Update shadow rendering

Shadows now render as three seprate MaskFilter.blur components per the most recent Material spec.

The shadows Map was replaced by a similar Map called elevationToShadow with entries that match the 10 elevations specifed by http://www.google.com/design/spec/what-is-material/elevation-shadows.html.

The "level" property (many classes) is now called "elevation", to match the Material spec.

BoxShadow now includes a spreadRadius parameter - as in CSS box-shadow. Renamed the BoxShadow blur property to blurRadius to further align BoxShadow with CSS box-shadow.

examples/rendering/shadowed_box.dart

@@ -13,7 +13,7 @@ void main() {
       gradient: new RadialGradient(
         center: Point.origin, radius: 500.0,
         colors: <Color>[Colors.yellow[500], Colors.blue[500]]),
-      boxShadow: shadows[3])
+      boxShadow: elevationToShadow[8])
   );
   var paddedBox = new RenderPadding(
     padding: const EdgeDims.all(50.0),

examples/stocks/lib/stock_home.dart

@@ -146,7 +146,7 @@ class StockHomeState extends State<StockHome> {
 
   Widget buildToolBar() {
     return new ToolBar(
-      level: 0,
+      elevation: 0,
       left: new IconButton(
         icon: "navigation/menu",
         onPressed: _showDrawer

examples/widgets/piano.dart

@@ -100,7 +100,7 @@ Widget statusBox(Widget child) {
       decoration: const BoxDecoration(
         boxShadow: const <BoxShadow>[
           const BoxShadow(
-            color: mediumGray, offset: const Offset(6.0, 6.0), blur: 5.0)
+            color: mediumGray, offset: const Offset(6.0, 6.0), blurRadius: 5.0)
         ],
         backgroundColor: darkGray
       ),

packages/flutter/lib/src/material/card.dart

@@ -23,7 +23,7 @@ class Card extends StatelessComponent {
       child: new Material(
         color: color,
         type: MaterialType.card,
-        level: 2,
+        elevation: 8,
         child: child
       )
     );

packages/flutter/lib/src/material/dialog.dart

@@ -102,7 +102,7 @@ class Dialog extends StatelessComponent {
         child: new ConstrainedBox(
           constraints: new BoxConstraints(minWidth: 280.0),
           child: new Material(
-            level: 4,
+            elevation: 24,
             color: _getColor(context),
             type: MaterialType.card,
             child: new IntrinsicWidth(

packages/flutter/lib/src/material/drawer.dart

@@ -36,7 +36,7 @@ class _Drawer extends StatelessComponent {
       child: new ConstrainedBox(
         constraints: const BoxConstraints.expand(width: _kWidth),
         child: new Material(
-          level: route.level,
+          elevation: route.elevation,
           child: route.child
         )
       )
@@ -51,10 +51,10 @@ enum _DrawerState {
 }
 
 class _DrawerRoute extends OverlayRoute {
-  _DrawerRoute({ this.child, this.level });
+  _DrawerRoute({ this.child, this.elevation });
 
   final Widget child;
-  final int level;
+  final int elevation;
 
   List<WidgetBuilder> get builders => <WidgetBuilder>[ _build ];
 
@@ -212,6 +212,6 @@ class _DrawerControllerState extends State<_DrawerController> {
   }
 }
 
-void showDrawer({ BuildContext context, Widget child, int level: 3 }) {
-  Navigator.of(context).push(new _DrawerRoute(child: child, level: level));
+void showDrawer({ BuildContext context, Widget child, int elevation: 16 }) {
+  Navigator.of(context).push(new _DrawerRoute(child: child, elevation: elevation));
 }

packages/flutter/lib/src/material/dropdown.dart

@@ -85,7 +85,7 @@ class _DropdownMenu extends StatusTransitionComponent {
     final BoxPainter menuPainter = new BoxPainter(new BoxDecoration(
       backgroundColor: Theme.of(context).canvasColor,
       borderRadius: 2.0,
-      boxShadow: shadows[route.level]
+      boxShadow: elevationToShadow[route.elevation]
     ));
 
