beziercurve.cpp Example File

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  #include "beziercurve.h"

  #include <QtQuick/qsgnode.h>
  #include <QtQuick/qsgflatcolormaterial.h>

  BezierCurve::BezierCurve(QQuickItem *parent)
      : QQuickItem(parent)
      , m_p1(0, 0)
      , m_p2(1, 0)
      , m_p3(0, 1)
      , m_p4(1, 1)
      , m_segmentCount(32)
  {
      setFlag(ItemHasContents, true);
  }

  BezierCurve::~BezierCurve()
  {
  }

  void BezierCurve::setP1(const QPointF &p)
  {
      if (p == m_p1)
          return;

      m_p1 = p;
      emit p1Changed(p);
      update();
  }

  void BezierCurve::setP2(const QPointF &p)
  {
      if (p == m_p2)
          return;

      m_p2 = p;
      emit p2Changed(p);
      update();
  }

  void BezierCurve::setP3(const QPointF &p)
  {
      if (p == m_p3)
          return;

      m_p3 = p;
      emit p3Changed(p);
      update();
  }

  void BezierCurve::setP4(const QPointF &p)
  {
      if (p == m_p4)
          return;

      m_p4 = p;
      emit p4Changed(p);
      update();
  }

  void BezierCurve::setSegmentCount(int count)
  {
      if (m_segmentCount == count)
          return;

      m_segmentCount = count;
      emit segmentCountChanged(count);
      update();
  }

  QSGNode *BezierCurve::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
  {
      QSGGeometryNode *node = 0;
      QSGGeometry *geometry = 0;

      if (!oldNode) {
          node = new QSGGeometryNode;
          geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), m_segmentCount);
          geometry->setLineWidth(2);
          geometry->setDrawingMode(GL_LINE_STRIP);
          node->setGeometry(geometry);
          node->setFlag(QSGNode::OwnsGeometry);
          QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
          material->setColor(QColor(255, 0, 0));
          node->setMaterial(material);
          node->setFlag(QSGNode::OwnsMaterial);
      } else {
          node = static_cast<QSGGeometryNode *>(oldNode);
          geometry = node->geometry();
          geometry->allocate(m_segmentCount);
      }

      QRectF bounds = boundingRect();
      QSGGeometry::Point2D *vertices = geometry->vertexDataAsPoint2D();
      for (int i = 0; i < m_segmentCount; ++i) {
          qreal t = i / qreal(m_segmentCount - 1);
          qreal invt = 1 - t;

          QPointF pos = invt * invt * invt * m_p1
                      + 3 * invt * invt * t * m_p2
                      + 3 * invt * t * t * m_p3
                      + t * t * t * m_p4;

          float x = bounds.x() + pos.x() * bounds.width();
          float y = bounds.y() + pos.y() * bounds.height();

          vertices[i].set(x, y);
      }
      node->markDirty(QSGNode::DirtyGeometry);

      return node;
  }