Using `<TiledLayer>` in `<layerStack>`.

src/components/map/LayerStack.tsx

@@ -7,10 +7,11 @@ import { coordinateSystemAtom } from './Map';
 import TileSet from './TileSet';
 import _, { floor, range } from 'lodash';
 import tileUri from './uris';
+import TiledLayer from './TiledLayer';
 
 export interface LayerStackProperties {
   /**
-   * A key identifying the initial top left tile
+   * A key identifying the top left tile
    */
   keyObject: TileKeyObject;
   /**
@@ -37,46 +38,10 @@ export const LayerStack: react.FC<LayerStackProperties> = (
   const numberOfTiledLayers =
     props.numberOfTiledLayers === undefined ? 1 : props.numberOfTiledLayers;
 
-  const activeTiledLayer = Math.min(
-    Math.max(
-      Math.round(Math.log2(coordinateSystem.zoom)) +
-        Math.floor(numberOfTiledLayers / 2),
-      0
-    ),
-    numberOfTiledLayers - 1
-  );
+  const activeTiledLayer = Math.floor(numberOfTiledLayers / 2);
 
-  const viewPort = {
-    topLeft: {
-      x:
-        props.keyObject.x +
-        Math.floor(-coordinateSystem.shift.x / coordinateSystem.zoom / 256),
-      y:
-        props.keyObject.y +
-        Math.floor(-coordinateSystem.shift.y / coordinateSystem.zoom / 256),
-    },
-    bottomRight: {
-      x:
-        props.keyObject.x +
-        Math.ceil(
-          (-coordinateSystem.shift.x + window.innerWidth) /
-            coordinateSystem.zoom /
-            256
-        ) -
-        1,
-      y:
-        props.keyObject.y +
-        Math.ceil(
-          (-coordinateSystem.shift.y + window.innerHeight) /
-            coordinateSystem.zoom /
-            256
-        ) -
-        1,
-    },
-  };
-
-  const getTileSet = (i: number) => {
-    const relativeZoomLevel = i - Math.floor(numberOfTiledLayers / 2);
+  const getTiledLayer = (i: number) => {
+    const relativeZoomLevel = i - activeTiledLayer;
     const zoom = 2 ** relativeZoomLevel;
     const origin = {
       x: props.keyObject.x * zoom,
@@ -89,8 +54,8 @@ export const LayerStack: react.FC<LayerStackProperties> = (
       y: Math.floor(origin.y),
     };
     const shift = {
-      x: origin.x - floor(origin.x),
-      y: origin.y - floor(origin.y),
+      x: -origin.x,
+      y: -origin.y,
     };
     const key = tileUri({
       provider: keyObject.provider,
@@ -98,19 +63,12 @@ export const LayerStack: react.FC<LayerStackProperties> = (
     });
 
     return (
-      <g
-        transform={`scale(${256 / zoom}) translate(${shift.x - keyObject.x}, ${
-          shift.y - keyObject.y
-        })`}
-        key={key}
-        data-testid={key}
-      >
-        <TileSet
-          key={key}
-          keyObject={keyObject}
-          viewPort={i === activeTiledLayer ? viewPort : undefined}
-        />
-      </g>
+      <TiledLayer
+        key={tileUri(keyObject)}
+        keyObject={keyObject}
+        shift={shift}
+        zoom={zoom * 256}
+      />
     );
   };
 
@@ -127,15 +85,17 @@ export const LayerStack: react.FC<LayerStackProperties> = (
       >
         {
           // Tiled layers with less detail
-          range(0, activeTiledLayer).map(getTileSet)
+          range(0, activeTiledLayer).map(getTiledLayer)
         }
         {
           // Tiled layers with more details
-          range(numberOfTiledLayers - 1, activeTiledLayer, -1).map(getTileSet)
+          range(numberOfTiledLayers - 1, activeTiledLayer, -1).map(
+            getTiledLayer
+          )
         }
         {
           // And the active one
-          getTileSet(activeTiledLayer)
+          getTiledLayer(activeTiledLayer)
         }
       </g>
     </svg>

src/components/map/TiledLayer.tsx

@@ -10,11 +10,11 @@ export interface TiledLayerProperties {
    */
   keyObject: TileKeyObject;
   /**
-   * A flag to indicate if the layer is active and should add tiles which are in its viewport or if it is "only" a backup.
+   * The translation to apply.
    */
   shift: Point;
   /**
-   * The zoom to apply. If equal to 1, the layer is considered active and should add tiles which are in its viewport
+   * The zoom to apply. If equal to 256 (the tile size), the layer is considered active and should add tiles which are in its viewport
    */
   zoom: number;
 }
@@ -24,14 +24,14 @@ export interface TiledLayerProperties {
  * @param props
  * @returns A layer of tiles.
  * This component wraps a `<TileSet>` in an SVG `<g>` element taking care of the scale and translation.
- * 
+ *
  */
 export const TiledLayer: react.FC<TiledLayerProperties> = (
   props: TiledLayerProperties
 ) => {
   const [coordinateSystem] = useAtom(coordinateSystemAtom);
   const viewPort =
-    props.zoom === 1
+    props.zoom === 256
       ? {
           topLeft: {
             x: