Initial import

1 files changed, 116 insertions, 0 deletions

diff --git a/Xamarin.Forms.Maps/MapSpan.cs b/Xamarin.Forms.Maps/MapSpan.cs
new file mode 100644
index 00000000..883e630f
--- /dev/null
+++ b/Xamarin.Forms.Maps/MapSpan.cs
@@ -0,0 +1,116 @@
+using System;
+
+namespace Xamarin.Forms.Maps
+{
+	public sealed class MapSpan
+	{
+		const double EarthRadiusKm = 6371;
+		const double EarthCircumferenceKm = EarthRadiusKm * 2 * Math.PI;
+		const double MinimumRangeDegrees = 0.001 / EarthCircumferenceKm * 360; // 1 meter
+
+		public MapSpan(Position center, double latitudeDegrees, double longitudeDegrees)
+		{
+			Center = center;
+			LatitudeDegrees = Math.Min(Math.Max(latitudeDegrees, MinimumRangeDegrees), 90.0);
+			LongitudeDegrees = Math.Min(Math.Max(longitudeDegrees, MinimumRangeDegrees), 180.0);
+		}
+
+		public Position Center { get; }
+
+		public double LatitudeDegrees { get; }
+
+		public double LongitudeDegrees { get; }
+
+		public Distance Radius
+		{
+			get
+			{
+				double latKm = LatitudeDegreesToKm(LatitudeDegrees);
+				double longKm = LongitudeDegreesToKm(Center, LongitudeDegrees);
+				return new Distance(1000 * Math.Min(latKm, longKm) / 2);
+			}
+		}
+
+		public MapSpan ClampLatitude(double north, double south)
+		{
+			north = Math.Min(Math.Max(north, 0), 90);
+			south = Math.Max(Math.Min(south, 0), -90);
+			double lat = Math.Max(Math.Min(Center.Latitude, north), south);
+			double maxDLat = Math.Min(north - lat, -south + lat) * 2;
+			return new MapSpan(new Position(lat, Center.Longitude), Math.Min(LatitudeDegrees, maxDLat), LongitudeDegrees);
+		}
+
+		public override bool Equals(object obj)
+		{
+			if (ReferenceEquals(null, obj))
+				return false;
+			if (ReferenceEquals(this, obj))
+				return true;
+			return obj is MapSpan && Equals((MapSpan)obj);
+		}
+
+		public static MapSpan FromCenterAndRadius(Position center, Distance radius)
+		{
+			return new MapSpan(center, 2 * DistanceToLatitudeDegrees(radius), 2 * DistanceToLongitudeDegrees(center, radius));
+		}
+
+		public override int GetHashCode()
+		{
+			unchecked
+			{
+				int hashCode = Center.GetHashCode();
+				hashCode = (hashCode * 397) ^ LongitudeDegrees.GetHashCode();
+				hashCode = (hashCode * 397) ^ LatitudeDegrees.GetHashCode();
+				return hashCode;
+			}
+		}
+
+		public static bool operator ==(MapSpan left, MapSpan right)
+		{
+			return Equals(left, right);
+		}
+
+		public static bool operator !=(MapSpan left, MapSpan right)
+		{
+			return !Equals(left, right);
+		}
+
+		public MapSpan WithZoom(double zoomFactor)
+		{
+			double maxDLat = Math.Min(90 - Center.Latitude, 90 + Center.Latitude) * 2;
+			return new MapSpan(Center, Math.Min(LatitudeDegrees / zoomFactor, maxDLat), LongitudeDegrees / zoomFactor);
+		}
+
+		static double DistanceToLatitudeDegrees(Distance distance)
+		{
+			return distance.Kilometers / EarthCircumferenceKm * 360;
+		}
+
+		static double DistanceToLongitudeDegrees(Position position, Distance distance)
+		{
+			double latCircumference = LatitudeCircumferenceKm(position);
+			return distance.Kilometers / latCircumference * 360;
+		}
+
+		bool Equals(MapSpan other)
+		{
+			return Center.Equals(other.Center) && LongitudeDegrees.Equals(other.LongitudeDegrees) && LatitudeDegrees.Equals(other.LatitudeDegrees);
+		}
+
+		static double LatitudeCircumferenceKm(Position position)
+		{
+			return EarthCircumferenceKm * Math.Cos(position.Latitude * Math.PI / 180.0);
+		}
+
+		static double LatitudeDegreesToKm(double latitudeDegrees)
+		{
+			return EarthCircumferenceKm * latitudeDegrees / 360;
+		}
+
+		static double LongitudeDegreesToKm(Position position, double longitudeDegrees)
+		{
+			double latCircumference = LatitudeCircumferenceKm(position);
+			return latCircumference * longitudeDegrees / 360;
+		}
+	}
+}
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