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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Painting on the Desktop</h1>
<p>
The desktop demo contains three routines, each of which draws
something on the desktop. It does some nice stuff with <a href="qpainter.html">QPainter</a>,
and also demonstrates how one can treat the desktop as a widget like
any other.
<p> <hr>
<p> Implementation:
<p> <pre>/****************************************************************************
** $Id: qt/desktop.cpp 3.0.2 edited Oct 12 12:18 $
**
** 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 <<a href="qimage-h.html">qimage.h</a>>
#include <<a href="qbitmap-h.html">qbitmap.h</a>>
#include <<a href="qpainter-h.html">qpainter.h</a>>
#include <<a href="qapplication-h.html">qapplication.h</a>>
#include <<a href="qdropsite-h.html">qdropsite.h</a>>
#include <<a href="qdragobject-h.html">qdragobject.h</a>>
#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()
{
<a name="x1716"></a> <a href="qwidget.html">QWidget</a> *d = QApplication::<a href="qapplication.html#desktop">desktop</a>();
<a name="x1756"></a> d-><a href="qwidget.html#setBackgroundColor">setBackgroundColor</a>( 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;
<a href="qpointarray.html">QPointArray</a> *a = new <a href="qpointarray.html">QPointArray</a>[ maxcurves ];
register QPointArray *p;
<a name="x1755"></a> <a href="qrect.html">QRect</a> r = d-><a href="qwidget.html#rect">rect</a>(); // 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
<a name="x1751"></a> p->setPoint( i, (kindaRand()&0x7fff) % r.<a href="qrect.html#width">width</a>(),
<a name="x1744"></a> (kindaRand()&0x7fff) % r.<a href="qrect.html#height">height</a>() );
xvel[i] = velocity(i);
yvel[i] = velocity(i);
}
<a href="qpainter.html">QPainter</a> paint;
<a name="x1728"></a> paint.<a href="qpainter.html#begin">begin</a>( d ); // start painting desktop
for ( int ntimes=0; ntimes<2000; ntimes++ ) {
paint.<a href="qpainter.html#setBrush">setBrush</a>( QColor(kindaRand()%360, 180, 255, QColor::Hsv) );
<a name="x1730"></a> paint.<a href="qpainter.html#drawPolygon">drawPolygon</a>( a[head] );
if ( ++tail >= maxcurves )
tail = 0;
<a name="x1746"></a><a name="x1745"></a> int minx=r.<a href="qrect.html#left">left</a>(), maxx=r.<a href="qrect.html#right">right</a>();
<a name="x1750"></a><a name="x1743"></a> int miny=r.<a href="qrect.html#top">top</a>(), maxy=r.<a href="qrect.html#bottom">bottom</a>();
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 );
}
}
<a name="x1732"></a> paint.<a href="qpainter.html#end">end</a>(); // painting done
delete[] a;
}
//
// Rotate pattern on desktop.
//
void rotate()
{
int i;
const int w = 64;
const int h = 64;
<a href="qimage.html">QImage</a> image( w, h, 8, 128 ); // create image
for ( i=0; i<128; i++ ) // build color table
<a name="x1725"></a> image.<a href="qimage.html#setColor">setColor</a>( i, qRgb(i,0,0) );
for ( int y=0; y<h; y++ ) { // set image pixels
<a name="x1724"></a> uchar *p = image.<a href="qimage.html#scanLine">scanLine</a>(y);
for ( int x=0; x<w; x++ )
*p++ = (x+y)%128;
}
<a href="qpixmap.html">QPixmap</a> pm;
pm = image; // convert image to pixmap
<a name="x1740"></a> pm.<a href="qpixmap.html#setOptimization">setOptimization</a>( QPixmap::BestOptim ); // rotation will be faster
<a href="qwidget.html">QWidget</a> *d = QApplication::<a href="qapplication.html#desktop">desktop</a>(); // w = desktop widget
for ( i=0; i<=360; i += 2 ) {
<a href="qwmatrix.html">QWMatrix</a> m;
<a name="x1759"></a> m.<a href="qwmatrix.html#rotate">rotate</a>( i ); // rotate coordinate system
<a name="x1742"></a> <a href="qpixmap.html">QPixmap</a> rpm = pm.<a href="qpixmap.html#xForm">xForm</a>( m ); // rpm = rotated pixmap
<a name="x1757"></a> d-><a href="qwidget.html#setBackgroundPixmap">setBackgroundPixmap</a>( rpm ); // set desktop pixmap
<a name="x1758"></a> d-><a href="qwidget.html#update">update</a>(); // repaint desktop
}
}
//
// Generates a marble-like pattern in pm.
