extracting animation from component, fix rotate around center bug, add width and height to PositionComponent

lib/components/animation.dart

@@ -0,0 +1,37 @@
+import '../sprite.dart';
+
+class Animation {
+  List<Sprite> sprites;
+  double stepTime = 0.1;
+  double lifeTime = 0.0;
+
+  Animation() {
+    this.sprites = [];
+  }
+
+  Animation.spriteList(this.sprites, {this.stepTime, this.lifeTime});
+
+  Animation.sequenced(String imagePath, int amount,
+      {double textureX = 0.0,
+      double textureY = 0.0,
+      double textureWidth = -1.0,
+      double textureHeight = -1.0}) {
+    sprites = new List<Sprite>(amount);
+    for (var i = 0; i < amount; i++) {
+      sprites[i] = new Sprite(imagePath,
+          x: textureX + i * textureWidth,
+          y: textureY,
+          width: textureWidth,
+          height: textureHeight);
+    }
+  }
+
+  Sprite getSprite() {
+    int i = (lifeTime / stepTime).round();
+    return sprites[i % sprites.length];
+  }
+
+  void update(double t) {
+    this.lifeTime += t;
+  }
+}

lib/components/animation_component.dart

@@ -1,41 +1,44 @@
 import 'dart:ui';
 
 import 'component.dart';
+import 'animation.dart';
 import '../sprite.dart';
 
 class AnimationComponent extends PositionComponent {
 
-  double width, height;
+  Animation animation;
 
-  List<Sprite> sprites;
+  AnimationComponent(double width, double height, this.animation) {
-  double stepTime = 0.1;
+    this.width = width;
-  double lifeTime = 0.0;
+    this.height = height;
+  }
 
-  AnimationComponent.spriteList(this.width, this.height, this.sprites, { this.stepTime, this.lifeTime });
+  AnimationComponent.sequenced(width, height, String imagePath, int amount, { double textureX = 0.0, double textureY = 0.0, double textureWidth = -1.0, double textureHeight = -1.0}) {
+    this.width = width;
+    this.height = height;
 
-  AnimationComponent.sequenced(this.width, this.height, String imagePath, int amount, { double textureX = 0.0, double textureY = 0.0, double textureWidth = -1.0, double textureHeight = -1.0}) {
     if (textureWidth == -1) {
       textureWidth = this.width;
     }
     if (textureHeight == -1) {
       textureHeight = this.height;
     }
-    sprites = new List<Sprite>(amount);
+
+    animation = new Animation();
+    animation.sprites = new List<Sprite>(amount);
     for (var i = 0; i < amount; i++) {
-      sprites[i] = new Sprite(imagePath, x: textureX + i*textureWidth, y: textureY, width: textureWidth, height: textureHeight);
+      animation.sprites[i] = new Sprite(imagePath, x: textureX + i*textureWidth, y: textureY, width: textureWidth, height: textureHeight);
     }
   }
 
   @override
   void render(Canvas canvas) {
     prepareCanvas(canvas);
-
+    animation.getSprite().render(canvas, width, height);
-    int i = (lifeTime / stepTime).round();
-    sprites[i % sprites.length].render(canvas, width, height);
   }
 
   @override
   void update(double t) {
-    this.lifeTime += t;
+    animation.update(t);
   }
 }

lib/components/component.dart

@@ -22,6 +22,7 @@ abstract class Component {
 
 abstract class PositionComponent extends Component {
   double x = 0.0, y = 0.0, angle = 0.0;
+  double width = 0.0, height = 0.0;
 
   double angleBetween(PositionComponent c) {
     return (atan2(c.x - this.x, this.y - c.y) - PI / 2) % (2 * PI);
@@ -33,12 +34,19 @@ abstract class PositionComponent extends Component {
 
   void prepareCanvas(Canvas canvas) {
     canvas.translate(x, y);
-    canvas.rotate(angle); // TODO: rotate around center
+
+    // rotate around center
+    canvas.translate(width/2, height/2);
+    canvas.rotate(angle);
+    canvas.translate(-width/2, -height/2);
+  }
+
+  Rect toRect() {
+    return new Rect.fromLTWH(x, y, width, height);
   }
 }
 
 class SpriteComponent extends PositionComponent {
-  double width, height;
   Sprite sprite;
 
   final Paint paint = new Paint()..color = new Color(0xffffffff);
@@ -46,11 +54,13 @@ class SpriteComponent extends PositionComponent {
   SpriteComponent.square(double size, String imagePath)
       : this.rectangle(size, size, imagePath);
 
-  SpriteComponent.rectangle(this.width, this.height, String imagePath) {
+  SpriteComponent.rectangle(double width, double height, String imagePath)
-    this.sprite = new Sprite(imagePath);
+      : this.fromSprite(width, height, new Sprite(imagePath));
-  }
 
-  SpriteComponent.fromSprite(this.width, this.height, this.sprite);
+  SpriteComponent.fromSprite(double width, double height, this.sprite) {
+    this.width = width;
+    this.height = height;
+  }
 
   @override
   render(Canvas canvas) {