pns_meander.cpp

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/*
 * KiRouter - a push-and-(sometimes-)shove PCB router
 *
 * Copyright (C) 2013-2014 CERN
 * Copyright (C) 2016-2023 KiCad Developers, see AUTHORS.txt for contributors.
 * Author: Tomasz Wlostowski <[email protected]>
 *
 * 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 3 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "pns_node.h"
#include "pns_itemset.h"
#include "pns_meander.h"
#include "pns_meander_placer_base.h"
#include "pns_router.h"
#include "pns_debug_decorator.h"
 
namespace PNS {
 
const long long int MEANDER_SETTINGS::DEFAULT_TOLERANCE( pcbIUScale.mmToIU( 0.1 ) );
const long long int MEANDER_SETTINGS::LENGTH_UNCONSTRAINED( 1000000 * pcbIUScale.IU_PER_MM );
const int MEANDER_SETTINGS::SKEW_UNCONSTRAINED( std::numeric_limits<int>::max() );
 
 
MEANDER_SETTINGS::MEANDER_SETTINGS()
{
 m_minAmplitude = 200000;
 m_maxAmplitude = 1000000;
 m_step = 50000;
 m_lenPadToDie = 0;
 m_spacing = 600000;
 SetTargetLength( LENGTH_UNCONSTRAINED );
 SetTargetSkew( 0 );
 m_overrideCustomRules = false;
 m_cornerStyle = MEANDER_STYLE_ROUND;
 m_cornerRadiusPercentage = 80;
 m_singleSided = false;
 m_initialSide = MEANDER_SIDE_LEFT;
 m_lengthTolerance = 0;
 m_keepEndpoints = false;
}
 
 
void MEANDER_SETTINGS::SetTargetLength( long long int aOpt )
{
 m_targetLength.SetOpt( aOpt );
 
 if( aOpt == PNS::MEANDER_SETTINGS::LENGTH_UNCONSTRAINED )
 {
 m_targetLength.SetMin( 0 );
 m_targetLength.SetMax( aOpt );
 }
 else
 {
 m_targetLength.SetMin( aOpt - DEFAULT_TOLERANCE );
 m_targetLength.SetMax( aOpt + DEFAULT_TOLERANCE );
 }
}
 
 
void MEANDER_SETTINGS::SetTargetLength( const MINOPTMAX<int>& aConstraint )
{
 SetTargetLength( aConstraint.Opt() );
 
 if( aConstraint.HasMin() )
 m_targetLength.SetMin( aConstraint.Min() );
 
 if( aConstraint.HasMax() )
 m_targetLength.SetMax( aConstraint.Max() );
}
 
 
void MEANDER_SETTINGS::SetTargetSkew( int aOpt )
{
 m_targetSkew.SetOpt( aOpt );
 
 if( aOpt == PNS::MEANDER_SETTINGS::SKEW_UNCONSTRAINED )
 {
 m_targetSkew.SetMin( 0 );
 m_targetSkew.SetMax( aOpt );
 }
 else
 {
 m_targetSkew.SetMin( aOpt - DEFAULT_TOLERANCE );
 m_targetSkew.SetMax( aOpt + DEFAULT_TOLERANCE );
 }
}
 
 
void MEANDER_SETTINGS::SetTargetSkew( const MINOPTMAX<int>& aConstraint )
{
 SetTargetSkew( aConstraint.Opt() );
 
 if( aConstraint.HasMin() )
 m_targetSkew.SetMin( aConstraint.Min() );
 
 if( aConstraint.HasMax() )
 m_targetSkew.SetMax( aConstraint.Max() );
}
 
 
const MEANDER_SETTINGS& MEANDER_SHAPE::Settings() const
{
 return m_placer->MeanderSettings();
}
 
 
const MEANDER_SETTINGS& MEANDERED_LINE::Settings() const
{
 return m_placer->MeanderSettings();
}
 
 
void MEANDERED_LINE::MeanderSegment( const SEG& aBase, bool aSide, int aBaseIndex )
{
 double base_len = aBase.Length();
 
