qgscompoundcurve.cpp

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/***************************************************************************
                         qgscompoundcurve.cpp
                         ----------------------
    begin                : September 2014
    copyright            : (C) 2014 by Marco Hugentobler
    email                : marco at sourcepole dot ch
 ***************************************************************************/
 
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgscompoundcurve.h"
 
#include <memory>
#include <nlohmann/json.hpp>
 
#include "qgsapplication.h"
#include "qgscircularstring.h"
#include "qgsfeedback.h"
#include "qgsgeometryutils.h"
#include "qgslinestring.h"
#include "qgsmessagelog.h"
#include "qgswkbptr.h"
 
#include <QJsonObject>
#include <QPainter>
#include <QPainterPath>
#include <QString>
 
using namespace Qt::StringLiterals;
 
QgsCompoundCurve::QgsCompoundCurve()
{
  mWkbType = Qgis::WkbType::CompoundCurve;
}
 
QgsCompoundCurve::~QgsCompoundCurve()
{
  clear();
}
 
QgsCompoundCurve *QgsCompoundCurve::createEmptyWithSameType() const
{
  auto result = std::make_unique< QgsCompoundCurve >();
  result->mWkbType = mWkbType;
  return result.release();
}
 
int QgsCompoundCurve::compareToSameClass( const QgsAbstractGeometry *other ) const
{
  const QgsCompoundCurve *otherCurve = qgsgeometry_cast<const QgsCompoundCurve *>( other );
  if ( !otherCurve )
    return -1;
 
  int i = 0;
  int j = 0;
  while ( i < mCurves.size() && j < otherCurve->mCurves.size() )
  {
    const QgsAbstractGeometry *aGeom = mCurves[i];
    const QgsAbstractGeometry *bGeom = otherCurve->mCurves[j];
    const int comparison = aGeom->compareTo( bGeom );
    if ( comparison != 0 )
    {
      return comparison;
    }
    i++;
    j++;
  }
  if ( i < mCurves.size() )
  {
    return 1;
  }
  if ( j < otherCurve->mCurves.size() )
  {
    return -1;
  }
  return 0;
}
 
QString QgsCompoundCurve::geometryType() const
{
  return u"CompoundCurve"_s;
}
 
int QgsCompoundCurve::dimension() const
{
  return 1;
}
 
QgsCompoundCurve::QgsCompoundCurve( const QgsCompoundCurve &curve )
  : QgsCurve( curve )
{
  mWkbType = curve.wkbType();
  mCurves.reserve( curve.mCurves.size() );
  for ( const QgsCurve *c : curve.mCurves )
  {
    mCurves.append( c->clone() );
  }
}
 
// cppcheck-suppress operatorEqVarError
QgsCompoundCurve &QgsCompoundCurve::operator=( const QgsCompoundCurve &curve )
{
  if ( &curve != this )
  {
    QgsCurve::operator=( curve );
    for ( const QgsCurve *c : curve.mCurves )
    {
      mCurves.append( c->clone() );
    }
  }
  return *this;
}
 
QgsCompoundCurve *QgsCompoundCurve::clone() const
{
  return new QgsCompoundCurve( *this );
}
 
void QgsCompoundCurve::clear()
{
  mWkbType = Qgis::WkbType::CompoundCurve;
  qDeleteAll( mCurves );
  mCurves.clear();
  clearCache();
}
 
QgsBox3D QgsCompoundCurve::calculateBoundingBox3D() const
{
  if ( mCurves.empty() )
  {
    return QgsBox3D();
  }
 
  QgsBox3D bbox = mCurves.at( 0 )->boundingBox3D();
  for ( int i = 1; i < mCurves.size(); ++i )
  {
    QgsBox3D curveBox = mCurves.at( i )->boundingBox3D();
    bbox.combineWith( curveBox );
  }
  return bbox;
}
 
void QgsCompoundCurve::scroll( int index )
{
  const int size = numPoints();
  if ( index < 1 || index >= size - 1 )
    return;
 
  auto [p1, p2] = splitCurveAtVertex( index );
 
  mCurves.clear();
  if ( QgsCompoundCurve *curve2 = qgsgeometry_cast< QgsCompoundCurve *>( p2.get() ) )
  {
    // take the curves from the second part and make them our first lot of curves
    mCurves = std::move( curve2->mCurves );
  }
  if ( QgsCompoundCurve *curve1 = qgsgeometry_cast< QgsCompoundCurve *>( p1.get() ) )
  {
    // take the curves from the first part and append them to our curves
    mCurves.append( curve1->mCurves );
    curve1->mCurves.clear();
  }
}
 
bool QgsCompoundCurve::fromWkb( QgsConstWkbPtr &wkbPtr )
{
  clear();
  if ( !wkbPtr )
  {
    return false;
  }
 
  Qgis::WkbType type = wkbPtr.readHeader();
  if ( QgsWkbTypes::flatType( type ) != Qgis::WkbType::CompoundCurve )
  {
    return false;
  }
  mWkbType = type;
 
  int nCurves;
  wkbPtr >> nCurves;
  QgsCurve *currentCurve = nullptr;
  for ( int i = 0; i < nCurves; ++i )
  {
    Qgis::WkbType curveType = wkbPtr.readHeader();
    wkbPtr -= 1 + sizeof( int );
    if ( QgsWkbTypes::flatType( curveType ) == Qgis::WkbType::LineString )
    {
      currentCurve = new QgsLineString();
    }
    else if ( QgsWkbTypes::flatType( curveType ) == Qgis::WkbType::CircularString )
    {
      currentCurve = new QgsCircularString();
    }
    else
    {
      return false;
    }
    currentCurve->fromWkb( wkbPtr ); // also updates wkbPtr
    mCurves.append( currentCurve );
  }
  return true;
}
 
bool QgsCompoundCurve::fromWkt( const QString &wkt )
{
  clear();
 
  QPair<Qgis::WkbType, QString> parts = QgsGeometryUtils::wktReadBlock( wkt );
 
  if ( QgsWkbTypes::flatType( parts.first ) != Qgis::WkbType::CompoundCurve )
    return false;
  mWkbType = parts.first;
 
  QString secondWithoutParentheses = parts.second;
  secondWithoutParentheses = secondWithoutParentheses.remove( '(' ).remove( ')' ).simplified().remove( ' ' );
  if ( ( parts.second.compare( "EMPTY"_L1, Qt::CaseInsensitive ) == 0 ) || secondWithoutParentheses.isEmpty() )
    return true;
 
