teardrop_utils.cpp

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2021 Jean-Pierre Charras, jp.charras at wanadoo.fr
 * Copyright (C) 2023 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * 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.
 *
 * 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, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/*
 * Some calculations (mainly computeCurvedForRoundShape) are derived from
 * https://github.com/NilujePerchut/kicad_scripts/tree/master/teardrops
 */
 
#include <board_design_settings.h>
#include <pcb_track.h>
#include <pad.h>
#include <zone_filler.h>
#include <board_commit.h>
 
#include "teardrop.h"
#include <geometry/convex_hull.h>
#include <geometry/shape_line_chain.h>
#include <convert_basic_shapes_to_polygon.h>
#include <bezier_curves.h>
 
#include <wx/log.h>
 
 
void TRACK_BUFFER::AddTrack( PCB_TRACK* aTrack, int aLayer, int aNetcode )
{
 auto item = m_map_tracks.find( idxFromLayNet( aLayer, aNetcode ) );
 std::vector<PCB_TRACK*>* buffer;
 
 if( item == m_map_tracks.end() )
 {
 buffer = new std::vector<PCB_TRACK*>;
 m_map_tracks[idxFromLayNet( aLayer, aNetcode )] = buffer;
 }
 else
 {
 buffer = (*item).second;
 }
 
 buffer->push_back( aTrack );
}
 
 
VIAPAD::VIAPAD( PCB_VIA* aVia ) :
 m_Parent( aVia )
{
 m_Pos = aVia->GetPosition();
 m_Width = aVia->GetWidth();
 m_Drill = aVia->GetDrillValue();
 m_NetCode = aVia->GetNetCode();
 m_IsRound = true;
 m_IsPad = false;
}
 
 
VIAPAD::VIAPAD( PAD* aPad ) :
 m_Parent( aPad )
{
 m_Pos = aPad->GetPosition();
 m_Width = std::min( aPad->GetSize().x, aPad->GetSize().y );
 m_Drill = std::min( aPad->GetDrillSizeX(), aPad->GetDrillSizeY() );
 m_NetCode = aPad->GetNetCode();
 m_IsRound = aPad->GetShape() == PAD_SHAPE::CIRCLE ||
 ( aPad->GetShape() == PAD_SHAPE::OVAL
 && aPad->GetSize().x == aPad->GetSize().y );
 m_IsPad = true;
}
 
 
VIAPAD::VIAPAD( PCB_TRACK* aTrack, ENDPOINT_T aEndPoint ) :
 m_Parent( aTrack )
{
 m_Pos = aEndPoint == ENDPOINT_START ? aTrack->GetStart() : aTrack->GetEnd();
 m_Width =aTrack->GetWidth();
 m_Drill = 0;
 m_NetCode = aTrack->GetNetCode();
 m_IsRound = true;
 m_IsPad = false;
}
 
 
void TEARDROP_MANAGER::collectVias( std::vector< VIAPAD >& aList ) const
{
 for( PCB_TRACK* item : m_board->Tracks() )
 {
 if( item->Type() != PCB_VIA_T )
 continue;
 
 aList.emplace_back( static_cast<PCB_VIA*>( item ) );
 }
}
 
 
void TEARDROP_MANAGER::collectPadsCandidate( std::vector< VIAPAD >& aList,
 bool aDrilledViaPad,
 bool aRoundShapesOnly,
 bool aIncludeNotDrilled ) const
{
 for( FOOTPRINT* fp : m_board->Footprints() )
 {
 for( PAD* pad : fp->Pads() )
 {
 if( !pad->IsOnCopperLayer() )
 continue;
 
 if( pad->GetNetCode() <= 0 ) // Not connected, so a teardrop cannot be attached
 continue;
 
 if( pad->GetShape() == PAD_SHAPE::CUSTOM ) // A teardrop shape cannot be built
 continue;
 
