Improved documentation for SkyGames and support for rotated textures

sky/examples/game/lib/sprite.dart

 part of sprites;
 
 /// A Sprite is a [Node] that renders a bitmap image to the screen.
 class Sprite extends NodeWithSize {
 
   /// The texture that the sprite will render to screen.
   ///
   /// If the texture is null, the sprite will be rendered as a red square
   /// marking the bounds of the sprite.
   ///
@@ skipping 85 matching lines @@
       Paint paint = new Paint();
       paint.color = new Color.fromARGB((255.0*_opacity).toInt(), 255, 255, 255);
       if (colorOverlay != null) {
         paint.setColorFilter(new ColorFilter.mode(colorOverlay, TransferMode.srcATop));
       }
       if (transferMode != null) {
         paint.setTransferMode(transferMode);
       }
 
       // Do actual drawing of the sprite
-      canvas.drawImageRect(texture.image, texture.frame, texture.spriteSourceSize, paint);
+      if (texture.rotated) {
+        // Calculate the rotated frame and spriteSourceSize
+        Size originalFrameSize = texture.frame.size;
+        Rect rotatedFrame = new Rect.fromPointAndSize(texture.frame.upperLeft, new Size(originalFrameSize.height, originalFrameSize.width));
+        Point rotatedSpriteSourcePoint = new Point(
+            -texture.spriteSourceSize.top - (texture.spriteSourceSize.bottom - texture.spriteSourceSize.top),
+            texture.spriteSourceSize.left);
+        Rect rotatedSpriteSourceSize = new Rect.fromPointAndSize(rotatedSpriteSourcePoint, new Size(originalFrameSize.height, originalFrameSize.width));
+
+        // Draw the rotated sprite
+        canvas.rotate(-Math.PI/2.0);
+        canvas.drawImageRect(texture.image, rotatedFrame, rotatedSpriteSourceSize, paint);
+      } else {
+        // Draw the sprite
+        canvas.drawImageRect(texture.image, texture.frame, texture.spriteSourceSize, paint);
+      }
     } else {
       // Paint a red square for missing texture
       canvas.drawRect(new Rect.fromLTRB(0.0, 0.0, size.width, size.height),
-          new Paint()..color = const Color.fromARGB(255, 255, 0, 0));
+      new Paint()..color = const Color.fromARGB(255, 255, 0, 0));
     }
     canvas.restore();
   }
 }