kicad/polygon/poly2tri/sweep/sweep.cc

/*
 * Poly2Tri Copyright (c) 2009-2010, Poly2Tri Contributors
 * http://code.google.com/p/poly2tri/
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * * Neither the name of Poly2Tri nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without specific
 *   prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <stdexcept>
#include "sweep.h"
#include "sweep_context.h"
#include "advancing_front.h"
#include "../common/utils.h"

namespace p2t {
// Triangulate simple polygon with holes
void Sweep::Triangulate( SweepContext& tcx )
{
    tcx.InitTriangulation();
    tcx.CreateAdvancingFront( nodes_ );
    // Sweep points; build mesh
    SweepPoints( tcx );
    // Clean up
    FinalizationPolygon( tcx );
}


void Sweep::SweepPoints( SweepContext& tcx )
{
    for( int jj = 1; jj < tcx.point_count(); jj++ )
    {
        Point& point    = *tcx.GetPoint( jj );
        Node* node      = &PointEvent( tcx, point );

        for( unsigned int i = 0; i < point.edge_list.size(); i++ )
        {
            EdgeEvent( tcx, point.edge_list[i], node );
        }
    }
}


void Sweep::FinalizationPolygon( SweepContext& tcx )
{
    // Get an Internal triangle to start with
    Triangle* t = tcx.front()->head()->next->triangle;
    Point* p = tcx.front()->head()->next->point;

    while( !t->GetConstrainedEdgeCW( *p ) )
    {
        t = t->NeighborCCW( *p );
    }

    // Collect interior triangles constrained by edges
    tcx.MeshClean( *t );
}


Node& Sweep::PointEvent( SweepContext& tcx, Point& point )
{
    Node& node = tcx.LocateNode( point );
    Node& new_node = NewFrontTriangle( tcx, point, node );

    // Only need to check +epsilon since point never have smaller
    // x value than node due to how we fetch nodes from the front
    if( point.x <= node.point->x + EPSILON )
    {
        Fill( tcx, node );
    }

    // tcx.AddNode(new_node);

    FillAdvancingFront( tcx, new_node );
    return new_node;
}


void Sweep::EdgeEvent( SweepContext& tcx, Edge* edge, Node* node )
{
    tcx.edge_event.constrained_edge = edge;
    tcx.edge_event.right = (edge->p->x > edge->q->x);

    if( IsEdgeSideOfTriangle( *node->triangle, *edge->p, *edge->q ) )
    {
        return;
    }

    // For now we will do all needed filling
    // TODO: integrate with flip process might give some better performance
    // but for now this avoid the issue with cases that needs both flips and fills
    FillEdgeEvent( tcx, edge, node );
    EdgeEvent( tcx, *edge->p, *edge->q, node->triangle, *edge->q );
}


void Sweep::EdgeEvent( SweepContext& tcx, Point& ep, Point& eq, Triangle* triangle, Point& point )
{
    if( IsEdgeSideOfTriangle( *triangle, ep, eq ) )
    {
        return;
    }

    Point* p1 = triangle->PointCCW( point );
    Orientation o1 = Orient2d( eq, *p1, ep );

    if( o1 == COLLINEAR )
    {
        if( triangle->Contains( &eq, p1 ) )
        {
            triangle->MarkConstrainedEdge( &eq, p1 );
            // We are modifying the constraint maybe it would be better to
            // not change the given constraint and just keep a variable for the new constraint
            tcx.edge_event.constrained_edge->q = p1;
            triangle = &triangle->NeighborAcross( point );
            EdgeEvent( tcx, ep, *p1, triangle, *p1 );
        }
        else
        {
            std::runtime_error( "EdgeEvent - collinear points not supported" );
            assert( 0 );
        }

        return;
    }

    Point* p2 = triangle->PointCW( point );
    Orientation o2 = Orient2d( eq, *p2, ep );