     final RenderBox renderBox = Navigator.of(context).context.findRenderObject();
@@ -129,13 +129,13 @@ class _MenuRoute extends TransitionRoute {
     this.items,
     this.selectedIndex,
     this.rect,
-    this.level: 4
+    this.elevation: 8
   });
 
   final Completer completer;
   final Rect rect;
   final List<DropdownMenuItem> items;
-  final int level;
+  final int elevation;
   final int selectedIndex;
 
   bool get opaque => false;
@@ -183,13 +183,13 @@ class DropdownButton<T> extends StatelessComponent {
     this.items,
     this.value,
     this.onChanged,
-    this.level: 4
+    this.elevation: 8
   }) : super(key: key);
 
   final List<DropdownMenuItem<T>> items;
   final T value;
   final ValueChanged<T> onChanged;
-  final int level;
+  final int elevation;
 
   void _showDropdown(BuildContext context, int selectedIndex, GlobalKey indexedStackKey) {
     final RenderBox renderBox = indexedStackKey.currentContext.findRenderObject();
@@ -200,7 +200,7 @@ class DropdownButton<T> extends StatelessComponent {
       items: items,
       selectedIndex: selectedIndex,
       rect: _kMenuHorizontalPadding.inflateRect(rect),
-      level: level
+      elevation: elevation
     ));
     completer.future.then((T newValue) {
       if (onChanged != null)

packages/flutter/lib/src/material/flat_button.dart

@@ -22,7 +22,7 @@ class FlatButton extends MaterialButton {
 
 class _FlatButtonState extends MaterialButtonState<FlatButton> {
 
-  int get level => 0;
+  int get elevation => 0;
 
   Color getColor(BuildContext context, { bool highlight }) {
     if (!config.enabled || !highlight)

packages/flutter/lib/src/material/floating_action_button.dart

@@ -50,7 +50,7 @@ class _FloatingActionButtonState extends State<FloatingActionButton> {
     return new Material(
       color: materialColor,
       type: MaterialType.circle,
-      level: _highlight ? 3 : 2,
+      elevation: _highlight ? 12 : 6,
       child: new ClipOval(
         child: new Container(
           width: _kSize,

packages/flutter/lib/src/material/material.dart

@@ -23,16 +23,16 @@ class Material extends StatelessComponent {
     Key key,
     this.child,
     this.type: MaterialType.canvas,
-    this.level: 0,
+    this.elevation: 0,
     this.color,
     this.textStyle
   }) : super(key: key) {
-    assert(level != null);
+    assert(elevation != null);
   }
 
   final Widget child;
   final MaterialType type;
-  final int level;
+  final int elevation;
   final Color color;
   final TextStyle textStyle;
 
@@ -72,7 +72,7 @@ class Material extends StatelessComponent {
         decoration: new BoxDecoration(
           backgroundColor: _getBackgroundColor(context),
           borderRadius: _kEdges[type],
-          boxShadow: level == 0 ? null : shadows[level],
+          boxShadow: elevation == 0 ? null : elevationToShadow[elevation],
           shape: type == MaterialType.circle ? Shape.circle : Shape.rectangle
         ),
         child: contents

packages/flutter/lib/src/material/material_button.dart

@@ -56,7 +56,7 @@ abstract class MaterialButton extends StatefulComponent {
 abstract class MaterialButtonState<T extends MaterialButton> extends State<T> {
   bool highlight = false;
 
-  int get level;
+  int get elevation;
   Color getColor(BuildContext context, { bool highlight });
   ThemeBrightness getColorBrightness(BuildContext context);
 
