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Painting on the Desktop

/****************************************************************************
** $Id: qt/examples/desktop/desktop.cpp   2.2.1   edited 2000-08-31 $
**
** 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 <qimage.h>
#include <qbitmap.h>
#include <qpainter.h>
#include <qapplication.h>
#include <qdropsite.h>
#include <qdragobject.h>
#include <stdio.h>

static double seed = 0.353535353535;
static const int KINDA_RAND_MAX = 32767;

static int kindaRand()
{
    seed = seed*147;
    seed = seed - (double) ((int) seed);
    return (int) ( seed*(KINDA_RAND_MAX + 1) );
}

static int velocity( int i )                    // change velocity
{
    const int velmax = 15;
    const int velmin = 4;
    if ( i == 1 || i == 2 )
        i = (kindaRand()&0x7fff % velmax)/3 + velmin;
    else
        i = (kindaRand()&0x7fff % velmax) + velmin;
    return i;
}

//
// Draw polygon on desktop.
//

void poly()
{
    QWidget *d = QApplication::desktop();
    d->setBackgroundColor( Qt::white );         // white desktop

    const int maxpoints = 5;
    const int maxcurves = 8;
    static int xvel[maxpoints];
    static int yvel[maxpoints];
    int head = 0;
    int tail = -maxcurves + 2;
    QPointArray *a = new QPointArray[ maxcurves ];
    register QPointArray *p;
    QRect r = d->rect();                        // desktop rectangle

    int i;
    for ( i=0; i<maxcurves; i++ )
        a[i].resize( maxpoints );
    p = &a[0];
    for ( i=0; i<maxpoints; i++ ) {             // setup first polygon points
        p->setPoint( i, (kindaRand()&0x7fff) % r.width(),
                        (kindaRand()&0x7fff) % r.height() );
        xvel[i] = velocity(i);
        yvel[i] = velocity(i);
    }

    QPainter paint;
    paint.begin( d );                           // start painting desktop

    for ( int ntimes=0; ntimes<2000; ntimes++ ) {
        paint.setBrush( QColor(kindaRand()%360, 180, 255, QColor::Hsv) );
        paint.drawPolygon( a[head] );
        if ( ++tail >= maxcurves )
            tail = 0;

        int minx=r.left(), maxx=r.right();
        int miny=r.top(),  maxy=r.bottom();
        int x, y;
        p = &a[head];
        if ( ++head >= maxcurves )
            head = 0;
        for ( i=0; i<maxpoints; i++ ) {         // calc new curve
            p->point( i, &x, &y );
            x += xvel[i];
            y += yvel[i];
            if ( x >= maxx ) {
                x = maxx - (x - maxx + 1);
                xvel[i] = -velocity(i);
            }
            if ( x <= minx ) {
                x = minx + (minx - x + 1);
                xvel[i] = velocity(i);
            }
            if ( y >= maxy ) {
                y = maxy - (y - maxy + 1);
                yvel[i] = -velocity(i);
            }
            if ( y <= miny ) {
                y = miny + (miny - y + 1);
                yvel[i] = velocity(i);
            }
            a[head].setPoint( i, x, y );
        }
    }
    paint.end();                                // painting done
    delete[] a;
}

//
// Rotate pattern on desktop.
//

void rotate()
{
    int i;
    const int w = 64;
    const int h = 64;
    QImage image( w, h, 8, 128 );               // create image
    for ( i=0; i<128; i++ )                     // build color table
        image.setColor( i, qRgb(i,0,0) );
    for ( int y=0; y<h; y++ ) {                 // set image pixels
        uchar *p = image.scanLine(y);
        for ( int x=0; x<w; x++ )
            *p++ = (x+y)%128;
    }

    QPixmap pm;
    pm = image;                                 // convert image to pixmap
    pm.setOptimization( QPixmap::BestOptim );   // rotation will be faster

    QWidget *d = QApplication::desktop();       // w = desktop widget

    for ( i=0; i<=360; i += 2 ) {
        QWMatrix m;
        m.rotate( i );                          // rotate coordinate system
        QPixmap rpm = pm.xForm( m );            // rpm = rotated pixmap
        d->setBackgroundPixmap( rpm );          // set desktop pixmap
        d->update();                            // repaint desktop
    }
}

//
// Generates a marble-like pattern in pm.
//

void generateStone( QPixmap *pm,
                    const QColor &c1, const QColor &c2, const QColor &c3 )
{
    QPainter p;
    QPen p1 ( c1, 0 );
    QPen p2 ( c2, 0 );
    QPen p3 ( c3, 0 );

    p.begin( pm );
    for( int i = 0 ; i < pm->width() ; i++ )
        for( int j = 0 ; j < pm->height() ; j++ ) {
            int r = kindaRand();
            if ( r < KINDA_RAND_MAX / 3 )
                p.setPen( p1 );
            else if ( r < KINDA_RAND_MAX / 3 * 2 )
                p.setPen( p2 );
            else
                p.setPen( p3 );
            p.drawPoint( i,j );
        }
    p.end();
}

void drawShadeText( QPainter *p, int x, int y, const char *text,
                    const QColor &topColor, const QColor &bottomColor,
                    int sw = 2 )
{
    if ( !p->isActive() )
        return;

    p->setPen( bottomColor );
    p->drawText( x+sw, y+sw, text );
    p->setPen( topColor );
    p->drawText( x, y, text );
}