    if( o2 == COLLINEAR )
    {
        if( triangle->Contains( &eq, p2 ) )
        {
            triangle->MarkConstrainedEdge( &eq, p2 );
            // We are modifying the constraint maybe it would be better to
            // not change the given constraint and just keep a variable for the new constraint
            tcx.edge_event.constrained_edge->q = p2;
            triangle = &triangle->NeighborAcross( point );
            EdgeEvent( tcx, ep, *p2, triangle, *p2 );
        }
        else
        {
            std::runtime_error( "EdgeEvent - collinear points not supported" );
            assert( 0 );
        }

        return;
    }

    if( o1 == o2 )
    {
        // Need to decide if we are rotating CW or CCW to get to a triangle
        // that will cross edge
        if( o1 == CW )
        {
            triangle = triangle->NeighborCCW( point );
        }
        else
        {
            triangle = triangle->NeighborCW( point );
        }

        EdgeEvent( tcx, ep, eq, triangle, point );
    }
    else
    {
        // This triangle crosses constraint so lets flippin start!
        FlipEdgeEvent( tcx, ep, eq, triangle, point );
    }
}


bool Sweep::IsEdgeSideOfTriangle( Triangle& triangle, Point& ep, Point& eq )
{
    int index = triangle.EdgeIndex( &ep, &eq );

    if( index != -1 )
    {
        triangle.MarkConstrainedEdge( index );
        Triangle* t = triangle.GetNeighbor( index );

        if( t )
        {
            t->MarkConstrainedEdge( &ep, &eq );
        }

        return true;
    }

    return false;
}


Node& Sweep::NewFrontTriangle( SweepContext& tcx, Point& point, Node& node )
{
    Triangle* triangle = new Triangle( point, *node.point, *node.next->point );

    triangle->MarkNeighbor( *node.triangle );
    tcx.AddToMap( triangle );

    Node* new_node = new Node( point );
    nodes_.push_back( new_node );

    new_node->next  = node.next;
    new_node->prev  = &node;
    node.next->prev = new_node;
    node.next = new_node;

    if( !Legalize( tcx, *triangle ) )
    {
        tcx.MapTriangleToNodes( *triangle );
    }

    return *new_node;
}


void Sweep::Fill( SweepContext& tcx, Node& node )
{
    Triangle* triangle = new Triangle( *node.prev->point, *node.point, *node.next->point );

    // TODO: should copy the constrained_edge value from neighbor triangles
    // for now constrained_edge values are copied during the legalize
    triangle->MarkNeighbor( *node.prev->triangle );
    triangle->MarkNeighbor( *node.triangle );

    tcx.AddToMap( triangle );

    // Update the advancing front
    node.prev->next = node.next;
    node.next->prev = node.prev;

    // If it was legalized the triangle has already been mapped
    if( !Legalize( tcx, *triangle ) )
    {
        tcx.MapTriangleToNodes( *triangle );
    }
}


void Sweep::FillAdvancingFront( SweepContext& tcx, Node& n )
{
    // Fill right holes
    Node* node = n.next;

    while( node->next )
    {
        // if HoleAngle exceeds 90 degrees then break.
        if( LargeHole_DontFill( node ) )
            break;

        Fill( tcx, *node );
        node = node->next;
    }

    // Fill left holes
    node = n.prev;

    while( node->prev )
    {
        // if HoleAngle exceeds 90 degrees then break.
        if( LargeHole_DontFill( node ) )
            break;

        Fill( tcx, *node );
        node = node->prev;
    }

    // Fill right basins
    if( n.next && n.next->next )
    {
        double angle = BasinAngle( n );

        if( angle < PI_3div4 )
        {
            FillBasin( tcx, n );
        }
    }
}


// True if HoleAngle exceeds 90 degrees.
bool Sweep::LargeHole_DontFill( Node* node )
{
    Node* nextNode = node->next;
    Node* prevNode = node->prev;

    if( !AngleExceeds90Degrees( node->point, nextNode->point, prevNode->point ) )
        return false;