 if( aRoundShapesOnly )
 {
 bool round_shape = pad->GetShape() == PAD_SHAPE::CIRCLE
 || ( pad->GetShape() == PAD_SHAPE::OVAL
 && pad->GetSize().x == pad->GetSize().y );
 if( !round_shape )
 continue;
 }
 
 if( pad->HasHole() && !aDrilledViaPad )
 continue;
 
 if( pad->HasHole() || aIncludeNotDrilled )
 aList.emplace_back( pad );
 }
 }
}
 
 
void TEARDROP_MANAGER::collectTeardrops( std::vector< ZONE* >& aList ) const
{
 for( ZONE* zone : m_board->Zones() )
 {
 if( zone->IsTeardropArea() )
 aList.push_back( zone );
 }
}
 
 
bool TEARDROP_MANAGER::isViaAndTrackInSameZone( VIAPAD& aViapad, PCB_TRACK* aTrack ) const
{
 for( ZONE* zone: m_board->Zones() )
 {
 // Skip teardrops
 if( zone->IsTeardropArea() )
 continue;
 
 // Only consider zones on the same layer
 if( !zone->IsOnLayer( aTrack->GetLayer() ) )
 continue;
 
 if( zone->GetNetCode() == aTrack->GetNetCode() )
 {
 if( zone->Outline()->Contains( VECTOR2I( aViapad.m_Pos ) ) )
 {
 // Ensure the pad (if it is a pad) can be connected by the zone
 if( aViapad.m_IsPad )
 {
 PAD *pad = static_cast< PAD* >( aViapad.m_Parent );
 
 if( zone->GetPadConnection() == ZONE_CONNECTION::NONE
 || pad->GetZoneConnection() == ZONE_CONNECTION::NONE )
  {
 return false;
 }
 }
 
 return true;
 }
 }
 }
 
 return false;
}
 
 
PCB_TRACK* TEARDROP_MANAGER::findTouchingTrack( EDA_ITEM_FLAGS& aMatchType, PCB_TRACK* aTrackRef,
 const VECTOR2I& aEndPoint,
 TRACK_BUFFER& aTrackLookupList ) const
{
 EDA_ITEM_FLAGS match = 0; // to return the end point EDA_ITEM_FLAGS:
 // 0, STARTPOINT, ENDPOINT
 int matches = 0; // Count of candidates: only 1 is acceptable
 PCB_TRACK* candidate = nullptr; // a reference to the track connected
 
 std::vector<PCB_TRACK*>* currlist = aTrackLookupList.GetTrackList( aTrackRef->GetLayer(),
 aTrackRef->GetNetCode() );
 
 for( PCB_TRACK* curr_track: *currlist )
 {
 if( curr_track == aTrackRef )
 continue;
 
 match = curr_track->IsPointOnEnds( aEndPoint, m_tolerance);
 
 if( match )
 {
 // if faced with a Y junction, choose the track longest segment as candidate
 matches++;
 
 if( matches > 1 )
 {
 double previous_len = candidate->GetLength();
 double curr_len = curr_track->GetLength();
 
 if( previous_len >= curr_len )
 continue;
 }
 
 aMatchType = match;
 candidate = curr_track;
 }
 }
 
 return candidate;
}
 
 
 
static VECTOR2D NormalizeVector( VECTOR2I aVector )
{
 VECTOR2D vect( aVector );
 double norm = vect.EuclideanNorm();
 return vect / norm;
}
 
 
/*
 * Compute the curve part points for teardrops connected to a round shape
 * The Bezier curve control points are optimized for a round pad/via shape,
 * and do not give a good curve shape for other pad shapes
 */
void TEARDROP_MANAGER::computeCurvedForRoundShape( TEARDROP_PARAMETERS* aCurrParams,
 std::vector<VECTOR2I>& aPoly,
 int aTrackHalfWidth,
 VECTOR2D aTrackDir, VIAPAD& aViaPad,
 std::vector<VECTOR2I>& pts ) const
{
 // in pts:
 // A and B are points on the track ( pts[0] and pts[1] )
 // C and E are points on the aViaPad ( pts[2] and pts[4] )
 // D is the aViaPad centre ( pts[3] )
 double Vpercent = aCurrParams->m_HeightRatio;
 int td_height = aViaPad.m_Width * Vpercent;
 
