public override bool HandleGeometry(IGeometryHandler handler)
{
var decoder = new GeometryDecoder(feature, layer);
// From https://github.com/mapbox/vector-tile-spec/tree/master/2.1
//
// The POINT geometry type encodes a point or multipoint geometry. The geometry command sequence for a point
// geometry MUST consist of a single MoveTo command with a command count greater than 0.
//
// The LINESTRING geometry type encodes a linestring or multilinestring geometry. The geometry command sequence
// for a linestring geometry MUST consist of one or more repetitions of the following sequence:
// 1. A MoveTo command with a command count of 1
// 2. A LineTo command with a command count greater than 0
//
// The POLYGON geometry type encodes a polygon or multipolygon geometry, each polygon consisting of exactly one
// exterior ring that contains zero or more interior rings. The geometry command sequence for a polygon consists
// of one or more repetitions of the following sequence:
// 1. An ExteriorRing
// 2. Zero or more InteriorRings
// Each ExteriorRing and InteriorRing MUST consist of the following sequence:
// 1. A MoveTo command with a command count of 1
// 2. A LineTo command with a command count greater than 1
// 3. A ClosePath command
switch (feature.Type)
{
case PbfGeomType.Point:
if (decoder.AdvanceCommand() && decoder.Command == CommandType.MoveTo)
{
for (int i = 0; i < decoder.Repeat; i++)
{
decoder.AdvanceCursor();
handler.OnPoint(decoder.CurrentPoint());
}
}
break;
case PbfGeomType.LineString:
while (decoder.AdvanceCommand() && (decoder.Command == CommandType.MoveTo && decoder.Repeat == 1))
{
decoder.AdvanceCursor();
if (decoder.AdvanceCommand() && (decoder.Command == CommandType.LineTo && decoder.Repeat > 0))
{
handler.OnBeginLineString();
handler.OnPoint(decoder.CurrentPoint());
for (int i = 0; i < decoder.Repeat; i++)
{
decoder.AdvanceCursor();
handler.OnPoint(decoder.CurrentPoint());
}
handler.OnEndLineString();
}
}
break;
case PbfGeomType.Polygon:
while (decoder.AdvanceCommand() && (decoder.Command == CommandType.MoveTo && decoder.Repeat == 1))
{
handler.OnBeginPolygon();
decoder.AdvanceCursor();
if (decoder.AdvanceCommand() && (decoder.Command == CommandType.LineTo && decoder.Repeat > 0))
{
handler.OnBeginLinearRing();
var start = decoder.CurrentPoint();
handler.OnPoint(start);
for (int i = 0; i < decoder.Repeat; i++)
{
decoder.AdvanceCursor();
handler.OnPoint(decoder.CurrentPoint());
}
handler.OnPoint(start);
handler.OnEndLinearRing();
}
if (decoder.AdvanceCommand() && decoder.Command == CommandType.ClosePath)
{
// We should assert that this condition holds.
}
handler.OnEndPolygon();
}
break;
case PbfGeomType.Unknown:
break;
}
return(true);
}