    // Check additional points on front.
    Node* next2Node = nextNode->next;

    // "..Plus.." because only want angles on same side as point being added.
    if( (next2Node != NULL)
        && !AngleExceedsPlus90DegreesOrIsNegative( node->point, next2Node->point,
                prevNode->point ) )
        return false;

    Node* prev2Node = prevNode->prev;

    // "..Plus.." because only want angles on same side as point being added.
    if( (prev2Node != NULL)
        && !AngleExceedsPlus90DegreesOrIsNegative( node->point, nextNode->point,
                prev2Node->point ) )
        return false;

    return true;
}


bool Sweep::AngleExceeds90Degrees( Point* origin, Point* pa, Point* pb )
{
    double angle = Angle( *origin, *pa, *pb );
    bool exceeds90Degrees = ( (angle > PI_div2) || (angle < -PI_div2) );

    return exceeds90Degrees;
}


bool Sweep::AngleExceedsPlus90DegreesOrIsNegative( Point* origin, Point* pa, Point* pb )
{
    double angle = Angle( *origin, *pa, *pb );
    bool exceedsPlus90DegreesOrIsNegative = (angle > PI_div2) || (angle < 0);

    return exceedsPlus90DegreesOrIsNegative;
}


double Sweep::Angle( Point& origin, Point& pa, Point& pb )
{
    /* Complex plane
     * ab = cosA +i*sinA
     * ab = (ax + ay*i)(bx + by*i) = (ax*bx + ay*by) + i(ax*by-ay*bx)
     * atan2(y,x) computes the principal value of the argument function
     * applied to the complex number x+iy
     * Where x = ax*bx + ay*by
     *       y = ax*by - ay*bx
     */
    double px   = origin.x;
    double py   = origin.y;
    double ax   = pa.x - px;
    double ay   = pa.y - py;
    double bx   = pb.x - px;
    double by   = pb.y - py;
    double x    = ax * by - ay * bx;
    double y    = ax * bx + ay * by;
    double angle = atan2( x, y );

    return angle;
}


double Sweep::BasinAngle( Node& node )
{
    double ax   = node.point->x - node.next->next->point->x;
    double ay   = node.point->y - node.next->next->point->y;

    return atan2( ay, ax );
}


double Sweep::HoleAngle( Node& node )
{
    /* Complex plane
     * ab = cosA +i*sinA
     * ab = (ax + ay*i)(bx + by*i) = (ax*bx + ay*by) + i(ax*by-ay*bx)
     * atan2(y,x) computes the principal value of the argument function
     * applied to the complex number x+iy
     * Where x = ax*bx + ay*by
     *       y = ax*by - ay*bx
     */
    double ax   = node.next->point->x - node.point->x;
    double ay   = node.next->point->y - node.point->y;
    double bx   = node.prev->point->x - node.point->x;
    double by   = node.prev->point->y - node.point->y;

    return atan2( ax * by - ay * bx, ax * bx + ay * by );
}


bool Sweep::Legalize( SweepContext& tcx, Triangle& t )
{
    // To legalize a triangle we start by finding if any of the three edges
    // violate the Delaunay condition
    for( int i = 0; i < 3; i++ )
    {
        if( t.delaunay_edge[i] )
            continue;

        Triangle* ot = t.GetNeighbor( i );

        if( ot )
        {
            Point* p = t.GetPoint( i );
            Point* op = ot->OppositePoint( t, *p );
            int oi = ot->Index( op );

            // If this is a Constrained Edge or a Delaunay Edge(only during recursive legalization)
            // then we should not try to legalize
            if( ot->constrained_edge[oi] || ot->delaunay_edge[oi] )
            {
                t.constrained_edge[i] = ot->constrained_edge[oi];
                continue;
            }

            bool inside = Incircle( *p, *t.PointCCW( *p ), *t.PointCW( *p ), *op );

            if( inside )
            {
                // Lets mark this shared edge as Delaunay
                t.delaunay_edge[i] = true;
                ot->delaunay_edge[oi] = true;