 // First, calculate a aVpercent equivalent to the td_height clamped by aTdMaxHeight
 // We cannot use the initial aVpercent because it gives bad shape with points
 // on aViaPad calculated for a clamped aViaPad size
 if( aCurrParams->m_TdMaxHeight > 0 && aCurrParams->m_TdMaxHeight < td_height )
 Vpercent *= (double)aCurrParams->m_TdMaxHeight / td_height;
 
 int radius = aViaPad.m_Width / 2;
 double minVpercent = double( aTrackHalfWidth ) / radius;
 double weaken = (Vpercent - minVpercent) / ( 1 - minVpercent ) / radius;
 
 double biasBC = 0.5 * SEG( pts[1], pts[2] ).Length();
 double biasAE = 0.5 * SEG( pts[4], pts[0] ).Length();
 
 VECTOR2I vecC = (VECTOR2I)pts[2] - aViaPad.m_Pos;
 VECTOR2I tangentC = VECTOR2I( pts[2].x - vecC.y * biasBC * weaken,
 pts[2].y + vecC.x * biasBC * weaken );
 VECTOR2I vecE = (VECTOR2I)pts[4] - aViaPad.m_Pos;
 VECTOR2I tangentE = VECTOR2I( pts[4].x + vecE.y * biasAE * weaken,
 pts[4].y - vecE.x * biasAE * weaken );
 
 VECTOR2I tangentB = VECTOR2I( pts[1].x - aTrackDir.x * biasBC, pts[1].y - aTrackDir.y * biasBC );
 VECTOR2I tangentA = VECTOR2I( pts[0].x - aTrackDir.x * biasAE, pts[0].y - aTrackDir.y * biasAE );
 
 std::vector<VECTOR2I> curve_pts;
 curve_pts.reserve( aCurrParams->m_CurveSegCount );
 BEZIER_POLY( pts[1], tangentB, tangentC, pts[2] ).GetPoly( curve_pts, 0,
 aCurrParams->m_CurveSegCount );
 
 for( VECTOR2I& corner: curve_pts )
 aPoly.push_back( corner );
 
 aPoly.push_back( pts[3] );
 
 curve_pts.clear();
 BEZIER_POLY( pts[4], tangentE, tangentA, pts[0] ).GetPoly( curve_pts, 0,
 aCurrParams->m_CurveSegCount );
 
 for( VECTOR2I& corner: curve_pts )
 aPoly.push_back( corner );
}
 
 
/*
 * Compute the curve part points for teardrops connected to a rectangular/polygonal shape
 * The Bezier curve control points are not optimized for a special shape
 */
void TEARDROP_MANAGER::computeCurvedForRectShape( TEARDROP_PARAMETERS* aCurrParams,
 std::vector<VECTOR2I>& aPoly, int aTdHeight,
 int aTrackHalfWidth, VIAPAD& aViaPad,
 std::vector<VECTOR2I>& aPts ) const
{
 // in aPts:
 // A and B are points on the track ( pts[0] and pts[1] )
 // C and E are points on the aViaPad ( pts[2] and pts[4] )
 // D is the aViaPad centre ( pts[3] )
 
 // side1 is( aPts[1], aPts[2] ); from track to via
 VECTOR2I side1( aPts[2] - aPts[1] ); // vector from track to via
 // side2 is ( aPts[4], aPts[0] ); from via to track
 VECTOR2I side2( aPts[4] - aPts[0] ); // vector from track to via
 
 std::vector<VECTOR2I> curve_pts;
 curve_pts.reserve( aCurrParams->m_CurveSegCount );
 
 // Note: This side is from track to via
 VECTOR2I ctrl1 = ( aPts[1] + aPts[1] + aPts[2] ) / 3;
 VECTOR2I ctrl2 = ( aPts[1] + aPts[2] + aPts[2] ) / 3;
 
