refactor: Make atlas status to be more readable

packages/flame/lib/sprite.dart

@@ -5,5 +5,5 @@
 
 export 'src/sprite.dart';
 export 'src/sprite_animation.dart';
-export 'src/sprite_batch.dart';
+export 'src/sprite_batch.dart' hide FlippedAtlasStatus;
 export 'src/spritesheet.dart';

packages/flame/lib/src/sprite_batch.dart

@@ -6,6 +6,7 @@ import 'package:flame/cache.dart';
 import 'package:flame/extensions.dart';
 import 'package:flame/flame.dart';
 import 'package:flame/game.dart';
+import 'package:meta/meta.dart';
 
 extension SpriteBatchExtension on Game {
  /// Utility method to load and cache the image for a [SpriteBatch] based on
@@ -76,6 +77,23 @@ class BatchItem {
  final Paint paint;
 }
 
+@internal
+enum FlippedAtlasStatus {
+ /// There is no need to generate a flipped atlas yet.
+ none,
+
+ /// The flipped atlas generation is currently in progress.
+ generating,
+
+ /// The flipped atlas image has been generated.
+ generated,
+ ;
+
+ bool get isNone => this == FlippedAtlasStatus.none;
+ bool get isGenerating => this == FlippedAtlasStatus.generating;
+ bool get isGenerated => this == FlippedAtlasStatus.generated;
+}
+
 /// The SpriteBatch API allows for rendering multiple items at once.
 ///
 /// This class allows for optimization when you want to draw many parts of an
@@ -127,6 +145,8 @@ class SpriteBatch {
  );
  }
 
+ FlippedAtlasStatus _flippedAtlasStatus = FlippedAtlasStatus.none;
+
  /// List of all the existing batch items.
  final _batchItems = <BatchItem>[];
 
@@ -180,12 +200,6 @@ class SpriteBatch {
  imageCache.findKeyForImage(atlas) ??
  'image[${identityHashCode(atlas)}]';
 
- /// Whether any [BatchItem]s needs a flippable atlas.
- bool _hasFlips = false;
-
- /// The status of the atlas image loading operations.
- bool _atlasReady = true;
-
  /// The default color, used as a background color for a [BatchItem].
  final Color defaultColor;
 
@@ -212,14 +226,13 @@ class SpriteBatch {
  bool get isEmpty => _batchItems.isEmpty;
 
  Future<void> _makeFlippedAtlas() async {
- _hasFlips = true;
- _atlasReady = false;
+ _flippedAtlasStatus = FlippedAtlasStatus.generating;
  final key = '$imageKey#with-flips';
  atlas = await imageCache.fetchOrGenerate(
  key,
  () => _generateFlippedAtlas(atlas),
  );
- _atlasReady = true;
+ _flippedAtlasStatus = FlippedAtlasStatus.generated;
  }
 
  Future<Image> _generateFlippedAtlas(Image image) {
@@ -261,15 +274,17 @@ class SpriteBatch {
  color: color ?? defaultColor,
  );
 
- if (flip && useAtlas && !_hasFlips) {
+ if (flip && useAtlas && _flippedAtlasStatus.isNone) {
  _makeFlippedAtlas();
  }
 
  _batchItems.add(batchItem);
  _sources.add(
  flip
  ? Rect.fromLTWH(
- (atlas.width * (!_atlasReady ? 2 : 1)) - source.right,
+ // The atlas is twice as wide when the flipped atlas is generated.
+ (atlas.width * (_flippedAtlasStatus.isGenerated ? 1 : 2)) -
+ source.right,
  source.top,
  source.width,
  source.height,
@@ -360,7 +375,7 @@ class SpriteBatch {
 
  paint ??= _emptyPaint;
 
- if (useAtlas && _atlasReady) {
+ if (useAtlas && !_flippedAtlasStatus.isGenerating) {
  canvas.drawAtlas(
  atlas,
  _transforms,