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# Transformed Graphics Demo

This example lets the user rotate, shear and scale text and graphics arbitrarily.

Implementation:

    /****************************************************************************
    ** $Id:  qt/xform.cpp   3.0.0   edited Jun 22 13:24 $
    **
    ** 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 <qdialog.h>
    #include <qlabel.h>
    #include <qlineedit.h>
    #include <qpushbutton.h>
    #include <qcheckbox.h>
    #include <qradiobutton.h>
    #include <qbuttongroup.h>
    #include <qlcdnumber.h>
    #include <qslider.h>
    #include <qmenubar.h>
    #include <qfontdialog.h>
    #include <qlayout.h>
    #include <qvbox.h>
    #include <qwidgetstack.h>

    #include <qpainter.h>
    #include <qpixmap.h>
    #include <qpicture.h>

    #include <stdlib.h>

    class ModeNames {
    public:
        enum Mode { Text, Image, Picture };
    };

    class XFormControl : public QVBox, public ModeNames
    {
        Q_OBJECT
    public:
        XFormControl( const QFont &initialFont, QWidget *parent=0, const char *name=0 );
       ~XFormControl() {}

        QWMatrix matrix();

    signals:
        void newMatrix( QWMatrix );
        void newText( const QString& );
        void newFont( const QFont & );
        void newMode( int );
    private slots:
        void newMtx();
        void newTxt(const QString&);
        void selectFont();
        void fontSelected( const QFont & );
        void changeMode(int);
        void timerEvent(QTimerEvent*);
    private:
        Mode mode;
        QSlider      *rotS;                // Rotation angle scroll bar
        QSlider      *shearS;              // Shear value scroll bar
        QSlider      *magS;                // Magnification value scroll bar
        QLCDNumber   *rotLCD;              // Rotation angle LCD display
        QLCDNumber   *shearLCD;            // Shear value LCD display
        QLCDNumber   *magLCD;              // Magnification value LCD display
        QCheckBox    *mirror;              // Checkbox for mirror image on/of
        QWidgetStack* optionals;
        QLineEdit    *textEd;              // Inp[ut field for xForm text
        QPushButton  *fpb;                 // Select font push button
        QRadioButton *rb_txt;              // Radio button for text
        QRadioButton *rb_img;              // Radio button for image
        QRadioButton *rb_pic;              // Radio button for picture
        QFont currentFont;
    };

    /*
      ShowXForm displays a text or a pixmap (QPixmap) using a coordinate
      transformation matrix (QWMatrix)
    */

    class ShowXForm : public QWidget, public ModeNames
    {
        Q_OBJECT
    public:
        ShowXForm( const QFont &f, QWidget *parent=0, const char *name=0 );
       ~ShowXForm() {}
        void showIt();                      // (Re)displays text or pixmap

        Mode mode() const { return m; }
    public slots:
        void setText( const QString& );
        void setMatrix( QWMatrix );
        void setFont( const QFont &f );
        void setPixmap( QPixmap );
        void setPicture( const QPicture& );
        void setMode( int );
    private:
        QSizePolicy sizePolicy() const;
        QSize sizeHint() const;
        void paintEvent( QPaintEvent * );
        void resizeEvent( QResizeEvent * );
        QWMatrix  mtx;                      // coordinate transform matrix
        QString   text;                     // text to be displayed
        QPixmap   pix;                      // pixmap to be displayed
        QPicture  picture;                  // text to be displayed
        QRect     eraseRect;                // covers last displayed text/pixmap
        Mode      m;
    };

