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Remove a bug, where polygons are not handled correctly #35

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Remove a bug, where polygons are not handled correctly #35

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8 changes: 5 additions & 3 deletions src/NetTopologySuite.IO.VectorTiles.Mapbox/MapboxTileReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -155,13 +155,14 @@ private Geometry CreatePolygonal(CoordinateSequence[] sequences)

LinearRing shell = null;
var holes = new List<LinearRing>();
bool reverse = false;

for (int i = 0; i < sequences.Length; i++)
{
var ring = _factory.CreateLinearRing(sequences[i]);

// Shell rings should be CW (https://docs.mapbox.com/vector-tiles/specification/#winding-order)
if (!ring.IsCCW)
if (!ring.IsCCW && !reverse)
{
if (shell != null)
{
Expand All @@ -175,13 +176,14 @@ private Geometry CreatePolygonal(CoordinateSequence[] sequences)
{
if (shell == null)
{
if (sequences.Length == 1)
if (sequences.Length >= 1)
{
// WARNING: this is not according to the spec but tiles exists like this in the wild
// that are rendered just fine by other tools, we can ignore them if we want to but
// should not throw an exception. The solution preferred here is to just read them
// but reverse them so the user gets what they expect according to the spec.
shell = ring.Reverse() as LinearRing;
reverse = true;
}
else
{
Expand All @@ -190,7 +192,7 @@ private Geometry CreatePolygonal(CoordinateSequence[] sequences)
}
else
{
holes.Add(ring);
holes.Add(reverse ? ring.Reverse() as LinearRing : ring);
}
}
}
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