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# graphwidget.cpp Example File
graphicsview/elasticnodes/graphwidget.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2006-2006 Trolltech ASA. All rights reserved.
    **
    ** This file is part of the example classes of the Qt Toolkit.
    **
    ** Licensees holding valid Qt Preview licenses may use this file in
    ** accordance with the Qt Preview License Agreement provided with the
    ** Software.
    **
    ** See http://www.trolltech.com/pricing.html or email sales@trolltech.com for
    ** information about Qt Commercial License Agreements.
    **
    ** Contact info@trolltech.com if any conditions of this licensing are
    ** not clear to you.
    **
    ** 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 "graphwidget.h"
    #include "edge.h"
    #include "node.h"

    #include <QDebug>
    #include <QGraphicsScene>
    #include <QWheelEvent>

    #include <math.h>

    GraphWidget::GraphWidget()
        : timerId(0)
    {
        QGraphicsScene *scene = new QGraphicsScene(this);
        scene->setItemIndexMethod(QGraphicsScene::NoIndex);
        scene->setSceneRect(-200, -200, 400, 400);
        setScene(scene);
        setCacheMode(CacheBackground);
        setRenderHint(QPainter::Antialiasing);
        setTransformationAnchor(AnchorUnderMouse);
        setResizeAnchor(AnchorViewCenter);

        Node *node1 = new Node(this);
        Node *node2 = new Node(this);
        Node *node3 = new Node(this);
        Node *node4 = new Node(this);
        centerNode = new Node(this);
        Node *node6 = new Node(this);
        Node *node7 = new Node(this);
        Node *node8 = new Node(this);
        Node *node9 = new Node(this);
        scene->addItem(node1);
        scene->addItem(node2);
        scene->addItem(node3);
        scene->addItem(node4);
        scene->addItem(centerNode);
        scene->addItem(node6);
        scene->addItem(node7);
        scene->addItem(node8);
        scene->addItem(node9);
        scene->addItem(new Edge(node1, node2));
        scene->addItem(new Edge(node2, node3));
        scene->addItem(new Edge(node2, centerNode));
        scene->addItem(new Edge(node3, node6));
        scene->addItem(new Edge(node4, node1));
        scene->addItem(new Edge(node4, centerNode));
        scene->addItem(new Edge(centerNode, node6));
        scene->addItem(new Edge(centerNode, node8));
        scene->addItem(new Edge(node6, node9));
        scene->addItem(new Edge(node7, node4));
        scene->addItem(new Edge(node8, node7));
        scene->addItem(new Edge(node9, node8));

        node1->setPos(-50, -50);
        node2->setPos(0, -50);
        node3->setPos(50, -50);
        node4->setPos(-50, 0);
        centerNode->setPos(0, 0);
        node6->setPos(50, 0);
        node7->setPos(-50, 50);
        node8->setPos(0, 50);
        node9->setPos(50, 50);

        scale(0.8, 0.8);
        setMinimumSize(400, 400);
        setWindowTitle(tr("Elastic Nodes"));
    }

    void GraphWidget::itemMoved()
    {
        if (!timerId)
            timerId = startTimer(1000 / 25);
    }

    void GraphWidget::keyPressEvent(QKeyEvent *event)
    {
        switch (event->key()) {
        case Qt::Key_Up:
            centerNode->moveBy(0, -20);
            break;
        case Qt::Key_Down:
            centerNode->moveBy(0, 20);
            break;
        case Qt::Key_Left:
            centerNode->moveBy(-20, 0);
            break;
        case Qt::Key_Right:
            centerNode->moveBy(20, 0);
            break;
        case Qt::Key_Plus:
            scaleView(1.2);
            break;
        case Qt::Key_Minus:
            scaleView(1 / 1.2);
            break;
        case Qt::Key_Space:
        case Qt::Key_Enter:
            foreach (QGraphicsItem *item, scene()->items()) {
                if (qgraphicsitem_cast<Node *>(item))
                    item->setPos(-150 + qrand() % 300, -150 + qrand() % 300);
            }
            break;
        default:
            QGraphicsView::keyPressEvent(event);
        }
    }

    void GraphWidget::timerEvent(QTimerEvent *event)
    {
        Q_UNUSED(event);

        QList<Node *> nodes;
        foreach (QGraphicsItem *item, scene()->items()) {
            if (Node *node = qgraphicsitem_cast<Node *>(item))
                nodes << node;
        }

        foreach (Node *node, nodes)
            node->calculateForces();

        bool itemsMoved = false;
        foreach (Node *node, nodes) {
            if (node->advance())
                itemsMoved = true;
        }

        if (!itemsMoved) {
            killTimer(timerId);
            timerId = 0;
        }
    }

    void GraphWidget::wheelEvent(QWheelEvent *event)
    {
        scaleView(pow((double)2, -event->delta() / 240.0));
    }

    void GraphWidget::drawBackground(QPainter *painter, const QRectF &rect)
    {
        Q_UNUSED(rect);

        // Shadow
        QRectF sceneRect = this->sceneRect();
        QRectF rightShadow(sceneRect.right(), sceneRect.top() + 5, 5, sceneRect.height());
        QRectF bottomShadow(sceneRect.left() + 5, sceneRect.bottom(), sceneRect.width(), 5);
        if (rightShadow.intersects(rect) || rightShadow.contains(rect))
            painter->fillRect(rightShadow, Qt::darkGray);
        if (bottomShadow.intersects(rect) || bottomShadow.contains(rect))
            painter->fillRect(bottomShadow, Qt::darkGray);

        // Fill
        QLinearGradient gradient(sceneRect.topLeft(), sceneRect.bottomRight());
        gradient.setColorAt(0, Qt::white);
        gradient.setColorAt(1, Qt::lightGray);
        painter->fillRect(rect.intersect(sceneRect), gradient);
        painter->setBrush(Qt::NoBrush);
        painter->drawRect(sceneRect);

        // Text
        QRectF textRect(sceneRect.left() + 4, sceneRect.top() + 4,
                        sceneRect.width() - 4, sceneRect.height() - 4);
        QString message(tr("Click and drag the nodes around, and zoom with the mouse "
                           "wheel or the '+' and '-' keys"));

        QFont font = painter->font();
        font.setBold(true);
        font.setPointSize(14);
        painter->setFont(font);
        painter->setPen(Qt::lightGray);
        painter->drawText(textRect.translated(2, 2), message);
        painter->setPen(Qt::black);
        painter->drawText(textRect, message);
    }

    void GraphWidget::scaleView(qreal scaleFactor)
    {
        qreal factor = matrix().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width();
        if (factor < 0.07 || factor > 100)
            return;

        scale(scaleFactor, scaleFactor);
    }