 // The control points must be moved toward the polygon inside, in order to give a curved shape
 // The move vector is perpendicular to the vertex (side 1 or side 2), and its
 // value is delta, depending on the sizes of via and track
 int delta = ( aTdHeight / 2 - aTrackHalfWidth );
 
 delta /= 4; // A scaling factor giving a fine shape, defined from tests.
 // However for short sides, the value of delta must be reduced, depending
 // on the side length
 // We use here a max delta value = side_length/8, defined from tests
 
 int side_length = side1.EuclideanNorm();
 int delta_effective = std::min( delta, side_length/8 );
 // The move vector depend on the quadrant: it must be always defined to create a
 // curve with a direction toward the track
 EDA_ANGLE angle1( side1 );
 int sign = std::abs( angle1 ) >= ANGLE_90 ? 1 : -1;
 VECTOR2I bias( 0, sign * delta_effective );
 
 // Does not works well with the current algo, due to an initial bug.
 // but I (JPC) keep it here because probably it will gives a better shape
 // if the algo is refined.
 // RotatePoint( bias, angle1 );
 
 ctrl1.x += bias.x;
 ctrl1.y += bias.y;
 ctrl2.x += bias.x;
 ctrl2.y += bias.y;
 
 BEZIER_POLY( aPts[1], ctrl1, ctrl2, aPts[2] ).GetPoly( curve_pts, 0,
 aCurrParams->m_CurveSegCount );
 
 for( VECTOR2I& corner: curve_pts )
 aPoly.push_back( corner );
 
 aPoly.push_back( aPts[3] );
 
 // Note: This side is from via to track
 curve_pts.clear();
 ctrl1 = ( aPts[4] + aPts[4] + aPts[0] ) / 3;
 ctrl2 = ( aPts[4] + aPts[0] + aPts[0] ) / 3;
 
 side_length = side2.EuclideanNorm();
 delta_effective = std::min( delta, side_length/8 );
 
 EDA_ANGLE angle2( side2 );
 sign = std::abs( angle2 ) <= ANGLE_90 ? 1 : -1;
 
 bias = VECTOR2I( 0, sign * delta_effective );
 
 // Does not works well with the current algo
 // RotatePoint( bias, angle2 );
 
 ctrl1.x += bias.x;
 ctrl1.y += bias.y;
 ctrl2.x += bias.x;
 ctrl2.y += bias.y;
 
 BEZIER_POLY( aPts[4], ctrl1, ctrl2, aPts[0] ).GetPoly( curve_pts, 0,
 aCurrParams->m_CurveSegCount );
 
 for( VECTOR2I& corner: curve_pts )
 aPoly.push_back( corner );
}
 
 
bool TEARDROP_MANAGER::ComputePointsOnPadVia( TEARDROP_PARAMETERS* aCurrParams,
 PCB_LAYER_ID aLayer,
 VIAPAD& aViaPad,
 std::vector<VECTOR2I>& aPts ) const
{
 // Compute the 2 anchor points on pad/via of the teardrop shape
 
 PAD* pad = ( aViaPad.m_Parent->Type() == PCB_PAD_T ) ? static_cast<PAD*>(aViaPad.m_Parent)
 : nullptr;
 SHAPE_POLY_SET c_buffer;
 
 // aHeightRatio is the factor to calculate the aViaPad teardrop preferred height
 // teardrop height = aViaPad size * aHeightRatio (aHeightRatio <= 1.0)
 // For rectangular (and similar) shapes, the preferred_height is calculated from the min
 // dim of the rectangle = aViaPad.m_Width
 
 int preferred_height = aViaPad.m_Width * aCurrParams->m_HeightRatio;
 
 // force_clip_shape = true to force the via/pad polygon to be clipped to follow
 // constraints
 // Clipping is also needed for rectangular shapes, because the teardrop shape is
 // restricted to a polygonal area smaller than the pad area (the teardrop height
 // use the smaller value of X and Y sizes).
 bool force_clip_shape = aCurrParams->m_HeightRatio < 1.0;
 
