Add dartdoc for the painting code

packages/flutter/lib/painting/box_painter.dart

@@ -10,22 +10,40 @@ import 'package:sky/base/image_resource.dart';
 import 'package:sky/base/lerp.dart';
 import 'package:sky/painting/shadows.dart';
 
+/// An immutable set of offsets in each of the four cardinal directions
+///
+/// Typically used for an offset from each of the four sides of a box. For
+/// example, the padding inside a box can be represented using this class.
 class EdgeDims {
-  // used for e.g. padding
+  // TODO(abarth): Remove this constructor or rename it to EdgeDims.fromTRBL.
+  /// Constructs an EdgeDims from offsets from the top, right, bottom and left
   const EdgeDims(this.top, this.right, this.bottom, this.left);
+
+  /// Constructs an EdgeDims where all the offsets are value
   const EdgeDims.all(double value)
       : top = value, right = value, bottom = value, left = value;
+
+  /// Constructs an EdgeDims with only the given values non-zero
   const EdgeDims.only({ this.top: 0.0,
                         this.right: 0.0,
                         this.bottom: 0.0,
                         this.left: 0.0 });
+
+  /// Constructs an EdgeDims with symmetrical vertical and horizontal offsets
   const EdgeDims.symmetric({ double vertical: 0.0,
                              double horizontal: 0.0 })
     : top = vertical, left = horizontal, bottom = vertical, right = horizontal;
 
+  /// The offset from the top
   final double top;
+
+  /// The offset from the right
   final double right;
+
+  /// The offset from the bottom
   final double bottom;
+
+  /// The offset from the left
   final double left;
 
   bool operator ==(other) {
@@ -52,6 +70,7 @@ class EdgeDims {
                         left - other.left);
   }
 
+  /// An EdgeDims with zero offsets in each direction
   static const EdgeDims zero = const EdgeDims(0.0, 0.0, 0.0, 0.0);
 
   int get hashCode {
@@ -65,14 +84,20 @@ class EdgeDims {
   String toString() => "EdgeDims($top, $right, $bottom, $left)";
 }
 
+/// A side of a border of a box
 class BorderSide {
   const BorderSide({
     this.color: const Color(0xFF000000),
     this.width: 1.0
   });
+
+  /// The color of this side of the border
   final Color color;
+
+  /// The width of this side of the border
   final double width;
 
+  /// A black border side of zero width
   static const none = const BorderSide(width: 0.0);
 
   int get hashCode {
@@ -84,6 +109,7 @@ class BorderSide {
   String toString() => 'BorderSide($color, $width)';
 }
 
+/// A border of a box, comprised of four sides
 class Border {
   const Border({
     this.top: BorderSide.none,
@@ -92,6 +118,7 @@ class Border {
     this.left: BorderSide.none
   });
 
+  /// A uniform border with all sides the same color and width
   factory Border.all({
     Color color: const Color(0xFF000000),
     double width: 1.0
@@ -100,11 +127,19 @@ class Border {
     return new Border(top: side, right: side, bottom: side, left: side);
   }
 
+  /// The top side of this border
   final BorderSide top;
+
+  /// The right side of this border
   final BorderSide right;
+
+  /// The bottom side of this border
   final BorderSide bottom;
+
+  /// The left side of this border
   final BorderSide left;
 
+  /// The widths of the sides of this border represented as an EdgeDims
   EdgeDims get dimensions {
     return new EdgeDims(top.width, right.width, bottom.width, left.width);
   }
@@ -120,6 +155,10 @@ class Border {
   String toString() => 'Border($top, $right, $bottom, $left)';
 }
 
+/// A shadow cast by a box
+///
+/// Note: BoxShadow can cast non-rectangular shadows if the box is
+/// non-rectangular (e.g., has a border radius or a circular shape).
 class BoxShadow {
   const BoxShadow({
     this.color,
@@ -127,10 +166,16 @@ class BoxShadow {
     this.blur
   });
 