//
void generateStone( <a href="qpixmap.html">QPixmap</a> *pm,
const <a href="qcolor.html">QColor</a> &c1, const <a href="qcolor.html">QColor</a> &c2, const <a href="qcolor.html">QColor</a> &c3 )
{
<a href="qpainter.html">QPainter</a> p;
<a href="qpen.html">QPen</a> p1 ( c1, 0 );
<a href="qpen.html">QPen</a> p2 ( c2, 0 );
<a href="qpen.html">QPen</a> p3 ( c3, 0 );
p.<a href="qpainter.html#begin">begin</a>( pm );
<a name="x1741"></a> for( int i = 0 ; i < pm-><a href="qpixmap.html#width">width</a>() ; i++ )
<a name="x1738"></a> for( int j = 0 ; j < pm-><a href="qpixmap.html#height">height</a>() ; j++ ) {
int r = kindaRand();
if ( r < KINDA_RAND_MAX / 3 )
<a name="x1736"></a> p.<a href="qpainter.html#setPen">setPen</a>( p1 );
else if ( r < KINDA_RAND_MAX / 3 * 2 )
p.<a href="qpainter.html#setPen">setPen</a>( p2 );
else
p.<a href="qpainter.html#setPen">setPen</a>( p3 );
<a name="x1729"></a> p.<a href="qpainter.html#drawPoint">drawPoint</a>( i,j );
}
p.<a href="qpainter.html#end">end</a>();
}
void drawShadeText( <a href="qpainter.html">QPainter</a> *p, int x, int y, const char *text,
const <a href="qcolor.html">QColor</a> &topColor, const <a href="qcolor.html">QColor</a> &bottomColor,
int sw = 2 )
{
<a name="x1734"></a> if ( !p-><a href="qpainter.html#isActive">isActive</a>() )
return;
p-><a href="qpainter.html#setPen">setPen</a>( bottomColor );
<a name="x1731"></a> p-><a href="qpainter.html#drawText">drawText</a>( x+sw, y+sw, text );
p-><a href="qpainter.html#setPen">setPen</a>( topColor );
p-><a href="qpainter.html#drawText">drawText</a>( x, y, text );
}
// NOTE: desktop drag/drop is experimental
class DesktopWidget : public <a href="qwidget.html">QWidget</a>, private QDropSite
{
public:
DesktopWidget( const char *s, QWidget *parent=0, const char *name=0 );
~DesktopWidget();
void paintEvent( <a href="qpaintevent.html">QPaintEvent</a> * );
void dragEnterEvent( <a href="qdragenterevent.html">QDragEnterEvent</a> *e )
{
<a name="x1726"></a> if ( QImageDrag::<a href="qimagedrag.html#canDecode">canDecode</a>(e) )
<a name="x1722"></a> e-><a href="qdragmoveevent.html#accept">accept</a>();
}
void dragLeaveEvent( <a href="qdragleaveevent.html">QDragLeaveEvent</a> * )
{
}
void dragMoveEvent( <a href="qdragmoveevent.html">QDragMoveEvent</a> *e )
{
e-><a href="qdragmoveevent.html#accept">accept</a>();
}
void dropEvent( <a href="qdropevent.html">QDropEvent</a> * e )
{
<a href="qpixmap.html">QPixmap</a> pmp;
<a name="x1727"></a> if ( QImageDrag::<a href="qimagedrag.html#decode">decode</a>( e, pmp ) ) {
<a href="qwidget.html#setBackgroundPixmap">setBackgroundPixmap</a>( pmp );
<a href="qwidget.html#update">update</a>();
}
}
private:
<a href="qpixmap.html">QPixmap</a> *pm;
<a href="qstring.html">QString</a> text;
};
<a name="f482"></a>DesktopWidget::DesktopWidget( const char *s, QWidget *parent, const char *name )
: <a href="qwidget.html">QWidget</a>( parent, name, WType_Desktop | WPaintDesktop),
QDropSite(this)
{
text = s;
pm = 0;
}
DesktopWidget::~DesktopWidget()
{
delete pm;
}
void DesktopWidget::<a href="qwidget.html#paintEvent">paintEvent</a>( <a href="qpaintevent.html">QPaintEvent</a> * )
{
<a href="qcolor.html">QColor</a> c1 = <a href="qwidget.html#backgroundColor">backgroundColor</a>();
<a name="x1721"></a> <a href="qcolor.html">QColor</a> c2 = c1.<a href="qcolor.html#light">light</a>(104);
<a name="x1720"></a> <a href="qcolor.html">QColor</a> c3 = c1.<a href="qcolor.html#dark">dark</a>(106);
if ( !pm ) {
pm = new <a href="qpixmap.html">QPixmap</a>( 64, 64 );
generateStone( pm, c1, c2, c3 );
