feat(flame): Add helper methods to create frame data on SpriteSheet (#2754)

Add two methods to SpriteSheet to create frame data for SpriteAnimation

doc/flame/rendering/images.md

@@ -331,21 +331,37 @@ a very simple example of how to use it:
 ```dart
 import 'package:flame/sprite.dart';
 
-final spritesheet = SpriteSheet(
+final spriteSheet = SpriteSheet(
   image: imageInstance,
   srcSize: Vector2.all(16.0),
 );
 
-final animation = spritesheet.createAnimation(0, stepTime: 0.1);
+final animation = spriteSheet.createAnimation(0, stepTime: 0.1);
 ```
 
 Now you can use the animation directly or use it in an animation component.
 
-You can also get a single frame of the sprite sheet using the `getSprite` method:
+You can also create a custom animation by retrieving individual `SpriteAnimationFrameData` using
+either `SpriteSheet.createFrameData` or `SpriteSheet.createFrameDataFromId`:
 
 ```dart
-spritesheet.getSprite(0, 0) // row, column;
+final animation = SpriteAnimation.fromFrameData(
+  imageInstance, 
+  SpriteAnimationData([
+    spriteSheet.createFrameDataFromId(1, stepTime: 0.1), // by id
+    spriteSheet.createFrameData(2, 3, stepTime: 0.3), // row, column
+    spriteSheet.createFrameDataFromId(4, stepTime: 0.1), // by id
+  ]),
+);
+```
+
+If you don't need any kind of animation and instead only want an instance of a `Sprite` on the
+`SpriteSheet` you can use the `getSprite` or `getSpriteById` methods:
+
+```dart
+spriteSheet.getSpriteById(2); // by id
+spriteSheet.getSprite(0, 0); // row, column
 ```
 
 You can see a full example of the `SpriteSheet` class
-[here](https://github.com/flame-engine/flame/blob/main/examples/lib/stories/sprites/spritesheet_example.dart).
+[here](https://github.com/flame-engine/flame/blob/main/examples/lib/stories/sprites/sprite_sheet_example.dart).