+  /// The color of the shadow
   final Color color;
+
+  /// The displacement of the shadow from the box
   final Offset offset;
+
+  /// The standard deviation of the Gaussian to convolve with the box's shape
   final double blur;
 
+  /// Returns a new box shadow with its offset and blur scaled by the given factor
   BoxShadow scale(double factor) {
     return new BoxShadow(
       color: color,
@@ -139,10 +184,12 @@ class BoxShadow {
     );
   }
 
-  String toString() => 'BoxShadow($color, $offset, $blur)';
-}
-
-BoxShadow lerpBoxShadow(BoxShadow a, BoxShadow b, double t) {
+  /// Linearly interpolate between two box shadows
+  ///
+  /// If either box shadow is null, this function linearly interpolates from a
+  /// a box shadow that matches the other box shadow in color but has a zero
+  /// offset and a zero blur.
+  static BoxShadow lerp(BoxShadow a, BoxShadow b, double t) {
     if (a == null && b == null)
       return null;
     if (a == null)
@@ -154,9 +201,12 @@ BoxShadow lerpBoxShadow(BoxShadow a, BoxShadow b, double t) {
       offset: lerpOffset(a.offset, b.offset, t),
       blur: lerpNum(a.blur, b.blur, t)
     );
-}
+  }
 
-List<BoxShadow> lerpListBoxShadow(List<BoxShadow> a, List<BoxShadow> b, double t) {
+  /// Linearly interpolate between two lists of box shadows
+  ///
+  /// If the lists differ in length, excess items are lerped with null.
+  static List<BoxShadow> lerpList(List<BoxShadow> a, List<BoxShadow> b, double t) {
     if (a == null && b == null)
       return null;
     if (a == null)
@@ -166,70 +216,140 @@ List<BoxShadow> lerpListBoxShadow(List<BoxShadow> a, List<BoxShadow> b, double t
     List<BoxShadow> result = new List<BoxShadow>();
     int commonLength = math.min(a.length, b.length);
     for (int i = 0; i < commonLength; ++i)
-    result.add(lerpBoxShadow(a[i], b[i], t));
+      result.add(BoxShadow.lerp(a[i], b[i], t));
     for (int i = commonLength; i < a.length; ++i)
       result.add(a[i].scale(1.0 - t));
     for (int i = commonLength; i < b.length; ++i)
       result.add(b[i].scale(t));
     return result;
+  }
+
+  String toString() => 'BoxShadow($color, $offset, $blur)';
 }
 
+/// A 2D gradient
 abstract class Gradient {
   sky.Shader createShader();
 }
 
+/// A 2D linear gradient
 class LinearGradient extends Gradient {
   LinearGradient({
-    this.endPoints,
+    this.begin,
+    this.end,
     this.colors,
-    this.colorStops,
+    this.stops,
     this.tileMode: sky.TileMode.clamp
-  });
+  }) {
+    assert(colors.length == stops.length);
+  }
+
+  /// The point at which stop 0.0 of the gradient is placed
+  final Point begin;
 
-  final List<Point> endPoints;
+  /// The point at which stop 1.0 of the gradient is placed
+  final Point end;
+
+  /// The colors the gradient should obtain at each of the stops
+  ///
+  /// Note: This list must have the same length as [stops].
   final List<Color> colors;
-  final List<double> colorStops;
+
+  /// A list of values from 0.0 to 1.0 that denote fractions of the vector from start to end
+  ///
+  /// Note: This list must have the same length as [colors].
+  final List<double> stops;
+
+  /// How this gradient should tile the plane
   final sky.TileMode tileMode;
 
   sky.Shader createShader() {
-    return new sky.Gradient.linear(this.endPoints, this.colors,
-                                   this.colorStops, this.tileMode);
+    return new sky.Gradient.linear([begin, end], this.colors,
+                                   this.stops, this.tileMode);
   }
 