  QString defaultChildWkbType = u"LineString%1%2"_s.arg( is3D() ? u"Z"_s : QString(), isMeasure() ? u"M"_s : QString() );
 
  const QStringList blocks = QgsGeometryUtils::wktGetChildBlocks( parts.second, defaultChildWkbType );
  for ( const QString &childWkt : blocks )
  {
    QPair<Qgis::WkbType, QString> childParts = QgsGeometryUtils::wktReadBlock( childWkt );
 
    if ( QgsWkbTypes::flatType( childParts.first ) == Qgis::WkbType::LineString )
      mCurves.append( new QgsLineString() );
    else if ( QgsWkbTypes::flatType( childParts.first ) == Qgis::WkbType::CircularString )
      mCurves.append( new QgsCircularString() );
    else
    {
      clear();
      return false;
    }
    if ( !mCurves.back()->fromWkt( childWkt ) )
    {
      clear();
      return false;
    }
  }
 
  //scan through curves and check if dimensionality of curves is different to compound curve.
  //if so, update the type dimensionality of the compound curve to match
  bool hasZ = false;
  bool hasM = false;
  for ( const QgsCurve *curve : std::as_const( mCurves ) )
  {
    hasZ = hasZ || curve->is3D();
    hasM = hasM || curve->isMeasure();
    if ( hasZ && hasM )
      break;
  }
  if ( hasZ )
    addZValue( 0 );
  if ( hasM )
    addMValue( 0 );
 
  return true;
}
 
int QgsCompoundCurve::wkbSize( QgsAbstractGeometry::WkbFlags flags ) const
{
  int binarySize = sizeof( char ) + sizeof( quint32 ) + sizeof( quint32 );
  for ( const QgsCurve *curve : mCurves )
  {
    binarySize += curve->wkbSize( flags );
  }
  return binarySize;
}
 
QByteArray QgsCompoundCurve::asWkb( WkbFlags flags ) const
{
  QByteArray wkbArray;
  wkbArray.resize( QgsCompoundCurve::wkbSize( flags ) );
  QgsWkbPtr wkb( wkbArray );
  wkb << static_cast<char>( QgsApplication::endian() );
  wkb << static_cast<quint32>( wkbType() );
  wkb << static_cast<quint32>( mCurves.size() );
  for ( const QgsCurve *curve : mCurves )
  {
    wkb << curve->asWkb( flags );
  }
  return wkbArray;
}
 
QString QgsCompoundCurve::asWkt( int precision ) const
{
  QString wkt = wktTypeStr();
  if ( isEmpty() )
    wkt += " EMPTY"_L1;
  else
  {
    wkt += " ("_L1;
    for ( const QgsCurve *curve : mCurves )
    {
      QString childWkt = curve->asWkt( precision );
      if ( qgsgeometry_cast<const QgsLineString *>( curve ) )
      {
        // Type names of linear geometries are omitted
        childWkt = childWkt.mid( childWkt.indexOf( '(' ) );
      }
      wkt += childWkt + ',';
    }
    if ( wkt.endsWith( ',' ) )
    {
      wkt.chop( 1 );
    }
    wkt += ')';
  }
  return wkt;
}
 
QDomElement QgsCompoundCurve::asGml2( QDomDocument &doc, int precision, const QString &ns, const AxisOrder axisOrder ) const
{
  // GML2 does not support curves
  std::unique_ptr< QgsLineString > line( curveToLine() );
  QDomElement gml = line->asGml2( doc, precision, ns, axisOrder );
  return gml;
}
 
QDomElement QgsCompoundCurve::asGml3( QDomDocument &doc, int precision, const QString &ns, const QgsAbstractGeometry::AxisOrder axisOrder ) const
{
  QDomElement compoundCurveElem = doc.createElementNS( ns, u"CompositeCurve"_s );
 
  if ( isEmpty() )
    return compoundCurveElem;
 
  for ( const QgsCurve *curve : mCurves )
  {
    QDomElement curveMemberElem = doc.createElementNS( ns, u"curveMember"_s );
    QDomElement curveElem = curve->asGml3( doc, precision, ns, axisOrder );
    curveMemberElem.appendChild( curveElem );
    compoundCurveElem.appendChild( curveMemberElem );
  }
 
  return compoundCurveElem;
}
 
json QgsCompoundCurve::asJsonObject( int precision ) const
{
  // GeoJSON does not support curves
  std::unique_ptr< QgsLineString > line( curveToLine() );
  return line->asJsonObject( precision );
}
 
double QgsCompoundCurve::length() const
{
  double length = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    length += curve->length();
  }
  return length;
}
 
QgsPoint QgsCompoundCurve::startPoint() const
{
  if ( mCurves.empty() )
  {
    return QgsPoint();
  }
  return mCurves.at( 0 )->startPoint();
}
 
QgsPoint QgsCompoundCurve::endPoint() const
{
  if ( mCurves.empty() )
  {
    return QgsPoint();
  }
  return mCurves.at( mCurves.size() - 1 )->endPoint();
}
 
void QgsCompoundCurve::points( QgsPointSequence &pts ) const
{
  pts.clear();
  if ( mCurves.empty() )
  {
    return;
  }
 
  mCurves[0]->points( pts );
  for ( int i = 1; i < mCurves.size(); ++i )
  {
    QgsPointSequence pList;
    mCurves[i]->points( pList );
    pList.removeFirst(); //first vertex already added in previous line
    pts.append( pList );
  }
}
 
int QgsCompoundCurve::numPoints() const
{
  int nPoints = 0;
  int nCurves = mCurves.size();
  if ( nCurves < 1 )
  {
    return 0;
  }
 
  for ( int i = 0; i < nCurves; ++i )
  {
    nPoints += mCurves.at( i )->numPoints() - 1; //last vertex is equal to first of next section
  }
  nPoints += 1; //last vertex was removed above
  return nPoints;
}
 
bool QgsCompoundCurve::isEmpty() const
{
  if ( mCurves.isEmpty() )
    return true;
 
  for ( QgsCurve *curve : mCurves )
  {
    if ( !curve->isEmpty() )
      return false;
  }
  return true;
}
 
bool QgsCompoundCurve::isValid( QString &error, Qgis::GeometryValidityFlags flags ) const
{
  if ( mCurves.isEmpty() )
    return true;
 
  for ( int i = 0; i < mCurves.size(); ++i )
  {
    if ( !mCurves[i]->isValid( error, flags ) )
    {
      error = QObject::tr( "Curve[%1]: %2" ).arg( i + 1 ).arg( error );
      return false;
    }
  }
  return QgsCurve::isValid( error, flags );
}
 
int QgsCompoundCurve::indexOf( const QgsPoint &point ) const
{
  int curveStart = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    const int curveIndex = curve->indexOf( point );
    if ( curveIndex >= 0 )
      return curveStart + curveIndex;
    // subtract 1 here, because the next curve will start with the same
    // vertex as this curve ended at
    curveStart += curve->numPoints() - 1;
  }
  return -1;
}
 