@@ -102,7 +102,7 @@ abstract class MaterialButtonState<T extends MaterialButton> extends State<T> {
       margin: new EdgeDims.all(8.0),
       child: new Material(
         type: MaterialType.button,
-        level: level,
+        elevation: elevation,
         textStyle: Theme.of(context).text.button.copyWith(color: getTextColor(context)),
         child: new InkWell(
           onTap: config.enabled ? config.onPressed : null,

packages/flutter/lib/src/material/popup_menu.dart

@@ -34,7 +34,7 @@ class _PopupMenu extends StatelessComponent {
     final BoxPainter painter = new BoxPainter(new BoxDecoration(
       backgroundColor: Theme.of(context).canvasColor,
       borderRadius: 2.0,
-      boxShadow: shadows[route.level]
+      boxShadow: elevationToShadow[route.elevation]
     ));
 
     double unit = 1.0 / (route.items.length + 1.5); // 1.0 for the width and 0.5 for the last item's fade.
@@ -93,11 +93,11 @@ class _PopupMenu extends StatelessComponent {
 }
 
 class _MenuRoute extends ModalRoute {
-  _MenuRoute({ Completer completer, this.position, this.items, this.level }) : super(completer: completer);
+  _MenuRoute({ Completer completer, this.position, this.items, this.elevation }) : super(completer: completer);
 
   final ModalPosition position;
   final List<PopupMenuItem> items;
-  final int level;
+  final int elevation;
 
   Performance createPerformance() {
     Performance result = super.createPerformance();
@@ -113,13 +113,13 @@ class _MenuRoute extends ModalRoute {
   Widget buildPage(BuildContext context) => new _PopupMenu(route: this);
 }
 
-Future showMenu({ BuildContext context, ModalPosition position, List<PopupMenuItem> items, int level: 4 }) {
+Future showMenu({ BuildContext context, ModalPosition position, List<PopupMenuItem> items, int elevation: 8 }) {
   Completer completer = new Completer();
   Navigator.of(context).pushEphemeral(new _MenuRoute(
     completer: completer,
     position: position,
     items: items,
-    level: level
+    elevation: elevation
   ));
   return completer.future;
 }

packages/flutter/lib/src/material/raised_button.dart

@@ -22,7 +22,7 @@ class RaisedButton extends MaterialButton {
 
 class _RaisedButtonState extends MaterialButtonState<RaisedButton> {
 
-  int get level => config.enabled ? (highlight ? 2 : 1) : 0;
+  int get elevation => config.enabled ? (highlight ? 8 : 2) : 0;
 
   Color getColor(BuildContext context, { bool highlight }) {
     if (config.enabled) {

packages/flutter/lib/src/material/shadows.dart

@@ -6,55 +6,72 @@ import 'dart:ui' show Color, Offset;
 
 import 'package:flutter/painting.dart';
 
