canvas.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation (qt-info@nokia.com)
 **
 ** This file is part of the examples of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:BSD$
 ** You may use this file under the terms of the BSD license as follows:
 **
 ** "Redistribution and use in source and binary forms, with or without
 ** modification, are permitted provided that the following conditions are
 ** met:
 **   * Redistributions of source code must retain the above copyright
 **     notice, this list of conditions and the following disclaimer.
 **   * Redistributions in binary form must reproduce the above copyright
 **     notice, this list of conditions and the following disclaimer in
 **     the documentation and/or other materials provided with the
 **     distribution.
 **   * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
 **     the names of its contributors may be used to endorse or promote
 **     products derived from this software without specific prior written
 **     permission.
 **
 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #include <QDateTime>
 #include <QMainWindow>
 #include <QStatusBar>
 #include <QMessageBox>
 #include <QMenuBar>
 #include <QApplication>
 #include <QPainter>
 #include <QPrinter>
 #include <QPrintDialog>
 #include <QLabel>
 #include <QImage>
 #include <QProgressDialog>
 #include <QPixmap>
 #include <QMouseEvent>
 #include <QStyleOptionGraphicsItem>
 #include <QDebug>

 #include "canvas.h"

 // We use a global variable to save memory - all the brushes and pens in
 // the mesh are shared.
 static QBrush *tb = 0;
 static QPen *tp = 0;

 class EdgeItem;
 class NodeItem;

 class EdgeItem: public QGraphicsLineItem
 {
 public:
     EdgeItem( NodeItem*, NodeItem* );
     void setFromPoint( int x, int y ) ;
     void setToPoint( int x, int y );
     static int count() { return c; }
 private:
     static int c;
 };

 class ImageItem: public QGraphicsRectItem
 {
 public:
     ImageItem( QImage img );
 protected:
     void paint( QPainter *, const QStyleOptionGraphicsItem *option, QWidget *widget );
 private:
     QImage image;
     QPixmap pixmap;
 };

 ImageItem::ImageItem( QImage img )
     : image(img)
 {
     setRect(0, 0, image.width(), image.height());
     setFlag(ItemIsMovable);
 #if !defined(Q_WS_QWS)
     pixmap.fromImage(image, Qt::OrderedAlphaDither);
 #endif
 }

 void ImageItem::paint( QPainter *p, const QStyleOptionGraphicsItem *option, QWidget * )
 {
 // On Qt/Embedded, we can paint a QImage as fast as a QPixmap,
 // but on other platforms, we need to use a QPixmap.
 #if defined(Q_WS_QWS)
     p->drawImage( option->exposedRect, image, option->exposedRect, Qt::OrderedAlphaDither );
 #else
     p->drawPixmap( option->exposedRect, pixmap, option->exposedRect );
 #endif
 }

 class NodeItem: public QGraphicsEllipseItem
 {
 public:
     NodeItem();
     ~NodeItem() {}

     void addInEdge( EdgeItem *edge ) { inList.append( edge ); }
     void addOutEdge( EdgeItem *edge ) { outList.append( edge ); }

 protected:
     QVariant itemChange(GraphicsItemChange change, const QVariant &value);

     //    QPoint center() { return boundingRect().center(); }
 private:
     QList<EdgeItem*> inList;
     QList<EdgeItem*> outList;
 };

 int EdgeItem::c = 0;

 EdgeItem::EdgeItem( NodeItem *from, NodeItem *to )
     : QGraphicsLineItem( )
 {
     c++;
     setPen( *tp );
     from->addOutEdge( this );
     to->addInEdge( this );
     setLine( QLineF(int(from->x()), int(from->y()), int(to->x()), int(to->y()) ));
     setZValue( 127 );
     setBoundingRegionGranularity(0.05);
 }

 void EdgeItem::setFromPoint( int x, int y )
 {
     setLine(QLineF( x,y, line().p2().x(), line().p2().y() ));
 }

 void EdgeItem::setToPoint( int x, int y )
 {
     setLine(QLineF( line().p1().x(), line().p1().y(), x, y ));
 }