QgsLineString *QgsCompoundCurve::curveToLine( double tolerance, SegmentationToleranceType toleranceType ) const
{
  QgsLineString *line = new QgsLineString();
  std::unique_ptr< QgsLineString > currentLine;
  for ( const QgsCurve *curve : mCurves )
  {
    currentLine.reset( curve->curveToLine( tolerance, toleranceType ) );
    line->append( currentLine.get() );
  }
  return line;
}
 
QgsCompoundCurve *QgsCompoundCurve::snappedToGrid( double hSpacing, double vSpacing, double dSpacing, double mSpacing, bool removeRedundantPoints ) const
{
  std::unique_ptr<QgsCompoundCurve> result( createEmptyWithSameType() );
 
  for ( QgsCurve *curve : mCurves )
  {
    std::unique_ptr<QgsCurve> gridified( static_cast< QgsCurve * >( curve->snappedToGrid( hSpacing, vSpacing, dSpacing, mSpacing, removeRedundantPoints ) ) );
    if ( gridified )
    {
      result->mCurves.append( gridified.release() );
    }
  }
 
  if ( result->mCurves.empty() )
    return nullptr;
  else
    return result.release();
}
 
QgsAbstractGeometry *QgsCompoundCurve::simplifyByDistance( double tolerance ) const
{
  std::unique_ptr< QgsLineString > line( curveToLine() );
  return line->simplifyByDistance( tolerance );
}
 
bool QgsCompoundCurve::removeDuplicateNodes( double epsilon, bool useZValues )
{
  bool result = false;
  const QVector< QgsCurve * > curves = mCurves;
  int i = 0;
  QgsPoint lastEnd;
  for ( QgsCurve *curve : curves )
  {
    result = curve->removeDuplicateNodes( epsilon, useZValues ) || result;
    if ( curve->numPoints() == 0 || qgsDoubleNear( curve->length(), 0.0, epsilon ) )
    {
      // empty curve, remove it
      delete mCurves.takeAt( i );
      result = true;
    }
    else
    {
      // ensure this line starts exactly where previous line ended
      if ( i > 0 )
      {
        curve->moveVertex( QgsVertexId( -1, -1, 0 ), lastEnd );
      }
      lastEnd = curve->vertexAt( QgsVertexId( -1, -1, curve->numPoints() - 1 ) );
    }
    i++;
  }
  return result;
}
 
bool QgsCompoundCurve::boundingBoxIntersects( const QgsBox3D &box3d ) const
{
  if ( mCurves.empty() )
    return false;
 
  // if we already have the bounding box calculated, then this check is trivial!
  if ( !mBoundingBox.isNull() )
  {
    return mBoundingBox.intersects( box3d );
  }
 
  // otherwise loop through each member curve and test the bounding box intersection.
  // This gives us a chance to use optimisations which may be present on the individual
  // curve subclasses, and at worst it will cause a calculation of the bounding box
  // of each individual member curve which we would have to do anyway... (and these
  // bounding boxes are cached, so would be reused without additional expense)
  for ( const QgsCurve *curve : mCurves )
  {
    if ( curve->boundingBoxIntersects( box3d ) )
      return true;
  }
 
  // even if we don't intersect the bounding box of any member curves, we may still intersect the
  // bounding box of the overall compound curve.
  // so here we fall back to the non-optimised base class check which has to first calculate
  // the overall bounding box of the compound curve..
  return QgsAbstractGeometry::boundingBoxIntersects( box3d );
}
 
const QgsAbstractGeometry *QgsCompoundCurve::simplifiedTypeRef() const
{
  if ( mCurves.size() == 1 )
    return mCurves.at( 0 );
  else
    return this;
}
 
const QgsCurve *QgsCompoundCurve::curveAt( int i ) const
{
  if ( i < 0 || i >= mCurves.size() )
  {
    return nullptr;
  }
  return mCurves.at( i );
}
 
void QgsCompoundCurve::addCurve( QgsCurve *c, const bool extendPrevious )
{
  if ( !c )
    return;
 
  if ( mCurves.empty() )
  {
    setZMTypeFromSubGeometry( c, Qgis::WkbType::CompoundCurve );
  }
 
  if ( QgsWkbTypes::hasZ( mWkbType ) && !QgsWkbTypes::hasZ( c->wkbType() ) )
  {
    c->addZValue();
  }
  else if ( !QgsWkbTypes::hasZ( mWkbType ) && QgsWkbTypes::hasZ( c->wkbType() ) )
  {
    c->dropZValue();
  }
  if ( QgsWkbTypes::hasM( mWkbType ) && !QgsWkbTypes::hasM( c->wkbType() ) )
  {
    c->addMValue();
  }
  else if ( !QgsWkbTypes::hasM( mWkbType ) && QgsWkbTypes::hasM( c->wkbType() ) )
  {
    c->dropMValue();
  }
 
  QgsLineString *previousLineString = !mCurves.empty() ? qgsgeometry_cast< QgsLineString * >( mCurves.constLast() ) : nullptr;
  const QgsLineString *newLineString = qgsgeometry_cast< const QgsLineString * >( c );
  const bool canExtendPrevious = extendPrevious && previousLineString && newLineString;
  if ( canExtendPrevious )
  {
    previousLineString->append( newLineString );
    // we are taking ownership, so delete the input curve
    delete c;
    c = nullptr;
  }
  else
  {
    mCurves.append( c );
  }
 
  clearCache();
}
 
void QgsCompoundCurve::removeCurve( int i )
{
  if ( i < 0 || i >= mCurves.size() )
  {
    return;
  }
 
  delete mCurves.takeAt( i );
  clearCache();
}
 
void QgsCompoundCurve::addVertex( const QgsPoint &pt )
{
  if ( mCurves.isEmpty() || mWkbType == Qgis::WkbType::Unknown )
  {
    setZMTypeFromSubGeometry( &pt, Qgis::WkbType::CompoundCurve );
  }
 
  //is last curve QgsLineString
  QgsCurve *lastCurve = nullptr;
  if ( !mCurves.isEmpty() )
  {
    lastCurve = mCurves.at( mCurves.size() - 1 );
  }
 
