Introduce ESM support

src/fallback.esm.js

@@ -0,0 +1,108 @@
+export function createTileLayerFallback(extend, TileLayer, Browser, Util) {
+	TileLayer.Fallback = TileLayer.extend({
+	  options: {
+		minNativeZoom: 0
+	  },
+	  initialize: function (urlTemplate, options) {
+		TileLayer.prototype.initialize.call(this, urlTemplate, options);
+	  },
+	  createTile: function (coords, done) {
+		var tile = TileLayer.prototype.createTile.call(this, coords, done);
+		tile._originalCoords = coords;
+		tile._originalSrc = tile.src;
+		return tile;
+	  },
+	  _createCurrentCoords: function (originalCoords) {
+		var currentCoords = this._wrapCoords(originalCoords);
+		currentCoords.fallback = true;
+		return currentCoords;
+	  },
+	  _originalTileOnError: TileLayer.prototype._tileOnError,
+	  _tileOnError: function (done, tile, e) {
+		var layer = this, // `this` is bound to the Tile Layer in TileLayer.prototype.createTile.
+		  originalCoords = tile._originalCoords,
+		  currentCoords = (tile._currentCoords =
+			tile._currentCoords || layer._createCurrentCoords(originalCoords)),
+		  fallbackZoom = (tile._fallbackZoom =
+			tile._fallbackZoom === undefined
+			  ? originalCoords.z - 1
+			  : tile._fallbackZoom - 1),
+		  scale = (tile._fallbackScale = (tile._fallbackScale || 1) * 2),
+		  tileSize = layer.getTileSize(),
+		  style = tile.style,
+		  newUrl,
+		  top,
+		  left;
+		// If no lower zoom tiles are available, fallback to errorTile.
+		if (fallbackZoom < layer.options.minNativeZoom) {
+		  return this._originalTileOnError(done, tile, e);
+		}
+		// Modify tilePoint for replacement img.
+		currentCoords.z = fallbackZoom;
+		currentCoords.x = Math.floor(currentCoords.x / 2);
+		currentCoords.y = Math.floor(currentCoords.y / 2);
+		// Generate new src path.
+		newUrl = layer.getTileUrl(currentCoords);
+		// Zoom replacement img.
+		style.width = tileSize.x * scale + "px";
+		style.height = tileSize.y * scale + "px";
+		// Compute margins to adjust position.
+		top = (originalCoords.y - currentCoords.y * scale) * tileSize.y;
+		style.marginTop = -top + "px";
+		left = (originalCoords.x - currentCoords.x * scale) * tileSize.x;
+		style.marginLeft = -left + "px";
+		// Crop (clip) image.
+		// `clip` is deprecated, but browsers support for `clip-path: inset()` is far behind.
+		// http://caniuse.com/#feat=css-clip-path
+		style.clip =
+		  "rect(" +
+		  top +
+		  "px " +
+		  (left + tileSize.x) +
+		  "px " +
+		  (top + tileSize.y) +
+		  "px " +
+		  left +
+		  "px)";
+		layer.fire("tilefallback", {
+		  tile: tile,
+		  url: tile._originalSrc,
+		  urlMissing: tile.src,
+		  urlFallback: newUrl
+		});
+		tile.src = newUrl;
+	  },
+	  getTileUrl: function (coords) {
+		var z = (coords.z = coords.fallback ? coords.z : this._getZoomForUrl());
+		var data = {
+		  r: Browser.retina ? "@2x" : "",
+		  s: this._getSubdomain(coords),
+		  x: coords.x,
+		  y: coords.y,
+		  z: z
+		};
+		if (this._map && !this._map.options.crs.infinite) {
+		  var invertedY = this._globalTileRange.max.y - coords.y;
+		  if (this.options.tms) {
+			data["y"] = invertedY;
+		  }
+		  data["-y"] = invertedY;
+		}
+		return Util.template(this._url, extend(data, this.options));
+	  }
+	});
+	// Supply with a factory for consistency with Leaflet.
+	TileLayer.fallback = function (urlTemplate, options) {
+	  return new TileLayer.Fallback(urlTemplate, options);
+	};
+  }
+
+  export function createTileLayerFallbackCompact(L) {
+	return createTileLayerFallback(L.extend, L.TileLayer, L.Browser, L.Util);
+  }
+
+  // Usage Example:
+  // import { createTileLayerFallbackCompact } from './path-to-this-module';
+  // import L from 'leaflet';
+  // createTileLayerFallback(L);
+