feat!: [WIP] modern tile layer

.gitignore

@@ -22,7 +22,7 @@ migrate_working_dir/
 # The .vscode folder contains launch configuration and tasks you configure in
 # VS Code which you may wish to be included in version control, so this line
 # is commented out by default.
-#.vscode/
+.vscode/
 
 # Flutter/Dart/Pub related
 # Libraries should not include pubspec.lock, per https://dart.dev/guides/libraries/private-files#pubspeclock.

lib/flutter_map.dart

@@ -29,6 +29,11 @@ export 'package:flutter_map/src/layer/attribution_layer/rich/widget.dart';
 export 'package:flutter_map/src/layer/attribution_layer/simple.dart';
 export 'package:flutter_map/src/layer/circle_layer/circle_layer.dart';
 export 'package:flutter_map/src/layer/marker_layer/marker_layer.dart';
+export 'package:flutter_map/src/layer/modern_tile_layer/tile_loader/bytes_fetchers/network/caching/built_in/built_in_caching_provider.dart';
+export 'package:flutter_map/src/layer/modern_tile_layer/tile_loader/bytes_fetchers/network/caching/caching_provider.dart';
+export 'package:flutter_map/src/layer/modern_tile_layer/tile_loader/bytes_fetchers/network/caching/disabled/disabled_caching_provider.dart';
+export 'package:flutter_map/src/layer/modern_tile_layer/tile_loader/bytes_fetchers/network/caching/tile_metadata.dart';
+export 'package:flutter_map/src/layer/modern_tile_layer/tile_loader/bytes_fetchers/network/caching/tile_read_failure_exception.dart';
 export 'package:flutter_map/src/layer/overlay_image_layer/overlay_image_layer.dart';
 export 'package:flutter_map/src/layer/polygon_layer/label/deprecated_placements.dart';
 export 'package:flutter_map/src/layer/polygon_layer/label/placement_calculators/placement_calculator.dart';
@@ -49,11 +54,6 @@ export 'package:flutter_map/src/layer/tile_layer/tile_provider/asset/provider.da
 export 'package:flutter_map/src/layer/tile_layer/tile_provider/base_tile_provider.dart';
 export 'package:flutter_map/src/layer/tile_layer/tile_provider/file/stub_tile_provider.dart'
     if (dart.library.io) 'package:flutter_map/src/layer/tile_layer/tile_provider/file/native_tile_provider.dart';
-export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/caching/built_in/built_in_caching_provider.dart';
-export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/caching/caching_provider.dart';
-export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/caching/disabled/disabled_caching_provider.dart';
-export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/caching/tile_metadata.dart';
-export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/caching/tile_read_failure_exception.dart';
 export 'package:flutter_map/src/layer/tile_layer/tile_provider/network/tile_provider.dart';
 export 'package:flutter_map/src/layer/tile_layer/tile_update_event.dart';
 export 'package:flutter_map/src/layer/tile_layer/tile_update_transformer.dart';

lib/src/layer/modern_tile_layer/README.md

@@ -0,0 +1,35 @@
+# Modern Tile Layer
+
+The modern tile layer is a rework of the original tile layer which:
+
+* should be significantly more flexible (-> provide better integration support for plugins)
+* resolve some hard-to-debug bugs
+* improve performance in the default case
+
+It does this by:
+
+* splitting the logic of the current `TileLayer` & `TileProvider` into 3-5 parts:
+  * `BaseTileLayer`: responsible for tile management (initial workings provided by @mootw)
+
+  * a tile loader: responsible for getting the data for individual tiles given the coordinates from the manager  
+    In the default implementation, this is further split:
+    * a source generator: responsible for telling the source fetcher what to fetch for the tile
+    * a source fetcher: responsible for actually fetching the tile data  
+      In the default implementation, this is further split:
+      * a bytes fetcher: responsible for actually fetching the tile data
+
+  * a tile renderer: responsible for painting tiled data
+
+* using a canvas implementation for the default raster tile layer
+
+Significant uestions remaining:
+
+* Is the default tile loader setup (with two stages) too much frameworking/overly-complicated?
+* Simulating retina mode affects all parts of the system - but only (conceptually/for reasoning) applies to raster tiles (although technically it's no different to a top layer option). How should this be represented?
+* What should the top-level options be (`TileLayerOptions`)? See also retina mode simulation.
+* Who's responsibility is enforcing the max-zoom level? Is max-zoom = native max-zoom or MapOptions.maxZoom?
+
+This new functionality has no deadline or estimated completion date - although it's something we've been wanting to do for a while, and we have some work in the
+background which may be integrating with this.
+
+Contribution greatly appriciated!

lib/src/layer/modern_tile_layer/base_tile_data.dart

@@ -0,0 +1,80 @@
+import 'dart:async';
+
+import 'package:flutter_map/src/layer/modern_tile_layer/base_tile_layer.dart';
+import 'package:meta/meta.dart';
+
+/// Data associated with a particular tile coordinate which 'loads'
+/// asynchronously.
+///
+/// These are generated by the [BaseTileLayer.tileLoader] and consumed by the
+/// [BaseTileLayer.renderer].
+///
+/// Association with a tile coordinate is made in the tile layer.
+///
+/// It is up to the implementation as to what 'loads' means. However, the
+/// [BaseTileLayer] will use [whenLoaded], [isLoaded], and [dispose] to manage
+/// (such as pruning) the tile for the renderer.
+abstract interface class BaseTileData {
+  /// Completes when the underlying resource is 'loaded'
+  Future<void> get whenLoaded;
+
+  /// Whether the underlying resource is 'loaded'
+  bool get isLoaded;
+
+  /// Called when a tile is removed from the map of visible tiles
+  ///
+  /// This should usually be used to abort loading of the underlying resource
+  /// if it has not yet loaded, or release the resources held by it if already
+  /// loaded.
+  ///
+  /// This should not usually be called externally.
+  @internal
+  void dispose();
+}
+
+/// Wrapper for custom-shape data as a [BaseTileData].
+///
+/// The data carried is usually made available asynchronously, for example as
+/// the result of an I/O operation or HTTP request. Alternatively, data may be
+/// available synchronously if the data is loaded from prepared memory. This
+/// container supports either form of data.
+class WrapperTileData<D extends Object?> implements BaseTileData {
+  D? _data;
+
+  /// Data resource
+  ///
+  /// This may be `null` if [D] is nullable & the data is `null`. In this case,
+  /// use [isLoaded] to determine whether this accurately reflects the `null`
+  /// data. Otherwise, `null` means the data is not yet available.
+  D? get data => _data;
+
+  final _loadedTracker = Completer<D>.sync();
+
+  /// Completes with loaded data when the data is loaded successfully
+  ///
+  /// This never completes if the data completes to an error.
+  @override
+  Future<D> get whenLoaded => _loadedTracker.future;
+
+  /// Whether [data] represents the loaded data
+  @override
+  bool get isLoaded => _loadedTracker.isCompleted;
+
+  @internal
+  @override
+  void dispose() => _dispose?.call();
+  final void Function()? _dispose;
+
+  /// Create a container with the specified data (or the data result of the
+  /// specified future)
+  WrapperTileData({
+    required FutureOr<D> data,
+    void Function()? dispose,
+  }) : _dispose = dispose {
+    if (data is Future<D>) {
+      data.then((data) => _loadedTracker.complete(_data = data));
+    } else {
+      _loadedTracker.complete(_data = data);
+    }
+  }
+}