  QgsLineString *line = nullptr;
  if ( !lastCurve || QgsWkbTypes::flatType( lastCurve->wkbType() ) != Qgis::WkbType::LineString )
  {
    line = new QgsLineString();
    mCurves.append( line );
    if ( lastCurve )
    {
      line->addVertex( lastCurve->endPoint() );
    }
    lastCurve = line;
  }
  else //create new QgsLineString* with point in it
  {
    line = static_cast<QgsLineString *>( lastCurve );
  }
  line->addVertex( pt );
  clearCache();
}
 
void QgsCompoundCurve::condenseCurves()
{
  QgsCurve *lastCurve = nullptr;
  QVector< QgsCurve * > newCurves;
  newCurves.reserve( mCurves.size() );
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    if ( lastCurve && lastCurve->wkbType() == curve->wkbType() )
    {
      if ( QgsLineString *ls = qgsgeometry_cast< QgsLineString * >( lastCurve ) )
      {
        ls->append( qgsgeometry_cast< QgsLineString * >( curve ) );
        delete curve;
      }
      else if ( QgsCircularString *cs = qgsgeometry_cast< QgsCircularString * >( lastCurve ) )
      {
        cs->append( qgsgeometry_cast< QgsCircularString * >( curve ) );
        delete curve;
      }
    }
    else
    {
      lastCurve = curve;
      newCurves << curve;
    }
  }
  mCurves = newCurves;
}
 
void QgsCompoundCurve::draw( QPainter &p ) const
{
  for ( const QgsCurve *curve : mCurves )
  {
    curve->draw( p );
  }
}
 
void QgsCompoundCurve::transform( const QgsCoordinateTransform &ct, Qgis::TransformDirection d, bool transformZ )
{
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->transform( ct, d, transformZ );
  }
  clearCache();
}
 
void QgsCompoundCurve::transform( const QTransform &t, double zTranslate, double zScale, double mTranslate, double mScale )
{
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->transform( t, zTranslate, zScale, mTranslate, mScale );
  }
  clearCache();
}
 
void QgsCompoundCurve::addToPainterPath( QPainterPath &path ) const
{
  QPainterPath pp;
 
  for ( const QgsCurve *curve : mCurves )
  {
    if ( curve != mCurves.at( 0 ) && pp.currentPosition() != curve->startPoint().toQPointF() )
    {
      pp.lineTo( curve->startPoint().toQPointF() );
    }
    curve->addToPainterPath( pp );
  }
  path.addPath( pp );
}
 
void QgsCompoundCurve::drawAsPolygon( QPainter &p ) const
{
  QPainterPath pp;
  for ( const QgsCurve *curve : mCurves )
  {
    if ( curve != mCurves.at( 0 ) && pp.currentPosition() != curve->startPoint().toQPointF() )
    {
      pp.lineTo( curve->startPoint().toQPointF() );
    }
    curve->addToPainterPath( pp );
  }
  p.drawPath( pp );
}
 
bool QgsCompoundCurve::insertVertex( QgsVertexId position, const QgsPoint &vertex )
{
  QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( position );
  if ( curveIds.empty() )
  {
    return false;
  }
  int curveId = curveIds.at( 0 ).first;
  if ( curveId >= mCurves.size() )
  {
    return false;
  }
 
  bool success = mCurves.at( curveId )->insertVertex( curveIds.at( 0 ).second, vertex );
  if ( success )
  {
    clearCache(); //bbox changed
  }
  return success;
}
 
bool QgsCompoundCurve::moveVertex( QgsVertexId position, const QgsPoint &newPos )
{
  QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( position );
  QVector< QPair<int, QgsVertexId> >::const_iterator idIt = curveIds.constBegin();
  for ( ; idIt != curveIds.constEnd(); ++idIt )
  {
    mCurves.at( idIt->first )->moveVertex( idIt->second, newPos );
  }
 
  bool success = !curveIds.isEmpty();
  if ( success )
  {
    clearCache(); //bbox changed
  }
  return success;
}
 
bool QgsCompoundCurve::deleteVertex( QgsVertexId position )
{
  const QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( position );
  if ( curveIds.isEmpty() )
    return false;
 
  const int curveId = curveIds.at( 0 ).first;
  QgsCurve *curve = mCurves.at( curveId );
  const QgsVertexId subVertexId = curveIds.at( 0 ).second;
 
  // We are on a vertex that belongs to one curve only
  if ( curveIds.size() == 1 )
  {
    const QgsCircularString *circularString = qgsgeometry_cast<const QgsCircularString *>( curve );
    // If the vertex to delete is the middle vertex of a CircularString, we transform
    // this CircularString into a LineString without the middle vertex
    if ( circularString && subVertexId.vertex % 2 == 1 )
    {
      {
        QgsPointSequence points;
        circularString->points( points );
 
        removeCurve( curveId );
 
        if ( subVertexId.vertex < points.length() - 2 )
        {
          auto curveC = std::make_unique<QgsCircularString>();
          curveC->setPoints( points.mid( subVertexId.vertex + 1 ) );
          mCurves.insert( curveId, curveC.release() );
        }
 
        const QgsPointSequence partB = QgsPointSequence() << points[subVertexId.vertex - 1] << points[subVertexId.vertex + 1];
        auto curveB = std::make_unique<QgsLineString>();
        curveB->setPoints( partB );
        mCurves.insert( curveId, curveB.release() );
        curve = mCurves.at( curveId );
 
        if ( subVertexId.vertex > 1 )
        {
          auto curveA = std::make_unique<QgsCircularString>();
          curveA->setPoints( points.mid( 0, subVertexId.vertex ) );
          mCurves.insert( curveId, curveA.release() );
        }
      }
    }
    else if ( !curve->deleteVertex( subVertexId ) )
    {
      clearCache(); //bbox may have changed
      return false;
    }
    if ( curve->numPoints() == 0 )
    {
      removeCurve( curveId );
    }
  }
  // We are on a vertex that belongs to two curves
  else if ( curveIds.size() == 2 )
  {
    const int nextCurveId = curveIds.at( 1 ).first;
    QgsCurve *nextCurve = mCurves.at( nextCurveId );
    const QgsVertexId nextSubVertexId = curveIds.at( 1 ).second;
 
    Q_ASSERT( nextCurveId == curveId + 1 );
    Q_ASSERT( subVertexId.vertex == curve->numPoints() - 1 );
    Q_ASSERT( nextSubVertexId.vertex == 0 );
 
    // globals start and end points
    const QgsPoint startPoint = curve->startPoint();
    const QgsPoint endPoint = nextCurve->endPoint();
 
    // delete the vertex on first curve
    if ( !curve->deleteVertex( subVertexId ) )
    {
      clearCache(); //bbox may have changed
      return false;
    }
 
    // delete the vertex on second curve
    if ( !nextCurve->deleteVertex( nextSubVertexId ) )
    {
      clearCache(); //bbox may have changed
      return false;
    }
 
