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Fix degenerate linestring relation on boundary of areal #1474

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Fix degenerate linestring relation on boundary of areal #1474

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adf0d00
Fix degenerate linestring relation on boundary of areal
mjacobse Jun 14, 2026
80cd1f6
Use hexadecimal for all interrupt flags
mjacobse Jun 17, 2026
4ff4b94
Also support single-point linestrings
mjacobse Jun 17, 2026
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38 changes: 25 additions & 13 deletions include/boost/geometry/algorithms/detail/relate/linear_areal.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -65,26 +65,31 @@ class no_turns_la_linestring_pred
, m_result(res)
, m_strategy(strategy)
, m_boundary_checker(boundary_checker)
, m_interrupt_flags(0)
, m_interrupt_flags(0x00)
{
if ( ! may_update<interior, interior, '1', TransposeResult>(m_result) )
{
m_interrupt_flags |= 1;
m_interrupt_flags |= 0x01;
}

if ( ! may_update<interior, exterior, '1', TransposeResult>(m_result) )
{
m_interrupt_flags |= 2;
m_interrupt_flags |= 0x02;
}

if ( ! may_update<boundary, interior, '0', TransposeResult>(m_result) )
{
m_interrupt_flags |= 4;
m_interrupt_flags |= 0x04;
}

if ( ! may_update<boundary, exterior, '0', TransposeResult>(m_result) )
{
m_interrupt_flags |= 8;
m_interrupt_flags |= 0x08;
}

if ( ! may_update<interior, boundary, '1', TransposeResult>(m_result) )
{
m_interrupt_flags |= 0x10;
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}
}

Expand All @@ -94,33 +99,40 @@ class no_turns_la_linestring_pred
std::size_t const count = boost::size(linestring);

// invalid input
if ( count < 2 )
if ( count < 1 )
{
// ignore
// TODO: throw an exception?
return true;
}

// if those flags are set nothing will change
if ( m_interrupt_flags == 0xF )
if ( m_interrupt_flags == 0x1F )
{
return false;
}

int const pig = detail::within::point_in_geometry(range::front(linestring),
m_geometry2,
m_strategy);
//BOOST_GEOMETRY_ASSERT_MSG(pig != 0, "There should be no IPs");

if ( pig > 0 )
{
update<interior, interior, '1', TransposeResult>(m_result);
m_interrupt_flags |= 1;
m_interrupt_flags |= 0x01;
}
else if ( pig == 0 )
{
// no turns but still point on boundary can actually happen when the
// linestring is degenerate. so handle this case explicitly here.
// for consistency let's still report dimension 1 instead of 0
update<interior, boundary, '1', TransposeResult>(m_result);
m_interrupt_flags |= 0x10;
}
else
{
update<interior, exterior, '1', TransposeResult>(m_result);
m_interrupt_flags |= 2;
m_interrupt_flags |= 0x02;
}

// check if there is a boundary
Expand All @@ -131,16 +143,16 @@ class no_turns_la_linestring_pred
if ( pig > 0 )
{
update<boundary, interior, '0', TransposeResult>(m_result);
m_interrupt_flags |= 4;
m_interrupt_flags |= 0x04;
}
else
{
update<boundary, exterior, '0', TransposeResult>(m_result);
m_interrupt_flags |= 8;
m_interrupt_flags |= 0x08;
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}
}

return m_interrupt_flags != 0xF
return m_interrupt_flags != 0x1F
&& ! m_result.interrupt;
}

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25 changes: 25 additions & 0 deletions test/algorithms/covered_by/covered_by.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,31 @@ void test_all()
test_geometry<box<P>, poly<P>>("BOX(1 1,2 2)", "POLYGON((0 0,0 3,3 1,1 0,0 0))", false);
test_geometry<box<P>, mpoly<P>>("BOX(1 1,2 2)", "MULTIPOLYGON(((0 0,0 3,3 3,3 0,0 0)),((-1 -1,-3 -4,-7 -7,-4 -3,-1 -1)))", true);
test_geometry<box<P>, mpoly<P>>("BOX(1 1,2 2)", "MULTIPOLYGON(((0 0,0 3,3 1,1 0,0 0)),((-1 -1,-3 -4,-7 -7,-4 -3,-1 -1)))", false);

// degenerate line segment - polygon
{
// on corner
test_geometry<ls<P>, poly<P>>("LINESTRING(0 0,0 0)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
test_geometry<ls<P>, poly<P>>("LINESTRING(0 0)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
// on edge
test_geometry<ls<P>, poly<P>>("LINESTRING(1 2,1 2)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
test_geometry<ls<P>, poly<P>>("LINESTRING(1 2)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
// inside
test_geometry<ls<P>, poly<P>>("LINESTRING(1 1,1 1)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
test_geometry<ls<P>, poly<P>>("LINESTRING(1 1)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", true);
// outside
test_geometry<ls<P>, poly<P>>("LINESTRING(1 3,1 3)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", false);
test_geometry<ls<P>, poly<P>>("LINESTRING(1 3)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", false);
// inside hole
test_geometry<ls<P>, poly<P>>("LINESTRING(2 2,2 2)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", false);
test_geometry<ls<P>, poly<P>>("LINESTRING(2 2)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", false);
// on corner of hole
test_geometry<ls<P>, poly<P>>("LINESTRING(3 3,3 3)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", true);
test_geometry<ls<P>, poly<P>>("LINESTRING(3 3)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", true);
// on edge of hole
test_geometry<ls<P>, poly<P>>("LINESTRING(2 1,2 1)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", true);
test_geometry<ls<P>, poly<P>>("LINESTRING(2 1)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", true);
}
}


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25 changes: 25 additions & 0 deletions test/algorithms/relate/relate_linear_areal.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,31 @@ void test_linestring_polygon()
test_geometry<ls, poly>("LINESTRING(2 9, 1 1, 10 1, 10 10, 1 10, 0 6, 5 6)",
"POLYGON((0 0,0 10,10 10,10 0,0 0),(4 4,4 6,6 6,6 4,4 4))",
"11F00F212");

// degenerate line segment
{
// on corner
test_geometry<ls, poly>("LINESTRING(0 0,0 0)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "F1FFFF212");
test_geometry<ls, poly>("LINESTRING(0 0)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "F1FFFF212");
// on edge
test_geometry<ls, poly>("LINESTRING(1 2,1 2)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "F1FFFF212");
test_geometry<ls, poly>("LINESTRING(1 2)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "F1FFFF212");
// inside
test_geometry<ls, poly>("LINESTRING(1 1,1 1)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "1FFFFF212");
test_geometry<ls, poly>("LINESTRING(1 1)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "1FFFFF212");
// outside
test_geometry<ls, poly>("LINESTRING(1 3,1 3)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "FF1FFF212");
test_geometry<ls, poly>("LINESTRING(1 3)", "POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))", "FF1FFF212");
// inside hole
test_geometry<ls, poly>("LINESTRING(2 2,2 2)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "FF1FFF212");
test_geometry<ls, poly>("LINESTRING(2 2)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "FF1FFF212");
// on corner of hole
test_geometry<ls, poly>("LINESTRING(3 3,3 3)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "F1FFFF212");
test_geometry<ls, poly>("LINESTRING(3 3)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "F1FFFF212");
// on edge of hole
test_geometry<ls, poly>("LINESTRING(2 1,2 1)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "F1FFFF212");
test_geometry<ls, poly>("LINESTRING(2 1)", "POLYGON((0 0, 0 4, 4 4, 4 0, 0 0),(1 1, 1 3, 3 3, 3 1, 1 1))", "F1FFFF212");
}
}

template <typename P>
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