Implementing a Marker component.

src/App.tsx

@@ -36,6 +36,7 @@ import GetLocation from './components/buttons/GetLocation';
 import { geoPoint } from './components/map/types';
 import Back from './components/buttons/Back';
 import Forward from './components/buttons/Forward';
+import Marker from './components/map/Marker';
 
 setupIonicReact();
 
@@ -62,6 +63,24 @@ const App: React.FC = () => {
   const [scope, setScope] = useAtom(scopeAtom);
 
   console.log(`App, scope: ${JSON.stringify(scope)}`);
+  const marker = (
+    <Marker
+      coordinates={{ lat: -37.8403508, lon: 77.5539501 }}
+      icon={
+        <circle
+          cx={0}
+          cy={0}
+          r={6 / 256}
+          fill='blue'
+          opacity='90%'
+          stroke='white'
+          strokeWidth={3 / 256}
+          strokeOpacity='100%'
+        ></circle>
+      }
+      key='current'
+    />
+  );
   return (
     <IonApp>
       <IonContent fullscreen={true}>
@@ -70,6 +89,7 @@ const App: React.FC = () => {
             scope={scope}
             setScope={debounce(setScope, 1000)}
             numberOfTiledLayers={5}
+            markers={[marker]}
           />
         </IonApp>
       </IonContent>

src/components/map/LayerStack.tsx

@@ -1,4 +1,10 @@
-import react from 'react';
+import react, {
+  cloneElement,
+  JSXElementConstructor,
+  ReactComponentElement,
+  ReactElement,
+  ReactNode,
+} from 'react';
 
 import { TileKeyObject } from './types';
 
@@ -6,6 +12,8 @@ import { CoordinateSystem } from './LiveMap';
 import { range } from 'lodash';
 import tileUri from './uris';
 import TiledLayer from './TiledLayer';
+import { ReactComponentOrElement } from '@ionic/react';
+import { KeyObject } from 'crypto';
 
 export interface LayerStackProperties {
   /**
@@ -20,6 +28,8 @@ export interface LayerStackProperties {
    * The coordinates system
    */
   coordinateSystem: CoordinateSystem;
+  /** Markers are non scalable SVG snippets tied to geo location */
+  markers?: ReactElement<any, string | JSXElementConstructor<any>>[];
 }
 
 /**
@@ -82,6 +92,7 @@ export const LayerStack: react.FC<LayerStackProperties> = (
     <svg width='100%' height='100%' data-testid='layer-stack'>
       <g
         transform={`translate(${props.coordinateSystem.shift.x}, ${props.coordinateSystem.shift.y}) scale(${props.coordinateSystem.zoom})`}
+        key='tiles'
       >
         {
           // Tiled layers with less detail
@@ -98,6 +109,23 @@ export const LayerStack: react.FC<LayerStackProperties> = (
           getTiledLayer(activeTiledLayer)
         }
       </g>
+      {props.markers !== undefined ? (
+        <g
+          key='markers'
+          transform={`translate(${props.coordinateSystem.shift.x}, ${props.coordinateSystem.shift.y}) scale(${props.coordinateSystem.zoom})`}
+        >
+          <g
+            transform={`scale(256) translate(-${props.keyObject.x}, -${props.keyObject.y})`}
+          >
+            {props.markers.map((marker) =>
+              cloneElement(marker, {
+                keyObject: props.keyObject,
+                zoom: props.coordinateSystem.zoom,
+              })
+            )}
+          </g>
+        </g>
+      ) : null}
     </svg>
   );
 };

src/components/map/LiveMap.tsx

@@ -1,9 +1,10 @@
-import react, { useEffect, useState } from 'react';
+import react, { JSXElementConstructor, ReactComponentElement, ReactElement, ReactNode, useEffect, useState } from 'react';
 import useDimensions from 'react-cool-dimensions';
 
 import { MapScope, Point } from './types';
 import Map from './Map';
 import Handlers from './Handlers';
+import Marker from './Marker';
 import { tileProviders } from './tile-providers';
 import { lon2tile, lat2tile, tile2lat, tile2long } from '../../lib/geo';
 