 QVariant NodeItem::itemChange(GraphicsItemChange change, const QVariant &value)
 {
     if (change == ItemPositionHasChanged) {
         EdgeItem *edge;
         foreach(edge, inList) {
             edge->setToPoint( int(x()), int(y()) );
         }

         foreach(edge, outList) {
             edge->setFromPoint( int(x()), int(y()) );
         }
     }

     return QGraphicsEllipseItem::itemChange(change, value);
 }

 NodeItem::NodeItem( )
     : QGraphicsEllipseItem( QRectF(-3, -3, 6, 6) )
 {
     setPen( *tp );
     setBrush( *tb );
     setZValue( 128 );
     setFlag(ItemIsMovable);
 }

 FigureEditor::FigureEditor(
         QGraphicsScene& c, QWidget* parent,
         const char* name, Qt::WindowFlags f) :
     QGraphicsView(&c,parent)
 {
     setObjectName(name);
     setWindowFlags(f);
     setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);
 }

 void FigureEditor::clear()
 {
     scene()->clear();
 }

 BouncyLogo::BouncyLogo() :
     xvel(0), yvel(0)
 {
     setPixmap(QPixmap(":/trolltech/examples/graphicsview/portedcanvas/qt-trans.xpm"));
 }

 const int logo_rtti = 1234;

 int BouncyLogo::type() const
 {
     return logo_rtti;
 }

 QPainterPath BouncyLogo::shape() const
 {
     QPainterPath path;
     path.addRect(boundingRect());
     return path;
 }

 void BouncyLogo::initPos()
 {
     initSpeed();
     int trial=1000;
     do {
         setPos(qrand()%int(scene()->width()),qrand()%int(scene()->height()));
         advance(0);
     } while (trial-- && xvel==0.0 && yvel==0.0);
 }

 void BouncyLogo::initSpeed()
 {
     const double speed = 4.0;
     double d = (double)(qrand()%1024) / 1024.0;
     xvel = d*speed*2-speed;
     yvel = (1-d)*speed*2-speed;
 }

 void BouncyLogo::advance(int stage)
 {
     switch ( stage ) {
       case 0: {
         double vx = xvel;
         double vy = yvel;

         if ( vx == 0.0 && vy == 0.0 ) {
             // stopped last turn
             initSpeed();
             vx = xvel;
             vy = yvel;
         }

         double nx = x() + vx;
         double ny = y() + vy;

         if ( nx < 0 || nx >= scene()->width() )
             vx = -vx;
         if ( ny < 0 || ny >= scene()->height() )
             vy = -vy;

         for (int bounce=0; bounce<4; bounce++) {
             QList<QGraphicsItem *> l=scene()->collidingItems(this);
             for (QList<QGraphicsItem *>::Iterator it=l.begin(); it!=l.end(); ++it) {
                 QGraphicsItem *hit = *it;
                 QPainterPath advancedShape = QMatrix().translate(xvel, yvel).map(shape());
                 if ( hit->type()==logo_rtti && hit->collidesWithPath(mapToItem(hit, advancedShape)) ) {
                     switch ( bounce ) {
                       case 0:
                         vx = -vx;
                         break;
                       case 1:
                         vy = -vy;
                         vx = -vx;
                         break;
                       case 2:
                         vx = -vx;
                         break;
                       case 3:
                         // Stop for this turn
                         vx = 0;
                         vy = 0;
                         break;
                     }
                     xvel = vx;
                     yvel = vy;
                     break;
                 }
             }
         }

         if ( x()+vx < 0 || x()+vx >= scene()->width() )
             vx = 0;
         if ( y()+vy < 0 || y()+vy >= scene()->height() )
             vy = 0;

         xvel = vx;
         yvel = vy;
       } break;
       case 1:
         moveBy(xvel, yvel);
         break;
     }
 }

 static uint mainCount = 0;
 static QImage *butterflyimg;
 static QImage *logoimg;

