graph.cpp Example File | Qt Quick 5.12.8

Qt 5.12 | Qt Quick | Scene Graph - Graph | graph.cpp Example File

Qt 5.12.8 Reference Documentation

# graph.cpp Example File

scenegraph/graph/graph.cpp

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      #include "graph.h"

      #include "noisynode.h"
      #include "gridnode.h"
      #include "linenode.h"

      Graph::Graph()
          : m_samplesChanged(false)
          , m_geometryChanged(false)
      {
          setFlag(ItemHasContents, true);
      }

      void Graph::appendSample(qreal value)
      {
          m_samples << value;
          m_samplesChanged = true;
          update();
      }

      void Graph::removeFirstSample()
      {
          m_samples.removeFirst();
          m_samplesChanged = true;
          update();
      }

      void Graph::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
      {
          m_geometryChanged = true;
          update();
          QQuickItem::geometryChanged(newGeometry, oldGeometry);
      }

      class GraphNode : public QSGNode
      {
      public:
          NoisyNode *background;
          GridNode *grid;
          LineNode *line;
          LineNode *shadow;
      };

      QSGNode *Graph::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
      {
          GraphNode *n= static_cast<GraphNode *>(oldNode);

          QRectF rect = boundingRect();

          if (rect.isEmpty()) {
              delete n;
              return nullptr;
          }

          if (!n) {
              n = new GraphNode();

              n->background = new NoisyNode(window());
              n->grid = new GridNode();
              n->line = new LineNode(10, 0.5, QColor("steelblue"));
              n->shadow = new LineNode(20, 0.2f, QColor::fromRgbF(0.2, 0.2, 0.2, 0.4));

              n->appendChildNode(n->background);
              n->appendChildNode(n->grid);
              n->appendChildNode(n->shadow);
              n->appendChildNode(n->line);
          }

          if (m_geometryChanged) {
              n->background->setRect(rect);
              n->grid->setRect(rect);
          }

          if (m_geometryChanged || m_samplesChanged) {
              n->line->updateGeometry(rect, m_samples);
              // We don't need to calculate the geometry twice, so just steal it from the other one...
              n->shadow->setGeometry(n->line->geometry());
          }

          m_geometryChanged = false;
          m_samplesChanged = false;

          return n;
      }