 // To find the anchor points on via/pad shape, we build the polygonal shape, and clip the polygon
 // to the max size (preferred_height or m_TdMaxHeight) by a rectangle centered on the
 // axis of the expected teardrop shape.
 // (only reduce the size of polygonal shape does not give good anchor points)
 if( aViaPad.m_IsRound )
 {
 TransformCircleToPolygon( c_buffer, aViaPad.m_Pos, aViaPad.m_Width/2 ,
 ARC_LOW_DEF, ERROR_INSIDE, 16 );
 }
 else // Only PADS can have a not round shape
 {
 wxCHECK( pad, false );
 
 force_clip_shape = true;
 
 preferred_height = aViaPad.m_Width * aCurrParams->m_HeightRatio;
 pad->TransformShapeToPolygon( c_buffer, aLayer, 0, ARC_LOW_DEF, ERROR_INSIDE );
 }
 
 // Clip the pad/via shape to match the m_TdMaxHeight constraint, and for
 // not rounded pad, clip the shape at the aViaPad.m_Width, i.e. the value
 // of the smallest value between size.x and size.y values.
 if( force_clip_shape || ( aCurrParams->m_TdMaxHeight > 0
 && aCurrParams->m_TdMaxHeight < preferred_height ) )
 {
 int halfsize = std::min( aCurrParams->m_TdMaxHeight, preferred_height )/2;
 
 // teardrop_axis is the line from anchor point on the track and the end point
 // of the teardrop in the pad/via
 // this is the teardrop_axis of the teardrop shape to build
 VECTOR2I ref_on_track = ( aPts[0] + aPts[1] ) / 2;
 VECTOR2I teardrop_axis( aPts[3] - ref_on_track );
 
 EDA_ANGLE orient( teardrop_axis );
 int len = teardrop_axis.EuclideanNorm();
 
 // Build the constraint polygon: a rectangle with
 // length = dist between the point on track and the pad/via pos
 // height = m_TdMaxHeight or aViaPad.m_Width
 SHAPE_POLY_SET clipping_rect;
 clipping_rect.NewOutline();
 
 // Build a horizontal rect: it will be rotated later
 clipping_rect.Append( 0, - halfsize );
 clipping_rect.Append( 0, halfsize );
 clipping_rect.Append( len, halfsize );
 clipping_rect.Append( len, - halfsize );
 
 clipping_rect.Rotate( -orient );
 clipping_rect.Move( ref_on_track );
 
 // Clip the shape to the max allowed teadrop area
 c_buffer.BooleanIntersection( clipping_rect, SHAPE_POLY_SET::PM_FAST );
 }
 
 /* in aPts:
 * A and B are points on the track ( aPts[0] and aPts[1] )
 * C and E are points on the aViaPad ( aPts[2] and aPts[4] )
 * D is midpoint behind the aViaPad centre ( aPts[3] )
 */
 
 SHAPE_LINE_CHAIN& padpoly = c_buffer.Outline(0);
 std::vector<VECTOR2I> points = padpoly.CPoints();
 
 std::vector<VECTOR2I> initialPoints;
 initialPoints.push_back( aPts[0] );
 initialPoints.push_back( aPts[1] );
 
 for( const VECTOR2I& pt: points )
 initialPoints.emplace_back( pt.x, pt.y );
 
 std::vector<VECTOR2I> hull;
 BuildConvexHull( hull, initialPoints );
 
 // Search for end points of segments starting at aPts[0] or aPts[1]
 // In some cases, in convex hull, only one point (aPts[0] or aPts[1]) is still in list
 VECTOR2I PointC;
 VECTOR2I PointE;
 int found_start = -1; // 2 points (one start and one end) should be found
 int found_end = -1;
 
