From e9f30fc1f8f43ddbd025807e398eb741596322bf Mon Sep 17 00:00:00 2001
From: "jh5.cho" <jh5.cho@samsung.com>
Date: Wed, 15 Mar 2017 20:42:39 +0900
Subject: Add Implementation of VisibleRegion

    - Implementation of 'VisibleRegion' property
    - update 'MoveToRegion()' to support Latitude/Longitude Degree(VisibleRegion)

Change-Id: Ia88657d9ddba25a1c766a16905dab8d1fca68100
---
 Xamarin.Forms.Maps.Tizen/MapRenderer.cs | 53 +++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/Xamarin.Forms.Maps.Tizen/MapRenderer.cs b/Xamarin.Forms.Maps.Tizen/MapRenderer.cs
index cf7ddf7f..752b021f 100755
--- a/Xamarin.Forms.Maps.Tizen/MapRenderer.cs
+++ b/Xamarin.Forms.Maps.Tizen/MapRenderer.cs
@@ -14,6 +14,7 @@ namespace Xamarin.Forms.Maps.Tizen
 	public class MapRenderer : ViewRenderer<Map, MapView>
 	{
 		const string MoveMessageName = "MapMoveToRegion";
+		const int BaseZoomLevel = 2;
 
 		bool _disposed;
 		Marker _marker;
@@ -40,6 +41,9 @@ namespace Xamarin.Forms.Maps.Tizen
 			if (Control == null)
 			{
 				var mapControl = new MapView(Platform.Tizen.Forms.Context.MainWindow, FormsMaps.MapService);
+
+				mapControl.RenderPost += OnVisibleRegionChanged;
+
 				SetNativeControl(mapControl);
 			}
 
@@ -63,6 +67,7 @@ namespace Xamarin.Forms.Maps.Tizen
 				UpdateHasScrollEnabled();
 				UpdateHasZoomEnabled();
 				UpdateIsShowingUser();
+				UpdateVisibleRegion();
 			}
 			base.OnElementChanged(e);
 		}
@@ -83,6 +88,7 @@ namespace Xamarin.Forms.Maps.Tizen
 				{
 					((ObservableCollection<Pin>)Element.Pins).CollectionChanged -= OnCollectionChanged;
 				}
+				Control.RenderPost -= OnVisibleRegionChanged;
 				Control.Unrealize();
 			}
 			base.Dispose(disposing);
@@ -104,8 +110,51 @@ namespace Xamarin.Forms.Maps.Tizen
 
 		void OnMoveToRegion(Map map, MapSpan span)
 		{
-			var newCenter = new Geocoordinates(span.Center.Latitude, span.Center.Longitude);
-			Control.Center = newCenter;
+			UpdateVisibleRegion();
+
+			int latitudeZoomFactor = GetZoomFactor(span.LatitudeDegrees, 90.0);
+			int longitudeZoomFactor = GetZoomFactor(span.LongitudeDegrees, 180.0);
+
+			Control.Center = new Geocoordinates(span.Center.Latitude, span.Center.Longitude); ;
+			Control.ZoomLevel = BaseZoomLevel + Math.Min(latitudeZoomFactor, longitudeZoomFactor);
+			UpdateVisibleRegion();
+		}
+
+		int GetZoomFactor(double degree, double targetDegree)
+		{
+			int factor = 0;
+			double tempDegree = degree;
+			while (true)
+			{
+				tempDegree = tempDegree * 2;
+				if (tempDegree > targetDegree)
+					break;
+				factor++;
+			}
+			return factor;
+		}
+
+		void OnVisibleRegionChanged(object sender, EventArgs e)
+		{
+			UpdateVisibleRegion();
+		}
+
+		void UpdateVisibleRegion()
+		{
+			int width = Control.Geometry.Width;
+			int height = Control.Geometry.Height;
+			int x = Control.Geometry.X;
+			int y = Control.Geometry.Y;
+
+			Geocoordinates ul = Control.ScreenToGeolocation(new ElmSharp.Point { X = x, Y = y});
+			Geocoordinates ur = Control.ScreenToGeolocation(new ElmSharp.Point { X = x + width, Y = y});
+			Geocoordinates ll = Control.ScreenToGeolocation(new ElmSharp.Point { X = x, Y = y + height });
+			Geocoordinates lr = Control.ScreenToGeolocation(new ElmSharp.Point { X = x + width, Y = y + height });
+
+			double dlat = Math.Max(Math.Abs(ul.Latitude - lr.Latitude), Math.Abs(ur.Latitude - ll.Latitude));
+			double dlong = Math.Max(Math.Abs(ul.Longitude - lr.Longitude), Math.Abs(ur.Longitude - ll.Longitude));
+
+			Element.VisibleRegion = new MapSpan(new Position(Control.Center.Latitude, Control.Center.Longitude), dlat, dlong);
 		}
 
 
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