private static SKPath ToSkia(IViewport viewport, Polygon polygon)
{
var vertices = polygon.ExteriorRing.Vertices;
var path = new SKPath();
{
// todo: use transform matrix
var first = viewport.WorldToScreen(vertices[0].X, vertices[0].Y);
path.MoveTo((float)first.X, (float) first.Y);
for (var i = 1; i < vertices.Count; i++)
{
var point = viewport.WorldToScreen(vertices[i].X, vertices[i].Y);
path.LineTo((float) point.X, (float) point.Y);
}
path.Close();
foreach (var interiorRing in polygon.InteriorRings)
{
// note: For Skia inner rings need to be clockwise and outer rings
// need to be counter clockwise (if this is the other way around it also
// seems to work)
// this is not a requirement of the OGC polygon.
var firstInner = viewport.WorldToScreen(interiorRing.Vertices[0].X, interiorRing.Vertices[0].Y);
path.MoveTo((float)firstInner.X, (float)firstInner.Y);
for (var i = 1; i < interiorRing.Vertices.Count; i++)
{
var point = viewport.WorldToScreen(interiorRing.Vertices[i].X, interiorRing.Vertices[i].Y);
path.LineTo((float)point.X, (float)point.Y);
}
}
path.Close();
return path;
}
}