    // if first curve is now empty and second is not then
    // create a LineString to link from the global start point to the
    // new start of the second curve and delete the first curve
    if ( curve->numPoints() == 0 && nextCurve->numPoints() != 0 )
    {
      QgsPoint startPointOfSecond = nextCurve->startPoint();
      removeCurve( curveId );
      QgsLineString *line = new QgsLineString();
      line->insertVertex( QgsVertexId( 0, 0, 0 ), startPoint );
      line->insertVertex( QgsVertexId( 0, 0, 1 ), startPointOfSecond );
      mCurves.insert( curveId, line );
    }
    // else, if the first curve is not empty and the second is
    // then create a LineString to link from the new end of the first curve to the
    // global end point and delete the first curve
    else if ( curve->numPoints() != 0 && nextCurve->numPoints() == 0 )
    {
      QgsPoint endPointOfFirst = curve->endPoint();
      removeCurve( nextCurveId );
      QgsLineString *line = new QgsLineString();
      line->insertVertex( QgsVertexId( 0, 0, 0 ), endPointOfFirst );
      line->insertVertex( QgsVertexId( 0, 0, 1 ), endPoint );
      mCurves.insert( nextCurveId, line );
    }
    // else, if both curves are empty then
    // remove both curves and create a LineString to link
    // the curves before and the curves after the whole geometry
    else if ( curve->numPoints() == 0 && nextCurve->numPoints() == 0 )
    {
      removeCurve( nextCurveId );
      removeCurve( curveId );
      QgsLineString *line = new QgsLineString();
      line->insertVertex( QgsVertexId( 0, 0, 0 ), startPoint );
      line->insertVertex( QgsVertexId( 0, 0, 1 ), endPoint );
      mCurves.insert( curveId, line );
    }
    // else, both curves still have vertices, create a LineString to link
    // the curves if needed
    else
    {
      QgsPoint endPointOfFirst = curve->endPoint();
      QgsPoint startPointOfSecond = nextCurve->startPoint();
      if ( endPointOfFirst != startPointOfSecond )
      {
        QgsLineString *line = new QgsLineString();
        line->insertVertex( QgsVertexId( 0, 0, 0 ), endPointOfFirst );
        line->insertVertex( QgsVertexId( 0, 0, 1 ), startPointOfSecond );
        mCurves.insert( nextCurveId, line );
      }
    }
    condenseCurves(); // We merge consecutive LineStrings and CircularStrings
  }
 
  bool success = !curveIds.isEmpty();
  if ( success )
    clearCache(); //bbox changed
  return success;
}
 
bool QgsCompoundCurve::deleteVertices( const QSet<QgsVertexId> &positions )
{
  // we create a list of vertices to delete for each curve
  QMap<int, QList<QgsVertexId >> curveVertices;
  for ( QgsVertexId position : positions )
  {
    if ( !hasVertex( position ) )
    {
      return false;
    }
 
    const QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( position );
 
    if ( curveIds.isEmpty() )
      return false;
 
    const int firstCurveId = curveIds.at( 0 ).first;
    const QgsVertexId firstCurveVertex = curveIds.at( 0 ).second;
    curveVertices[firstCurveId].append( firstCurveVertex );
    if ( curveIds.size() == 2 ) // vertex is shared between two curves
    {
      const int secondCurveId = curveIds.at( 1 ).first;
      const QgsVertexId secondCurveVertex = curveIds.at( 1 ).second;
      curveVertices[secondCurveId].append( secondCurveVertex );
    }
  }
 
  // loop through the curves in reverse order and delete vertices
  QMapIterator<int, QList<QgsVertexId >> curveVerticesIt( curveVertices );
  curveVerticesIt.toBack();
  while ( curveVerticesIt.hasPrevious() )
  {
    curveVerticesIt.previous();
    const int curveId = curveVerticesIt.key();
    QgsCurve *curve = mCurves.at( curveId );
    QList<QgsVertexId> vertices = curveVerticesIt.value();
 
    const QgsCircularString *circularString = qgsgeometry_cast<const QgsCircularString *>( curve );
    // If the vertex to delete is the middle vertex of a circularstring arc, we transform
    // this circularstring arc into a linestring without the middle vertex
    if ( circularString )
    {
      // we loop through the vertices to see if we need to handle special case
      // of a middle vertex (see deleteVertex)
      std::sort( vertices.begin(), vertices.end(), []( const QgsVertexId &a, const QgsVertexId &b ) { return a.vertex < b.vertex; } );
      QList<QgsVertexId> circularVerticesToDelete;
      circularVerticesToDelete.reserve( vertices.size() );
 
      QListIterator<QgsVertexId> curveVerticesIt( vertices );
 
      // search for odd vertices (middle vertices of an arc)
      for ( size_t i = vertices.size(); i-- > 0; )
      {
        const QgsVertexId curveVertexId = vertices.at( i );
 
        // check if a middle vertex of an arc
        if ( curveVertexId.vertex % 2 == 1 )
        {
          // check if neighbouring vertices are also to be deleted
          // if so, we just add this vertex to the list and continue iterating
          if ( !circularVerticesToDelete.isEmpty() )
          {
            if ( curveVertexId.vertex == circularVerticesToDelete.last().vertex - 1 )
            {
              circularVerticesToDelete.append( curveVertexId );
              continue;
            }
          }
          else if ( i != 0 && curveVertexId.vertex - 1 == vertices.at( i - 1 ).vertex )
          {
            circularVerticesToDelete.append( curveVertexId );
            continue;
          }
 
          // we found a middle vertex of an arc and none of its neighbours are to be deleted
          // we need to handle special case of middle vertex of an arc deletion
          // first we delete all the vertices that come before it in this circularstring
          if ( !circularVerticesToDelete.isEmpty() )
          {
            if ( !curve->deleteVertices( QSet<QgsVertexId>( circularVerticesToDelete.begin(), circularVerticesToDelete.end() ) ) )
            {
              Q_ASSERT( false ); // shouldn't happen after all the checks
              return false;
            }
          }
          circularVerticesToDelete.clear();
 
          // next, we remove that arc and replace it with a linestring that skips the middle vertex
          QgsPointSequence points;
          circularString->points( points );
 
          removeCurve( curveId );
 
          if ( curveVertexId.vertex < points.length() - 2 )
          {
            auto curveC = std::make_unique<QgsCircularString>();
            curveC->setPoints( points.mid( curveVertexId.vertex + 1 ) );
            mCurves.insert( curveId, curveC.release() );
          }
 
          const QgsPointSequence partB = QgsPointSequence() << points[curveVertexId.vertex - 1] << points[curveVertexId.vertex + 1];
          auto curveB = std::make_unique<QgsLineString>();
          curveB->setPoints( partB );
          mCurves.insert( curveId, curveB.release() );
          curve = mCurves.at( curveId );
 
          if ( curveVertexId.vertex > 1 )
          {
            auto curveA = std::make_unique<QgsCircularString>();
            curveA->setPoints( points.mid( 0, curveVertexId.vertex ) );
            mCurves.insert( curveId, curveA.release() );
          }
          curve = mCurves.at( curveId ); // we need to get the new curve
          circularString = qgsgeometry_cast<const QgsCircularString *>( curve );
 
          continue;
        }
 
        // not a middle vertex of an arc
        circularVerticesToDelete.append( curveVertexId );
      }
 