   String toString() {
-    return 'LinearGradient($endPoints, $colors, $colorStops, $tileMode)';
+    return 'LinearGradient($begin, $end, $colors, $stops, $tileMode)';
   }
 }
 
+/// A 2D radial gradient
 class RadialGradient extends Gradient {
   RadialGradient({
     this.center,
     this.radius,
     this.colors,
-    this.colorStops,
+    this.stops,
     this.tileMode: sky.TileMode.clamp
   });
 
+  /// The center of the gradient
   final Point center;
+
+  /// The radius at which stop 1.0 is placed
   final double radius;
+
+  /// The colors the gradient should obtain at each of the stops
+  ///
+  /// Note: This list must have the same length as [stops].
   final List<Color> colors;
-  final List<double> colorStops;
+
+  /// A list of values from 0.0 to 1.0 that denote concentric rings
+  ///
+  /// The rings are centered at [center] and have a radius equal to the value of
+  /// the stop times [radius].
+  ///
+  /// Note: This list must have the same length as [colors].
+  final List<double> stops;
+
+  /// How this gradient should tile the plane
   final sky.TileMode tileMode;
 
   sky.Shader createShader() {
-    return new sky.Gradient.radial(this.center, this.radius, this.colors,
-                                   this.colorStops, this.tileMode);
+    return new sky.Gradient.radial(center, radius, colors, stops, tileMode);
   }
 
   String toString() {
-    return 'RadialGradient($center, $radius, $colors, $colorStops, $tileMode)';
+    return 'RadialGradient($center, $radius, $colors, $stops, $tileMode)';
   }
 }
 
-enum ImageFit { fill, contain, cover, none, scaleDown }
+/// How an image should be inscribed into a box
+enum ImageFit {
+  /// Fill the box by distorting the image's aspect ratio
+  fill,
+
+  /// As large as possible while still containing the image entirely within the box
+  contain,
+
+  /// As small as possible while still covering the entire box
+  cover,
+
+  /// Center the image within the box and discard any portions of the image that
+  /// lie outside the box
+  none,
+
+  /// Center the image within the box and, if necessary, scale the image down to
+  /// ensure that the image fits within the box
+  scaleDown
+}
+
+/// How to paint any portions of a box not covered by an image
+enum ImageRepeat {
+  /// Repeat the image in both the x and y directions until the box is filled
+  repeat,
+
+  /// Repeat the image in the x direction until the box is filled horizontally
+  repeatX,
 
-enum ImageRepeat { repeat, repeatX, repeatY, noRepeat }
+  /// Repeat the image in the y direction until the box is filled vertically
+  repeatY,
 
+  /// Leave uncovered poritions of the box transparent
+  noRepeat
+}
+
+/// Paint an image into the given rectangle in the canvas
 void paintImage({
   sky.Canvas canvas,
   Rect rect,
@@ -289,9 +409,15 @@ void paintImage({
 
 typedef void BackgroundImageChangeListener();
 
+/// A background image for a box
 class BackgroundImage {
+  /// How the background image should be inscribed into the box
   final ImageFit fit;
+
+  /// How to paint any portions of the box not covered by the background image
   final ImageRepeat repeat;
+
+  /// A color filter to apply to the background image before painting it
   final sky.ColorFilter colorFilter;
 
   BackgroundImage({
@@ -302,6 +428,7 @@ class BackgroundImage {
   }) : _imageResource = image;
 
   sky.Image _image;
+  /// The image to be painted into the background
   sky.Image get image => _image;
 
   ImageResource _imageResource;
@@ -309,6 +436,7 @@ class BackgroundImage {
   final List<BackgroundImageChangeListener> _listeners =
       new List<BackgroundImageChangeListener>();
 