doc/flame/rendering/particles.md

@@ -308,7 +308,7 @@ it's fully played during the `Particle` lifespan. It's possible to override this
 `alignAnimationTime` argument.
 
 ```dart
-final spritesheet = SpriteSheet(
+final spriteSheet = SpriteSheet(
   image: yourSpriteSheetImage,
   srcSize: Vector2.all(16.0),
 );
@@ -316,7 +316,7 @@ final spritesheet = SpriteSheet(
 game.add(
   ParticleSystemComponent(
     particle: SpriteAnimationParticle(
-      animation: spritesheet.createAnimation(0, stepTime: 0.1),
+      animation: spriteSheet.createAnimation(0, stepTime: 0.1),
     );
   ),
 );

examples/lib/stories/rendering/particles_example.dart

@@ -501,12 +501,12 @@ class ParticlesExample extends FlameGame {
     const rows = 8;
     const frames = columns * rows;
     final spriteImage = images.fromCache('boom.png');
-    final spritesheet = SpriteSheet.fromColumnsAndRows(
+    final spriteSheet = SpriteSheet.fromColumnsAndRows(
       image: spriteImage,
       columns: columns,
       rows: rows,
     );
-    final sprites = List<Sprite>.generate(frames, spritesheet.getSpriteById);
+    final sprites = List<Sprite>.generate(frames, spriteSheet.getSpriteById);
     return SpriteAnimation.spriteList(sprites, stepTime: 0.1);
   }
 }

examples/lib/stories/sprites/sprite_sheet_example.dart

@@ -2,7 +2,7 @@ import 'package:flame/components.dart';
 import 'package:flame/game.dart';
 import 'package:flame/sprite.dart';
 
-class SpritesheetExample extends FlameGame {
+class SpriteSheetExample extends FlameGame {
   static const String description = '''
     In this example we show how to load images and how to create animations from
     sprite sheets.
@@ -11,7 +11,7 @@ class SpritesheetExample extends FlameGame {
   @override
   Future<void> onLoad() async {
     final spriteSheet = SpriteSheet(
-      image: await images.load('spritesheet.png'),
+      image: await images.load('sprite_sheet.png'),
       srcSize: Vector2(16.0, 18.0),
     );
 
@@ -28,6 +28,19 @@ class SpritesheetExample extends FlameGame {
       stepTimes: [0.1, 0.1, 0.3, 0.3, 0.5, 0.3, 0.1],
     );
 
+    final customVampireAnimation = SpriteAnimation.fromFrameData(
+      spriteSheet.image,
+      SpriteAnimationData([
+        spriteSheet.createFrameData(0, 0, stepTime: 0.1),
+        spriteSheet.createFrameData(0, 1, stepTime: 0.1),
+        spriteSheet.createFrameData(0, 2, stepTime: 0.3),
+        spriteSheet.createFrameDataFromId(4, stepTime: 0.3),
+        spriteSheet.createFrameDataFromId(5, stepTime: 0.5),
+        spriteSheet.createFrameDataFromId(6, stepTime: 0.3),
+        spriteSheet.createFrameDataFromId(7, stepTime: 0.1),
+      ]),
+    );
+
     final spriteSize = Vector2(80.0, 90.0);
 
     final vampireComponent = SpriteAnimationComponent(
@@ -44,13 +57,20 @@ class SpritesheetExample extends FlameGame {
 
     final ghostAnimationVariableStepTimesComponent = SpriteAnimationComponent(
       animation: ghostAnimationVariableStepTimes,
-      position: Vector2(150, 340),
+      position: Vector2(250, 220),
+      size: spriteSize,
+    );
+
+    final customVampireComponent = SpriteAnimationComponent(
+      animation: customVampireAnimation,
+      position: Vector2(250, 100),
       size: spriteSize,
     );
 
     add(vampireComponent);
     add(ghostComponent);
     add(ghostAnimationVariableStepTimesComponent);
+    add(customVampireComponent);
 
     // Some plain sprites
     final vampireSpriteComponent = SpriteComponent(
@@ -65,14 +85,7 @@ class SpritesheetExample extends FlameGame {
       position: Vector2(50, 220),
     );
 
-    final ghostVariableSpriteComponent = SpriteComponent(
-      sprite: spriteSheet.getSprite(1, 0),
-      size: spriteSize,
-      position: Vector2(50, 340),
-    );
-
     add(vampireSpriteComponent);
     add(ghostSpriteComponent);
-    add(ghostVariableSpriteComponent);
   }
 }

examples/lib/stories/sprites/sprites.dart

@@ -5,7 +5,7 @@ import 'package:examples/stories/sprites/basic_sprite_example.dart';
 import 'package:examples/stories/sprites/sprite_batch_example.dart';
 import 'package:examples/stories/sprites/sprite_batch_load_example.dart';
 import 'package:examples/stories/sprites/sprite_group_example.dart';
-import 'package:examples/stories/sprites/spritesheet_example.dart';
+import 'package:examples/stories/sprites/sprite_sheet_example.dart';
 import 'package:flame/game.dart';
 
 void addSpritesStories(Dashbook dashbook) {
@@ -23,10 +23,10 @@ void addSpritesStories(Dashbook dashbook) {
