private static PolygonCrossing FindPreviousCrossingNotEqual(
PolygonCrossing currentCrossing,
PolygonCrossing[] crossingsOnRing,
IComparer <PolygonCrossing> crossingComparer
)
{
Contract.Requires(currentCrossing != null);
Contract.Requires(crossingsOnRing != null);
Contract.Requires(Contract.ForAll(crossingsOnRing, x => x != null));
Contract.Requires(crossingComparer != null);
var currentPoint = currentCrossing.Point;
int currentCrossingIndex = Array.BinarySearch(crossingsOnRing, currentCrossing, crossingComparer);
if (currentCrossingIndex < 0)
{
return(null);
}
int crossingsCount = crossingsOnRing.Length;
// find the first crossing before this one that has a different point location
for (
int i = IterationUtils.RetreatLoopingIndex(currentCrossingIndex, crossingsCount);
i != currentCrossingIndex;
i = IterationUtils.RetreatLoopingIndex(i, crossingsCount)
)
{
var crossing = crossingsOnRing[i];
if (crossing.Point != currentPoint)
{
return(crossing);
}
}
return(null);
}
private static IEnumerable <PolygonCrossing> TraverseCrossings(
PolygonCrossing fromCrossing,
PolygonCrossing[] ringCrossings,
int fromCrossingIndex
)
{
Contract.Requires(fromCrossing != null);
Contract.Requires(ringCrossings != null);
//Contract.Requires(crossingComparer != null);
Contract.Requires(fromCrossingIndex >= 0);
Contract.Ensures(Contract.Result <IEnumerable <PolygonCrossing> >() != null);
//var fromCrossingIndex = ringCrossings.BinarySearch(fromCrossing, crossingComparer);
var ringCrossingsCount = ringCrossings.Length;
Stack <PolygonCrossing> priorResults = null;
var backTrackIndex = fromCrossingIndex;
do
{
var priorIndex = IterationUtils.RetreatLoopingIndex(backTrackIndex, ringCrossingsCount);
var priorCrossing = ringCrossings[priorIndex];
if (priorCrossing.Point != fromCrossing.Point)
{
break;
}
backTrackIndex = priorIndex;
(priorResults ?? (priorResults = new Stack <PolygonCrossing>()))
.Push(priorCrossing);
} while (backTrackIndex != fromCrossingIndex);
if (null != priorResults)
{
while (priorResults.Count > 0)
{
yield return(priorResults.Pop());
}
}
for (
int i = IterationUtils.AdvanceLoopingIndex(fromCrossingIndex, ringCrossingsCount);
i != fromCrossingIndex;
i = IterationUtils.AdvanceLoopingIndex(i, ringCrossingsCount)
)
{
yield return(ringCrossings[i]);
}
}
private static Point2 FindPreviousRingPoint(
PolygonCrossing currentCrossing,
PolygonCrossing[] crossingsOnRing,
Ring2 ring,
Func <PolygonCrossing, PolygonBoundaryLocation> getLocation,
IComparer <PolygonCrossing> crossingComparer
)
{
Contract.Requires(currentCrossing != null);
Contract.Requires(crossingsOnRing != null);
Contract.Requires(Contract.ForAll(crossingsOnRing, x => x != null));
Contract.Requires(ring != null);
Contract.Requires(getLocation != null);
Contract.Requires(crossingComparer != null);
var currentLocation = getLocation(currentCrossing);
var segmentCount = ring.SegmentCount;
Contract.Assume(currentLocation.SegmentIndex < segmentCount);
var previousSegmentIndex = IterationUtils.RetreatLoopingIndex(currentLocation.SegmentIndex, segmentCount);
var previousCrossing = FindPreviousCrossingNotEqual(currentCrossing, crossingsOnRing, crossingComparer);
if (null == previousCrossing)
{
return(ring[
currentLocation.SegmentRatio == 0
? previousSegmentIndex
: currentLocation.SegmentIndex
]);
}
var previousCrossingLocation = getLocation(previousCrossing);
Contract.Assume(previousCrossingLocation != null);
if (currentLocation.SegmentRatio == 0)
{
return(previousSegmentIndex == previousCrossingLocation.SegmentIndex
? previousCrossing.Point
: ring[previousSegmentIndex]);
}
return(currentLocation.SegmentIndex == previousCrossingLocation.SegmentIndex &&
currentLocation.SegmentRatio > previousCrossingLocation.SegmentRatio
? previousCrossing.Point
: ring[currentLocation.SegmentIndex]);
}