Qt visualization of graph, from the Elastic Nodes Example

lib/qtgraph/CMakeLists.txt

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+cmake_minimum_required (VERSION 2.6)
+project (PROJECT_QGRAPH)
+
+set (CXX_FLAGS "-Wall -Wextra -pedantic -Wshadow "
+               "-Wpointer-arith -Wcast-qual "
+               "-ggdb "
+               "--std=c++0x " )
+
+add_definitions( ${CXX_FLAGS} )
+
+FIND_PACKAGE(Qt4 REQUIRED)
+INCLUDE(${QT_USE_FILE})
+QT4_WRAP_CPP(qtgraph_HEADERS_MOC node.hpp edge.hpp graphwidget.hpp)
+
+add_executable ( qtgraph main.cpp edge.cpp node.cpp graphwidget.cpp ${qtgraph_HEADERS_MOC} )
+target_link_libraries ( qtgraph ${QT_LIBRARIES} )

lib/qtgraph/edge.cpp

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+#include "edge.hpp"
+#include "node.hpp"
+
+#include <QtGui/QPainter>
+
+#include <math.h>
+
+static const double Pi = 3.14159265358979323846264338327950288419717;
+static double TwoPi = 2.0 * Pi;
+
+Edge::Edge(Node *sourceNode, Node *destNode)
+    : arrowSize(10)
+{
+    setAcceptedMouseButtons(0);
+    source = sourceNode;
+    dest = destNode;
+    source->addEdge(this);
+    dest->addEdge(this);
+    adjust();
+}
+
+Node *Edge::sourceNode() const
+{
+    return source;
+}
+
+Node *Edge::destNode() const
+{
+    return dest;
+}
+
+void Edge::adjust()
+{
+    if (!source || !dest)
+        return;
+
+    QLineF line(mapFromItem(source, 0, 0), mapFromItem(dest, 0, 0));
+    qreal length = line.length();
+
+    prepareGeometryChange();
+
+    if (length > qreal(20.)) {
+        QPointF edgeOffset((line.dx() * 10) / length, (line.dy() * 10) / length);
+        sourcePoint = line.p1() + edgeOffset;
+        destPoint = line.p2() - edgeOffset;
+    } else {
+        sourcePoint = destPoint = line.p1();
+    }
+}
+
+QRectF Edge::boundingRect() const
+{
+    if (!source || !dest)
+        return QRectF();
+
+    qreal penWidth = 1;
+    qreal extra = (penWidth + arrowSize) / 2.0;
+
+    return QRectF(sourcePoint, QSizeF(destPoint.x() - sourcePoint.x(),
+                                      destPoint.y() - sourcePoint.y()))
+        .normalized()
+        .adjusted(-extra, -extra, extra, extra);
+}
+
+void Edge::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
+{
+    if (!source || !dest)
+        return;
+
+    QLineF line(sourcePoint, destPoint);
+    if (qFuzzyCompare(line.length(), qreal(0.)))
+        return;
+
+    // Draw the line itself
+    painter->setPen(QPen(Qt::black, 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
+    painter->drawLine(line);
+
+    // Draw the arrows
+    double angle = ::acos(line.dx() / line.length());
+    if (line.dy() >= 0)
+        angle = TwoPi - angle;
+
+    QPointF sourceArrowP1 = sourcePoint + QPointF(sin(angle + Pi / 3) * arrowSize,
+                                                  cos(angle + Pi / 3) * arrowSize);
+    QPointF sourceArrowP2 = sourcePoint + QPointF(sin(angle + Pi - Pi / 3) * arrowSize,
+                                                  cos(angle + Pi - Pi / 3) * arrowSize);
+    QPointF destArrowP1 = destPoint + QPointF(sin(angle - Pi / 3) * arrowSize,
+                                              cos(angle - Pi / 3) * arrowSize);
+    QPointF destArrowP2 = destPoint + QPointF(sin(angle - Pi + Pi / 3) * arrowSize,
+                                              cos(angle - Pi + Pi / 3) * arrowSize);
+
+    painter->setBrush(Qt::black);
+    painter->drawPolygon(QPolygonF() << line.p1() << sourceArrowP1 << sourceArrowP2);
+    painter->drawPolygon(QPolygonF() << line.p2() << destArrowP1 << destArrowP2);
+}

lib/qtgraph/edge.hpp

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+#ifndef EDGE_H
+#define EDGE_H
+
+#include <QtGui/QGraphicsItem>
+
+class Node;
+
+class Edge : public QGraphicsItem
+{
+public:
+    Edge(Node *sourceNode, Node *destNode);
+
+    Node *sourceNode() const;
+    Node *destNode() const;
+
+    void adjust();
+
+    enum { Type = UserType + 2 };
+    int type() const { return Type; }
+
+protected:
+    QRectF boundingRect() const;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+
+private:
+    Node *source, *dest;
+
+    QPointF sourcePoint;
+    QPointF destPoint;
+    qreal arrowSize;
+};
+
+#endif