    XFormControl::XFormControl( const QFont &initialFont,
                                QWidget *parent, const char *name )
            : QVBox( parent, name )
    {
        setSpacing(6);
        setMargin(6);
        currentFont = initialFont;
        mode = Image;

        rotLCD      = new QLCDNumber( 4, this, "rotateLCD" );
        rotS        = new QSlider( QSlider::Horizontal, this,
                                      "rotateSlider" );
        shearLCD    = new QLCDNumber( 5,this, "shearLCD" );
        shearS      = new QSlider( QSlider::Horizontal, this,
                                      "shearSlider" );
        mirror      = new QCheckBox( this, "mirrorCheckBox" );
        rb_txt = new QRadioButton( this, "text" );
        rb_img = new QRadioButton( this, "image" );
        rb_pic = new QRadioButton( this, "picture" );
        optionals = new QWidgetStack(this);
        QVBox* optionals_text = new QVBox(optionals);
        optionals_text->setSpacing(6);
        QVBox* optionals_other = new QVBox(optionals);
        optionals_other->setSpacing(6);
        optionals->addWidget(optionals_text,0);
        optionals->addWidget(optionals_other,1);
        fpb         = new QPushButton( optionals_text, "text" );
        textEd      = new QLineEdit( optionals_text, "text" );
        textEd->setFocus();

        rotLCD->display( "  0'" );

        rotS->setRange( -180, 180 );
        rotS->setValue( 0 );
        connect( rotS, SIGNAL(valueChanged(int)), SLOT(newMtx()) );

        shearLCD->display( "0.00" );

        shearS->setRange( -25, 25 );
        shearS->setValue( 0 );
        connect( shearS, SIGNAL(valueChanged(int)), SLOT(newMtx()) );

        mirror->setText( tr("Mirror") );
        connect( mirror, SIGNAL(clicked()), SLOT(newMtx()) );

        QButtonGroup *bg = new QButtonGroup(this);
        bg->hide();
        bg->insert(rb_txt,0);
        bg->insert(rb_img,1);
        bg->insert(rb_pic,2);
        rb_txt->setText( tr("Text") );
        rb_img->setText( tr("Image") );
        rb_img->setChecked(TRUE);
        rb_pic->setText( tr("Picture") );
        connect( bg, SIGNAL(clicked(int)), SLOT(changeMode(int)) );

        fpb->setText( tr("Select font...") );
        connect( fpb, SIGNAL(clicked()), SLOT(selectFont()) );

        textEd->setText( "Troll" );
        connect( textEd, SIGNAL(textChanged(const QString&)),
                         SLOT(newTxt(const QString&)) );

        magLCD = new QLCDNumber( 4,optionals_other, "magLCD" );
        magLCD->display( "100" );
        magS = new QSlider( QSlider::Horizontal, optionals_other,
                               "magnifySlider" );
        magS->setRange( 0, 800 );
        connect( magS, SIGNAL(valueChanged(int)), SLOT(newMtx()) );
        magS->setValue( 0 );
        connect( magS, SIGNAL(valueChanged(int)), magLCD, SLOT(display(int)));

        optionals_text->adjustSize();
        optionals_other->adjustSize();
        changeMode(Image);

        startTimer(20); // start an initial animation
    }

    void XFormControl::timerEvent(QTimerEvent*)
    {
        int v = magS->value();
        v = (v+2)+v/10;
        if ( v >= 200 ) {
            v = 200;
            killTimers();
        }
        magS->setValue(v);
    }

    /*
        Called whenever the user has changed one of the matrix parameters
        (i.e. rotate, shear or magnification)
    */
    void XFormControl::newMtx()
    {
        emit newMatrix( matrix() );
    }

    void XFormControl::newTxt(const QString& s)
    {
        emit newText(s);
        changeMode(Text);
    }

    /*
        Calculates the matrix appropriate for the current controls,
        and updates the displays.
    */
    QWMatrix XFormControl::matrix()
    {
        QWMatrix m;
        if (mode != Text) {
            double magVal = 1.0*magS->value()/100;
            m.scale( magVal, magVal );
        }
        double shearVal = 1.0*shearS->value()/25;
        m.shear( shearVal, shearVal );
        m.rotate( rotS->value() );
        if ( mirror->isChecked() ) {
            m.scale( 1, -1 );
            m.rotate( 180 );
        }