      // remove any remaining circular vertices to delete
      if ( !circularVerticesToDelete.isEmpty() )
      {
        if ( !curve->deleteVertices( QSet<QgsVertexId>( circularVerticesToDelete.begin(), circularVerticesToDelete.end() ) ) )
        {
          Q_ASSERT( false );
          return false;
        }
      }
      continue; // circularstring handled, continue to next curve
    }
 
    if ( !curve->deleteVertices( QSet<QgsVertexId>( vertices.begin(), vertices.end() ) ) )
    {
      Q_ASSERT( false );
      return false;
    }
  }
 
  // remove any empty curves
  for ( int i = mCurves.size() - 1; i >= 0; i-- )
  {
    QgsCurve *curve = mCurves.at( i );
    if ( curve->numPoints() == 0 )
    {
      removeCurve( i );
    }
  }
 
  if ( mCurves.isEmpty() )
  {
    clearCache();
    return true;
  }
 
  // ensure all curves are connected
  for ( size_t i = mCurves.size() - 1; i > 0; i-- )
  {
    QgsCurve *curve = mCurves.at( i );
    QgsCurve *previousCurve = mCurves.at( i - 1 );
    if ( previousCurve->endPoint() != curve->startPoint() )
    {
      QgsLineString *line = new QgsLineString();
      line->insertVertex( QgsVertexId( 0, 0, 0 ), previousCurve->endPoint() );
      line->insertVertex( QgsVertexId( 0, 0, 1 ), curve->startPoint() );
      mCurves.insert( i, line );
    }
  }
 
  condenseCurves(); // merge consecutive LineStrings and CircularStrings
  clearCache();
  return true;
}
 
QVector< QPair<int, QgsVertexId> > QgsCompoundCurve::curveVertexId( QgsVertexId id ) const
{
  QVector< QPair<int, QgsVertexId> > curveIds;
 
  int currentVertexIndex = 0;
  for ( int i = 0; i < mCurves.size(); ++i )
  {
    int increment = mCurves.at( i )->numPoints() - 1;
    if ( id.vertex >= currentVertexIndex && id.vertex <= currentVertexIndex + increment )
    {
      int curveVertexId = id.vertex - currentVertexIndex;
      QgsVertexId vid;
      vid.part = 0;
      vid.ring = 0;
      vid.vertex = curveVertexId;
      curveIds.append( qMakePair( i, vid ) );
      if ( curveVertexId == increment && i < ( mCurves.size() - 1 ) ) //add first vertex of next curve
      {
        vid.vertex = 0;
        curveIds.append( qMakePair( i + 1, vid ) );
      }
      break;
    }
    else if ( id.vertex >= currentVertexIndex && id.vertex == currentVertexIndex + increment + 1 && i == ( mCurves.size() - 1 ) )
    {
      int curveVertexId = id.vertex - currentVertexIndex;
      QgsVertexId vid;
      vid.part = 0;
      vid.ring = 0;
      vid.vertex = curveVertexId;
      curveIds.append( qMakePair( i, vid ) );
      break;
    }
    currentVertexIndex += increment;
  }
 
  return curveIds;
}
 
bool QgsCompoundCurve::toggleCircularAtVertex( QgsVertexId position )
{
  // First we find out the sub-curves that are contain that vertex.
 
  // If there is more than one, it means the vertex was at the beginning or end
  // of an arc, which we don't support.
 
  // If there is exactly one, we may either be on a LineString, or on a CircularString.
 
  // If on CircularString, we need to check if the vertex is a CurveVertex (odd index).
  // If so, we split the subcurve at vertex -1 and +1, , drop the middle part and insert a LineString/CircularString
  // instead with the same points.
 
  // At the end, we call condenseCurves() to merge successible line/circular strings
 
  QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( position );
 
  // We cannot convert points at start/end of subcurves
  if ( curveIds.length() != 1 )
    return false;
 
  int curveId = curveIds[0].first;
  QgsVertexId subVertexId = curveIds[0].second;
  QgsCurve *curve = mCurves[curveId];
 
  // We cannot convert first/last point of curve
  if ( subVertexId.vertex == 0 || subVertexId.vertex == curve->numPoints() - 1 )
    return false;
 
  if ( const QgsCircularString *circularString = qgsgeometry_cast<const QgsCircularString *>( curve ) )
  {
    // If it's a circular string, we convert to LineString
 
    // We cannot convert start/end points of arcs
    if ( subVertexId.vertex % 2 == 0 ) // for some reason, subVertexId.type is always SegmentVertex...
      return false;
 
    QgsPointSequence points;
    circularString->points( points );
 
    const QgsPointSequence partA = points.mid( 0, subVertexId.vertex );
    const QgsPointSequence partB = QgsPointSequence() << points[subVertexId.vertex - 1] << points[subVertexId.vertex] << points[subVertexId.vertex + 1];
    const QgsPointSequence partC = points.mid( subVertexId.vertex + 1 );
 
    auto curveA = std::make_unique<QgsCircularString>();
    curveA->setPoints( partA );
    auto curveB = std::make_unique<QgsLineString>();
    curveB->setPoints( partB );
    auto curveC = std::make_unique<QgsCircularString>();
    curveC->setPoints( partC );
 
    removeCurve( curveId );
    if ( subVertexId.vertex < points.length() - 2 )
      mCurves.insert( curveId, curveC.release() );
    mCurves.insert( curveId, curveB.release() );
    if ( subVertexId.vertex > 1 )
      mCurves.insert( curveId, curveA.release() );
  }
  else if ( const QgsLineString *lineString = dynamic_cast<const QgsLineString *>( curve ) )
  {
    // If it's a linestring, we split and insert a curve
 
    QgsPointSequence points;
    lineString->points( points );
 
    const QgsPointSequence partA = points.mid( 0, subVertexId.vertex );
    const QgsPointSequence partB = QgsPointSequence() << points[subVertexId.vertex - 1] << points[subVertexId.vertex] << points[subVertexId.vertex + 1];
    const QgsPointSequence partC = points.mid( subVertexId.vertex + 1 );
 
    auto curveA = std::make_unique<QgsLineString>();
    curveA->setPoints( partA );
    auto curveB = std::make_unique<QgsCircularString>();
    curveB->setPoints( partB );
    auto curveC = std::make_unique<QgsLineString>();
    curveC->setPoints( partC );
 
    removeCurve( curveId );
    if ( subVertexId.vertex < points.length() - 2 )
      mCurves.insert( curveId, curveC.release() );
    mCurves.insert( curveId, curveB.release() );
    if ( subVertexId.vertex > 1 )
      mCurves.insert( curveId, curveA.release() );
  }
 