                // Lets rotate shared edge one vertex CW to legalize it
                RotateTrianglePair( t, *p, *ot, *op );

                // We now got one valid Delaunay Edge shared by two triangles
                // This gives us 4 new edges to check for Delaunay

                // Make sure that triangle to node mapping is done only one time for a specific triangle
                bool not_legalized = !Legalize( tcx, t );

                if( not_legalized )
                {
                    tcx.MapTriangleToNodes( t );
                }

                not_legalized = !Legalize( tcx, *ot );

                if( not_legalized )
                    tcx.MapTriangleToNodes( *ot );

                // Reset the Delaunay edges, since they only are valid Delaunay edges
                // until we add a new triangle or point.
                // XXX: need to think about this. Can these edges be tried after we
                // return to previous recursive level?
                t.delaunay_edge[i] = false;
                ot->delaunay_edge[oi] = false;

                // If triangle have been legalized no need to check the other edges since
                // the recursive legalization will handles those so we can end here.
                return true;
            }
        }
    }

    return false;
}


bool Sweep::Incircle( Point& pa, Point& pb, Point& pc, Point& pd )
{
    double adx  = pa.x - pd.x;
    double ady  = pa.y - pd.y;
    double bdx  = pb.x - pd.x;
    double bdy  = pb.y - pd.y;

    double adxbdy   = adx * bdy;
    double bdxady   = bdx * ady;
    double oabd = adxbdy - bdxady;

    if( oabd <= 0 )
        return false;

    double cdx  = pc.x - pd.x;
    double cdy  = pc.y - pd.y;

    double cdxady   = cdx * ady;
    double adxcdy   = adx * cdy;
    double ocad = cdxady - adxcdy;

    if( ocad <= 0 )
        return false;

    double bdxcdy   = bdx * cdy;
    double cdxbdy   = cdx * bdy;

    double alift = adx * adx + ady * ady;
    double blift = bdx * bdx + bdy * bdy;
    double clift = cdx * cdx + cdy * cdy;

    double det = alift * (bdxcdy - cdxbdy) + blift * ocad + clift * oabd;

    return det > 0;
}


void Sweep::RotateTrianglePair( Triangle& t, Point& p, Triangle& ot, Point& op )
{
    Triangle* n1, * n2, * n3, * n4;

    n1  = t.NeighborCCW( p );
    n2  = t.NeighborCW( p );
    n3  = ot.NeighborCCW( op );
    n4  = ot.NeighborCW( op );

    bool ce1, ce2, ce3, ce4;
    ce1 = t.GetConstrainedEdgeCCW( p );
    ce2 = t.GetConstrainedEdgeCW( p );
    ce3 = ot.GetConstrainedEdgeCCW( op );
    ce4 = ot.GetConstrainedEdgeCW( op );

    bool de1, de2, de3, de4;
    de1 = t.GetDelunayEdgeCCW( p );
    de2 = t.GetDelunayEdgeCW( p );
    de3 = ot.GetDelunayEdgeCCW( op );
    de4 = ot.GetDelunayEdgeCW( op );

    t.Legalize( p, op );
    ot.Legalize( op, p );

    // Remap delaunay_edge
    ot.SetDelunayEdgeCCW( p, de1 );
    t.SetDelunayEdgeCW( p, de2 );
    t.SetDelunayEdgeCCW( op, de3 );
    ot.SetDelunayEdgeCW( op, de4 );

    // Remap constrained_edge
    ot.SetConstrainedEdgeCCW( p, ce1 );
    t.SetConstrainedEdgeCW( p, ce2 );
    t.SetConstrainedEdgeCCW( op, ce3 );
    ot.SetConstrainedEdgeCW( op, ce4 );