        QString tmp;
        tmp.sprintf( "%1.2f", shearVal  );
        if ( shearVal >= 0 )
            tmp.insert( 0, " " );
        shearLCD->display( tmp );

        int rot = rotS->value();
        if ( rot < 0 )
            rot = rot + 360;
        tmp.sprintf( "%3i'", rot );
        rotLCD->display( tmp );
        return m;
    }

    void XFormControl::selectFont()
    {
        bool ok;
        QFont f = QFontDialog::getFont( &ok, currentFont );
        if ( ok ) {
            currentFont = f;
            fontSelected( f );
        }
    }

    void XFormControl::fontSelected( const QFont &font )
    {
        emit newFont( font );
        changeMode(Text);
    }

    /*
        Sets the mode - Text, Image, or Picture.
    */

    void XFormControl::changeMode(int m)
    {
        mode = (Mode)m;

        emit newMode( m );
        newMtx();
        if ( mode == Text ) {
            optionals->raiseWidget(0);
            rb_txt->setChecked(TRUE);
        } else {
            optionals->raiseWidget(1);
            if ( mode == Image )
                rb_img->setChecked(TRUE);
            else
                rb_pic->setChecked(TRUE);
        }
        qApp->flushX();
    }

    ShowXForm::ShowXForm( const QFont &initialFont,
                          QWidget *parent, const char *name )
            : QWidget( parent, name, WResizeNoErase )
    {
        setFont( initialFont );
        setBackgroundColor( white );
        m = Text;
        eraseRect = QRect( 0, 0, 0, 0 );
    }

    QSizePolicy ShowXForm::sizePolicy() const
    {
        return QSizePolicy( QSizePolicy::Expanding, QSizePolicy::Expanding );
    }

    QSize ShowXForm::sizeHint() const
    {
        return QSize(400,400);
    }

    void ShowXForm::paintEvent( QPaintEvent * )
    {
        showIt();
    }

    void ShowXForm::resizeEvent( QResizeEvent * )
    {
        eraseRect = QRect( width()/2, height()/2, 0, 0 );
        repaint(rect());
    }

    void ShowXForm::setText( const QString& s )
    {
        text = s;
        showIt();
    }

    void ShowXForm::setMatrix( QWMatrix w )
    {
        mtx = w;
        showIt();
    }

    void ShowXForm::setFont( const QFont &f )
    {
        m = Text;
        QWidget::setFont( f );
    }

    void ShowXForm::setPixmap( QPixmap pm )
    {
        pix  = pm;
        m    = Image;
        showIt();
    }

    void ShowXForm::setPicture( const QPicture& p )
    {
        picture = p;
        m = Picture;
        showIt();
    }

    void ShowXForm::setMode( int mode )
    {
        m = (Mode)mode;
    }

    void ShowXForm::showIt()
    {
        QPainter p;
        QRect r;      // rectangle covering new text/pixmap in virtual coordinates
        QWMatrix um;  // copy user specified transform
        int textYPos = 0; // distance from boundingRect y pos to baseline
        int textXPos = 0; // distance from boundingRect x pos to text start
        QRect br;
        QFontMetrics fm( fontMetrics() );   // get widget font metrics
        switch ( mode() ) {
          case Text:
            br = fm.boundingRect( text );   // rectangle covering text
            r  = br;
            textYPos = -r.y();
            textXPos = -r.x();
            br.moveTopLeft( QPoint( -br.width()/2, -br.height()/2 ) );
            break;
          case Image:
            r = pix.rect();
            break;
          case Picture:
            // ### need QPicture::boundingRect()
            r = QRect(0,0,1000,1000);
            break;
        }
        r.moveTopLeft( QPoint(-r.width()/2, -r.height()/2) );
              // compute union of new and old rect
              // the resulting rectangle will cover what is already displayed
              // and have room for the new text/pixmap
        eraseRect = eraseRect.unite( mtx.map(r) );
        eraseRect.moveBy( -1, -1 ); // add border for matrix round off
        eraseRect.setSize( QSize( eraseRect.width() + 2,eraseRect.height() + 2 ) );
        int pw = QMIN(eraseRect.width(),width());
        int ph = QMIN(eraseRect.height(),height());
        QPixmap pm( pw, ph );               // off-screen drawing pixmap
        pm.fill( backgroundColor() );

