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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
part of google_maps_flutter_web;
/// This wraps a [TileOverlay] in a [gmaps.MapType].
class TileOverlayController {
/// Creates a `TileOverlayController` that wraps a [TileOverlay] object and its corresponding [gmaps.MapType].
required TileOverlay tileOverlay,
}) {
/// The size in pixels of the (square) tiles passed to the Maps SDK.
/// Even though the web supports any size, and rectangular tiles, for
/// for consistency with mobile, this is not configurable on the web.
/// (Both Android and iOS prefer square 256px tiles @ 1x DPI)
/// For higher DPI screens, the Tile that is actually returned can be larger
/// than 256px square.
static const int logicalTileSize = 256;
/// Updates the [gmaps.MapType] and cached properties with an updated
/// [TileOverlay].
void update(TileOverlay tileOverlay) {
_tileOverlay = tileOverlay;
_gmMapType = gmaps.MapType()
..tileSize = gmaps.Size(logicalTileSize, logicalTileSize)
..getTile = _getTile;
/// Renders a Tile for gmaps; delegating to the configured [TileProvider].
HtmlElement? _getTile(
gmaps.Point? tileCoord,
num? zoom,
Document? ownerDocument,
) {
if (_tileOverlay.tileProvider == null) {
return null;
final ImageElement img =
ownerDocument!.createElement('img') as ImageElement;
img.width = img.height = logicalTileSize;
img.hidden = true;
img.setAttribute('decoding', 'async');
.getTile(tileCoord!.x!.toInt(), tileCoord.y!.toInt(), zoom?.toInt())
.then((Tile tile) {
if ( == null) {
// Using img lets us take advantage of native decoding.
final String src = Url.createObjectUrl(Blob(<Object?>[]));
img.src = src;
img.addEventListener('load', (_) {
img.hidden = false;
return img;
/// The [gmaps.MapType] produced by this controller.
gmaps.MapType get gmMapType => _gmMapType;
late gmaps.MapType _gmMapType;
/// The [TileOverlay] providing data for this controller.
TileOverlay get tileOverlay => _tileOverlay;
late TileOverlay _tileOverlay;