 SHAPE_LINE_CHAIN lc;
 
 bool singleSided = Settings().m_singleSided;
 bool side = aSide;
 VECTOR2D dir( aBase.B - aBase.A );
 
 if( !m_dual )
 AddCorner( aBase.A );
 
 bool turning = false;
 bool started = false;
 
 m_last = aBase.A;
 
 do
 {
 MEANDER_SHAPE m( m_placer, m_width, m_dual );
 
 m.SetBaselineOffset( m_baselineOffset );
 m.SetBaseIndex( aBaseIndex );
 
 double thr = (double) m.spacing();
 
 bool fail = false;
 double remaining = base_len - ( m_last - aBase.A ).EuclideanNorm();
 
 auto flipInitialSide =
 [&]()
 {
 MEANDER_SETTINGS settings = m_placer->MeanderSettings();
 settings.m_initialSide = (PNS::MEANDER_SIDE) -settings.m_initialSide;
 m_placer->UpdateSettings( settings );
 };
 
 auto addSingleIfFits =
 [&]()
 {
 fail = true;
 
 if( m.Fit( MT_SINGLE, aBase, m_last, side ) )
 {
 AddMeander( new MEANDER_SHAPE( m ) );
 fail = false;
 started = false;
 }
 
 if( fail && !singleSided )
 {
 if( m.Fit( MT_SINGLE, aBase, m_last, !side ) )
 {
 if( !started )
 flipInitialSide();
 
 AddMeander( new MEANDER_SHAPE( m ) );
 fail = false;
 started = false;
 side = !side;
 }
 }
 };
 
 if( remaining < Settings( ).m_step )
 break;
 
 if( !singleSided && remaining > 3.0 * thr )
 {
 if( !turning )
 {
 for( int i = 0; i < 2; i++ )
 {
 bool checkSide = ( i == 0 ) ? side : !side;
 
 if( m.Fit( MT_CHECK_START, aBase, m_last, checkSide ) )
 {
 if( !started && checkSide != side )
 flipInitialSide();
 
 turning = true;
 AddMeander( new MEANDER_SHAPE( m ) );
 side = !checkSide;
 started = true;
 break;
 }
 }
 
 if( !turning )
 addSingleIfFits();
 }
 else
 {
 bool rv = m.Fit( MT_CHECK_FINISH, aBase, m_last, side );
 
 if( rv )
 {
 m.Fit( MT_TURN, aBase, m_last, side );
 AddMeander( new MEANDER_SHAPE( m ) );
 side = !side;
 started = true;
 }
 else
 {
 m.Fit( MT_FINISH, aBase, m_last, side );
 started = false;
 AddMeander( new MEANDER_SHAPE( m ) );
 turning = false;
 }
 }
 }
 else if( !singleSided && started )
 {
 bool rv = m.Fit( MT_FINISH, aBase, m_last, side );
 
 if( rv )
 AddMeander( new MEANDER_SHAPE( m ) );
 
 break;
 
 }
 else if( !turning && remaining > thr * 2.0 )
 {
 addSingleIfFits();
 }
 else
 {
 fail = true;
 }
 
 remaining = base_len - ( m_last - aBase.A ).EuclideanNorm( );
 
 if( remaining < Settings( ).m_step )
 break;
 
 if( fail )
 {
 MEANDER_SHAPE tmp( m_placer, m_width, m_dual );
 tmp.SetBaselineOffset( m_baselineOffset );
 tmp.SetBaseIndex( aBaseIndex );
 
 int nextP = tmp.spacing() - 2 * tmp.cornerRadius() + Settings().m_step;
 VECTOR2I pn = m_last + dir.Resize( nextP );
 
 if( aBase.Contains( pn ) && !m_dual )
 AddCorner( pn );
 else
 break;
 }
 
 
 } while( true );
 
 if( !m_dual )
 AddCorner( aBase.B );
}
 
 
int MEANDER_SHAPE::MinAmplitude() const
{
 int minAmplitude = Settings().m_minAmplitude;
 
 if( m_placer->MeanderSettings().m_cornerStyle == MEANDER_STYLE_ROUND )
 {
 minAmplitude = std::max( minAmplitude, std::abs( m_baselineOffset ) + m_width );
 }
 else
 {
 int correction = m_width * tan( 1 - tan( DEG2RAD( 22.5 ) ) );
 minAmplitude = std::max( minAmplitude, std::abs( m_baselineOffset ) + correction );
 }
 
 return minAmplitude;
}
 
 
int MEANDER_SHAPE::cornerRadius() const
{
 if( m_amplitude == 0 )
 return 0;
 
 int minCr = 0;
 
