static VECTOR2I pushoutForce( const SHAPE_CIRCLE& aA, const SEG& aB, int aClearance )
{
    VECTOR2I f( 0, 0 );

    const VECTOR2I c = aA.GetCenter();
    const VECTOR2I nearest = aB.NearestPoint( c );

    const int r = aA.GetRadius();

    int dist = ( nearest - c ).EuclideanNorm();
    int min_dist = aClearance + r;

    if( dist < min_dist )
    {
        for( int corr = 0; corr < 5; corr++ )
        {
            f = ( aA.GetCenter() - nearest ).Resize( min_dist - dist + corr );

            if( aB.Distance( c + f ) >= min_dist )
                break;
        }
    }

    return f;
}

const SHAPE_LINE_CHAIN PNS_SOLID::Hull( int aClearance, int aWalkaroundThickness ) const
{
    int cl = aClearance + aWalkaroundThickness / 2;

    switch( m_shape->Type() )
    {
    case SH_RECT:
    {
        SHAPE_RECT* rect = static_cast<SHAPE_RECT*>( m_shape );
        return OctagonalHull( rect->GetPosition(), rect->GetSize(), cl + 1, 0.2 * cl );
    }

    case SH_CIRCLE:
    {
        SHAPE_CIRCLE* circle = static_cast<SHAPE_CIRCLE*>( m_shape );
        int r = circle->GetRadius();
        return OctagonalHull( circle->GetCenter() - VECTOR2I( r, r ), VECTOR2I( 2 * r, 2 * r ),
                              cl + 1, 0.52 * ( r + cl ) );
    }

    case SH_SEGMENT:
    {
        SHAPE_SEGMENT* seg = static_cast<SHAPE_SEGMENT*> ( m_shape );
        return SegmentHull( *seg, aClearance, aWalkaroundThickness );
    }

    default:
        break;
    }

    return SHAPE_LINE_CHAIN();
}

static VECTOR2I pushoutForce( const SHAPE_CIRCLE& aA, const SEG& aB, int aClearance )
{
    VECTOR2I nearest = aB.NearestPoint( aA.GetCenter() );
    VECTOR2I f (0, 0);

    int dist = ( nearest - aA.GetCenter() ).EuclideanNorm();
    int min_dist = aClearance + aA.GetRadius();

    if( dist < min_dist )
        f = ( aA.GetCenter() - nearest ).Resize ( min_dist - dist + 10 );

    return f;
}

static inline bool Collide( const SHAPE_CIRCLE& aA, const SHAPE_LINE_CHAIN& aB, int aClearance,
                            bool aNeedMTV, VECTOR2I& aMTV )
{
    bool found = false;

    for( int s = 0; s < aB.SegmentCount(); s++ )
    {
        if( aA.Collide( aB.CSegment( s ), aClearance ) )
        {
            found = true;
            break;
        }
    }

    if( !aNeedMTV || !found )
        return found;

    SHAPE_CIRCLE cmoved( aA );
    VECTOR2I f_total( 0, 0 );

    for( int s = 0; s < aB.SegmentCount(); s++ )
    {
        VECTOR2I f = pushoutForce( cmoved, aB.CSegment( s ), aClearance );
        cmoved.SetCenter( cmoved.GetCenter() + f );
        f_total += f;
    }

    aMTV = f_total;
    return found;
}

static inline bool Collide( const SHAPE_CIRCLE& aA, const SHAPE_LINE_CHAIN& aB, int aClearance,
                            bool aNeedMTV, VECTOR2I& aMTV )
{
    for( int s = 0; s < aB.SegmentCount(); s++ )
    {
        if( aA.Collide( aB.CSegment( s ), aClearance ) )
            return true;
    }

    return false;
}