Qt 5.11 | Qt Widgets | Elastic Nodes Example | graphwidget.cpp Example File

Qt 5.11.3 Reference Documentation

# graphwidget.cpp Example File

graphicsview/elasticnodes/graphwidget.cpp

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

      #include <math.h>

      #include <QKeyEvent>
      #include <QRandomGenerator>

      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->advancePosition())
                  itemsMoved = true;
          }

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

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

      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.intersected(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 + QRandomGenerator::global()->bounded(300), -150 + QRandomGenerator::global()->bounded(300));
          }
      }

      void GraphWidget::zoomIn()
      {
          scaleView(qreal(1.2));
      }

      void GraphWidget::zoomOut()
      {
          scaleView(1 / qreal(1.2));
      }