 VECTOR2I start = aPts[0];
 VECTOR2I pend = aPts[1];
 
 for( unsigned ii = 0, jj = 0; jj < hull.size(); ii++, jj++ )
 {
 unsigned next = ii+ 1;
 
 if( next >= hull.size() )
 next = 0;
 
 int prev = ii -1;
 
 if( prev < 0 )
 prev = hull.size()-1;
 
 if( hull[ii] == start )
 {
 // the previous or the next point is candidate:
 if( hull[next] != pend )
 PointE = hull[next];
 else
 PointE = hull[prev];
 
 found_start = ii;
 }
 
 if( hull[ii] == pend )
 {
 if( hull[next] != start )
 PointC = hull[next];
 else
 PointC = hull[prev];
 
 found_end = ii;
 }
 }
 
 if( found_start < 0 ) // PointE was not initialized, because start point does not exit
 {
 int ii = found_end-1;
 
 if( ii < 0 )
 ii = hull.size()-1;
 
 PointE = hull[ii];
 }
 
 if( found_end < 0 ) // PointC was not initialized, because end point does not exit
 {
 int ii = found_start-1;
 
 if( ii < 0 )
 ii = hull.size()-1;
 
 PointC = hull[ii];
 }
 
 aPts[2] = PointC;
 aPts[4] = PointE;
 
 // Now we have to know if the choice aPts[2] = PointC is the best, or if
 // aPts[2] = PointE is better.
 // A criteria is to calculate the polygon area in these 2 cases, and choose the case
 // that gives the bigger area, because the segments starting at PointC and PointE
 // maximize their distance.
 SHAPE_LINE_CHAIN dummy1( aPts, true );
 double area1 = dummy1.Area();
 
 std::swap( aPts[2], aPts[4] );
 SHAPE_LINE_CHAIN dummy2( aPts, true );
 double area2 = dummy2.Area();
 
 if( area1 > area2 ) // The first choice (without swapping) is the better.
 std::swap( aPts[2], aPts[4] );
 
 return true;
}
 
 
bool TEARDROP_MANAGER::findAnchorPointsOnTrack( TEARDROP_PARAMETERS* aCurrParams,
 VECTOR2I& aStartPoint, VECTOR2I& aEndPoint,
 PCB_TRACK*& aTrack, VIAPAD& aViaPad,
 int* aEffectiveTeardropLen,
 bool aFollowTracks,
 TRACK_BUFFER& aTrackLookupList ) const
{
 bool found = true;
 VECTOR2I start = aTrack->GetStart(); // one reference point on the track, inside teardrop
 VECTOR2I end = aTrack->GetEnd(); // the second reference point on the track, outside teardrop
 int radius = aViaPad.m_Width / 2;
 
 // Requested length of the teardrop:
 int targetLength = aViaPad.m_Width * aCurrParams->m_LengthRatio;
 
 if( aCurrParams->m_TdMaxLen > 0 )
 targetLength = std::min( aCurrParams->m_TdMaxLen, targetLength );
 
 // actualTdLen is the distance between start and the teardrop point on the segment from start to end
 int actualTdLen;
 bool need_swap = false; // true if the start and end points of the current track are swapped
 
 // ensure that start is at the via/pad end
 if( SEG( end, aViaPad.m_Pos ).Length() < radius )
 {
 std::swap( start, end );
 need_swap = true;
 }
 
 SHAPE_POLY_SET shapebuffer;
 
 if( aViaPad.m_IsRound )
 {
 TransformCircleToPolygon( shapebuffer, aViaPad.m_Pos, radius,
 ARC_LOW_DEF, ERROR_INSIDE, 16 );
 }
 else
 {
 PAD* pad = static_cast<PAD*>( aViaPad.m_Parent );
 pad->TransformShapeToPolygon( shapebuffer, aTrack->GetLayer(), 0,
 ARC_LOW_DEF, ERROR_INSIDE );
 }
 
 SHAPE_LINE_CHAIN& outline = shapebuffer.Outline(0);
 outline.SetClosed( true );
 
 // Search the intersection point between the pad/via shape and the current track
 // This this the starting point to define the teardrop length
 SHAPE_LINE_CHAIN::INTERSECTIONS pts;
 int pt_count = outline.Intersect( SEG( start, end ), pts );
 