<a href="qwidget.html#setBackgroundPixmap">setBackgroundPixmap</a>( *pm );
<a href="qwidget.html#update">update</a>();
}
<a href="qrect.html">QRect</a> br = <a href="qwidget.html#fontMetrics">fontMetrics</a>().boundingRect( text );
<a href="qpixmap.html">QPixmap</a> offscreen( br.<a href="qrect.html#width">width</a>(), br.<a href="qrect.html#height">height</a>() );
int x = <a href="qwidget.html#width">width</a>()/2 - br.<a href="qrect.html#width">width</a>()/2;
int y = <a href="qwidget.html#height">height</a>()/2 - br.<a href="qrect.html#height">height</a>()/2;
<a name="x1737"></a> offscreen.<a href="qpixmap.html#fill">fill</a>( this, x, y );
<a href="qpainter.html">QPainter</a> p;
p.<a href="qpainter.html#begin">begin</a>( &offscreen );
<a name="x1753"></a><a name="x1752"></a> drawShadeText( &p, -br.<a href="qrect.html#x">x</a>(), -br.<a href="qrect.html#y">y</a>(), text, c2, c3, 3 );
p.<a href="qpainter.html#end">end</a>();
<a href="qpaintdevice.html#bitBlt-2">bitBlt</a>( this, x, y, &offscreen );
}
void desktopWidget( const char *s = "Trolltech" )
{
DesktopWidget *t = new DesktopWidget(s);
t-><a href="qwidget.html#update">update</a>();
qApp-><a href="qapplication.html#exec">exec</a>();
delete t;
}
void desktopText( const char *s = "Trolltech" )
{
const int border = 20;
<a name="x1718"></a> <a href="qcolor.html">QColor</a> c1 = qApp-><a href="qapplication.html#palette">palette</a>().inactive().background();
<a href="qcolor.html">QColor</a> c2 = c1.<a href="qcolor.html#light">light</a>(104);
<a href="qcolor.html">QColor</a> c3 = c1.<a href="qcolor.html#dark">dark</a>(106);
<a href="qpixmap.html">QPixmap</a> pm(10,10);
<a href="qpainter.html">QPainter</a> p;
p.<a href="qpainter.html#begin">begin</a>( &pm );
<a name="x1733"></a> <a href="qrect.html">QRect</a> r = p.<a href="qpainter.html#fontMetrics">fontMetrics</a>().boundingRect( s );
p.<a href="qpainter.html#end">end</a>();
int appWidth = qApp-><a href="qapplication.html#desktop">desktop</a>()->width();
int appHeight = qApp-><a href="qapplication.html#desktop">desktop</a>()->height();
if ( r.<a href="qrect.html#width">width</a>() > appWidth - border*2 )
<a name="x1748"></a> r.<a href="qrect.html#setWidth">setWidth</a>( appWidth - border*2 );
if ( r.<a href="qrect.html#height">height</a>() > appHeight - border*2 )
<a name="x1747"></a> r.<a href="qrect.html#setHeight">setHeight</a>( appHeight - border*2 );
<a name="x1749"></a><a name="x1739"></a> pm.<a href="qpixmap.html#resize">resize</a>( r.<a href="qrect.html#size">size</a>() + QSize( border*2, border*2 ) );
generateStone( &pm, c1, c2, c3 );
p.<a href="qpainter.html#begin">begin</a>( &pm );
drawShadeText( &p, -r.<a href="qrect.html#x">x</a>() + border, -r.<a href="qrect.html#y">y</a>() + border, s, c2, c3 );
p.<a href="qpainter.html#end">end</a>();
qApp-><a href="qapplication.html#desktop">desktop</a>()->setBackgroundPixmap( pm );
}
//
// The program starts here.
//
int main( int argc, char **argv )
{
<a href="qapplication.html">QApplication</a> app( argc, argv );
if ( argc > 1 ) {
<a href="qfont.html">QFont</a> f( "charter", 96, QFont::Black );
<a name="x1723"></a> f.<a href="qfont.html#setStyleHint">setStyleHint</a>( QFont::Times );
<a name="x1719"></a> app.<a href="qapplication.html#setFont">setFont</a>( 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;
}
</pre>
<p>See also <a href="examples.html">Examples</a>.
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<td>Copyright © 2001
<a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
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