/// <summary>
/// Purpose: insert right-going edges into the edge dictionary, and update
/// winding numbers and mesh connectivity appropriately. All right-going
/// edges share a common origin vOrg. Edges are inserted CCW starting at
/// eFirst; the last edge inserted is eLast.Oprev. If vOrg has any
/// left-going edges already processed, then eTopLeft must be the edge
/// such that an imaginary upward vertical segment from vOrg would be
/// contained between eTopLeft.Oprev and eTopLeft; otherwise eTopLeft
/// should be null.
/// </summary>
private void AddRightEdges(ActiveRegion regUp, MeshUtils.Edge eFirst, MeshUtils.Edge eLast, MeshUtils.Edge eTopLeft, bool cleanUp)
{
bool firstTime = true;
MeshUtils.Edge e = eFirst; do
{
Debug.Assert(Geom.VertLeq(e._Org, e._Dst));
AddRegionBelow(regUp, e._Sym);
e = e._Onext;
} while (e != eLast);
eTopLeft = eTopLeft switch
{
// Walk *all* right-going edges from e.Org, in the dictionary order,
// updating the winding numbers of each region, and re-linking the mesh
// edges to match the dictionary ordering (if necessary).
null => RegionBelow(regUp)._eUp._Rprev,
_ => eTopLeft
};
ActiveRegion regPrev = regUp, reg;
MeshUtils.Edge ePrev = eTopLeft;
while (true)
{
reg = RegionBelow(regPrev);
e = reg._eUp._Sym;
if (e._Org != ePrev._Org)
{
break;
}
if (e._Onext != ePrev)
{
// Unlink e from its current position, and relink below ePrev
Mesh.Splice(_pool, e._Oprev, e);
Mesh.Splice(_pool, ePrev._Oprev, e);
}
// Compute the winding number and "inside" flag for the new regions
reg._windingNumber = regPrev._windingNumber - e._winding;
reg._inside = Geom.IsWindingInside(_windingRule, reg._windingNumber);
// Check for two outgoing edges with same slope -- process these
// before any intersection tests (see example in tessComputeInterior).
regPrev._dirty = true;
switch (firstTime)
{
case false when CheckForRightSplice(regPrev):
Geom.AddWinding(e, ePrev);
DeleteRegion(regPrev);
Mesh.Delete(_pool, ePrev);
break;
}
firstTime = false;
regPrev = reg;
ePrev = e;
}
regPrev._dirty = true;
Debug.Assert(regPrev._windingNumber - e._winding == reg._windingNumber);
switch (cleanUp)
{
case true:
// Check for intersections between newly adjacent edges.
WalkDirtyRegions(regPrev);
break;
}
}
private void ComputeWinding(ActiveRegion reg)
{
reg._windingNumber = RegionAbove(reg)._windingNumber + reg._eUp._winding;
reg._inside = Geom.IsWindingInside(_windingRule, reg._windingNumber);
}