 if( m_placer->MeanderSettings().m_cornerStyle == MEANDER_STYLE_ROUND )
 minCr = std::abs( m_baselineOffset ) + m_width / 2;
 else
 minCr = std::abs( m_baselineOffset ) + m_width / 2 * ( 1 - tan( DEG2RAD( 22.5 ) ) );
 
 int maxCr1 = ( m_amplitude + std::abs( m_baselineOffset ) ) / 2;
 int maxCr2 = spacing() / 2;
 int maxCr = std::min( maxCr1, maxCr2 );
 
 wxCHECK2_MSG( maxCr >= minCr, return maxCr,
 wxString::Format( "cornerRadius %d < %d amp %d spc %d w %d off %d", maxCr, minCr,
 m_amplitude, spacing(), m_width, m_baselineOffset ) );
 
 int rPercent = Settings().m_cornerRadiusPercentage;
 int optCr = static_cast<int>( static_cast<SEG::ecoord>( spacing() ) * rPercent / 200 );
 
 return std::clamp( optCr, minCr, maxCr );
}
 
 
int MEANDER_SHAPE::spacing( ) const
{
 if( !m_dual )
 {
 return std::max( m_width + m_placer->Clearance(), Settings().m_spacing );
 }
 else
 {
 int sp = m_width + m_placer->Clearance() + ( 2 * std::abs( m_baselineOffset ) );
 return std::max( sp, Settings().m_spacing );
 }
}
 
 
SHAPE_LINE_CHAIN MEANDER_SHAPE::makeMiterShape( const VECTOR2D& aP, const VECTOR2D& aDir,
 bool aSide )
{
 SHAPE_LINE_CHAIN lc;
 
 if( aDir.EuclideanNorm( ) == 0.0f )
 {
 lc.Append( aP );
 return lc;
 }
 
 VECTOR2D dir_u( aDir );
 VECTOR2D dir_v( aDir.Perpendicular() );
 
 VECTOR2D endPoint = aP + dir_u + dir_v * ( aSide ? -1.0 : 1.0 );
 VECTOR2D p = aP;
 lc.Append( ( int ) p.x, ( int ) p.y );
 
 // fixme: refactor
 switch( m_placer->MeanderSettings().m_cornerStyle )
 {
 case MEANDER_STYLE_ROUND:
 {
 VECTOR2I arcEnd( (int) endPoint.x, (int) endPoint.y );
 
 SHAPE_ARC arc;
 arc.ConstructFromStartEndAngle( aP, arcEnd, ( aSide ? -ANGLE_90 : ANGLE_90 ) );
 lc.Append( arc );
 break;
 }
 
 case MEANDER_STYLE_CHAMFER:
 {
 double radius = (double) aDir.EuclideanNorm();
 double correction = 0;
 
 if( m_dual && radius > m_meanCornerRadius )
 correction = (double) ( -2 * abs( m_baselineOffset ) ) * tan( DEG2RAD( 22.5 ) );
 
 VECTOR2D dir_cu = dir_u.Resize( correction );
 VECTOR2D dir_cv = dir_v.Resize( correction );
 
 p = aP - dir_cu;
 lc.Append( ( int ) p.x, ( int ) p.y );
 p = aP + dir_u + (dir_v + dir_cv) * ( aSide ? -1.0 : 1.0 );
 lc.Append( ( int ) p.x, ( int ) p.y );
 
 p = endPoint;
 lc.Append( (int) p.x, (int) p.y );
 break;
 }
 
 default:
 break;
 }
 
 return lc;
}
 
 
void MEANDER_SHAPE::start( SHAPE_LINE_CHAIN* aTarget, const VECTOR2D& aWhere, const VECTOR2D& aDir )
{
 m_currentTarget = aTarget;
 m_currentTarget->Clear();
 m_currentTarget->Append( aWhere );
 m_currentDir = aDir;
 m_currentPos = aWhere;
}
 
 
void MEANDER_SHAPE::forward( int aLength )
{
 // Very small segments cause problems.
 if( aLength < 5 )
 return;
 
 m_currentPos += m_currentDir.Resize( aLength );
 m_currentTarget->Append( m_currentPos );
}
 
 
void MEANDER_SHAPE::turn( const EDA_ANGLE& aAngle )
{
 RotatePoint( m_currentDir, aAngle );
}
 
 
void MEANDER_SHAPE::miter( int aRadius, bool aSide )
{
 if( aRadius <= 0 )
 {
 turn( aSide ? ANGLE_90 : -ANGLE_90 );
 return;
 }
 
