Add support for text styles.

sky/sdk/lib/framework/rendering/paragraph.dart

Index: sky/sdk/lib/framework/rendering/paragraph.dart
diff --git a/sky/sdk/lib/framework/rendering/paragraph.dart b/sky/sdk/lib/framework/rendering/paragraph.dart
index c0823a7b591e1456d9e54bf315baaaf46c38a6ed..7494b2c6c2b988e6013d1a08c57f182ffed9475e 100644
--- a/sky/sdk/lib/framework/rendering/paragraph.dart
+++ b/sky/sdk/lib/framework/rendering/paragraph.dart
@@ -11,6 +11,40 @@ class RenderInline extends RenderObject {
   String data;
 }
 
+enum FontWeight {
+  light, // 300
+  regular, // 400
+  medium, // 500
+}
+
+int trueTypeWeightNumber(FontWeight weight) {

[jackson, 2015/06/12 01:32:50]

This global function might make sense as a getter on TextStyle (if you want to
make it public) or you could just put it in paint if you're only going to use it
once.

+  switch(weight) {
+    case FontWeight.light:
+      return 300;
+    case FontWeight.regular:
+      return 400;
+    case FontWeight.medium:
+      return 500;
+  }
+}
+
+class TextStyle {
+  final Color color;
+  final String fontSize;
+  final FontWeight fontWeight;
+
+  const TextStyle({
+    this.color,
+    this.fontSize,
+    this.fontWeight
+  });
+
+  bool operator ==(other) => other is TextStyle &&
+    color == other.color &&
+    fontSize == other.fontSize &&
+    fontWeight == other.fontWeight;
+}
+
 // Unfortunately, using full precision floating point here causes bad layouts
 // because floating point math isn't associative. If we add and subtract
 // padding, for example, we'll get different values when we estimate sizes and
@@ -26,8 +60,9 @@ class RenderParagraph extends RenderBox {
 
   RenderParagraph({
     String text,
-    Color color
-  }) : _color = color {
+    Color color,
+    TextStyle style
+  }) : _style = style {
     _layoutRoot.rootElement = _document.createElement('p');
     this.text = text;
   }
@@ -41,12 +76,13 @@ class RenderParagraph extends RenderBox {
     markNeedsLayout();
   }
 
-  Color _color = const Color(0xFF000000);
-  Color get color => _color;
-  void set color (Color value) {
-    if (_color != value) {
-      _color = value;
-      markNeedsPaint();
+  TextStyle _style;
+  TextStyle get style => _style;
+  void set style (TextStyle value) {
+    if (_style != value) {
+      // TODO(hansmuller): decide if a new layout or paint is needed
+      markNeedsLayout();
+      _style = value;
     }
   }
 
@@ -106,9 +142,19 @@ class RenderParagraph extends RenderBox {
     if (_constraintsForCurrentLayout != constraints && constraints != null)
       _layout(constraints);
 
-    if (_color != null) {
-      _layoutRoot.rootElement.style['color'] =
-          'rgba(${_color.red}, ${_color.green}, ${_color.blue}, ${_color.alpha / 255.0 })';
+    if (style != null) {
+      var cssStyle = _layoutRoot.rootElement.style;
+      if (style.color != null) {
+        Color c = style.color;
+        cssStyle['color'] =
+            'rgba(${c.red}, ${c.green}, ${c.blue}, ${c.alpha / 255.0 })';

[jackson, 2015/06/12 01:32:50]

you've got an extra space here

+      }
+      if (style.fontSize != null) {
+        cssStyle['font-size'] = style.fontSize;
+      }
+      if (style.fontWeight != null) {
+        cssStyle['font-weight'] = trueTypeWeightNumber(style.fontWeight).toString();
+      }
     }
     _layoutRoot.paint(canvas);
   }