 Main::Main(QGraphicsScene& c, QWidget* parent, Qt::WindowFlags f) :
     QMainWindow(parent, f),
     canvas(c)
 {
     editor = new FigureEditor(canvas,this);

     QMenuBar* menu = menuBar();

     QMenu* file = new QMenu("&File", menu );
     file->addAction("&Fill canvas", this, SLOT(init()), Qt::CTRL+Qt::Key_F);
     file->addAction("&Erase canvas", this, SLOT(clear()), Qt::CTRL+Qt::Key_E);
     file->addAction("&New view", this, SLOT(newView()), Qt::CTRL+Qt::Key_N);
     file->addSeparator();
     file->addAction("&Print...", this, SLOT(print()), Qt::CTRL+Qt::Key_P);
     file->addSeparator();
     file->addAction("E&xit", qApp, SLOT(quit()), Qt::CTRL+Qt::Key_Q);
     menu->addMenu(file);

     QMenu* edit = new QMenu("&Edit", menu );
     edit->addAction("Add &Circle", this, SLOT(addCircle()), Qt::ALT+Qt::Key_C);
     edit->addAction("Add &Hexagon", this, SLOT(addHexagon()), Qt::ALT+Qt::Key_H);
     edit->addAction("Add &Polygon", this, SLOT(addPolygon()), Qt::ALT+Qt::Key_P);
     edit->addAction("Add Spl&ine", this, SLOT(addSpline()), Qt::ALT+Qt::Key_I);
     edit->addAction("Add &Text", this, SLOT(addText()), Qt::ALT+Qt::Key_T);
     edit->addAction("Add &Line", this, SLOT(addLine()), Qt::ALT+Qt::Key_L);
     edit->addAction("Add &Rectangle", this, SLOT(addRectangle()), Qt::ALT+Qt::Key_R);
     edit->addAction("Add &Sprite", this, SLOT(addSprite()), Qt::ALT+Qt::Key_S);
     edit->addAction("Create &Mesh", this, SLOT(addMesh()), Qt::ALT+Qt::Key_M );
     edit->addAction("Add &Alpha-blended image", this, SLOT(addButterfly()), Qt::ALT+Qt::Key_A);
     menu->addMenu(edit);

     QMenu* view = new QMenu("&View", menu );
     view->addAction("&Enlarge", this, SLOT(enlarge()), Qt::SHIFT+Qt::CTRL+Qt::Key_Plus);
     view->addAction("Shr&ink", this, SLOT(shrink()), Qt::SHIFT+Qt::CTRL+Qt::Key_Minus);
     view->addSeparator();
     view->addAction("&Rotate clockwise", this, SLOT(rotateClockwise()), Qt::CTRL+Qt::Key_PageDown);
     view->addAction("Rotate &counterclockwise", this, SLOT(rotateCounterClockwise()), Qt::CTRL+Qt::Key_PageUp);
     view->addAction("&Zoom in", this, SLOT(zoomIn()), Qt::CTRL+Qt::Key_Plus);
     view->addAction("Zoom &out", this, SLOT(zoomOut()), Qt::CTRL+Qt::Key_Minus);
     view->addAction("Translate left", this, SLOT(moveL()), Qt::CTRL+Qt::Key_Left);
     view->addAction("Translate right", this, SLOT(moveR()), Qt::CTRL+Qt::Key_Right);
     view->addAction("Translate up", this, SLOT(moveU()), Qt::CTRL+Qt::Key_Up);
     view->addAction("Translate down", this, SLOT(moveD()), Qt::CTRL+Qt::Key_Down);
     view->addAction("&Mirror", this, SLOT(mirror()), Qt::CTRL+Qt::Key_Home);
     menu->addMenu(view);

     menu->addSeparator();

