private bool SegmentCompare(SweepEvent e1, SweepEvent e2)
{
if (e1.Equals(e2))
{
return(false);
}
if (signedArea(e1.p, e1.otherSE.p, e2.p) != 0 || signedArea(e1.p, e1.otherSE.p, e2.otherSE.p) != 0)
{
// Segments are not collinear
// If they share their left endpoint use the right endpoint to sort
if (Point.EqualsBoth(e1.p, e2.p))
{
return(e1.isBelow(e2.otherSE.p));
}
if (CompareSweepEvent(e1, e2))
{
return(e2.isAbove(e1.p));
}
return(e1.isBelow(e2.p));
}
if (Point.EqualsBoth(e1.p, e2.p)) // Segments colinear
{
return(false);
}
return(CompareSweepEvent(e1, e2));
}
// The ordering is reversed because push and pop are faster.
int CompareSweepEvent(SweepEvent e1, SweepEvent e2)
{
if (e1.Equals(e2))
{
return(0);
}
if (e1.p.x - e2.p.x > Point.PRECISION) // Different x coordinate
{
return(-1);
}
if (e1.p.x - e2.p.x < -Point.PRECISION) // Different x coordinate
{
return(1);
}
if (e1.p.y - e2.p.y > Point.PRECISION) // Different points, but same x coordinate. The event with lower y coordinate is processed first
{
return(-1);
}
if (e1.p.y - e2.p.y < -Point.PRECISION) // Different points, but same x coordinate. The event with lower y coordinate is processed first
{
return(1);
}
if (e1.isLeft != e2.isLeft) // Same point, but one is a left endpoint and the other a right endpoint. The right endpoint is processed first
{
return((e1.isLeft) ? -1 : 1);
}
// Same point, both events are left endpoints or both are right endpoints. The event associate to the bottom segment is processed first
bool isAbove = e1.isAbove(e2.otherSE.p);
return(isAbove ? -1 : 1);
}