@@ -39,6 +40,8 @@ export interface LiveMapProperties {
   numberOfTiledLayers?: number;
   /** If provided, a function to call when the scope is updated. */
   setScope?: (scope: MapScope) => void;
+  /** Markers are non scalable SVG snippets tied to geo location */
+  markers?: ReactElement<any, string | JSXElementConstructor<any>>[];
 }
 
 /**
@@ -132,7 +135,11 @@ export const LiveMap: react.FC<LiveMapProperties> = (
   return (
     <div style={{ width: '100%', height: '100%' }} ref={observe}>
       <Handlers transformMap={transform} />
-      <Map scope={scope} numberOfTiledLayers={props.numberOfTiledLayers} />
+      <Map
+        scope={scope}
+        numberOfTiledLayers={props.numberOfTiledLayers}
+        markers={props.markers}
+      />
     </div>
   );
 };

src/components/map/Map.tsx

@@ -1,7 +1,9 @@
-import react from 'react';
+import react, { JSXElementConstructor, ReactElement, ReactNode } from 'react';
 import useDimensions from 'react-cool-dimensions';
 
 import { Point, MapScope } from './types';
+import Marker from './Marker';
+
 import LayerStack from './LayerStack';
 import { tileProviders } from './tile-providers';
 import { lon2tile, lat2tile } from '../../lib/geo';
@@ -9,6 +11,8 @@ import { lon2tile, lat2tile } from '../../lib/geo';
 export interface MapProperties {
   scope: MapScope;
   numberOfTiledLayers?: number;
+  /** Markers are non scalable SVG snippets tied to geo location */
+  markers?: ReactElement<any, string | JSXElementConstructor<any>>[];
 }
 
 /**
@@ -58,6 +62,7 @@ export const Map: react.FC<MapProperties> = (props: MapProperties) => {
           },
           zoom: relativeScale,
         }}
+        markers={props.markers}
       />
     </div>
   );

src/components/map/Marker.tsx

@@ -0,0 +1,26 @@
+import { KeyObject } from 'crypto';
+import react, { ReactNode } from 'react';
+import { lat2tile, lon2tile } from '../../lib/geo';
+import { CoordinateSystem } from './LiveMap';
+import { geoPoint, TileKeyObject } from './types';
+
+export interface MarkerProperties {
+  coordinates: geoPoint;
+  icon: ReactNode;
+  keyObject?: TileKeyObject;
+  zoom?: number;
+}
+
+export const Marker: react.FC<MarkerProperties> = (props: MarkerProperties) => {
+  if (props.keyObject === undefined || props.zoom === undefined) return null;
+
+  const x = lon2tile(props.coordinates.lon, props.keyObject.zoomLevel);
+  const y = lat2tile(props.coordinates.lat, props.keyObject.zoomLevel);
+  return (
+    <g transform={`translate(${x}, ${y}) scale(${1 / props.zoom})`}>
+      {props.icon}
+    </g>
+  );
+};
+
+export default Marker;

src/components/map/TiledLayer.tsx

@@ -1,4 +1,4 @@
-import react, { useRef } from 'react';
+import react, { ReactNode, useRef } from 'react';
 import TileSet from './TileSet';
 import { Point, TileKeyObject } from './types';
 import { CoordinateSystem } from './LiveMap';
@@ -75,6 +75,7 @@ export const TiledLayer: react.FC<TiledLayerProperties> = (
     };
   }
   return (
+    <>
       <g
         transform={`scale(${props.zoom}) translate(${props.shift.x}, ${props.shift.y})`}
         ref={g}
@@ -89,6 +90,7 @@ export const TiledLayer: react.FC<TiledLayerProperties> = (
           viewPort={viewPort}
         />
       </g>
+    </>
   );
 };