implemented a map zone selector based on squares

traque-front/components/util/map.jsx

@@ -0,0 +1,20 @@
+export class TileNumber {
+    constructor(x, y) {
+        this.x = x;
+        this.y = y;
+    }
+    equals(other) {
+        return this.x === other.x && this.y === other.y;
+    }
+}
+
+export function latLngToTileNumber(latLng, tileSize) {
+    const numTilesX = 2 ** tileSize;
+    const numTilesY = 2 ** tileSize;
+    const lngDegrees = latLng.lng;
+    const latRadians = latLng.lat * (Math.PI / 180);
+    return new L.Point(
+        numTilesX * ((lngDegrees + 180) / 360),
+        numTilesY * (1 - Math.log(Math.tan(latRadians) + 1 / Math.cos(latRadians)) / Math.PI) / 2
+    );
+}