Qt 5.11 | Qt Quick | Scene Graph - Custom Geometry | beziercurve.cpp Example File

Qt 5.11.3 Reference Documentation

# beziercurve.cpp Example File

scenegraph/customgeometry/beziercurve.cpp

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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 = nullptr;
          QSGGeometry *geometry = nullptr;

          if (!oldNode) {
              node = new QSGGeometryNode;
              geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), m_segmentCount);
              geometry->setLineWidth(2);
              geometry->setDrawingMode(QSGGeometry::DrawLineStrip);
              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);
          }

          QSizeF itemSize = size();
          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 = pos.x() * itemSize.width();
              float y = pos.y() * itemSize.height();

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

          return node;
      }