lib/qtgraph/graphwidget.cpp

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+#include "graphwidget.hpp"
+
+#include "edge.hpp"
+#include "node.hpp"
+
+#include <QtGui>
+
+#include <math.h>
+
+GraphWidget::GraphWidget(QWidget *parent)
+    : QGraphicsView(parent), timerId(0)
+{
+    QGraphicsScene *scene = new QGraphicsScene(this);
+    scene->setItemIndexMethod(QGraphicsScene::NoIndex);
+    scene->setSceneRect(-200, -200, 400, 400);
+    setScene(scene);
+    setCacheMode(CacheBackground);
+    setViewportUpdateMode(BoundingRectViewportUpdate);
+    setRenderHint(QPainter::Antialiasing);
+    setTransformationAnchor(AnchorUnderMouse);
+    scale(qreal(0.8), qreal(0.8));
+    setMinimumSize(400, 400);
+    setWindowTitle(tr("Elastic Nodes"));
+
+    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);
+}
+
+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:
+        zoomIn();
+        break;
+    case Qt::Key_Minus:
+        zoomOut();
+        break;
+    case Qt::Key_Space:
+    case Qt::Key_Enter:
+        shuffle();
+        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 = transform().scale(scaleFactor, scaleFactor).mapRect(QRectF(0, 0, 1, 1)).width();
+    if (factor < 0.07 || factor > 100)
+        return;
+
+    scale(scaleFactor, scaleFactor);
+}
+
+void GraphWidget::shuffle()
+{
+    foreach (QGraphicsItem *item, scene()->items()) {
+        if (qgraphicsitem_cast<Node *>(item))
+            item->setPos(-150 + qrand() % 300, -150 + qrand() % 300);
+    }
+}
+
+void GraphWidget::zoomIn()
+{
+    scaleView(qreal(1.2));
+}
+
+void GraphWidget::zoomOut()
+{
+    scaleView(1 / qreal(1.2));
+}

lib/qtgraph/graphwidget.hpp

@@ -0,0 +1,35 @@
+#ifndef GRAPHWIDGET_H
+#define GRAPHWIDGET_H
+
+#include <QtGui/QGraphicsView>
+
+class Node;
+
+class GraphWidget : public QGraphicsView
+{
+  Q_OBJECT
+
+public:
+  GraphWidget(QWidget *parent = 0);
+
+  void itemMoved();
+
+public slots:
+  void shuffle();
+  void zoomIn();
+  void zoomOut();
+
+protected:
+  void keyPressEvent(QKeyEvent *event);
+  void timerEvent(QTimerEvent *event);
+  void wheelEvent(QWheelEvent *event);
+  void drawBackground(QPainter *painter, const QRectF &rect);
+
+  void scaleView(qreal scaleFactor);
+
+private:
+  int timerId;
+  Node *centerNode;
+};
+
+#endif

lib/qtgraph/main.cpp

@@ -0,0 +1,27 @@
+#include <QtGui/QApplication>
+#include <QtGui/QMainWindow>
+#include <QtGui/QMenuBar>
+
+#include <QtCore/QTime>
+
+
+#include "graphwidget.hpp"
+
+int main(int argc, char **argv)
+{
+  QApplication app(argc, argv);
+  qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
+
+  GraphWidget *widget = new GraphWidget;
+
+  QMainWindow mainWindow;
+  mainWindow.setCentralWidget(widget);
+
+
+  mainWindow.menuBar()->addAction("Shuffle", widget, SLOT(shuffle()));
+  mainWindow.menuBar()->addAction("Zoom In", widget, SLOT(zoomIn()));
+  mainWindow.menuBar()->addAction("Zoom Out", widget, SLOT(zoomOut()));
+
+  mainWindow.show();
+  return app.exec();
+}

lib/qtgraph/node.cpp

@@ -0,0 +1,147 @@
+#include "edge.hpp"
+#include "node.hpp"
+#include "graphwidget.hpp"
+
+#include <QtGui/QGraphicsScene>
+#include <QtGui/QGraphicsSceneMouseEvent>
+#include <QtGui/QPainter>
+#include <QtGui/QStyleOption>
+
+
+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
+{
+    qreal adjust = 2;
+    return QRectF( -10 - adjust, -10 - adjust,
+                  23 + adjust, 23 + adjust);
+}
+
+QPainterPath Node::shape() const
+{
+    QPainterPath path;
+    path.addEllipse(-10, -10, 20, 20);
+    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);
+}

lib/qtgraph/node.hpp

@@ -0,0 +1,41 @@
+#ifndef NODE_H
+#define NODE_H
+
+#include <QtGui/QGraphicsItem>
+#include <QtCore/QList>
+
+class Edge;
+class GraphWidget;
+class QGraphicsSceneMouseEvent;
+
+class Node : public QGraphicsItem
+{
+public:
+  Node(GraphWidget *graphWidget);
+
+  void addEdge(Edge *edge);
+  QList<Edge *> edges() const;
+
+  enum { Type = UserType + 1 };
+  int type() const { return Type; }
+
+  void calculateForces();
+  bool advance();
+
+  QRectF boundingRect() const;
+  QPainterPath shape() const;
+  void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+
+protected:
+  QVariant itemChange(GraphicsItemChange change, const QVariant &value);
+
+  void mousePressEvent(QGraphicsSceneMouseEvent *event);
+  void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
+
+private:
+  QList<Edge *> edgeList;
+  QPointF newPos;
+  GraphWidget *graph;
+};
+
+#endif