Qt Reference Documentation

- Qt 4.8
- ALL VERSIONS

- A
- A
- A
- Print

# canvas.cpp Example File

graphicsview/portedcanvas/canvas.cpp

     /****************************************************************************
     **
     ** Copyright (C) 2015 The Qt Company Ltd.
     ** Contact: http://www.qt.io/licensing/
     **
     ** 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 The Qt Company Ltd 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);
     }