internal static int?compareSegments(SweepEvent le1, SweepEvent le2)
{
if (le1.Equals(le2))
{
return(0);
}
// Segments are not collinear
if (signedArea(le1.point, le1.otherEvent.point, le2.point) != 0 || signedArea(le1.point, le1.otherEvent.point, le2.otherEvent.point) != 0)
{
// If they share their left endpoint use the right endpoint to sort
if (equals(le1.point, le2.point))
{
return(le1.isBelow(le2.otherEvent.point) ? -1 : 1);
}
// Different left endpoint: use the left endpoint to sort
if (le1.point.X == le2.point.X)
{
return(le1.point.Y < le2.point.Y ? -1 : 1);
}
// has the line segment associated to e1 been inserted
// into S after the line segment associated to e2 ?
if (compareEvents(le1, le2) == 1)
{
return(le2.isAbove(le1.point) ? -1 : 1);
}
// The line segment associated to e2 has been inserted
// into S after the line segment associated to e1
return(le1.isBelow(le2.point) ? -1 : 1);
}
if (le1.isSubject == le2.isSubject) // same polygon
{
if (equals(le1.point, le2.point))
{
if (equals(le1.otherEvent.point, le2.otherEvent.point))
{
return(0);
}
else
{
return(le1.contourId > le2.contourId ? 1 : -1);
}
}
}
else // Segments are collinear, but belong to separate polygons
{
return(le1.isSubject ? -1 : 1);
}
return(compareEvents(le1, le2) == 1 ? 1 : -1);
}