+  /// Call listener when the background images changes (e.g., arrives from the network)
   void addChangeListener(BackgroundImageChangeListener listener) {
     // We add the listener to the _imageResource first so that the first change
     // listener doesn't get callback synchronously if the image resource is
@@ -318,6 +446,7 @@ class BackgroundImage {
     _listeners.add(listener);
   }
 
+  /// No longer call listener when the background image changes
   void removeChangeListener(BackgroundImageChangeListener listener) {
     _listeners.remove(listener);
     // We need to remove ourselves as listeners from the _imageResource so that
@@ -340,9 +469,17 @@ class BackgroundImage {
   String toString() => 'BackgroundImage($fit, $repeat)';
 }
 
-enum Shape { rectangle, circle }
+// TODO(abarth): Rename to BoxShape?
+/// A 2D geometrical shape
+enum Shape {
+  /// An axis-aligned, 2D rectangle
+  rectangle,
 
-// This must be immutable, because we won't notice when it changes
+  /// A 2D locus of points equidistant from a single point
+  circle
+}
+
+/// An immutable description of how to paint a box
 class BoxDecoration {
   const BoxDecoration({
     this.backgroundColor, // null = don't draw background color
@@ -354,14 +491,33 @@ class BoxDecoration {
     this.shape: Shape.rectangle
   });
 
+  /// The color to fill in the background of the box
+  ///
+  /// The color is filled into the shape of the box (e.g., either a rectangle,
+  /// potentially with a border radius, or a circle).
   final Color backgroundColor;
+
+  /// An image to paint above the background color
   final BackgroundImage backgroundImage;
-  final double borderRadius;
+
+  /// A border to draw above the background
   final Border border;
+
+  /// If non-null, the corners of this box are rounded by this radius
+  ///
+  /// Applies only to boxes with rectangular shapes.
+  final double borderRadius;
+
+  /// A list of shadows cast by this box behind the background
   final List<BoxShadow> boxShadow;
+
+  /// A graident to use when filling the background
   final Gradient gradient;
+
+  /// The shape to fill the background color into and to cast as a shadow
   final Shape shape;
 
+  /// Returns a new box decoration that is scalled by the given factor
   BoxDecoration scale(double factor) {
     // TODO(abarth): Scale ALL the things.
     return new BoxDecoration(
@@ -369,12 +525,34 @@ class BoxDecoration {
       backgroundImage: backgroundImage,
       border: border,
       borderRadius: lerpNum(null, borderRadius, factor),
-      boxShadow: lerpListBoxShadow(null, boxShadow, factor),
+      boxShadow: BoxShadow.lerpList(null, boxShadow, factor),
       gradient: gradient,
       shape: shape
     );
   }
 
+  /// Linearly interpolate between two box decorations
+  ///
+  /// Interpolates each parameter of the box decoration separately.
+  static BoxDecoration lerp(BoxDecoration a, BoxDecoration b, double t) {
+    if (a == null && b == null)
+      return null;
+    if (a == null)
+      return b.scale(t);
+    if (b == null)
+      return a.scale(1.0 - t);
+    // TODO(abarth): lerp ALL the fields.
+    return new BoxDecoration(
+      backgroundColor: lerpColor(a.backgroundColor, b.backgroundColor, t),
+      backgroundImage: b.backgroundImage,
+      border: b.border,
+      borderRadius: lerpNum(a.borderRadius, b.borderRadius, t),
+      boxShadow: BoxShadow.lerpList(a.boxShadow, b.boxShadow, t),
+      gradient: b.gradient,
+      shape: b.shape
+    );
+  }
+
   String toString([String prefix = '']) {
     List<String> result = [];
     if (backgroundColor != null)
@@ -397,31 +575,14 @@ class BoxDecoration {
   }
 }
 
