feat(projectBack): added projectBack method as inverse method to project

projectBack maps an on screen coordinate to a map coordinate. This is the inverse method to project which maps a map coordinate to an on screen coordinate.

Author: benedictstrube

src/ui-mapbox/common.ts

@@ -703,6 +703,8 @@ export interface MapboxApi {
 
     removeImage(imageId: string, nativeMap?: any): Promise<void>;
     project(data: LatLng): { x: number; y: number };
+
+    projectBack(point: { x: number, y: number }): LatLng;
 }
 
 // ------------------------------------------------------------
@@ -1061,6 +1063,9 @@ export abstract class MapboxViewCommonBase extends ContentView implements Mapbox
     project(data: LatLng) {
         return this.mapbox && this.mapbox.project(data);
     }
+    projectBack(screenCoordinate: { x: number, y: number }): LatLng {
+        return this.mapbox && this.mapbox.projectBack(screenCoordinate);
+    }
 }
 
 // -----------------------------------------------------------------

src/ui-mapbox/index.android.ts

@@ -3391,4 +3391,12 @@ export class Mapbox extends MapboxCommon implements MapboxApi {
         const screenLocation = this._mapboxMapInstance.getProjection().toScreenLocation(mapboxPoint);
         return { x: Utils.layout.toDeviceIndependentPixels(screenLocation.x), y: Utils.layout.toDeviceIndependentPixels(screenLocation.y) };
     }
+    projectBack(screenCoordinate: { x: number, y: number }): LatLng {
+        const pointf = new android.graphics.PointF(screenCoordinate.x, screenCoordinate.y);
+        const coordinate = this._mapboxMapInstance.getProjection().fromScreenLocation(pointf);
+        return {
+            lat: coordinate.getLatitude(),
+            lng: coordinate.getLongitude()
+        }
+    }
 }

src/ui-mapbox/index.d.ts

@@ -97,4 +97,5 @@ export declare class Mapbox extends MapboxCommon implements MapboxApi {
         x: number;
         y: number;
     };
-}
+    projectBack(screenCoordinate: { x: number, y: number }): LatLng;
+}

src/ui-mapbox/index.ios.ts

@@ -3159,6 +3159,19 @@ export class Mapbox extends MapboxCommon implements MapboxApi {
         const { x, y } = theMap.convertCoordinateToPointToView({ latitude: data.lat, longitude: data.lng }, theMap);
         return { x, y };
     }
+
+    projectBack(screenCoordinate: { x: number, y: number }): LatLng {
+        const theMap: MGLMapView = this._mapboxViewInstance;
+        const cgPoint = {
+            x: screenCoordinate.x,
+            y: screenCoordinate.y
+        }
+        const coordinate = theMap.convertPointToCoordinateFromView(cgPoint, theMap);
+        return {
+            lat: coordinate.latitude,
+            lng: coordinate.longitude
+        }
+    }
 }
 
 const _addObserver = (eventName, callback) => NSNotificationCenter.defaultCenter.addObserverForNameObjectQueueUsingBlock(eventName, null, NSOperationQueue.mainQueue, callback);