       info: Base64SpriteExample.description,
     )
     ..add(
-      'Spritesheet',
-      (_) => GameWidget(game: SpritesheetExample()),
-      codeLink: baseLink('sprites/spritesheet_example.dart'),
-      info: SpritesheetExample.description,
+      'SpriteSheet',
+      (_) => GameWidget(game: SpriteSheetExample()),
+      codeLink: baseLink('sprites/sprite_sheet_example.dart'),
+      info: SpriteSheetExample.description,
     )
     ..add(
       'SpriteBatch',

packages/flame/lib/sprite.dart

@@ -7,4 +7,4 @@ export 'src/sprite.dart';
 export 'src/sprite_animation.dart';
 export 'src/sprite_animation_ticker.dart';
 export 'src/sprite_batch.dart' hide FlippedAtlasStatus;
-export 'src/spritesheet.dart';
+export 'src/sprite_sheet.dart';

packages/flame/lib/src/components/isometric_tile_map_component.dart

@@ -1,7 +1,7 @@
 import 'dart:ui';
 
 import 'package:flame/components.dart';
-import 'package:flame/src/spritesheet.dart';
+import 'package:flame/src/sprite_sheet.dart';
 import 'package:meta/meta.dart';
 
 /// This is just a pair of <int, int>.

packages/flame/lib/src/sprite_sheet.dart

@@ -68,6 +68,34 @@ class SpriteSheet {
     return _spriteCache[spriteId] ??= _computeSprite(spriteId);
   }
 
+  /// Create a [SpriteAnimationFrameData] for the sprite in the position
+  /// (row, column) on the sprite sheet grid.
+  SpriteAnimationFrameData createFrameData(
+    int row,
+    int column, {
+    required double stepTime,
+  }) {
+    return createFrameDataFromId(row * columns + column, stepTime: stepTime);
+  }
+
+  /// Create a [SpriteAnimationFrameData] for the sprite with id [spriteId]
+  /// from the grid.
+  ///
+  /// The ids are defined as starting at 0 on the top left and going
+  /// sequentially on each row.
+  SpriteAnimationFrameData createFrameDataFromId(
+    int spriteId, {
+    required double stepTime,
+  }) {
+    final i = spriteId % columns;
+    final j = spriteId ~/ columns;
+    return SpriteAnimationFrameData(
+      srcPosition: Vector2Extension.fromInts(i, j)..multiply(srcSize),
+      srcSize: srcSize,
+      stepTime: stepTime,
+    );
+  }
+
   Sprite _computeSprite(int spriteId) {
     final i = spriteId % columns;
     final j = spriteId ~/ columns;

packages/flame/test/components/input/sprite_button_component_test.dart

@@ -5,7 +5,7 @@ import 'package:flame/input.dart';
 import 'package:flame/src/anchor.dart';
 import 'package:flame/src/components/sprite_group_component.dart';
 import 'package:flame/src/events/flame_game_mixins/multi_tap_dispatcher.dart';
-import 'package:flame/src/spritesheet.dart';
+import 'package:flame/src/sprite_sheet.dart';
 import 'package:flame_test/flame_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flame/test/spritesheet_test.dart

@@ -54,5 +54,69 @@ void main() {
         );
       },
     );
+
+    test('return sprite based on row and column', () {
+      final spriteSheet = SpriteSheet(
+        image: image,
+        srcSize: Vector2(50, 50),
+      );
+
+      expect(
+        spriteSheet.getSprite(1, 1),
+        isA<Sprite>().having(
+          (sprite) => sprite.srcPosition,
+          'srcPosition',
+          equals(Vector2(50, 50)),
+        ),
+      );
+    });
+
+    test('return sprite based on id', () {
+      final spriteSheet = SpriteSheet(
+        image: image,
+        srcSize: Vector2(50, 50),
+      );
+
+      expect(
+        spriteSheet.getSpriteById(3),
+        isA<Sprite>().having(
+          (sprite) => sprite.srcPosition,
+          'srcPosition',
+          equals(Vector2(50, 50)),
+        ),
+      );
+    });
+
+    test('create sprite animation frame data based on row and column', () {
+      final spriteSheet = SpriteSheet(
+        image: image,
+        srcSize: Vector2(50, 50),
+      );
+
+      expect(
+        spriteSheet.createFrameData(1, 1, stepTime: 0.1),
+        isA<SpriteAnimationFrameData>().having(
+          (frame) => frame.srcPosition,
+          'srcPosition',
+          equals(Vector2(50, 50)),
+        ),
+      );
+    });
+
+    test('create sprite animation frame data based on id', () {
+      final spriteSheet = SpriteSheet(
+        image: image,
+        srcSize: Vector2(50, 50),
+      );
+
+      expect(
+        spriteSheet.createFrameDataFromId(3, stepTime: 0.1),
+        isA<SpriteAnimationFrameData>().having(
+          (frame) => frame.srcPosition,
+          'srcPosition',
+          equals(Vector2(50, 50)),
+        ),
+      );
+    });
   });
 }