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# Source code for tutorial 10: cannon.cpp

    /****************************************************************
    **
    ** Implementation CannonField class, Qt tutorial 10
    **
    ****************************************************************/

    #include "cannon.h"
    #include <qpainter.h>
    #include <qpixmap.h>

    CannonField::CannonField( QWidget *parent, const char *name )
            : QWidget( parent, name )
    {
        ang = 45;
        f = 0;
        setPalette( QPalette( QColor( 250, 250, 200) ) );
    }

    void CannonField::setAngle( int degrees )
    {
        if ( degrees < 5 )
            degrees = 5;
        if ( degrees > 70 )
            degrees = 70;
        if ( ang == degrees )
            return;
        ang = degrees;
        repaint( cannonRect(), FALSE );
        emit angleChanged( ang );
    }

    void CannonField::setForce( int newton )
    {
        if ( newton < 0 )
            newton = 0;
        if ( f == newton )
            return;
        f = newton;
        emit forceChanged( f );
    }

    void CannonField::paintEvent( QPaintEvent *e )
    {
        if ( !e->rect().intersects( cannonRect() ) )
            return;

        QRect cr = cannonRect();
        QPixmap pix( cr.size() );
        pix.fill( this, cr.topLeft() );

        QPainter p( &pix );
        p.setBrush( blue );
        p.setPen( NoPen );
        p.translate( 0, pix.height() - 1 );
        p.drawPie( QRect( -35,-35, 70, 70 ), 0, 90*16 );
        p.rotate( -ang );
        p.drawRect( QRect(33, -4, 15, 8) );
        p.end();

        p.begin( this );
        p.drawPixmap( cr.topLeft(), pix );
    }

    QRect CannonField::cannonRect() const
    {
        QRect r( 0, 0, 50, 50 );
        r.moveBottomLeft( rect().bottomLeft() );
        return r;
    }

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