 VECTOR2D dir = m_currentDir.Resize( (double) aRadius );
 SHAPE_LINE_CHAIN lc = makeMiterShape( m_currentPos, dir, aSide );
 
 m_currentPos = lc.CPoint( -1 );
 turn( aSide ? ANGLE_90 : -ANGLE_90 );
 
 m_currentTarget->Append( lc );
}
 
 
void MEANDER_SHAPE::uShape( int aSides, int aCorner, int aTop )
{
 forward( aSides );
 miter( aCorner, true );
 forward( aTop );
 miter( aCorner, true );
 forward( aSides );
}
 
 
SHAPE_LINE_CHAIN MEANDER_SHAPE::genMeanderShape( const VECTOR2D& aP, const VECTOR2D& aDir,
 bool aSide, MEANDER_TYPE aType,
 int aBaselineOffset )
{
 int cr = cornerRadius();
 int offset = aBaselineOffset;
 int spc = spacing();
 int amplitude = m_amplitude;
 int targetBaseLen = m_targetBaseLen;
 
 if( aSide )
 offset *= -1;
 
 VECTOR2D dir_u_b( aDir.Resize( offset ) );
 VECTOR2D dir_v_b( dir_u_b.Perpendicular() );
 
 if( 2 * cr > amplitude + std::abs( offset ) )
 cr = ( amplitude + std::abs( offset ) ) / 2;
 
 if( 2 * cr > spc )
 cr = spc / 2;
 
 if( cr - offset < 0 )
 cr = offset;
 
 m_meanCornerRadius = cr;
 
 int sCorner = cr - offset;
 int uCorner = cr + offset;
 int startSide = amplitude - 2 * cr + std::abs( offset );
 int turnSide = amplitude - cr;
 int top = spc - 2 * cr;
 
 SHAPE_LINE_CHAIN lc;
 
 start( &lc, aP + dir_v_b, aDir );
 
 switch( aType )
 {
 case MT_EMPTY:
 {
 lc.Append( aP + dir_v_b + aDir );
 break;
 }
 case MT_START:
 {
 if( targetBaseLen )
 top = std::max( top, targetBaseLen - sCorner - uCorner * 2 + offset );
 
 miter( sCorner, false );
 uShape( startSide, uCorner, top );
 forward( std::min( sCorner, uCorner ) );
 forward( std::abs( offset ) );
 break;
 }
 
 case MT_FINISH:
 {
 if( targetBaseLen )
 top = std::max( top, targetBaseLen - cr - spc );
 
 start( &lc, aP - dir_u_b, aDir );
 turn( -ANGLE_90 );
 forward( std::min( sCorner, uCorner ) );
 forward( std::abs( offset ) );
 uShape( startSide, uCorner, top );
 miter( sCorner, false );
 
 if( targetBaseLen >= spc + cr )
 lc.Append( aP + dir_v_b + aDir.Resize( targetBaseLen ) );
 else
 lc.Append( aP + dir_v_b + aDir.Resize( 2 * spc - cr ) );
 
 break;
 }
 
 case MT_TURN:
 {
 if( targetBaseLen )
 top = std::max( top, targetBaseLen - uCorner * 2 + offset * 2 );
 
 start( &lc, aP - dir_u_b, aDir );
 turn( -ANGLE_90 );
 forward( std::abs( offset ) );
 uShape( turnSide, uCorner, top );
 forward( std::abs( offset ) );
 break;
 }
 
 case MT_SINGLE:
 {
 if( targetBaseLen )
 top = std::max( top, ( targetBaseLen - sCorner * 2 - uCorner * 2 ) / 2 );
 
 miter( sCorner, false );
 uShape( startSide, uCorner, top );
 miter( sCorner, false );
 lc.Append( aP + dir_v_b + aDir.Resize( 2 * spc ) );
 break;
 }
 
 default:
 break;
 }
 
 if( aSide )
 {
 SEG axis( aP, aP + aDir );
 
 lc.Mirror( axis );
 }
 
 return lc;
}
 
 
bool MEANDERED_LINE::CheckSelfIntersections( MEANDER_SHAPE* aShape, int aClearance )
{
 for( int i = m_meanders.size() - 1; i >= 0; i-- )
 {
 MEANDER_SHAPE* m = m_meanders[i];
 