        p.begin( &pm );
        um.translate( pw/2, ph/2 ); // 0,0 is center
        um = mtx * um;
        p.setWorldMatrix( um );
        switch ( mode() ) {
          case Text:
            p.setFont( font() );            // use widget font
            p.drawText( r.left() + textXPos, r.top() + textYPos, text );
    #if 0
            p.setPen( red );
            p.drawRect( br );
    #endif
            break;
          case Image:
            p.drawPixmap( -pix.width()/2, -pix.height()/2, pix );
            //QPixmap rotated = pix.xForm(mtx);
            //bitBlt( &pm, pm.width()/2 - rotated.width()/2,
                    //pm.height()/2 - rotated.height()/2, &rotated );
            break;
          case Picture:
            // ### need QPicture::boundingRect()
            p.scale(0.25,0.25);
            p.translate(-230,-180);
            p.drawPicture( picture );
        }
        p.end();

        int xpos = width()/2  - pw/2;
        int ypos = height()/2 - ph/2;
        bitBlt( this, xpos, ypos,                   // copy pixmap to widget
                &pm, 0, 0, -1, -1 );
        eraseRect =  mtx.map( r );
    }

    /*
        Grand unifying widget, putting ShowXForm and XFormControl
        together.
    */

    class XFormCenter : public QHBox, public ModeNames
    {
        Q_OBJECT
    public:
        XFormCenter( QWidget *parent=0, const char *name=0 );
    public slots:
        void setFont( const QFont &f ) { sx->setFont( f ); }
        void newMode( int );
    private:
        ShowXForm   *sx;
        XFormControl *xc;
    };

    void XFormCenter::newMode( int m )
    {
        static bool first_i = TRUE;
        static bool first_p = TRUE;

        if ( sx->mode() == m )
            return;
        if ( m == Image && first_i ) {
            first_i = FALSE;
            QPixmap pm;
            if ( pm.load( "image.any" ) )
                sx->setPixmap( pm );
            return;
        }
        if ( m == Picture && first_p ) {
            first_p = FALSE;
            QPicture p;
            if (p.load( "picture.any" ))
                sx->setPicture( p );
            return;
        }
        sx->setMode(m);
    }

    XFormCenter::XFormCenter( QWidget *parent, const char *name )
        : QHBox( parent, name )
    {
        QFont f( "Charter", 36, QFont::Bold );

        xc = new XFormControl( f, this );
        sx = new ShowXForm( f, this );
        setStretchFactor(sx,1);
        xc->setFrameStyle( QFrame::Panel | QFrame::Raised );
        xc->setLineWidth( 2 );
        connect( xc, SIGNAL(newText(const QString&)), sx,
                     SLOT(setText(const QString&)) );
        connect( xc, SIGNAL(newMatrix(QWMatrix)),
                 sx, SLOT(setMatrix(QWMatrix)) );
        connect( xc, SIGNAL(newFont(const QFont&)), sx,
                     SLOT(setFont(const QFont&)) );
        connect( xc, SIGNAL(newMode(int)), SLOT(newMode(int)) );
        sx->setText( "Troll" );
        newMode( Image );
        sx->setMatrix(xc->matrix());
    }

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

        XFormCenter *xfc = new XFormCenter;

        a.setMainWidget( xfc );
        xfc->setCaption("Qt Example - XForm");
        xfc->show();
        return a.exec();
    }

    #include "xform.moc"                  // include metadata generated by the moc

See also Examples.