    // Remap neighbors
    // XXX: might optimize the markNeighbor by keeping track of
    // what side should be assigned to what neighbor after the
    // rotation. Now mark neighbor does lots of testing to find
    // the right side.
    t.ClearNeighbors();
    ot.ClearNeighbors();

    if( n1 )
        ot.MarkNeighbor( *n1 );

    if( n2 )
        t.MarkNeighbor( *n2 );

    if( n3 )
        t.MarkNeighbor( *n3 );

    if( n4 )
        ot.MarkNeighbor( *n4 );

    t.MarkNeighbor( ot );
}


void Sweep::FillBasin( SweepContext& tcx, Node& node )
{
    if( Orient2d( *node.point, *node.next->point, *node.next->next->point ) == CCW )
    {
        tcx.basin.left_node = node.next->next;
    }
    else
    {
        tcx.basin.left_node = node.next;
    }

    // Find the bottom and right node
    tcx.basin.bottom_node = tcx.basin.left_node;

    while( tcx.basin.bottom_node->next
           && tcx.basin.bottom_node->point->y >= tcx.basin.bottom_node->next->point->y )
    {
        tcx.basin.bottom_node = tcx.basin.bottom_node->next;
    }

    if( tcx.basin.bottom_node == tcx.basin.left_node )
    {
        // No valid basin
        return;
    }

    tcx.basin.right_node = tcx.basin.bottom_node;

    while( tcx.basin.right_node->next
           && tcx.basin.right_node->point->y < tcx.basin.right_node->next->point->y )
    {
        tcx.basin.right_node = tcx.basin.right_node->next;
    }

    if( tcx.basin.right_node == tcx.basin.bottom_node )
    {
        // No valid basins
        return;
    }

    tcx.basin.width = tcx.basin.right_node->point->x - tcx.basin.left_node->point->x;
    tcx.basin.left_highest = tcx.basin.left_node->point->y > tcx.basin.right_node->point->y;

    FillBasinReq( tcx, tcx.basin.bottom_node );
}


void Sweep::FillBasinReq( SweepContext& tcx, Node* node )
{
    // if shallow stop filling
    if( IsShallow( tcx, *node ) )
    {
        return;
    }

    Fill( tcx, *node );

    if( node->prev == tcx.basin.left_node && node->next == tcx.basin.right_node )
    {
        return;
    }
    else if( node->prev == tcx.basin.left_node )
    {
        Orientation o = Orient2d( *node->point, *node->next->point, *node->next->next->point );

        if( o == CW )
        {
            return;
        }

        node = node->next;
    }
    else if( node->next == tcx.basin.right_node )
    {
        Orientation o = Orient2d( *node->point, *node->prev->point, *node->prev->prev->point );

        if( o == CCW )
        {
            return;
        }

        node = node->prev;
    }
    else
    {
        // Continue with the neighbor node with lowest Y value
        if( node->prev->point->y < node->next->point->y )
        {
            node = node->prev;
        }
        else
        {
            node = node->next;
        }
    }

    FillBasinReq( tcx, node );
}


bool Sweep::IsShallow( SweepContext& tcx, Node& node )
{
    double height;

    if( tcx.basin.left_highest )
    {
        height = tcx.basin.left_node->point->y - node.point->y;
    }
    else
    {
        height = tcx.basin.right_node->point->y - node.point->y;
    }

    // if shallow stop filling
    if( tcx.basin.width > height )
    {
        return true;
    }

    return false;
}


void Sweep::FillEdgeEvent( SweepContext& tcx, Edge* edge, Node* node )
{
    if( tcx.edge_event.right )
    {
        FillRightAboveEdgeEvent( tcx, edge, node );
    }
    else
    {
        FillLeftAboveEdgeEvent( tcx, edge, node );
    }
}


void Sweep::FillRightAboveEdgeEvent( SweepContext& tcx, Edge* edge, Node* node )
{
    while( node->next->point->x < edge->p->x )
    {
        // Check if next node is below the edge
        if( Orient2d( *edge->q, *node->next->point, *edge->p ) == CCW )
        {
            FillRightBelowEdgeEvent( tcx, edge, *node );
        }
        else
        {
            node = node->next;
        }
    }
}


