Initial support for labels in skysprites

packages/flutter_sprites/lib/label.dart

+part of skysprites;
+
+class Label extends Node {
+
+  Label(this._text, [this._textStyle]) {
+    if (_textStyle == null) {
+      _textStyle = new TextStyle();
+    }
+  }
+
+  String _text;
+
+  String get text => _text;
+
+  set text(String text) {
+    _text = text;
+    _painter = null;
+  }
+
+  TextStyle _textStyle;
+
+  TextStyle get textStyle => _textStyle;
+
+  set textStyle(TextStyle textStyle) {
+    _textStyle = textStyle;
+    _painter = null;
+  }
+
+  TextPainter _painter;
+  double _width;
+
+  final double _maxWidth = 10000.0;
+
+  void paint(PaintingCanvas canvas) {
+    if (_painter == null) {
+      PlainTextSpan textSpan = new PlainTextSpan(_text);
+      StyledTextSpan styledTextSpan = new StyledTextSpan(_textStyle, [textSpan]);
+      _painter = new TextPainter(styledTextSpan);
+
+      _painter.maxWidth = _maxWidth;
+      _painter.minWidth = _maxWidth;
+      _painter.layout();
+
+      _width = _painter.maxContentWidth;
+    }
+
+    Offset offset = Offset.zero;
+    if (_textStyle.textAlign == TextAlign.center) {
+      //canvas.translate(-_maxWidth / 2.0, 0.0);
+      offset = new Offset(-_maxWidth / 2.0, 0.0);
+    } else if (_textStyle.textAlign == TextAlign.right) {
+      //canvas.translate(-_maxWidth, 0.0);
+      offset = new Offset(-_maxWidth, 0.0);
+    }
+
+    _painter.paint(canvas, offset);
+  }
+}

packages/flutter_sprites/lib/skysprites.dart

@@ -17,6 +17,7 @@ import 'package:sky/mojo/asset_bundle.dart';
 import 'package:sky/mojo/shell.dart' as shell;
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
+import 'package:sky/painting/text_painter.dart';
 import 'package:sky/widgets/framework.dart';
 import 'package:sky_services/media/media.mojom.dart';
 import 'package:vector_math/vector_math.dart';
@@ -26,6 +27,7 @@ part 'constraint.dart';
 part 'action_spline.dart';
 part 'color_secuence.dart';
 part 'image_map.dart';
+part 'label.dart';
 part 'layer.dart';
 part 'node.dart';
 part 'node3d.dart';