-BoxDecoration lerpBoxDecoration(BoxDecoration a, BoxDecoration b, double t) {
-  if (a == null && b == null)
-    return null;
-  if (a == null)
-    return b.scale(t);
-  if (b == null)
-    return a.scale(1.0 - t);
-  // TODO(abarth): lerp ALL the fields.
-  return new BoxDecoration(
-    backgroundColor: lerpColor(a.backgroundColor, b.backgroundColor, t),
-    backgroundImage: b.backgroundImage,
-    border: b.border,
-    borderRadius: lerpNum(a.borderRadius, b.borderRadius, t),
-    boxShadow: lerpListBoxShadow(a.boxShadow, b.boxShadow, t),
-    gradient: b.gradient,
-    shape: b.shape
-  );
-}
-
+/// An object that paints a [BoxDecoration] into a canvas
 class BoxPainter {
   BoxPainter(BoxDecoration decoration) : _decoration = decoration {
     assert(decoration != null);
   }
 
   BoxDecoration _decoration;
+  /// The box decoration to paint
   BoxDecoration get decoration => _decoration;
   void set decoration (BoxDecoration value) {
     assert(value != null);
@@ -611,6 +772,7 @@ class BoxPainter {
     canvas.drawCircle(center, radius, paint);
   }
 
+  /// Paint the box decoration into the given location on the given canvas
   void paint(sky.Canvas canvas, Rect rect) {
     _paintBackgroundColor(canvas, rect);
     _paintBackgroundImage(canvas, rect);

packages/flutter/lib/painting/radial_reaction.dart

@@ -20,6 +20,9 @@ int _roundOpacity(double opacity) {
   return (255 * opacity).round();
 }
 
+/// A material design radial ink reaction
+///
+/// See [https://www.google.com/design/spec/animation/responsive-interaction.html#responsive-interaction-radial-action]
 class RadialReaction {
   RadialReaction({
     this.center,
@@ -41,7 +44,10 @@ class RadialReaction {
       ..duration =_kHideDuration;
   }
 
+  /// The center of the circle in which the reaction occurs
   final Point center;
+
+  /// The radius of the circle in which the reaction occurs
   final double radius;
 
   AnimationPerformance _showPerformance;
@@ -54,15 +60,22 @@ class RadialReaction {
   AnimationPerformance _hidePerformance;
   AnimatedValue<double> _fade;
 
-  void show() {
-    _showComplete = _showPerformance.forward();
+  /// Show the reaction
+  ///
+  /// Returns a future that resolves when the reaction is completely revealed.
+  Future show() {
+    return _showComplete = _showPerformance.forward();
   }
 
+  /// Hide the reaction
+  ///
+  /// Returns a future that resolves when the reaction is completely hidden.
   Future hide() async {
     await _showComplete;
     await _hidePerformance.forward();
   }
 
+  /// Call listener whenever the visual appearance of the reaction changes
   void addListener(Function listener) {
     _showPerformance.addListener(listener);
     _hidePerformance.addListener(listener);
@@ -71,6 +84,7 @@ class RadialReaction {
   final Paint _outerPaint = new Paint();
   final Paint _innerPaint = new Paint();
 
+  /// Paint the reaction onto the given canvas at the given offset
   void paint(sky.Canvas canvas, Offset offset) {
     _outerPaint.color = _kOuterColor.withAlpha(_roundOpacity(_outerOpacity.value * _fade.value));
     canvas.drawCircle(center + offset, radius, _outerPaint);

packages/flutter/lib/painting/shadows.dart

@@ -4,11 +4,11 @@
 
 import 'dart:sky' as sky;
 
-/// Helper class to build a Paint DrawLooper that adds shadows to the Paint's
-/// operation.
+/// A helper class to build a [sky.DrawLooper] for drawing shadows
 class ShadowDrawLooperBuilder {
   var builder_ = new sky.LayerDrawLooperBuilder();
 
+  /// Add a shadow with the given parameters
   void addShadow(sky.Offset offset, sky.Color color, double blur) {
     builder_.addLayerOnTop(
           new sky.DrawLooperLayerInfo()
@@ -20,6 +20,7 @@ class ShadowDrawLooperBuilder {
             ..setMaskFilter(new sky.MaskFilter.blur(sky.BlurStyle.normal, blur)));
   }
 
