graph.cpp Example File

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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 0;
      }

      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, 0.2, 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;
  }