     QMenu* help = new QMenu("&Help", menu );
     help->addAction("&About", this, SLOT(help()), Qt::Key_F1);
     menu->addMenu(help);

     statusBar();

     setCentralWidget(editor);

 #if !defined(Q_OS_SYMBIAN)
     printer = 0;
 #endif

     init();
 }

 void Main::init()
 {
     clear();

     static int r=24;
     qsrand(++r);

     mainCount++;
     butterflyimg = 0;
     logoimg = 0;

     int i;
     for ( i=0; i < int(canvas.width()) / 56; i++) {
         addButterfly();
     }
     for ( i=0; i < int(canvas.width()) / 85; i++) {
         addHexagon();
     }
     for ( i=0; i < int(canvas.width()) / 128; i++) {
         addLogo();
     }
 }

 Main::~Main()
 {
 #if !defined(Q_OS_SYMBIAN)
     delete printer;
 #endif
     if ( !--mainCount ) {
         delete[] butterflyimg;
         butterflyimg = 0;
         delete[] logoimg;
         logoimg = 0;
     }
 }

 void Main::newView()
 {
     // Open a new view... have it delete when closed.
     Main *m = new Main(canvas, 0); // AKr, Qt::WA_DeleteOnClose);
     m->show();
 }

 void Main::clear()
 {
     editor->clear();
 }

 void Main::help()
 {
     static QMessageBox* about = new QMessageBox( "Qt Canvas Example",
             "<h3>The QCanvas classes example</h3>"
             "<ul>"
                 "<li> Press ALT-S for some sprites."
                 "<li> Press ALT-C for some circles."
                 "<li> Press ALT-L for some lines."
                 "<li> Drag the objects around."
                 "<li> Read the code!"
             "</ul>", QMessageBox::Information, 1, 0, 0, this, 0);
     about->setButtonText( 1, "Dismiss" );
     about->show();
 }

 void Main::aboutQt()
 {
     QMessageBox::aboutQt( this, "Qt Canvas Example" );
 }

 void Main::enlarge()
 {
     canvas.setSceneRect(0, 0, canvas.width()*4/3, canvas.height()*4/3);
 }

 void Main::shrink()
 {
     canvas.setSceneRect(0, 0, qMax(canvas.width()*3/4, qreal(1.0)), qMax(canvas.height()*3/4, qreal(1.0)));
 }

 void Main::rotateClockwise()
 {
     editor->rotate( 22.5 );
 }

 void Main::rotateCounterClockwise()
 {
     editor->rotate( -22.5 );
 }

 void Main::zoomIn()
 {
     editor->scale( 2.0, 2.0 );
 }

 void Main::zoomOut()
 {
     editor->scale( 0.5, 0.5 );
 }

 void Main::mirror()
 {
     editor->scale( -1, 1 );
 }

 void Main::moveL()
 {
     editor->translate( -16, 0 );
 }

 void Main::moveR()
 {
     editor->translate( +16, 0 );
 }

 void Main::moveU()
 {
     editor->translate( 0, -16 );
 }

 void Main::moveD()
 {
     editor->translate( 0, +16 );
 }

 void Main::print()
 {
 #if !defined(Q_OS_SYMBIAN)
     if ( !printer ) printer = new QPrinter;
     QPrintDialog dialog(printer, this);
     if(dialog.exec()) {
         QPainter pp(printer);
         canvas.render(&pp);
     }
 #endif
 }

 void Main::addSprite()
 {
     BouncyLogo* i = new BouncyLogo;
     canvas.addItem(i);
     i->initPos();
     i->setZValue(qrand()%256);
 }