 if( m->Type() == MT_EMPTY || m->Type() == MT_CORNER )
 continue;
 
 const SEG& b1 = aShape->BaseSegment();
 const SEG& b2 = m->BaseSegment();
 
 if( b1.ApproxParallel( b2 ) )
 continue;
 
 int n = m->CLine( 0 ).SegmentCount();
 
 for( int j = n - 1; j >= 0; j-- )
 {
 if( aShape->CLine( 0 ).Collide( m->CLine( 0 ) .CSegment( j ), aClearance ) )
 return false;
 }
 }
 
 return true;
}
 
 
bool MEANDER_SHAPE::Fit( MEANDER_TYPE aType, const SEG& aSeg, const VECTOR2I& aP, bool aSide )
{
 const MEANDER_SETTINGS& st = Settings();
 
 bool checkMode = false;
 MEANDER_TYPE prim1, prim2;
 
 if( aType == MT_CHECK_START )
 {
 prim1 = MT_START;
 prim2 = MT_TURN;
 checkMode = true;
 }
 else if( aType == MT_CHECK_FINISH )
 {
 prim1 = MT_TURN;
 prim2 = MT_FINISH;
 checkMode = true;
 }
 
 if( checkMode )
 {
 MEANDER_SHAPE m1( m_placer, m_width, m_dual );
 MEANDER_SHAPE m2( m_placer, m_width, m_dual );
 
 m1.SetBaselineOffset( m_baselineOffset );
 m2.SetBaselineOffset( m_baselineOffset );
 
 bool c1 = m1.Fit( prim1, aSeg, aP, aSide );
 bool c2 = false;
 
 if( c1 )
 c2 = m2.Fit( prim2, aSeg, m1.End(), !aSide );
 
 if( c1 && c2 )
 {
 m_type = prim1;
 m_shapes[0] = m1.m_shapes[0];
 m_shapes[1] = m1.m_shapes[1];
 m_baseSeg =aSeg;
 m_p0 = aP;
 m_side = aSide;
 m_amplitude = m1.Amplitude();
 m_dual = m1.m_dual;
 m_baseSeg = m1.m_baseSeg;
 m_baseIndex = m1.m_baseIndex;
 updateBaseSegment();
 m_baselineOffset = m1.m_baselineOffset;
 return true;
 }
 else
 {
 return false;
 }
 }
 
 int minAmpl = MinAmplitude();
 int maxAmpl = std::max( st.m_maxAmplitude, minAmpl );
 
 for( int ampl = maxAmpl; ampl >= minAmpl; ampl -= st.m_step )
 {
 m_amplitude = ampl;
 
 if( m_dual )
 {
 m_shapes[0] = genMeanderShape( aP, aSeg.B - aSeg.A, aSide, aType, m_baselineOffset );
 m_shapes[1] = genMeanderShape( aP, aSeg.B - aSeg.A, aSide, aType, -m_baselineOffset );
 }
 else
 {
 m_shapes[0] = genMeanderShape( aP, aSeg.B - aSeg.A, aSide, aType, 0 );
 }
 
 m_type = aType;
 m_baseSeg = aSeg;
 m_p0 = aP;
 m_side = aSide;
 
 updateBaseSegment();
 
 if( m_placer->CheckFit( this ) )
 return true;
 }
 
 return false;
}
 
 
void MEANDER_SHAPE::Recalculate()
{
 m_shapes[0] = genMeanderShape( m_p0, m_baseSeg.B - m_baseSeg.A, m_side, m_type,
 m_dual ? m_baselineOffset : 0 );
 
 if( m_dual )
 m_shapes[1] = genMeanderShape( m_p0, m_baseSeg.B - m_baseSeg.A, m_side, m_type,
 -m_baselineOffset );
 
 updateBaseSegment();
}
 
 
void MEANDER_SHAPE::Resize( int aAmpl )
{
 if( aAmpl < 0 )
 return;
 
 m_amplitude = aAmpl;
 
 Recalculate();
}
 
 
void MEANDER_SHAPE::MakeEmpty()
{
 updateBaseSegment();
 