 // Ensure a intersection point was found, otherwise we cannot built the teardrop
 // using this track (it is fully outside or inside the pad/via shape)
 if( pt_count < 1 )
 return false;
 
 VECTOR2I intersect = pts[0].p;
 start = intersect; // This is currently the reference point of the teardrop lenght
 
 // actualTdLen for now the distance between start and the teardrop point on the (start end)segment
 // It cannot be bigger than the lenght of this segment
 actualTdLen = std::min( targetLength, SEG( start, end ).Length() );
 VECTOR2I ref_lenght_point = start; // the reference point of actualTdLen
 
 // If the first track is too short to allow a teardrop having the requested length
 // explore the connected track(s), and try to find a anchor point at targetLength from initial start
 if( actualTdLen < targetLength && aFollowTracks )
 {
 int consumed = 0;
 
 while( actualTdLen+consumed < targetLength )
 {
 EDA_ITEM_FLAGS matchType;
 
 PCB_TRACK* connected_track = findTouchingTrack( matchType, aTrack, end, aTrackLookupList );
 
 if( connected_track == nullptr )
 break;
 
 // TODO: stop if angle between old and new segment is > 45 deg to avoid bad shape
 consumed += actualTdLen;
 // actualTdLen is the new distance from new start point and the teardrop anchor point
 actualTdLen = std::min( targetLength-consumed, int( connected_track->GetLength() ) );
 aTrack = connected_track;
 end = connected_track->GetEnd();
 start = connected_track->GetStart();
 need_swap = false;
 
 if( matchType != STARTPOINT )
 {
 std::swap( start, end );
 need_swap = true;
 }
 
 // If we do not want to explore more than one connected track, stop search here
 break;
 }
 }
 
 // if aTrack is an arc, find the best teardrop end point on the arc
 // It is currently on the segment from arc start point to arc end point,
 // therefore not really on the arc, because we have used only the track end points.
 if( aTrack->Type() == PCB_ARC_T )
 {
 // To find the best start and end points to build the teardrop shape, we convert
 // the arc to segments, and search for the segment havig its start point at a dist
 // < actualTdLen, and its end point at adist > actualTdLen:
 SHAPE_ARC arc( aTrack->GetStart(), static_cast<PCB_ARC*>( aTrack )->GetMid(),
 aTrack->GetEnd(), aTrack->GetWidth() );
 
 if( need_swap )
 arc.Reverse();
 
 SHAPE_LINE_CHAIN poly = arc.ConvertToPolyline();
 
 // Now, find the segment of the arc at a distance < actualTdLen from ref_lenght_point.
 // We just search for the first segment (starting from the farest segment) with its
 // start point at a distance < actualTdLen dist
 // This is basic, but it is probably enough.
 if( poly.PointCount() > 2 )
 {
 // Note: the first point is inside or near the pad/via shape
 // The last point is outside and the farest from the ref_lenght_point
 // So we explore segments from the last to the first
 for( int ii = poly.PointCount()-1; ii >= 0 ; ii-- )
 {
 int dist_from_start = ( poly.CPoint( ii ) - start ).EuclideanNorm();
 
 // The first segment at a distance of the reference point < actualTdLen is OK
 // and is suitable to define the reference segment of the teardrop anchor.
 if( dist_from_start < actualTdLen || ii == 0 )
 {
 start = poly.CPoint( ii );
 
 if( ii < poly.PointCount()-1 )
 end = poly.CPoint( ii+1 );
 
 // actualTdLen is the distance between start (the reference segment start point)
 // and the point on track of the teardrop.
 // This is the difference between the initial actualTdLen value and the
 // distance between start and ref_lenght_point.
 actualTdLen -= (start - ref_lenght_point).EuclideanNorm();
 
