half_line.cpp

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2024 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.,
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 */
 
#include "geometry/half_line.h"
 
#include <math/box2.h>
 
#include <geometry/shape_utils.h>
 
 
bool VectorsInSameQuadrant( const VECTOR2I& aA, const VECTOR2I& aB )
{
 // The sign of the x and y components of the vectors must be the same
 return ( ( aA.x >= 0 ) == ( aB.x >= 0 ) ) && ( ( aA.y >= 0 ) == ( aB.y >= 0 ) );
}
 
 
bool HALF_LINE::Contains( const VECTOR2I& aPoint ) const
{
 // Check that the point is on the right side of the ray from
 // the start point
 // This is quick, so we can do it first
 if( !VectorsInSameQuadrant( m_seg.B - m_seg.A, aPoint - m_seg.A ) )
 {
 return false;
 }
 
 // Check that the point is within a distance of 1 from the
 // infinite line of the ray
 return m_seg.LineDistance( aPoint ) <= 1;
}
 
 
OPT_VECTOR2I HALF_LINE::Intersect( const SEG& aSeg ) const
{
 // Intsersection of two infinite lines
 const SEG seg = GetContainedSeg();
 OPT_VECTOR2I intersection = aSeg.Intersect( seg, false, true );
 
 // Reject parallel lines
 if( !intersection )
 {
 return std::nullopt;
 }
 
 // Check that the intersection is on the right side of the
 // ray's start point (i.e. equal quadrants)
 if( !VectorsInSameQuadrant( m_seg.B - m_seg.A, *intersection - m_seg.A ) )
 {
 return std::nullopt;
 }
 
 // Check that the intersection is not somewhere past the end
 // of the segment
 if( !aSeg.Contains( *intersection ) )
 {
 return std::nullopt;
 }
 
 return intersection;
}
 
OPT_VECTOR2I HALF_LINE::Intersect( const HALF_LINE& aOther ) const
{
 // Intsersection of two infinite lines
 const SEG otherSeg = aOther.GetContainedSeg();
 OPT_VECTOR2I intersection = m_seg.Intersect( otherSeg, false, true );
 
 // Reject parallel lines
 if( !intersection )
 {
 return std::nullopt;
 }
 
 // Check that the intersection is on the right side of both
 // rays' start points (i.e. equal quadrants)
 if( !VectorsInSameQuadrant( m_seg.B - m_seg.A, *intersection - m_seg.A )
 || !VectorsInSameQuadrant( aOther.m_seg.B - aOther.m_seg.A,
 *intersection - aOther.m_seg.A ) )
 {
 return std::nullopt;
 }
 
 return intersection;
}
 
VECTOR2I HALF_LINE::NearestPoint( const VECTOR2I& aPoint ) const
{
 // Same as the SEG implementation, but without the early return
 // if the point isn't on the segment.
 
 // Inlined for performance reasons
 VECTOR2L d( m_seg.B.x - m_seg.A.x, m_seg.B.y - m_seg.A.y );
 SEG::ecoord l_squared( d.x * d.x + d.y * d.y );
 
 if( l_squared == 0 )
 return m_seg.A;
 
 SEG::ecoord t = d.Dot( aPoint - m_seg.A );
 
 if( t < 0 )
 return m_seg.A;
 
 SEG::ecoord xp = rescale( t, (SEG::ecoord) d.x, l_squared );
 SEG::ecoord yp = rescale( t, (SEG::ecoord) d.y, l_squared );
 
 return VECTOR2<SEG::ecoord>( m_seg.A.x + xp, m_seg.A.y + yp );
}