  // We merge consecutive LineStrings
  condenseCurves();
 
  clearCache();
  return true;
}
 
 
double QgsCompoundCurve::closestSegment( const QgsPoint &pt, QgsPoint &segmentPt, QgsVertexId &vertexAfter, int *leftOf, double epsilon ) const
{
  return QgsGeometryUtils::closestSegmentFromComponents( mCurves, QgsGeometryUtils::Vertex, pt, segmentPt, vertexAfter, leftOf, epsilon );
}
 
bool QgsCompoundCurve::pointAt( int node, QgsPoint &point, Qgis::VertexType &type ) const
{
  int currentVertexId = 0;
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
    if ( ( node - currentVertexId ) < nCurvePoints )
    {
      return ( mCurves.at( j )->pointAt( node - currentVertexId, point, type ) );
    }
    currentVertexId += ( nCurvePoints - 1 );
  }
  return false;
}
 
double QgsCompoundCurve::xAt( int index ) const
{
  int currentVertexId = 0;
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
    if ( ( index - currentVertexId ) < nCurvePoints )
    {
      return mCurves.at( j )->xAt( index - currentVertexId );
    }
    currentVertexId += ( nCurvePoints - 1 );
  }
  return 0.0;
}
 
double QgsCompoundCurve::yAt( int index ) const
{
  int currentVertexId = 0;
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
    if ( ( index - currentVertexId ) < nCurvePoints )
    {
      return mCurves.at( j )->yAt( index - currentVertexId );
    }
    currentVertexId += ( nCurvePoints - 1 );
  }
  return 0.0;
}
 
double QgsCompoundCurve::zAt( int index ) const
{
  int currentVertexId = 0;
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
    if ( ( index - currentVertexId ) < nCurvePoints )
    {
      return mCurves.at( j )->zAt( index - currentVertexId );
    }
    currentVertexId += ( nCurvePoints - 1 );
  }
  return 0.0;
}
 
double QgsCompoundCurve::mAt( int index ) const
{
  int currentVertexId = 0;
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
    if ( ( index - currentVertexId ) < nCurvePoints )
    {
      return mCurves.at( j )->mAt( index - currentVertexId );
    }
    currentVertexId += ( nCurvePoints - 1 );
  }
  return 0.0;
}
 
bool QgsCompoundCurve::transform( QgsAbstractGeometryTransformer *transformer, QgsFeedback *feedback )
{
  bool res = true;
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    if ( !curve->transform( transformer ) )
    {
      res = false;
      break;
    }
 
    if ( feedback && feedback->isCanceled() )
    {
      res = false;
      break;
    }
  }
  clearCache();
  return res;
}
 
void QgsCompoundCurve::filterVertices( const std::function<bool( const QgsPoint & )> &filter )
{
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->filterVertices( filter );
  }
  clearCache();
}
 
void QgsCompoundCurve::transformVertices( const std::function<QgsPoint( const QgsPoint & )> &transform )
{
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->transformVertices( transform );
  }
  clearCache();
}
 
std::tuple<std::unique_ptr<QgsCurve>, std::unique_ptr<QgsCurve> > QgsCompoundCurve::splitCurveAtVertex( int index ) const
{
  if ( mCurves.empty() )
    return std::make_tuple( std::make_unique< QgsCompoundCurve >(), std::make_unique< QgsCompoundCurve >() );
 
  int curveStart = 0;
 
  auto curve1 = std::make_unique< QgsCompoundCurve >();
  std::unique_ptr< QgsCompoundCurve > curve2;
 
  for ( const QgsCurve *curve : mCurves )
  {
    const int curveSize = curve->numPoints();
    if ( !curve2 && index < curveStart + curveSize )
    {
      // split the curve
      auto [p1, p2] = curve->splitCurveAtVertex( index - curveStart );
      if ( !p1->isEmpty() )
        curve1->addCurve( p1.release() );
 
      curve2 = std::make_unique< QgsCompoundCurve >();
      if ( !p2->isEmpty() )
        curve2->addCurve( p2.release() );
    }
    else
    {
      if ( curve2 )
        curve2->addCurve( curve->clone() );
      else
        curve1->addCurve( curve->clone() );
    }
 
    // subtract 1 here, because the next curve will start with the same
    // vertex as this curve ended at
    curveStart += curve->numPoints() - 1;
  }
 
  return std::make_tuple( std::move( curve1 ), curve2 ? std::move( curve2 ) : std::make_unique< QgsCompoundCurve >() );
}
 
void QgsCompoundCurve::sumUpArea( double &sum ) const
{
  if ( mHasCachedSummedUpArea )
  {
    sum += mSummedUpArea;
    return;
  }
 
  mSummedUpArea = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    curve->sumUpArea( mSummedUpArea );
  }
  mHasCachedSummedUpArea = true;
  sum += mSummedUpArea;
}
 
void QgsCompoundCurve::sumUpArea3D( double &sum ) const
{
  if ( mHasCachedSummedUpArea3D )
  {
    sum += mSummedUpArea3D;
    return;
  }
 
  mSummedUpArea3D = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    curve->sumUpArea3D( mSummedUpArea3D );
  }
  mHasCachedSummedUpArea3D = true;
  sum += mSummedUpArea3D;
}
 
void QgsCompoundCurve::close()
{
  if ( numPoints() < 1 || isClosed() )
  {
    return;
  }
  addVertex( startPoint() );
}
 
bool QgsCompoundCurve::hasCurvedSegments() const
{
  for ( const QgsCurve *curve : mCurves )
  {
    if ( curve->hasCurvedSegments() )
    {
      return true;
    }
  }
  return false;
}
 
double QgsCompoundCurve::vertexAngle( QgsVertexId vertex ) const
{
  QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( vertex );
  if ( curveIds.size() == 1 )
  {
    QgsCurve *curve = mCurves[curveIds.at( 0 ).first];
    return curve->vertexAngle( curveIds.at( 0 ).second );
  }
  else if ( curveIds.size() > 1 )
  {
    QgsCurve *curve1 = mCurves[curveIds.at( 0 ).first];
    QgsCurve *curve2 = mCurves[curveIds.at( 1 ).first];
    double angle1 = curve1->vertexAngle( curveIds.at( 0 ).second );
    double angle2 = curve2->vertexAngle( curveIds.at( 1 ).second );
    return QgsGeometryUtilsBase::averageAngle( angle1, angle2 );
  }
  else
  {
    return 0.0;
  }
}
 
double QgsCompoundCurve::segmentLength( QgsVertexId startVertex ) const
{
  QVector< QPair<int, QgsVertexId> > curveIds = curveVertexId( startVertex );
  double length = 0.0;
  for ( auto it = curveIds.constBegin(); it != curveIds.constEnd(); ++it )
  {
    length += mCurves.at( it->first )->segmentLength( it->second );
  }
  return length;
}
 
QgsCompoundCurve *QgsCompoundCurve::reversed() const
{
  QgsCompoundCurve *clone = new QgsCompoundCurve();
  for ( int i = mCurves.count() - 1; i >= 0; --i )
  {
    QgsCurve *reversedCurve = mCurves.at( i )->reversed();
    clone->addCurve( reversedCurve );
  }
  return clone;
}
 
