CSG2d bugfix

Fixes bug in IsInside(p) test for splines if p lies on an edge of the surrounding triangle.
Do a fast check using (new) function IsCloseToTrig() instead of IsInsideTrig().

libsrc/geom2d/csg2d.cpp

@@ -402,6 +402,12 @@ bool IsInsideTrig( const array<Point<2>,3> & t, Point<2> r )
   return ( (w % 2) != 0 );
 }
 
+bool IsCloseToTrig( const array<Point<2>,3> & t, Point<2> r, double eps=1e-4 )
+{
+  r += eps * (Center(t[0], t[1], t[2])-r); // move point a bit to center of trig
+  return IsInsideTrig( t, r );
+}
+
 
 IntersectionType IntersectTrig( Point<2> p0, Point<2> p1, const array<Point<2>,3> & trig)
 {
@@ -1612,7 +1618,7 @@ bool Loop :: IsInside( Point<2> r ) const
       auto s0 = s.StartPI();
       auto s1 = s.TangentPoint();
       auto s2 = s.EndPI();
-      if(!IsInsideTrig( {s0, s1, s2} , r ))
+      if(!IsCloseToTrig( {s0, s1, s2} , r ))
         w += w_simple;
       else
       {

tests/pytest/test_csg2d.py

@@ -54,6 +54,35 @@ def test_trig_and_circle():
     ngs.Draw(mesh)
 
 
+def test_circle_plus_rect():
+    circle = Circle( center=(0,0), radius=1 )
+    rect = Rectangle( pmin=(-0.5,0.0), pmax=(0.5,0.5) )
+
+    geo = CSG2d()
+    geo.Add(circle+rect)
+    m = geo.GenerateMesh(maxh=0.2)
+
+
+    ngs = pytest.importorskip("ngsolve")
+    mesh = ngs.Mesh(m)
+    mesh.Curve(5)
+    assert ngs.Integrate(1.0, mesh) == approx(math.pi)
+
+def test_circle_plus_rect1():
+    circle = Circle( center=(0,0), radius=1 )
+    rect = Rectangle( pmin=(-0.5,-0.5), pmax=(0.5,0.5) )
+
+    geo = CSG2d()
+    geo.Add(circle+rect)
+    m = geo.GenerateMesh(maxh=0.2)
+
+
+    ngs = pytest.importorskip("ngsolve")
+    mesh = ngs.Mesh(m)
+    mesh.Curve(5)
+    assert ngs.Integrate(1.0, mesh) == approx(math.pi)
+
+
 if __name__ == "__main__":
     test_two_circles()
     test_two_edge()