+  /// Returns the draw looper built for the added shadows
   sky.DrawLooper build() {
     builder_.addLayerOnTop(new sky.DrawLooperLayerInfo(), new sky.Paint());
     return builder_.build();

packages/flutter/lib/painting/text_painter.dart

@@ -8,8 +8,9 @@ import 'package:sky/painting/text_style.dart';
 
 export 'package:sky/painting/text_style.dart';
 
-// This must be immutable, because we won't notice when it changes
+/// An immutable span of text
 abstract class TextSpan {
+  // This class must be immutable, because we won't notice when it changes
   sky.Node _toDOM(sky.Document owner);
   String toString([String prefix = '']);
 
@@ -17,11 +18,13 @@ abstract class TextSpan {
   }
 }
 
+/// An immutable span of unstyled text
 class PlainTextSpan extends TextSpan {
   PlainTextSpan(this.text) {
     assert(text != null);
   }
 
+  /// The text contained in the span
   final String text;
 
   sky.Node _toDOM(sky.Document owner) {
@@ -34,13 +37,17 @@ class PlainTextSpan extends TextSpan {
   String toString([String prefix = '']) => '${prefix}${runtimeType}: "${text}"';
 }
 
+/// An immutable text span that applies a style to a list of children
 class StyledTextSpan extends TextSpan {
   StyledTextSpan(this.style, this.children) {
     assert(style != null);
     assert(children != null);
   }
 
+  /// The style to apply to the children
   final TextStyle style;
+
+  /// The children to which the style is applied
   final List<TextSpan> children;
 
   sky.Node _toDOM(sky.Document owner) {
@@ -90,6 +97,7 @@ class StyledTextSpan extends TextSpan {
   }
 }
 
+/// An object that paints a [TextSpan] into a canvas
 class TextPainter {
   TextPainter(TextSpan text) {
     _layoutRoot.rootElement = _document.createElement('p');
@@ -102,6 +110,7 @@ class TextPainter {
   bool _needsLayout = true;
 
   TextSpan _text;
+  /// The (potentially styled) text to paint
   TextSpan get text => _text;
   void set text(TextSpan value) {
     if (_text == value)
@@ -113,6 +122,7 @@ class TextPainter {
     _needsLayout = true;
   }
 
+  /// The minimum width at which to layout the text
   double get minWidth => _layoutRoot.minWidth;
   void set minWidth(value) {
     if (_layoutRoot.minWidth == value)
@@ -121,6 +131,7 @@ class TextPainter {
     _needsLayout = true;
   }
 
+  /// The maximum width at which to layout the text
   double get maxWidth => _layoutRoot.maxWidth;
   void set maxWidth(value) {
     if (_layoutRoot.maxWidth == value)
@@ -129,6 +140,7 @@ class TextPainter {
     _needsLayout = true;
   }
 
+  /// The minimum height at which to layout the text
   double get minHeight => _layoutRoot.minHeight;
   void set minHeight(value) {
     if (_layoutRoot.minHeight == value)
@@ -137,6 +149,7 @@ class TextPainter {
     _needsLayout = true;
   }
 
+  /// The maximum height at which to layout the text
   double get maxHeight => _layoutRoot.maxHeight;
   void set maxHeight(value) {
     if (_layoutRoot.maxHeight == value)
@@ -144,21 +157,25 @@ class TextPainter {
     _layoutRoot.maxHeight = value;
   }
 
+  /// The width at which decreasing the width of the text would prevent it from painting itself completely within its bounds
   double get minContentWidth {
     assert(!_needsLayout);
     return _layoutRoot.rootElement.minContentWidth;
   }
 
