/// <summary>
/// Visits all crossings of the current edge with all edges of the given index
/// cell of B. Terminates early and returns false if visitor_ returns false.
/// </summary>
private bool VisitEdgeCellCrossings(ShapeEdge a, S2ShapeIndexCell b_cell)
{
// Test the current edge of A against all edges of "b_cell".
// Note that we need to use a new S2EdgeCrosser (or call Init) whenever we
// replace the contents of b_shape_edges_, since S2EdgeCrosser requires that
// its S2Point arguments point to values that persist between Init() calls.
GetShapeEdges(b_index_, b_cell, b_shape_edges_);
var crosser = new S2EdgeCrosser(a.V0, a.V1);
foreach (var b in b_shape_edges_)
{
if (crosser.C == S2Point.Empty || crosser.C != b.V0)
{
crosser.RestartAt(b.V0);
}
int sign = crosser.CrossingSign(b.V1);
if (sign >= min_crossing_sign_)
{
if (!VisitEdgePair(a, b, sign == 1))
{
return(false);
}
}
}
return(true);
}
/// <summary>
/// Given a vector of edges within an S2ShapeIndexCell, visit all pairs of
/// crossing edges (of the given CrossingType).
/// </summary>
private static bool VisitCrossings(ShapeEdgeVector shape_edges, CrossingType type, bool need_adjacent, EdgePairVisitor visitor)
{
var min_crossing_sign = type == CrossingType.INTERIOR ? 1 : 0;
var num_edges = shape_edges.Count;
for (int i = 0; i + 1 < num_edges; i++)
{
var a = shape_edges[i];
var j = i + 1;
// A common situation is that an edge AB is followed by an edge BC. We
// only need to visit such crossings if "need_adjacent" is true (even if
// AB and BC belong to different edge chains).
if (!need_adjacent && a.V1 == shape_edges[j].V0)
{
j++;
if (j >= num_edges)
{
break;
}
}
var crosser = new S2EdgeCrosser(a.V0, a.V1);
for (; j < num_edges; j++)
{
var b = shape_edges[j];
if (crosser.C == S2Point.Empty || crosser.C != b.V0)
{
crosser.RestartAt(b.V0);
}
var sign = crosser.CrossingSign(b.V1);
if (sign >= min_crossing_sign)
{
if (!visitor(a, b, sign == 1))
{
return(false);
}
}
}
}
return(true);
}
// Visits all crossings of any edge in "a_edges" with any edge in "b_edges".
private bool VisitEdgesEdgesCrossings(ShapeEdgeVector a_edges, ShapeEdgeVector b_edges)
{
// Test all edges of "a_edges" against all edges of "b_edges".
foreach (var a in a_edges)
{
var crosser = new S2EdgeCrosser(a.V0, a.V1);
foreach (var b in b_edges)
{
if (crosser.C == S2Point.Empty || crosser.C != b.V0)
{
crosser.RestartAt(b.V0);
}
int sign = crosser.CrossingSign(b.V1);
if (sign >= min_crossing_sign_)
{
if (!VisitEdgePair(a, b, sign == 1))
{
return(false);
}
}
}
}
return(true);
}