QgsPoint *QgsCompoundCurve::interpolatePoint( const double distance ) const
{
  if ( distance < 0 )
    return nullptr;
 
  double distanceTraversed = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    const double thisCurveLength = curve->length();
    if ( distanceTraversed + thisCurveLength > distance || qgsDoubleNear( distanceTraversed + thisCurveLength, distance ) )
    {
      // point falls on this segment - truncate to segment length if qgsDoubleNear test was actually > segment length
      const double distanceToPoint = std::min( distance - distanceTraversed, thisCurveLength );
 
      // point falls on this curve
      return curve->interpolatePoint( distanceToPoint );
    }
 
    distanceTraversed += thisCurveLength;
  }
 
  return nullptr;
}
 
QgsCompoundCurve *QgsCompoundCurve::curveSubstring( double startDistance, double endDistance ) const
{
  if ( startDistance < 0 && endDistance < 0 )
    return createEmptyWithSameType();
 
  endDistance = std::max( startDistance, endDistance );
  auto substring = std::make_unique< QgsCompoundCurve >();
 
  double distanceTraversed = 0;
  for ( const QgsCurve *curve : mCurves )
  {
    const double thisCurveLength = curve->length();
    if ( distanceTraversed + thisCurveLength < startDistance )
    {
      // keep going - haven't found start yet, so no need to include this curve at all
    }
    else
    {
      std::unique_ptr< QgsCurve > part( curve->curveSubstring( startDistance - distanceTraversed, endDistance - distanceTraversed ) );
      if ( part )
        substring->addCurve( part.release() );
    }
 
    distanceTraversed += thisCurveLength;
    if ( distanceTraversed > endDistance )
      break;
  }
 
  return substring.release();
}
 
bool QgsCompoundCurve::addZValue( double zValue )
{
  if ( QgsWkbTypes::hasZ( mWkbType ) )
    return false;
 
  mWkbType = QgsWkbTypes::addZ( mWkbType );
 
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->addZValue( zValue );
  }
  clearCache();
  return true;
}
 
bool QgsCompoundCurve::addMValue( double mValue )
{
  if ( QgsWkbTypes::hasM( mWkbType ) )
    return false;
 
  mWkbType = QgsWkbTypes::addM( mWkbType );
 
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->addMValue( mValue );
  }
  clearCache();
  return true;
}
 
bool QgsCompoundCurve::dropZValue()
{
  if ( !QgsWkbTypes::hasZ( mWkbType ) )
    return false;
 
  mWkbType = QgsWkbTypes::dropZ( mWkbType );
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->dropZValue();
  }
  clearCache();
  return true;
}
 
bool QgsCompoundCurve::dropMValue()
{
  if ( !QgsWkbTypes::hasM( mWkbType ) )
    return false;
 
  mWkbType = QgsWkbTypes::dropM( mWkbType );
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->dropMValue();
  }
  clearCache();
  return true;
}
 
void QgsCompoundCurve::swapXy()
{
  for ( QgsCurve *curve : std::as_const( mCurves ) )
  {
    curve->swapXy();
  }
  clearCache();
}
 
double QgsCompoundCurve::distanceBetweenVertices( QgsVertexId fromVertex, QgsVertexId toVertex ) const
{
  // Ensure fromVertex < toVertex for simplicity
  if ( fromVertex.vertex > toVertex.vertex )
  {
    return distanceBetweenVertices( toVertex, fromVertex );
  }
 
  // Convert QgsVertexId to simple vertex numbers for compound curves (single ring, single part)
  if ( fromVertex.part != 0 || fromVertex.ring != 0 || toVertex.part != 0 || toVertex.ring != 0 )
    return -1.0;
 
  const int fromVertexNumber = fromVertex.vertex;
  const int toVertexNumber = toVertex.vertex;
 
  const int totalVertices = numPoints();
  if ( fromVertexNumber < 0 || fromVertexNumber >= totalVertices || toVertexNumber < 0 || toVertexNumber >= totalVertices )
    return -1.0;
 
  if ( fromVertexNumber == toVertexNumber )
    return 0.0;
 
  double totalDistance = 0.0;
 
  // Find which curves contain our vertices and accumulate distances
  int currentVertexId = 0;
  int fromCurve = -1, toCurve = -1;
  int fromCurveVertex = -1, toCurveVertex = -1;
 
  // First pass: find which curves contain from and to vertices
  for ( int j = 0; j < mCurves.size(); ++j )
  {
    int nCurvePoints = mCurves.at( j )->numPoints();
 
    // Check if fromVertex is in this curve
    if ( fromCurve == -1 && fromVertexNumber >= currentVertexId && fromVertexNumber < currentVertexId + nCurvePoints )
    {
      fromCurve = j;
      fromCurveVertex = fromVertexNumber - currentVertexId;
    }
 
    // Check if toVertex is in this curve
    if ( toCurve == -1 && toVertexNumber >= currentVertexId && toVertexNumber < currentVertexId + nCurvePoints )
    {
      toCurve = j;
      toCurveVertex = toVertexNumber - currentVertexId;
      break;
    }
 
    currentVertexId += ( nCurvePoints - 1 ); // Subtract 1 because curves share endpoints
  }
 
  if ( fromCurve == -1 || toCurve == -1 )
    return -1.0; // Invalid vertex IDs
 
  if ( fromCurve == toCurve )
  {
    // Both vertices are on the same curve
    QgsVertexId fromId( 0, 0, fromCurveVertex );
    QgsVertexId toId( 0, 0, toCurveVertex );
    return mCurves.at( fromCurve )->distanceBetweenVertices( fromId, toId );
  }
  else
  {
    // Vertices are on different curves - accumulate distances across multiple curves
 
    // Distance from fromVertex to end of its curve
    if ( fromCurveVertex < mCurves.at( fromCurve )->numPoints() - 1 )
    {
      QgsVertexId fromId( 0, 0, fromCurveVertex );
      QgsVertexId endId( 0, 0, mCurves.at( fromCurve )->numPoints() - 1 );
      totalDistance += mCurves.at( fromCurve )->distanceBetweenVertices( fromId, endId );
    }
 
    // Distance of complete intermediate curves
    for ( int j = fromCurve + 1; j < toCurve; ++j )
    {
      totalDistance += mCurves.at( j )->length();
    }
 
    // Distance from start of toCurve to toVertex
    if ( toCurveVertex > 0 )
    {
      QgsVertexId startId( 0, 0, 0 );
      QgsVertexId toId( 0, 0, toCurveVertex );
      totalDistance += mCurves.at( toCurve )->distanceBetweenVertices( startId, toId );
    }
  }
 
  return totalDistance;
}