beziercurve.cpp Example File | Qt Quick 5.12.8

- Qt 5.12
- Qt Quick
- Scene Graph - Custom Geometry
- beziercurve.cpp Example File
- Qt 5.12.8 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;
     }