 QString butterfly_fn;
 QString logo_fn;

 void Main::addButterfly()
 {
     if ( butterfly_fn.isEmpty() )
         return;
     if ( !butterflyimg ) {
         butterflyimg = new QImage[4];
         butterflyimg[0].load( butterfly_fn );
         butterflyimg[1] = butterflyimg[0].scaled( int(butterflyimg[0].width()*0.75),
                 int(butterflyimg[0].height()*0.75), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
         butterflyimg[2] = butterflyimg[0].scaled( int(butterflyimg[0].width()*0.5),
                 int(butterflyimg[0].height()*0.5), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
         butterflyimg[3] = butterflyimg[0].scaled( int(butterflyimg[0].width()*0.25),
                 int(butterflyimg[0].height()*0.25), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
     }
     QAbstractGraphicsShapeItem* i = new ImageItem(butterflyimg[qrand()%4]);
     canvas.addItem(i);
     i->setPos(qrand()%int(canvas.width()-butterflyimg->width()),
             qrand()%int(canvas.height()-butterflyimg->height()));
     i->setZValue(qrand()%256+250);
 }

 void Main::addLogo()
 {
     if ( logo_fn.isEmpty() )
         return;
     if ( !logoimg ) {
         logoimg = new QImage[4];
         logoimg[0].load( logo_fn );
         logoimg[1] = logoimg[0].scaled( int(logoimg[0].width()*0.75),
                 int(logoimg[0].height()*0.75), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
         logoimg[2] = logoimg[0].scaled( int(logoimg[0].width()*0.5),
                 int(logoimg[0].height()*0.5), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
         logoimg[3] = logoimg[0].scaled( int(logoimg[0].width()*0.25),
                 int(logoimg[0].height()*0.25), Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
     }
     QAbstractGraphicsShapeItem* i = new ImageItem(logoimg[qrand()%4]);
     canvas.addItem(i);
     i->setPos(qrand()%int(canvas.width()-logoimg->width()),
             qrand()%int(canvas.height()-logoimg->width()));
     i->setZValue(qrand()%256+256);
 }

 void Main::addCircle()
 {
     QAbstractGraphicsShapeItem* i = canvas.addEllipse(QRectF(0,0,50,50));
     i->setFlag(QGraphicsItem::ItemIsMovable);
     i->setPen(Qt::NoPen);
     i->setBrush( QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8) );
     i->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
     i->setZValue(qrand()%256);
 }

 void Main::addHexagon()
 {
     const int size = int(canvas.width() / 25);
     QPolygon polygon;
     polygon << QPoint(2*size,0)
             << QPoint(size,-size*173/100)
             << QPoint(-size,-size*173/100)
             << QPoint(-2*size,0)
             << QPoint(-size,size*173/100)
             << QPoint(size,size*173/100);

     QGraphicsPolygonItem* i = canvas.addPolygon(polygon);
     i->setFlag(QGraphicsItem::ItemIsMovable);
     i->setPen(Qt::NoPen);
     i->setBrush( QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8) );
     i->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
     i->setZValue(qrand()%256);
 }

 void Main::addPolygon()
 {
     const int size = int(canvas.width()/2);
     QPolygon polygon;
     polygon << QPoint(0,0)
             << QPoint(size,size/5)
             << QPoint(size*4/5,size)
             << QPoint(size/6,size*5/4)
             << QPoint(size*3/4,size*3/4)
             << QPoint(size*3/4,size/4);

     QGraphicsPolygonItem* i = canvas.addPolygon(polygon);
     i->setFlag(QGraphicsItem::ItemIsMovable);
     i->setPen(Qt::NoPen);
     i->setBrush( QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8) );
     i->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
     i->setZValue(qrand()%256);
 }

 void Main::addSpline()
 {
     const int size = int(canvas.width()/6);

     QPolygon polygon;
     polygon << QPoint(0,0)
             << QPoint(size/2,0)
             << QPoint(size,size/2)
             << QPoint(size,size)
             << QPoint(size,size*3/2)
             << QPoint(size/2,size*2)
             << QPoint(0,size*2)
             << QPoint(-size/2,size*2)
             << QPoint(size/4,size*3/2)
             << QPoint(0,size)
             << QPoint(-size/4,size/2)
             << QPoint(-size/2,0);

