L.TileLayer.NoGap.js

// @class TileLayer

L.TileLayer.mergeOptions({
	// @option keepBuffer
	// The amount of tiles outside the visible map area to be kept in the stitched
	// `TileLayer`.

	// @option dumpToCanvas: Boolean = true
	// Whether to dump loaded tiles to a `<canvas>` to prevent some rendering
	// artifacts. (Disabled by default in IE)
	dumpToCanvas: L.Browser.canvas && !L.Browser.ie,
});

L.TileLayer.include({
	_onUpdateLevel: function(z, zoom) {
		if (this.options.dumpToCanvas) {
			this._levels[z].canvas.style.zIndex =
				this.options.maxZoom - Math.abs(zoom - z);
		}
	},

	_onRemoveLevel: function(z) {
		if (this.options.dumpToCanvas) {
			L.DomUtil.remove(this._levels[z].canvas);
		}
	},

	_onCreateLevel: function(level) {
		if (this.options.dumpToCanvas) {
			level.canvas = L.DomUtil.create(
				"canvas",
				"leaflet-tile-container leaflet-zoom-animated",
				this._container
			);
			level.ctx = level.canvas.getContext("2d");
			this._resetCanvasSize(level);
		}
	},

	_removeTile: function(key) {
		if (this.options.dumpToCanvas) {
			var tile = this._tiles[key];
			var level = this._levels[tile.coords.z];
			var tileSize = this.getTileSize();

			if (level) {
				// Where in the canvas should this tile go?
				var offset = L.point(tile.coords.x, tile.coords.y)
					.subtract(level.canvasRange.min)
					.scaleBy(this.getTileSize());

				level.ctx.clearRect(offset.x, offset.y, tileSize.x, tileSize.y);
			}
		}

		L.GridLayer.prototype._removeTile.call(this, key);
	},

	_resetCanvasSize: function(level) {
		var buff = this.options.keepBuffer,
			pixelBounds = this._getTiledPixelBounds(this._map.getCenter()),
			tileRange = this._pxBoundsToTileRange(pixelBounds),
			tileSize = this.getTileSize();

		tileRange.min = tileRange.min.subtract([buff, buff]); // This adds the no-prune buffer
		tileRange.max = tileRange.max.add([buff + 1, buff + 1]);

		var pixelRange = L.bounds(
				tileRange.min.scaleBy(tileSize),
				tileRange.max.add([1, 1]).scaleBy(tileSize) // This prevents an off-by-one when checking if tiles are inside
			),
			mustRepositionCanvas = false,
			neededSize = pixelRange.max.subtract(pixelRange.min);

		// Resize the canvas, if needed, and only to make it bigger.
		if (
			neededSize.x > level.canvas.width ||
			neededSize.y > level.canvas.height
		) {
			// Resizing canvases erases the currently drawn content, I'm afraid.
			// To keep it, dump the pixels to another canvas, then display it on
			// top. This could be done with getImageData/putImageData, but that
			// would break for tainted canvases (in non-CORS tilesets)
			var oldSize = { x: level.canvas.width, y: level.canvas.height };
			// console.info('Resizing canvas from ', oldSize, 'to ', neededSize);

			var tmpCanvas = L.DomUtil.create("canvas");
			tmpCanvas.style.width = (tmpCanvas.width = oldSize.x) + "px";
			tmpCanvas.style.height = (tmpCanvas.height = oldSize.y) + "px";
			tmpCanvas.getContext("2d").drawImage(level.canvas, 0, 0);
			// var data = level.ctx.getImageData(0, 0, oldSize.x, oldSize.y);

			level.canvas.style.width = (level.canvas.width = neededSize.x) + "px";
			level.canvas.style.height = (level.canvas.height = neededSize.y) + "px";
			level.ctx.drawImage(tmpCanvas, 0, 0);
			// level.ctx.putImageData(data, 0, 0, 0, 0, oldSize.x, oldSize.y);
		}

		// Translate the canvas contents if it's moved around
		if (level.canvasRange) {
			var offset = level.canvasRange.min
				.subtract(tileRange.min)
				.scaleBy(this.getTileSize());