void Sweep::FillRightBelowEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    if( node.point->x < edge->p->x )
    {
        if( Orient2d( *node.point, *node.next->point, *node.next->next->point ) == CCW )
        {
            // Concave
            FillRightConcaveEdgeEvent( tcx, edge, node );
        }
        else
        {
            // Convex
            FillRightConvexEdgeEvent( tcx, edge, node );
            // Retry this one
            FillRightBelowEdgeEvent( tcx, edge, node );
        }
    }
}


void Sweep::FillRightConcaveEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    Fill( tcx, *node.next );

    if( node.next->point != edge->p )
    {
        // Next above or below edge?
        if( Orient2d( *edge->q, *node.next->point, *edge->p ) == CCW )
        {
            // Below
            if( Orient2d( *node.point, *node.next->point, *node.next->next->point ) == CCW )
            {
                // Next is concave
                FillRightConcaveEdgeEvent( tcx, edge, node );
            }
            else
            {
                // Next is convex
            }
        }
    }
}


void Sweep::FillRightConvexEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    // Next concave or convex?
    if( Orient2d( *node.next->point, *node.next->next->point,
                *node.next->next->next->point ) == CCW )
    {
        // Concave
        FillRightConcaveEdgeEvent( tcx, edge, *node.next );
    }
    else
    {
        // Convex
        // Next above or below edge?
        if( Orient2d( *edge->q, *node.next->next->point, *edge->p ) == CCW )
        {
            // Below
            FillRightConvexEdgeEvent( tcx, edge, *node.next );
        }
        else
        {
            // Above
        }
    }
}


void Sweep::FillLeftAboveEdgeEvent( SweepContext& tcx, Edge* edge, Node* node )
{
    while( node->prev->point->x > edge->p->x )
    {
        // Check if next node is below the edge
        if( Orient2d( *edge->q, *node->prev->point, *edge->p ) == CW )
        {
            FillLeftBelowEdgeEvent( tcx, edge, *node );
        }
        else
        {
            node = node->prev;
        }
    }
}


void Sweep::FillLeftBelowEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    if( node.point->x > edge->p->x )
    {
        if( Orient2d( *node.point, *node.prev->point, *node.prev->prev->point ) == CW )
        {
            // Concave
            FillLeftConcaveEdgeEvent( tcx, edge, node );
        }
        else
        {
            // Convex
            FillLeftConvexEdgeEvent( tcx, edge, node );
            // Retry this one
            FillLeftBelowEdgeEvent( tcx, edge, node );
        }
    }
}


void Sweep::FillLeftConvexEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    // Next concave or convex?
    if( Orient2d( *node.prev->point, *node.prev->prev->point,
                *node.prev->prev->prev->point ) == CW )
    {
        // Concave
        FillLeftConcaveEdgeEvent( tcx, edge, *node.prev );
    }
    else
    {
        // Convex
        // Next above or below edge?
        if( Orient2d( *edge->q, *node.prev->prev->point, *edge->p ) == CW )
        {
            // Below
            FillLeftConvexEdgeEvent( tcx, edge, *node.prev );
        }
        else
        {
            // Above
        }
    }
}


void Sweep::FillLeftConcaveEdgeEvent( SweepContext& tcx, Edge* edge, Node& node )
{
    Fill( tcx, *node.prev );

    if( node.prev->point != edge->p )
    {
        // Next above or below edge?
        if( Orient2d( *edge->q, *node.prev->point, *edge->p ) == CW )
        {
            // Below
            if( Orient2d( *node.point, *node.prev->point, *node.prev->prev->point ) == CW )
            {
                // Next is concave
                FillLeftConcaveEdgeEvent( tcx, edge, node );
            }
            else
            {
                // Next is convex
            }
        }
    }
}