+  /// The width at which increasing the width of the text no longer decreases the height
   double get maxContentWidth {
     assert(!_needsLayout);
     return _layoutRoot.rootElement.maxContentWidth;
   }
 
+  /// The height required to paint the text completely within its bounds
   double get height {
     assert(!_needsLayout);
     return _layoutRoot.rootElement.height;
   }
 
+  /// The distance from the top of the text to the first baseline of the given type
   double computeDistanceToActualBaseline(TextBaseline baseline) {
     assert(!_needsLayout);
     sky.Element root = _layoutRoot.rootElement;
@@ -168,6 +185,7 @@ class TextPainter {
     }
   }
 
+  /// Compute the visual position of the glyphs for painting the text
   void layout() {
     if (!_needsLayout)
       return;
@@ -175,6 +193,7 @@ class TextPainter {
     _needsLayout = false;
   }
 
+  /// Paint the text onto the given canvas at the given offset
   void paint(sky.Canvas canvas, sky.Offset offset) {
     assert(!_needsLayout && "Please call layout() before paint() to position the text before painting it." is String);
     // TODO(ianh): Make LayoutRoot support a paint offset so we don't

packages/flutter/lib/painting/text_style.dart

@@ -4,23 +4,118 @@
 
 import 'dart:sky';
 
-enum FontWeight { w100, w200, w300, w400, w500, w600, w700, w800, w900 }
+/// The thickness of the glyphs used to draw the text
+enum FontWeight {
+  /// Thin, the least thick
+  w100,
+
+  /// Extra-light
+  w200,
+
+  /// Light
+  w300,
+
+  /// Normal / regular / plain
+  w400,
+
+  /// Medium
+  w500,
+
+  /// Semi-bold
+  w600,
+
+  /// Bold
+  w700,
+
+  /// Extra-bold
+  w800,
+
+  /// Black, the most thick
+  w900
+}
+
+/// A normal font weight
 const normal = FontWeight.w400;
+
+/// A bold font weight
 const bold = FontWeight.w700;
 
-enum FontStyle { normal, italic, oblique }
+/// Whether to slant the glyphs in the font
+enum FontStyle {
+  /// Use the upright glyphs
+  normal,
+
+  /// Use glyphs designed for slanting
+  italic,
+
+  /// Use the upright glyphs but slant them during painting
+  oblique  // TODO(abarth): Remove. We don't really support this value.
+}
+
+/// Whether to align text horizontally
+enum TextAlign {
+  /// Align the text on the left edge of the container
+  left,
+
+  /// Align the text on the right edge of the container
+  right,
+
+  /// Align the text in the center of the container
+  center
+}
+
+/// A horizontal line used for aligning text
+enum TextBaseline {
+  // The horizontal line used to align the bottom of glyphs for alphabetic characters
+  alphabetic,
+
+  // The horizontal line used to align ideographic characters
+  ideographic
+}
 
-enum TextAlign { left, right, center }
+/// A linear decoration to draw near the text
+enum TextDecoration {
+  /// Do not draw a decoration
+  none,
 
-enum TextBaseline { alphabetic, ideographic }
+  /// Draw a line underneath each line of text
+  underline,
 
-enum TextDecoration { none, underline, overline, lineThrough }
+  /// Draw a line above each line of text
+  overline,
+
+  /// Draw a line through each line of text
+  lineThrough
+}
+
+/// Draw a line underneath each line of text
 const underline = const <TextDecoration>[TextDecoration.underline];
+
+/// Draw a line above each line of text
 const overline = const <TextDecoration>[TextDecoration.overline];
+
+/// Draw a line through each line of text
 const lineThrough = const <TextDecoration>[TextDecoration.lineThrough];
 
-enum TextDecorationStyle { solid, double, dotted, dashed, wavy }
+/// The style in which to draw a text decoration
+enum TextDecorationStyle {
+  /// Draw a solid line
+  solid,
+
+  /// Draw two lines
+  double,
+
+  /// Draw a dotted line
+  dotted,
+
+  /// Draw a dashed line
+  dashed,
+
+  /// Draw a sinusoidal line
+  wavy
+}
 
