draw atlas painter

diff.txt

diff --git a/bench_flutter/lib/game/game_screen.dart b/bench_flutter/lib/game/game_screen.dart
index 16843e0..87da9d4 100644
--- a/bench_flutter/lib/game/game_screen.dart
+++ b/bench_flutter/lib/game/game_screen.dart
@@ -1,3 +1,5 @@
+import 'dart:ui' as ui;
+
 import 'package:bench_flutter/audio/audio_controller.dart';
 import 'package:bench_flutter/game/button.dart';
 import 'package:bench_flutter/game/game_world.dart';
@@ -22,7 +24,7 @@ class GameScreen extends StatelessWidget {
               'assets/images/wood-background.jpg',
               fit: BoxFit.cover,
             ),
-            const GameWorldWidget(),
+            const RepaintBoundary(child: GameWorldWidget()),
             const RepaintBoundary(child: LogoWidget()),
             const _DisappearingButtons(),
             Positioned(
diff --git a/bench_flutter/lib/game/game_world.dart b/bench_flutter/lib/game/game_world.dart
index 4516bdc..4da2dff 100644
--- a/bench_flutter/lib/game/game_world.dart
+++ b/bench_flutter/lib/game/game_world.dart
@@ -1,6 +1,8 @@
 import 'dart:math';
+import 'dart:ui' as ui;
 
 import 'package:bench_flutter/game/wanderer.dart';
+import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 import 'package:logging/logging.dart';
 import 'package:provider/provider.dart';
@@ -63,31 +65,88 @@ class GameWorldWidget extends StatefulWidget {
   State<GameWorldWidget> createState() => _GameWorldWidgetState();
 }
 
+Future<ui.Image> loadAsset(String asset) async {
+  ui.ImmutableBuffer buffer = await ui.ImmutableBuffer.fromAsset(asset);
+  ui.ImageDescriptor descriptor = await ui.ImageDescriptor.encoded(buffer);
+  ui.Codec codec = await descriptor.instantiateCodec();
+  ui.FrameInfo info = await codec.getNextFrame();
+
+  buffer.dispose();
+  descriptor.dispose();
+  codec.dispose();
+
+  return info.image;
+}
+
 class _GameWorldWidgetState extends State<GameWorldWidget>
     with SingleTickerProviderStateMixin {
-  late AnimationController _controller;
+  late Ticker _ticker;
+  ui.Image? sprite;
 
   @override
   Widget build(BuildContext context) {
+    if (sprite == null) {
+      return const Placeholder();
+    }
+
     final world = context.watch<GameWorld>();
+    return CustomPaint(painter: WandererPainter(sprite!, world.wanderers));
+  }
 
-    return Stack(
-      children: [
-        for (final wanderer in world.wanderers)
-          PairedWandererWidget(wanderer: wanderer),
-      ],
-    );
+  @override
+  void initState() {
+    super.initState();
+    loadAsset('assets/images/sprite.png').then((ui.Image image) {
+      setState(() {
+        sprite = image;
+      });
+    });
+    _ticker = createTicker(_onTick);
+    _ticker.start();
   }
 
   @override
   void dispose() {
-    _controller.dispose();
+    _ticker.dispose();
     super.dispose();
   }
 
+  void _onTick(Duration elapsed) {
+    final world = Provider.of<GameWorld>(context, listen: false);
+
+    for (final wanderer in world.wanderers) {
+      final dt = (elapsed - wanderer.lastElapsed).inMicroseconds / 1000000;
+      wanderer.update(dt);
+      wanderer.lastElapsed = elapsed;
+    }
+
+    setState(() {
+      //
+    });
+  }
+}
+
+class WandererPainter extends CustomPainter {
+  const WandererPainter(this.sprite, this.wanderers);
+
+  final ui.Image sprite;
+  final List<PairedWanderer> wanderers;
+
+  @override
+  void paint(ui.Canvas canvas, ui.Size size) {
+    var wholeImage = Rect.fromLTWH(0, 0, sprite.width.toDouble(), sprite.height.toDouble());
+    canvas.drawAtlas(sprite, [
+      for (var wanderer in wanderers)
+        ui.RSTransform.fromComponents(rotation: 0, scale: 1, anchorX: 0, anchorY: 0, translateX: wanderer.position.x - 128 / 4, translateY: wanderer.position.y - 128 / 4)
+    ], [
+      for (var _ in wanderers)
+        wholeImage
+    ], null, null, Offset.zero & size, Paint());
+  }
+
   @override
-  void initState() {
-    super.initState();
-    _controller = AnimationController(vsync: this);
+  bool shouldRepaint(covariant CustomPainter oldDelegate) {
+    return true;
   }
+
 }
diff --git a/bench_flutter/lib/game/wanderer.dart b/bench_flutter/lib/game/wanderer.dart
index cc35ce2..6bc9270 100644
--- a/bench_flutter/lib/game/wanderer.dart
+++ b/bench_flutter/lib/game/wanderer.dart
@@ -1,5 +1,4 @@
 import 'package:flutter/cupertino.dart';
-import 'package:flutter/scheduler.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 class PairedWanderer {
@@ -11,6 +10,8 @@ class PairedWanderer {
 
   final Size worldSize;
 
+  Duration lastElapsed = Duration.zero;
+
   PairedWanderer({
     required this.position,
     required this.velocity,
@@ -35,48 +36,3 @@ class PairedWanderer {
     }
   }
 }
-
-class PairedWandererWidget extends StatefulWidget {
-  final PairedWanderer wanderer;
-
-  const PairedWandererWidget({required this.wanderer, super.key});
-
-  @override
-  State<PairedWandererWidget> createState() => _PairedWandererWidgetState();
-}
-
-class _PairedWandererWidgetState extends State<PairedWandererWidget>
-    with SingleTickerProviderStateMixin {
-  late Ticker _ticker;
-
-  Duration _lastElapsed = Duration.zero;
-
-  @override
-  void initState() {
-    super.initState();
-    _ticker = createTicker(_onTick);
-    _ticker.start();
-  }
-
-  @override
-  void dispose() {
-    _ticker.dispose();
-    super.dispose();
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Positioned(
-      left: widget.wanderer.position.x - 128 / 4,
-      top: widget.wanderer.position.y - 128 / 4,
-      child: Image.asset('assets/images/sprite.png', scale: 2),
-    );
-  }
-
-  void _onTick(Duration elapsed) {
-    final dt = (elapsed - _lastElapsed).inMicroseconds / 1000000;
-    widget.wanderer.update(dt);
-    _lastElapsed = elapsed;
-    setState(() {});
-  }
-}