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<td align="right" valign="top" width="230"><a href="http://www.trolltech.com"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></a></td></tr></table><h1 align="center">node.cpp Example File<br /><sup><sup>graphicsview/elasticnodes/node.cpp</sup></sup></h1>

<pre> /****************************************************************************

** This file is part of the example classes of the Qt Toolkit.

** This file may be used under the terms of the GNU General Public

** License version 2.0 as published by the Free Software Foundation

** and appearing in the file LICENSE.GPL included in the packaging of

** this file. Please review the following information to ensure GNU

** General Public Licensing requirements will be met:

** http:<span class="comment">//www.trolltech.com/products/qt/opensource.html</span>

** If you are unsure which license is appropriate for your use, please

** review the following information:

** http:<span class="comment">//www.trolltech.com/products/qt/licensing.html or contact the</span>

** sales department at sales@trolltech.com.

** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE

** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

****************************************************************************/

#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);

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;

}

<span class="comment">// Sum up all forces pushing this item away</span>

qreal xvel = 0;

qreal yvel = 0;

foreach (QGraphicsItem *item, scene()->items()) {

Node *node = qgraphicsitem_cast<Node *>(item);

if (!node)

continue;

QLineF line(mapFromItem(node, 0, 0), QPointF(0, 0));

qreal dx = line.dx();

qreal dy = line.dy();

double l = 2.0 * (dx * dx + dy * dy);

if (l > 0) {

xvel += (dx * 150.0) / l;

yvel += (dy * 150.0) / l;

}

<span class="comment">// Now subtract all forces pulling items together</span>

double weight = (edgeList.size() + 1) * 10;

foreach (Edge *edge, edgeList) {

QPointF pos;

if (edge->sourceNode() == this)

pos = mapFromItem(edge->destNode(), 0, 0);

else

pos = mapFromItem(edge->sourceNode(), 0, 0);

xvel += pos.x() / weight;

yvel += pos.y() / weight;

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}

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if (qAbs(xvel) < 0.1 && qAbs(yvel) < 0.1)

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xvel = yvel = 0;

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QRectF sceneRect = scene()->sceneRect();

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newPos = pos() + QPointF(xvel, yvel);

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newPos.setX(qMin(qMax(newPos.x(), sceneRect.left() + 10), sceneRect.right() - 10));

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newPos.setY(qMin(qMax(newPos.y(), sceneRect.top() + 10), sceneRect.bottom() - 10));

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}

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bool Node::advance()

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{

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if (newPos == pos())

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return false;

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setPos(newPos);

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return true;

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}

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QRectF Node::boundingRect() const

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{

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qreal adjust = 2;

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return QRectF(-10 - adjust, -10 - adjust,

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23 + adjust, 23 + adjust);

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}

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QPainterPath Node::shape() const

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{

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QPainterPath path;

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path.addEllipse(-10, -10, 20, 20);

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return path;

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}

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void Node::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)

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{

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painter->setPen(Qt::NoPen);

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painter->setBrush(Qt::darkGray);

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painter->drawEllipse(-7, -7, 20, 20);

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QRadialGradient gradient(-3, -3, 10);

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if (option->state & QStyle::State_Sunken) {

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gradient.setCenter(3, 3);

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gradient.setFocalPoint(3, 3);

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gradient.setColorAt(1, QColor(Qt::yellow).light(120));

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gradient.setColorAt(0, QColor(Qt::darkYellow).light(120));

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} else {

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gradient.setColorAt(0, Qt::yellow);

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gradient.setColorAt(1, Qt::darkYellow);

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}

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painter->setBrush(gradient);

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painter->setPen(QPen(Qt::black, 0));

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painter->drawEllipse(-10, -10, 20, 20);

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}

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QVariant Node::itemChange(GraphicsItemChange change, const QVariant &value)

156

{

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switch (change) {

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case ItemPositionChange:

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foreach (Edge *edge, edgeList)

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edge->adjust();

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graph->itemMoved();

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break;

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default:

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break;

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};

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return QGraphicsItem::itemChange(change, value);

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}

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void Node::mousePressEvent(QGraphicsSceneMouseEvent *event)

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{

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update();

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QGraphicsItem::mousePressEvent(event);

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}

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void Node::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)

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{

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update();

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QGraphicsItem::mouseReleaseEvent(event);

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}</pre>

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