+/// An immutable style in which paint text
 class TextStyle {
   const TextStyle({
     this.color,
@@ -36,18 +131,42 @@ class TextStyle {
     this.decorationStyle
   });
 
+  /// The color to use when painting the text
   final Color color;
+
+  /// The name of the font to use when painting the text
   final String fontFamily;
-  final double fontSize; // in pixels
+
+  /// The size of gyphs (in logical pixels) to use when painting the text
+  final double fontSize;
+
+  /// The font weight to use when painting the text
   final FontWeight fontWeight;
+
+  /// The font style to use when painting the text
   final FontStyle fontStyle;
+
+  /// How the text should be aligned (applies only to the outermost
+  /// StyledTextSpan, which establishes the container for the text)
   final TextAlign textAlign;
+
+  /// The baseline to use for aligning the text
   final TextBaseline textBaseline;
-  final double height; // multiple of fontSize
+
+  /// The distance between the text baselines, as a multiple of the font size
+  final double height;
+
+  /// A list of decorations to paint near the text
   final List<TextDecoration> decoration; // TODO(ianh): Switch this to a Set<> once Dart supports constant Sets
+
+  /// The color in which to paint the text decorations
   final Color decorationColor;
+
+  /// The style in which to paint the text decorations
   final TextDecorationStyle decorationStyle;
 
+  /// Returns a new text style that matches this text style but with the given
+  /// values replaced
   TextStyle copyWith({
     Color color,
     String fontFamily,
@@ -76,6 +195,8 @@ class TextStyle {
     );
   }
 
+  /// Returns a new text style that matches this text style but with some values
+  /// replaced by the non-null parameters of the given text style
   TextStyle merge(TextStyle other) {
     return copyWith(
       color: other.color,
@@ -124,6 +245,10 @@ class TextStyle {
     return toCSS[decorationStyle];
   }
 
+  /// Program this text style into the engine
+  ///
+  /// Note: This function will likely be removed when we refactor the interface
+  /// between the framework and the engine
   void applyToCSSStyle(CSSStyleDeclaration cssStyle) {
     if (color != null) {
       cssStyle['color'] = _colorToCSSString(color);
@@ -163,6 +288,10 @@ class TextStyle {
     }
   }
 
+  /// Program the container aspects of this text style into the engine
+  ///
+  /// Note: This function will likely be removed when we refactor the interface
+  /// between the framework and the engine
   void applyToContainerCSSStyle(CSSStyleDeclaration cssStyle) {
     if (textAlign != null) {
       cssStyle['text-align'] = const {

packages/flutter/lib/widgets/README.md

@@ -131,7 +131,8 @@ import 'package:sky/widgets.dart';
 final BoxDecoration _decoration = new BoxDecoration(
   borderRadius: 5.0,
   gradient: new LinearGradient(
-    endPoints: [ Point.origin, const Point(0.0, 36.0) ],
+    start: Point.origin,
+    end: const Point(0.0, 36.0),
     colors: [ const Color(0xFFEEEEEE), const Color(0xFFCCCCCC) ]
   )
 );

packages/flutter/lib/widgets/animated_container.dart

@@ -25,7 +25,7 @@ class AnimatedBoxDecorationValue extends AnimatedValue<BoxDecoration> {
   AnimatedBoxDecorationValue(BoxDecoration begin, { BoxDecoration end, Curve curve: linear })
     : super(begin, end: end, curve: curve);
 
-  BoxDecoration lerp(double t) => lerpBoxDecoration(begin, end, t);
+  BoxDecoration lerp(double t) => BoxDecoration.lerp(begin, end, t);
 }
 
 class AnimatedEdgeDimsValue extends AnimatedValue<EdgeDims> {