void Sweep::FlipEdgeEvent( SweepContext& tcx, Point& ep, Point& eq, Triangle* t, Point& p )
{
    Triangle& ot = t->NeighborAcross( p );
    Point& op = *ot.OppositePoint( *t, p );

    if( InScanArea( p, *t->PointCCW( p ), *t->PointCW( p ), op ) )
    {
        // Lets rotate shared edge one vertex CW
        RotateTrianglePair( *t, p, ot, op );
        tcx.MapTriangleToNodes( *t );
        tcx.MapTriangleToNodes( ot );

        if( p == eq && op == ep )
        {
            if( eq == *tcx.edge_event.constrained_edge->q
                && ep == *tcx.edge_event.constrained_edge->p )
            {
                t->MarkConstrainedEdge( &ep, &eq );
                ot.MarkConstrainedEdge( &ep, &eq );
                Legalize( tcx, *t );
                Legalize( tcx, ot );
            }
            else
            {
                // XXX: I think one of the triangles should be legalized here?
            }
        }
        else
        {
            Orientation o = Orient2d( eq, op, ep );
            t = &NextFlipTriangle( tcx, (int) o, *t, ot, p, op );
            FlipEdgeEvent( tcx, ep, eq, t, p );
        }
    }
    else
    {
        Point& newP = NextFlipPoint( ep, eq, ot, op );
        FlipScanEdgeEvent( tcx, ep, eq, *t, ot, newP );
        EdgeEvent( tcx, ep, eq, t, p );
    }
}


Triangle& Sweep::NextFlipTriangle( SweepContext& tcx,
        int o,
        Triangle& t,
        Triangle& ot,
        Point& p,
        Point& op )
{
    if( o == CCW )
    {
        // ot is not crossing edge after flip
        int edge_index = ot.EdgeIndex( &p, &op );
        ot.delaunay_edge[edge_index] = true;
        Legalize( tcx, ot );
        ot.ClearDelunayEdges();
        return t;
    }

    // t is not crossing edge after flip
    int edge_index = t.EdgeIndex( &p, &op );

    t.delaunay_edge[edge_index] = true;
    Legalize( tcx, t );
    t.ClearDelunayEdges();
    return ot;
}


Point& Sweep::NextFlipPoint( Point& ep, Point& eq, Triangle& ot, Point& op )
{
    Orientation o2d = Orient2d( eq, op, ep );

    if( o2d == CW )
    {
        // Right
        return *ot.PointCCW( op );
    }
    else if( o2d == CCW )
    {
        // Left
        return *ot.PointCW( op );
    }

    // throw new RuntimeException("[Unsupported] Opposing point on constrained edge");
    assert( 0 );

    // Never executed, due tu assert( 0 ). Just to avoid compil warning
    return ep;
}


void Sweep::FlipScanEdgeEvent( SweepContext& tcx, Point& ep, Point& eq, Triangle& flip_triangle,
        Triangle& t, Point& p )
{
    Triangle& ot = t.NeighborAcross( p );
    Point& op = *ot.OppositePoint( t, p );

    if( InScanArea( eq, *flip_triangle.PointCCW( eq ), *flip_triangle.PointCW( eq ), op ) )
    {
        // flip with new edge op->eq
        FlipEdgeEvent( tcx, eq, op, &ot, op );
        // TODO: Actually I just figured out that it should be possible to
        // improve this by getting the next ot and op before the the above
        // flip and continue the flipScanEdgeEvent here
        // set new ot and op here and loop back to inScanArea test
        // also need to set a new flip_triangle first
        // Turns out at first glance that this is somewhat complicated
        // so it will have to wait.
    }
    else
    {
        Point& newP = NextFlipPoint( ep, eq, ot, op );
        FlipScanEdgeEvent( tcx, ep, eq, flip_triangle, ot, newP );
    }
}


Sweep::~Sweep()
{
    // Clean up memory
    for( unsigned i = 0; i < nodes_.size(); i++ )
    {
        delete nodes_[i];
    }
}
}