开源项目推荐：CNC+CRC/SoftPLC/OpenCASCADE/CAD/CAM（二）

qcad的dxf读取在\src\io\dxf\RDxfImporter.cpp
void RDxfImporter::endEntity()
{
    QSharedPointer<RSplineEntity> entity(new RSplineEntity(document, RSplineData(spline)));
    importEntity(entity);
}
qcad的样条曲线的绘图在/src/core/RPainterPath.cpp
void RPainterPath::addSpline(const RSpline& spline) {
    int degree = spline.getDegree();
    if (degree<=3) {
        moveTo(spline.getStartPoint());
    }
    QList<RSpline> list = spline.getBezierSegments();
    for (int i=0; i<list.count(); i++) {
        QList<RVector> cps = list[i].getControlPoints();
        // very rare splines of degree >= 4:
        if ((cps.size()>=5 && degree==cps.size()-1)) {
            QList<QSharedPointer<RShape> > segments = spline.getExploded(16);
            for (int k=0; k<segments.length(); k++) {
                QSharedPointer<RLine> l = segments[k].dynamicCast<RLine>();
                if (k==0) {
                    moveTo(l->getStartPoint());
                }
                lineTo(l->getEndPoint());
            }
        }
        else if (cps.size()==4 && degree==3) {
            cubicTo(cps[1], cps[2], cps[3]);
        }
        else if (cps.size()==3 && degree==2) {
            quadTo(cps[1], cps[2]);
        }
        else if (cps.size()==2 && degree==1) {
            lineTo(cps[1]);
        }
        else {
            qWarning() << "RPainterPath::addSpline: invalid bezier segment: " << list[i];
            continue;
        }
    }
}
//\src\core\RPainterPath.h
void quadTo(qreal ctrlPtx, qreal ctrlPty, qreal endPtx, qreal endPty) {
    QPainterPath::quadTo(ctrlPtx, ctrlPty, endPtx, endPty);
}
void cubicTo(qreal ctrlPt1x, qreal ctrlPt1y, qreal ctrlPt2x, qreal ctrlPt2y, qreal endPtx, qreal endPty) {
    QPainterPath::cubicTo(ctrlPt1x, ctrlPt1y, ctrlPt2x, ctrlPt2y, endPtx, endPty);
}
//QPainterPath源码来自Qt官方\Qt\Qt5.12.7\5.12.7\Src\qtbase\src\gui\painting
//cubicTo和quadTo都是用来实现贝塞尔曲线的，那有什么不一样呢？
官方是这么说的：
Same as cubicTo, but the coordinates are considered relative to the current point on this contour.
说白了，就是多了一个控制点而已。
//https://doc.qt.io/qt-5/qpainterpath.html
//https://qtdebug.com/qt-smooth-curve/

\pcbnew\import_gfx\dxf_import_plugin.cpp
#include "tinyspline_lib/tinysplinecpp.h"
void DXF_IMPORT_PLUGIN::insertSpline( int aWidth )
{
    unsigned imax = m_curr_entity.m_SplineControlPointList.size();
    if( imax < 2 )  // malformed spline
        return;
    // Use bezier curves, supported by pcbnew, to approximate the spline
  tinyspline::BSpline dxfspline( m_curr_entity.m_SplineControlPointList.size(),
                                   /* coord dim */ 2, m_curr_entity.m_SplineDegree );
    std::vector<double> ctrlp;
    for( unsigned ii = 0; ii < imax; ++ii )
    {
        ctrlp.push_back( m_curr_entity.m_SplineControlPointList[ii].m_x );
        ctrlp.push_back( m_curr_entity.m_SplineControlPointList[ii].m_y );
    }
  dxfspline.setCtrlp( ctrlp );
  dxfspline.setKnots( m_curr_entity.m_SplineKnotsList );
  tinyspline::BSpline beziers( dxfspline.toBeziers() );
    std::vector<double> coords = beziers.ctrlp();
    // Each Bezier curve uses 4 vertices (a start point, 2 control points and a end point).
    // So we can have more than one Bezier curve ( there are one curve each four vertices)
    for( unsigned ii = 0; ii < coords.size(); ii += 8 )
    {
        VECTOR2D start( mapX( coords[ii] ), mapY( coords[ii+1] ) );
        VECTOR2D bezierControl1( mapX( coords[ii+2] ), mapY( coords[ii+3] ) );
        VECTOR2D bezierControl2( mapX( coords[ii+4] ), mapY( coords[ii+5] ) );
        VECTOR2D end( mapX( coords[ii+6] ), mapY( coords[ii+7] ) );
        m_internalImporter.AddSpline( start, bezierControl1, bezierControl2, end , aWidth );
    }
}
\pcbnew\import_gfx\graphics_importer_buffer.h
void ImportTo( GRAPHICS_IMPORTER& aImporter ) const override
{
    aImporter.AddSpline( m_start, m_bezierControl1, m_bezierControl2, m_end, m_width );
}
\pcbnew\import_gfx\graphics_importer_pcbnew.cpp
void GRAPHICS_IMPORTER_PCBNEW::AddSpline( const VECTOR2D& aStart, const VECTOR2D& BezierControl1,
                const VECTOR2D& BezierControl2, const VECTOR2D& aEnd, double aWidth )
{
    unique_ptr<DRAWSEGMENT> spline( createDrawing() );
    spline->SetShape( S_CURVE );
    spline->SetLayer( GetLayer() );
    spline->SetWidth( MapLineWidth( aWidth ) );
    spline->SetStart( MapCoordinate( aStart ) );
    spline->SetBezControl1( MapCoordinate( BezierControl1 ) );
    spline->SetBezControl2( MapCoordinate( BezierControl2 ) );
    spline->SetEnd( MapCoordinate( aEnd ) );
    spline->RebuildBezierToSegmentsPointsList( aWidth );
    if( spline->Type() == PCB_MODULE_EDGE_T )
        static_cast<EDGE_MODULE*>( spline.get() )->SetLocalCoord();
    addItem( std::move( spline ) );
}
\pcbnew\class_drawsegment.cpp
void DRAWSEGMENT::RebuildBezierToSegmentsPointsList( int aMinSegLen )
{
    // Has meaning only for S_CURVE DRAW_SEGMENT shape
    if( m_Shape != S_CURVE )
    {
        m_BezierPoints.clear();
        return;
    }
    // Rebuild the m_BezierPoints vertex list that approximate the Bezier curve
    std::vector<wxPoint> ctrlPoints = { m_Start, m_BezierC1, m_BezierC2, m_End };
    BEZIER_POLY converter( ctrlPoints );
    converter.GetPoly( m_BezierPoints, aMinSegLen );
}
\common\bezier_curves.cpp
void BEZIER_POLY::GetPoly( std::vector<wxPoint>& aOutput, int aMinSegLen )
{
}