			// 			console.info('Offsetting by ', offset);

			if (!L.Browser.safari) {
				// By default, canvases copy things "on top of" existing pixels, but we want
				// this to *replace* the existing pixels when doing a drawImage() call.
				// This will also clear the sides, so no clearRect() calls are needed to make room
				// for the new tiles.
				level.ctx.globalCompositeOperation = "copy";
				level.ctx.drawImage(level.canvas, offset.x, offset.y);
				level.ctx.globalCompositeOperation = "source-over";
			} else {
				// Safari clears the canvas when copying from itself :-(
				if (!this._tmpCanvas) {
					var t = (this._tmpCanvas = L.DomUtil.create("canvas"));
					t.width = level.canvas.width;
					t.height = level.canvas.height;
					this._tmpContext = t.getContext("2d");
				}
				this._tmpContext.clearRect(
					0,
					0,
					level.canvas.width,
					level.canvas.height
				);
				this._tmpContext.drawImage(level.canvas, 0, 0);
				level.ctx.clearRect(0, 0, level.canvas.width, level.canvas.height);
				level.ctx.drawImage(this._tmpCanvas, offset.x, offset.y);
			}

			mustRepositionCanvas = true; // Wait until new props are set
		}

		level.canvasRange = tileRange;
		level.canvasPxRange = pixelRange;
		level.canvasOrigin = pixelRange.min;

		// console.log('Canvas tile range: ', level, tileRange.min, tileRange.max );
		// console.log('Canvas pixel range: ', pixelRange.min, pixelRange.max );
		// console.log('Level origin: ', level.origin );

		if (mustRepositionCanvas) {
			this._setCanvasZoomTransform(
				level,
				this._map.getCenter(),
				this._map.getZoom()
			);
		}
	},

	/// set transform/position of canvas, in addition to the transform/position of the individual tile container
	_setZoomTransform: function(level, center, zoom) {
		L.GridLayer.prototype._setZoomTransform.call(this, level, center, zoom);
		if (this.options.dumpToCanvas) {
			this._setCanvasZoomTransform(level, center, zoom);
		}
	},

	// This will get called twice:
	// * From _setZoomTransform
	// * When the canvas has shifted due to a new tile being loaded
	_setCanvasZoomTransform: function(level, center, zoom) {
		// console.log('_setCanvasZoomTransform', level, center, zoom);
		if (!level.canvasOrigin) {
			return;
		}
		var scale = this._map.getZoomScale(zoom, level.zoom),
			translate = level.canvasOrigin
				.multiplyBy(scale)
				.subtract(this._map._getNewPixelOrigin(center, zoom))
				.round();

		if (L.Browser.any3d) {
			L.DomUtil.setTransform(level.canvas, translate, scale);
		} else {
			L.DomUtil.setPosition(level.canvas, translate);
		}
	},

	_onOpaqueTile: function(tile) {
		if (!this.options.dumpToCanvas) {
			return;
		}

		// Guard against an NS_ERROR_NOT_AVAILABLE (or similar) exception
		// when a non-image-tile has been loaded (e.g. a WMS error).
		// Checking for tile.el.complete is not enough, as it has been
		// already marked as loaded and ready somehow.
		try {
			this.dumpPixels(tile.coords, tile.el);
		} catch (ex) {
			return this.fire("tileerror", {
				error: "Could not copy tile pixels: " + ex,
				tile: tile,
				coods: tile.coords,
			});
		}

		// If dumping the pixels was successful, then hide the tile.
		// Do not remove the tile itself, as it is needed to check if the whole
		// level (and its canvas) should be removed (via level.el.children.length)
		tile.el.style.display = "none";
	},

	// @section Extension methods
	// @uninheritable

	// @method dumpPixels(coords: Object, imageSource: CanvasImageSource): this
	// Dumps pixels from the given `CanvasImageSource` into the layer, into
	// the space for the tile represented by the `coords` tile coordinates (an object
	// like `{x: Number, y: Number, z: Number}`; the image source must have the
	// same size as the `tileSize` option for the layer. Has no effect if `dumpToCanvas`
	// is `false`.
	dumpPixels: function(coords, imageSource) {
		var level = this._levels[coords.z],
			tileSize = this.getTileSize();

		if (!level.canvasRange || !this.options.dumpToCanvas) {
			return;
		}

		// Check if the tile is inside the currently visible map bounds
		// There is a possible race condition when tiles are loaded after they
		// have been panned outside of the map.
		if (!level.canvasRange.contains(coords)) {
			this._resetCanvasSize(level);
		}

		// Where in the canvas should this tile go?
		var offset = L.point(coords.x, coords.y)
			.subtract(level.canvasRange.min)
			.scaleBy(this.getTileSize());

		level.ctx.drawImage(imageSource, offset.x, offset.y, tileSize.x, tileSize.y);

		// TODO: Clear the pixels of other levels' canvases where they overlap
		// this newly dumped tile.
		return this;
	},
});