     QPainterPath path;
     path.moveTo(polygon[0]);
     for (int i = 1; i < polygon.size(); i += 3)
         path.cubicTo(polygon[i], polygon[(i + 1) % polygon.size()], polygon[(i + 2) % polygon.size()]);

     QGraphicsPathItem* item = canvas.addPath(path);
     item->setFlag(QGraphicsItem::ItemIsMovable);
     item->setPen(Qt::NoPen);
     item->setBrush( QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8) );
     item->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
     item->setZValue(qrand()%256);
 }

 void Main::addText()
 {
     QGraphicsTextItem* i = canvas.addText("QCanvasText");
     i->setFlag(QGraphicsItem::ItemIsMovable);
     i->setPos(qrand()%int(canvas.width()),qrand()%int(canvas.height()));
     i->setZValue(qrand()%256);
 }

 void Main::addLine()
 {
     QGraphicsLineItem* i = canvas.addLine(QLineF( qrand()%int(canvas.width()), qrand()%int(canvas.height()),
                                                   qrand()%int(canvas.width()), qrand()%int(canvas.height()) ));
     i->setFlag(QGraphicsItem::ItemIsMovable);
     i->setPen( QPen(QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8), 6) );
     i->setZValue(qrand()%256);
 }

 void Main::addMesh()
 {
     int x0 = 0;
     int y0 = 0;

     if ( !tb ) tb = new QBrush( Qt::red );
     if ( !tp ) tp = new QPen( Qt::black );

     int nodecount = 0;

     int w = int(canvas.width());
     int h = int(canvas.height());

     const int dist = 30;
     int rows = h / dist;
     int cols = w / dist;

 #ifndef QT_NO_PROGRESSDIALOG
     QProgressDialog progress("Creating mesh...", "Abort", 0, rows, this);
 #endif

     canvas.update();

     QVector<NodeItem*> lastRow(cols);
     for ( int j = 0; j < rows; j++ ) {
         int n = j%2 ? cols-1 : cols;
         NodeItem *prev = 0;
         for ( int i = 0; i < n; i++ ) {
             NodeItem *el = new NodeItem;
             canvas.addItem(el);
             nodecount++;
             int r = qrand();
             int xrand = r %20;
             int yrand = (r/20) %20;
             el->setPos( xrand + x0 + i*dist + (j%2 ? dist/2 : 0 ),
                         yrand + y0 + j*dist );

             if ( j > 0 ) {
                 if ( i < cols-1 )
                     canvas.addItem(new EdgeItem( lastRow[i], el));
                 if ( j%2 )
                     canvas.addItem(new EdgeItem( lastRow[i+1], el));
                 else if ( i > 0 )
                     canvas.addItem(new EdgeItem( lastRow[i-1], el));
             }
             if ( prev ) {
                 canvas.addItem(new EdgeItem( prev, el));
             }
             if ( i > 0 ) lastRow[i-1] = prev;
             prev = el;
         }
         lastRow[n-1]=prev;
 #ifndef QT_NO_PROGRESSDIALOG
         progress.setValue( j );
         if ( progress.wasCanceled() )
             break;
 #endif
     }
 #ifndef QT_NO_PROGRESSDIALOG
     progress.setValue( rows );
 #endif
     // qDebug( "%d nodes, %d edges", nodecount, EdgeItem::count() );
 }

 void Main::addRectangle()
 {
     QAbstractGraphicsShapeItem *i = canvas.addRect( QRectF(qrand()%int(canvas.width()),
                                                           qrand()%int(canvas.height()),
                                                           canvas.width()/5,
                                                           canvas.width()/5) );
     i->setFlag(QGraphicsItem::ItemIsMovable);
     int z = qrand()%256;
     i->setBrush( QColor(z,z,z) );
     i->setPen( QPen(QColor(qrand()%32*8,qrand()%32*8,qrand()%32*8), 6) );
     i->setZValue(z);
 }