// NOTE: desktop drag/drop is experimental

class DesktopWidget : public QWidget, private QDropSite
{
public:
    DesktopWidget( const char *s, QWidget *parent=0, const char *name=0 );
   ~DesktopWidget();
    void paintEvent( QPaintEvent * );

    void dragEnterEvent( QDragEnterEvent *e )
    {
        if ( QImageDrag::canDecode(e) )
            e->accept();
    }

    void dragLeaveEvent( QDragLeaveEvent * )
    {
    }

    void dragMoveEvent( QDragMoveEvent *e )
    {
        e->accept();
    }

    void dropEvent( QDropEvent * e )
    {
        QPixmap pmp;
        if ( QImageDrag::decode( e, pmp ) ) {
            setBackgroundPixmap( pmp );
            update();
        }
    }

private:
    QPixmap *pm;
    QString text;
};

DesktopWidget::DesktopWidget( const char *s, QWidget *parent, const char *name )
    : QWidget( parent, name, WType_Desktop | WPaintDesktop),
        QDropSite(this)
{
    text = s;
    pm   = 0;
}

DesktopWidget::~DesktopWidget()
{
    delete pm;
}

void DesktopWidget::paintEvent( QPaintEvent * )
{
    QColor c1 = backgroundColor();
    QColor c2 = c1.light(104);
    QColor c3 = c1.dark(106);
    if ( !pm ) {
        pm = new QPixmap( 64, 64 );
        generateStone( pm, c1, c2, c3 );
        setBackgroundPixmap( *pm );
        update();
    }
    QRect br = fontMetrics().boundingRect( text );
    QPixmap offscreen( br.width(), br.height() );
    int x = width()/2  - br.width()/2;
    int y = height()/2 - br.height()/2;
    offscreen.fill( this, x, y );
    QPainter p;
    p.begin( &offscreen );
    drawShadeText( &p, -br.x(), -br.y(), text, c2, c3, 3 );
    p.end();
    bitBlt( this, x, y, &offscreen );
}

void desktopWidget( const char *s = "Trolltech" )
{
    DesktopWidget *t = new DesktopWidget(s);
    t->update();
    qApp->exec();
    delete t;
}

void desktopText( const char *s = "Trolltech" )
{
    const int border = 20;

    QColor c1 =  qApp->palette().normal().background();
    QColor c2 = c1.light(104);
    QColor c3 = c1.dark(106);

    QPixmap pm(10,10);

    QPainter p;
    p.begin( &pm );
    QRect r = p.fontMetrics().boundingRect( s );
    p.end();

    int appWidth  =  qApp->desktop()->width();
    int appHeight =  qApp->desktop()->height();
    if ( r.width() > appWidth - border*2 )
        r.setWidth( appWidth - border*2 );
    if ( r.height() > appHeight - border*2 )
        r.setHeight( appHeight - border*2 );

    pm.resize( r.size() + QSize( border*2, border*2 ) );
    generateStone( &pm, c1, c2, c3 );
    p.begin( &pm );
    drawShadeText( &p, -r.x() + border, -r.y() + border, s, c2, c3 );
    p.end();

    qApp->desktop()->setBackgroundPixmap( pm );
}

//
// The program starts here.
//

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

    if ( argc > 1 ) {
        QFont f( "charter", 96, QFont::Black );
        f.setStyleHint( QFont::Times );
        app.setFont( f );
    }

    bool validOptions = FALSE;

    if ( argc == 2 ) {
        validOptions = TRUE;
        if ( strcmp(argv[1],"-poly") == 0 )
            poly();
        else if ( strcmp(argv[1],"-rotate") == 0 )
            rotate();
        else if ( strcmp(argv[1],"-troll") == 0 )
            desktopText();
        else if ( strcmp(argv[1],"-trollwidget") == 0 )
            desktopWidget();
        else
            validOptions = FALSE;
    }
    if ( argc == 3 ) {
        validOptions = TRUE;
        if ( strcmp(argv[1],"-shadetext") == 0 )
            desktopText( argv[2] );
        else if ( strcmp(argv[1],"-shadewidget") == 0 )
            desktopWidget( argv[2] );
        else
            validOptions = FALSE;
    }
    if ( !validOptions ) {
        fprintf( stderr, "Usage:\n\tdesktop -poly"
                               "\n\tdesktop -rotate"
                               "\n\tdesktop -troll"
                               "\n\tdesktop -trollwidget"
                               "\n\tdesktop -shadetext <text>"
                               "\n\tdesktop -shadewidget <text>\n" );
        rotate();
    }
    return 0;
}