 VECTOR2I dir = m_clippedBaseSeg.B - m_clippedBaseSeg.A;
 
 m_type = MT_EMPTY;
 m_amplitude = 0;
 
 m_shapes[0] = genMeanderShape( m_p0, dir, m_side, m_type, m_dual ? m_baselineOffset : 0 );
 
 if( m_dual )
 m_shapes[1] = genMeanderShape( m_p0, dir, m_side, m_type, -m_baselineOffset );
}
 
 
void MEANDERED_LINE::AddCorner( const VECTOR2I& aA, const VECTOR2I& aB )
{
 MEANDER_SHAPE* m = new MEANDER_SHAPE( m_placer, m_width, m_dual );
 
 m->MakeCorner( aA, aB );
 m_last = aA;
 
 m_meanders.push_back( m );
}
 
 
void MEANDERED_LINE::AddArc( const SHAPE_ARC& aArc1, const SHAPE_ARC& aArc2 )
{
 MEANDER_SHAPE* m = new MEANDER_SHAPE( m_placer, m_width, m_dual );
 
 m->MakeArc( aArc1, aArc2 );
 m_last = aArc1.GetP1();
 
 m_meanders.push_back( m );
}
 
 
void MEANDERED_LINE::AddArcAndPt( const SHAPE_ARC& aArc1, const VECTOR2I& aPt2 )
{
 SHAPE_ARC arc2( aPt2, aPt2, aPt2, 0 );
 
 AddArc( aArc1, arc2 );
}
 
 
void MEANDERED_LINE::AddPtAndArc( const VECTOR2I& aPt1, const SHAPE_ARC& aArc2 )
{
 SHAPE_ARC arc1( aPt1, aPt1, aPt1, 0 );
 
 AddArc( arc1, aArc2 );
}
 
 
void MEANDER_SHAPE::MakeCorner( const VECTOR2I& aP1, const VECTOR2I& aP2 )
{
 SetType( MT_CORNER );
 m_shapes[0].Clear();
 m_shapes[1].Clear();
 m_shapes[0].Append( aP1 );
 m_shapes[1].Append( aP2 );
 m_clippedBaseSeg.A = aP1;
 m_clippedBaseSeg.B = aP1;
}
 
 
void MEANDER_SHAPE::MakeArc( const SHAPE_ARC& aArc1, const SHAPE_ARC& aArc2 )
{
 SetType( MT_CORNER );
 m_shapes[0].Clear();
 m_shapes[1].Clear();
 m_shapes[0].Append( aArc1 );
 m_shapes[1].Append( aArc2 );
 m_clippedBaseSeg.A = aArc1.GetP1();
 m_clippedBaseSeg.B = aArc1.GetP1();
}
 
 
void MEANDERED_LINE::AddMeander( MEANDER_SHAPE* aShape )
{
 m_last = aShape->BaseSegment().B;
 m_meanders.push_back( aShape );
}
 
 
void MEANDERED_LINE::Clear()
{
 for( MEANDER_SHAPE* m : m_meanders )
 delete m;
 
 m_meanders.clear( );
}
 
 
int MEANDER_SHAPE::BaselineLength() const
{
 return m_clippedBaseSeg.Length();
}
 
 
long long int MEANDER_SHAPE::CurrentLength() const
{
 return CLine( 0 ).Length();
}
 
 
long long int MEANDER_SHAPE::MinTunableLength() const
{
 MEANDER_SHAPE copy = *this;
 
 copy.SetTargetBaselineLength( BaselineLength() );
 copy.Resize( copy.MinAmplitude() );
 
 return copy.CurrentLength();
}
 
 
void MEANDER_SHAPE::updateBaseSegment( )
{
 if( m_dual )
 {
 VECTOR2I midpA = ( CLine( 0 ).CPoint( 0 ) + CLine( 1 ).CPoint( 0 ) ) / 2;
 VECTOR2I midpB = ( CLine( 0 ).CPoint( -1 ) + CLine( 1 ).CPoint( -1 ) ) / 2;
 
 m_clippedBaseSeg.A = m_baseSeg.LineProject( midpA );
 m_clippedBaseSeg.B = m_baseSeg.LineProject( midpB );
 }
 else
 {
 m_clippedBaseSeg.A = m_baseSeg.LineProject( CLine( 0 ).CPoint( 0 ) );
 m_clippedBaseSeg.B = m_baseSeg.LineProject( CLine( 0 ).CPoint( -1 ) );
 }
}
 
}