node.cpp Example File

 /****************************************************************************
 **
 ** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** 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 Digia Plc 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 <QGraphicsScene>
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 #include <QStyleOption>

 #include "edge.h"
 #include "node.h"
 #include "graphwidget.h"

 Node::Node(GraphWidget *graphWidget)
     : graph(graphWidget)
 {
     setFlag(ItemIsMovable);
     setFlag(ItemSendsGeometryChanges);
     setCacheMode(DeviceCoordinateCache);
     setZValue(-1);
 }

 void Node::addEdge(Edge *edge)
 {
     edgeList << edge;
     edge->adjust();
 }

 QList<Edge *> Node::edges() const
 {
     return edgeList;
 }

 void Node::calculateForces()
 {
     if (!scene() || scene()->mouseGrabberItem() == this) {
         newPos = pos();
         return;
     }

     // Sum up all forces pushing this item away
     qreal xvel = 0;
     qreal yvel = 0;
     foreach (QGraphicsItem *item, scene()->items()) {
         Node *node = qgraphicsitem_cast<Node *>(item);
         if (!node)
             continue;

         QPointF vec = mapToItem(node, 0, 0);
         qreal dx = vec.x();
         qreal dy = vec.y();
         double l = 2.0 * (dx * dx + dy * dy);
         if (l > 0) {
             xvel += (dx * 150.0) / l;
             yvel += (dy * 150.0) / l;
         }
     }

     // Now subtract all forces pulling items together
     double weight = (edgeList.size() + 1) * 10;
     foreach (Edge *edge, edgeList) {
         QPointF vec;
         if (edge->sourceNode() == this)
             vec = mapToItem(edge->destNode(), 0, 0);
         else
             vec = mapToItem(edge->sourceNode(), 0, 0);
         xvel -= vec.x() / weight;
         yvel -= vec.y() / weight;
     }

     if (qAbs(xvel) < 0.1 && qAbs(yvel) < 0.1)
         xvel = yvel = 0;

     QRectF sceneRect = scene()->sceneRect();
     newPos = pos() + QPointF(xvel, yvel);
     newPos.setX(qMin(qMax(newPos.x(), sceneRect.left() + 10), sceneRect.right() - 10));
     newPos.setY(qMin(qMax(newPos.y(), sceneRect.top() + 10), sceneRect.bottom() - 10));
 }

 bool Node::advance()
 {
     if (newPos == pos())
         return false;

     setPos(newPos);
     return true;
 }

 QRectF Node::boundingRect() const
 {
 #if defined(Q_OS_SYMBIAN) || defined(Q_WS_MAEMO_5)
     // Add some extra space around the circle for easier touching with finger
     qreal adjust = 30;
     return QRectF( -10 - adjust, -10 - adjust,
                   20 + adjust * 2, 20 + adjust * 2);
 #else
     qreal adjust = 2;
     return QRectF( -10 - adjust, -10 - adjust,
                   23 + adjust, 23 + adjust);
 #endif
 }

 QPainterPath Node::shape() const
 {
     QPainterPath path;
 #if defined(Q_OS_SYMBIAN) || defined(Q_WS_MAEMO_5)
     // Add some extra space around the circle for easier touching with finger
     path.addEllipse( -40, -40, 80, 80);
 #else
     path.addEllipse(-10, -10, 20, 20);
 #endif
     return path;
 }

 void Node::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
 {
     painter->setPen(Qt::NoPen);
     painter->setBrush(Qt::darkGray);
     painter->drawEllipse(-7, -7, 20, 20);

     QRadialGradient gradient(-3, -3, 10);
     if (option->state & QStyle::State_Sunken) {
         gradient.setCenter(3, 3);
         gradient.setFocalPoint(3, 3);
         gradient.setColorAt(1, QColor(Qt::yellow).light(120));
         gradient.setColorAt(0, QColor(Qt::darkYellow).light(120));
     } else {
         gradient.setColorAt(0, Qt::yellow);
         gradient.setColorAt(1, Qt::darkYellow);
     }
     painter->setBrush(gradient);

     painter->setPen(QPen(Qt::black, 0));
     painter->drawEllipse(-10, -10, 20, 20);
 }

 QVariant Node::itemChange(GraphicsItemChange change, const QVariant &value)
 {
     switch (change) {
     case ItemPositionHasChanged:
         foreach (Edge *edge, edgeList)
             edge->adjust();
         graph->itemMoved();
         break;
     default:
         break;
     };

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

 void Node::mousePressEvent(QGraphicsSceneMouseEvent *event)
 {
     update();
     QGraphicsItem::mousePressEvent(event);
 }

 void Node::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 {
     update();
     QGraphicsItem::mouseReleaseEvent(event);
 }