 // Ensure validity of actualTdLen: >= 0, and <= segment lenght
 if( actualTdLen < 0 ) // should not happen, but...
 actualTdLen = 0;
 
 actualTdLen = std::min( actualTdLen, (end - start).EuclideanNorm() );
 
 break;
 }
 }
 }
 }
 
 // aStartPoint and aEndPoint will define later a segment to build the 2 anchors points
 // of the teardrop on the aTrack shape.
 // they are two points (both outside the pad/via shape) of aTrack if aTrack is a segment,
 // or a small segment on aTrack if aTrack is an ARC
 aStartPoint = start;
 aEndPoint = end;
 
 *aEffectiveTeardropLen = actualTdLen;
 return found;
}
 
 
bool TEARDROP_MANAGER::computeTeardropPolygonPoints( TEARDROP_PARAMETERS* aCurrParams,
 std::vector<VECTOR2I>& aCorners,
 PCB_TRACK* aTrack, VIAPAD& aViaPad,
 bool aFollowTracks,
 TRACK_BUFFER& aTrackLookupList ) const
{
 VECTOR2I start, end; // Start and end points of the track anchor of the teardrop
 // the start point is inside the teardrop shape
  // the end point is outside.
 int track_stub_len; // the dist between the start point and the anchor point
 // on the track
 
 // Note: aTrack can be modified if the initial track is too short
 if( !findAnchorPointsOnTrack( aCurrParams, start, end, aTrack, aViaPad, &track_stub_len,
 aFollowTracks, aTrackLookupList ) )
 return false;
 
 // The start and end points must be different to calculate a valid polygon shape
 if( start == end )
 return false;
 
 VECTOR2D vecT = NormalizeVector(end - start);
 
 // find the 2 points on the track, sharp end of the teardrop
 int track_halfwidth = aTrack->GetWidth() / 2;
 VECTOR2I pointB = start + VECTOR2I( vecT.x * track_stub_len + vecT.y * track_halfwidth,
 vecT.y * track_stub_len - vecT.x * track_halfwidth );
 VECTOR2I pointA = start + VECTOR2I( vecT.x * track_stub_len - vecT.y * track_halfwidth,
 vecT.y * track_stub_len + vecT.x * track_halfwidth );
 
 // To build a polygonal valid shape pointA and point B must be outside the pad
 // It can be inside with some pad shapes having very different X and X sizes
 if( !aViaPad.m_IsRound )
 {
 PAD* pad = static_cast<PAD*>( aViaPad.m_Parent );
 
 if( pad->HitTest( pointA ) )
 return false;
 
 if( pad->HitTest( pointB ) )
 return false;
 }
 
 // Introduce a last point to cover the via centre to ensure it is seen as connected
 VECTOR2I pointD = aViaPad.m_Pos;
 // add a small offset in order to have the aViaPad.m_Pos reference point inside
 // the teardrop area, just in case...
 int offset = pcbIUScale.mmToIU( 0.001 );
 pointD += VECTOR2I( int( -vecT.x*offset), int(-vecT.y*offset) );
 
 VECTOR2I pointC, pointE; // Point on PADVIA outlines
 std::vector<VECTOR2I> pts = {pointA, pointB, pointC, pointD, pointE};
 
 ComputePointsOnPadVia( aCurrParams, aTrack->GetLayer(), aViaPad, pts );
 
 if( !aCurrParams->IsCurved() )
 {
 aCorners = pts;
 return true;
 }
 
 // See if we can use curved teardrop shape
 if( aViaPad.m_IsRound )
 {
 computeCurvedForRoundShape( aCurrParams, aCorners, track_halfwidth, vecT, aViaPad, pts );
 }
 else
 {
 int td_height = aViaPad.m_Width * aCurrParams->m_HeightRatio;
 
 if( aCurrParams->m_TdMaxHeight > 0 && aCurrParams->m_TdMaxHeight < td_height )
 td_height = aCurrParams->m_TdMaxHeight;
 
 computeCurvedForRectShape( aCurrParams, aCorners, td_height, track_halfwidth,
 aViaPad, pts );
 }
 
 return true;
}