...\n"
                           "  END CHARMAP\n"
                    );
                }
            }
        }
    #endif
    }

    bool Editor::saveAs( const QString& fileName, int code )
    {
        QFile f( fileName );
        if ( no_writing || !f.open( IO_WriteOnly ) ) {
            QMessageBox::warning(this,"I/O Error",
                        QString("The file could not be opened.\n\n")
                            +fileName);
            return FALSE;
        }
        QTextStream t(&f);
        if ( code >= Codec )
            t.setCodec( codecList->at(code-Codec) );
        else if ( code == Uni )
            t.setEncoding( QTextStream::Unicode );
        else if ( code == MBug )
            t.setEncoding( QTextStream::UnicodeReverse );
        else if ( code == Lat1 )
            t.setEncoding( QTextStream::Latin1 );
        t << e->text();
        f.close();
        setCaption( fileName );
        changed = FALSE;
        return TRUE;
    }

    void Editor::print()
    {
    #ifndef QT_NO_PRINTER
        if ( printer.setup(this) ) {                // opens printer dialog
            printer.setFullPage(TRUE);              // we'll set our own margins
            QPainter p;
            p.begin( &printer );                    // paint on printer
            p.setFont( e->font() );
            QFontMetrics fm = p.fontMetrics();
            QPaintDeviceMetrics metrics( &printer ); // need width/height
                                                     // of printer surface
            const int MARGIN = metrics.logicalDpiX() / 2; // half-inch margin
            int yPos        = MARGIN;               // y position for each line

            for( int i = 0 ; i < e->numLines() ; i++ ) {
                if ( printer.aborted() )
                    break;
                if ( yPos + fm.lineSpacing() > metrics.height() - MARGIN ) {
                    // no more room on this page
                    if ( !printer.newPage() )          // start new page
                        break;                           // some error
                    yPos = MARGIN;                   // back to top of page
                }
                p.drawText( MARGIN, yPos, metrics.width() - 2*MARGIN,
                            fm.lineSpacing(), ExpandTabs, e->textLine( i ) );
                yPos += fm.lineSpacing();
            }
            p.end();                                // send job to printer
        }
    #endif
    }

    void Editor::resizeEvent( QResizeEvent * )
    {
        if ( e && m )
            e->setGeometry( 0, m->height(), width(), height() - m->height() );
    }

    void Editor::closeEvent( QCloseEvent *event )
    {
        event->accept();

        if ( changed ) { // the text has been changed
            switch ( QMessageBox::warning( this, "Qwerty",
                                            "Save changes to Document?",
                                            tr("&Yes"),
                                            tr("&No"),
                                            tr("Cancel"),
                                            0, 2) ) {
            case 0: // yes
                if ( save() )
                    event->accept();
                else
                    event->ignore();
                break;
            case 1: // no
                event->accept();
                break;
            default: // cancel
                event->ignore();
                break;
            }
        }
    }

    void Editor::toUpper()
    {
        e->setText(e->text().upper());
    }

    void Editor::toLower()
    {
        e->setText(e->text().lower());
    }

    void Editor::textChanged()
    {
        changed = TRUE;
    }

Main:

    /****************************************************************************
    ** $Id: qt/main.cpp   3.3.8   edited Jan 11 14:37 $
    **
    ** Copyright (C) 1992-2007 Trolltech ASA.  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 "qwerty.h"

    int main( int argc, char **argv )
    {
        QApplication a( argc, argv );

        bool isSmall =  qApp->desktop()->size().width() < 450
                      || qApp->desktop()->size().height() < 450;

        int i;
        for ( i= argc <= 1 ? 0 : 1; i<argc; i++ ) {
            Editor *e = new Editor;
            e->setCaption("Qt Example - QWERTY");
            if ( i > 0 )
                e->load( argv[i] );
            if ( isSmall ) {
                e->showMaximized();
            } else {
                e->resize( 400, 400 );
                e->show();
            }
        }
        a.connect( &a, SIGNAL(lastWindowClosed()), &a, SLOT(quit()) );
        return a.exec();
    }

See also Examples.