-const Map<int, List<BoxShadow>> shadows = const <int, List<BoxShadow>>{
+// Based on http://www.google.com/design/spec/what-is-material/elevation-shadows.html
+// Currently, only the elevation values that are bound to one or more components are
+// defined here.
+
+const Color _kKeyUmbraOpacity = const Color(0x33000000); // alpha = 0.2
+const Color _kKeyPenumbraOpacity = const Color(0x24000000); // alpha = 0.14
+const Color _kAmbientShadowOpacity = const Color(0x1F000000); // alpha = 0.12
+
+const Map<int, List<BoxShadow>> elevationToShadow = const <int, List<BoxShadow>>{
   1: const <BoxShadow>[
-    const BoxShadow(
-      color: const Color(0x1F000000),
-      offset: const Offset(0.0, 1.0),
-      blur: 3.0),
-    const BoxShadow(
-      color: const Color(0x3D000000),
-      offset: const Offset(0.0, 1.0),
-      blur: 2.0),
+    const BoxShadow(offset: const Offset(0.0, 2.0), blurRadius: 1.0, spreadRadius: -1.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 1.0, spreadRadius: 0.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 3.0, spreadRadius: 0.0, color: _kAmbientShadowOpacity),
   ],
+
   2: const <BoxShadow>[
-    const BoxShadow(
-      color: const Color(0x29000000),
-      offset: const Offset(0.0, 3.0),
-      blur: 6.0),
-    const BoxShadow(
-      color: const Color(0x3B000000),
-      offset: const Offset(0.0, 3.0),
-      blur: 6.0),
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 1.0, spreadRadius: -2.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 2.0), blurRadius: 2.0, spreadRadius: 0.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 5.0, spreadRadius: 0.0, color: _kAmbientShadowOpacity),
   ],
+
   3: const <BoxShadow>[
-    const BoxShadow(
-      color: const Color(0x30000000),
-      offset: const Offset(0.0, 10.0),
-      blur: 20.0),
-    const BoxShadow(
-      color: const Color(0x3B000000),
-      offset: const Offset(0.0, 6.0),
-      blur: 6.0),
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 3.0, spreadRadius: -2.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 4.0, spreadRadius: 0.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 8.0, spreadRadius: 0.0, color: _kAmbientShadowOpacity),
   ],
+
   4: const <BoxShadow>[
-    const BoxShadow(
-      color: const Color(0x40000000),
-      offset: const Offset(0.0, 14.0),
-      blur: 28.0),
-    const BoxShadow(
-      color: const Color(0x38000000),
-      offset: const Offset(0.0, 10.0),
-      blur: 10.0),
-  ],
-  5: const <BoxShadow>[
-    const BoxShadow(
-      color: const Color(0x4E000000),
-      offset: const Offset(0.0, 19.0),
-      blur: 28.0),
-    const BoxShadow(
-      color: const Color(0x38000000),
-      offset: const Offset(0.0, 15.0),
-      blur: 12.0),
+    const BoxShadow(offset: const Offset(0.0, 2.0), blurRadius: 4.0, spreadRadius: -1.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 4.0), blurRadius: 5.0, spreadRadius: 0.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 10.0, spreadRadius: 0.0, color: _kAmbientShadowOpacity),
+  ],
+
+  6: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 5.0, spreadRadius: -1.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 6.0), blurRadius: 10.0, spreadRadius: 0.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 1.0), blurRadius: 18.0, spreadRadius: 0.0, color: _kAmbientShadowOpacity),
+  ],
+
+  8: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 5.0), blurRadius: 5.0, spreadRadius: -3.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 8.0), blurRadius: 10.0, spreadRadius: 1.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 14.0, spreadRadius: 2.0, color: _kAmbientShadowOpacity),
+  ],
+
+  9: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 5.0), blurRadius: 6.0, spreadRadius: -3.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 9.0), blurRadius: 12.0, spreadRadius: 1.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 3.0), blurRadius: 16.0, spreadRadius: 2.0, color: _kAmbientShadowOpacity),
+  ],
+
+  12: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 7.0), blurRadius: 8.0, spreadRadius: -4.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 12.0), blurRadius: 17.0, spreadRadius: 2.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 5.0), blurRadius: 22.0, spreadRadius: 4.0, color: _kAmbientShadowOpacity),
+  ],
+
+  16: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 8.0), blurRadius: 10.0, spreadRadius: -5.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 16.0), blurRadius: 24.0, spreadRadius: 2.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 6.0), blurRadius: 30.0, spreadRadius: 5.0, color: _kAmbientShadowOpacity),
+  ],
+
+  24: const <BoxShadow>[
+    const BoxShadow(offset: const Offset(0.0, 11.0), blurRadius: 15.0, spreadRadius: -7.0, color: _kKeyUmbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 24.0), blurRadius: 38.0, spreadRadius: 3.0, color: _kKeyPenumbraOpacity),
+    const BoxShadow(offset: const Offset(0.0, 9.0), blurRadius: 46.0, spreadRadius: 8.0, color: _kAmbientShadowOpacity),
   ],
 };

packages/flutter/lib/src/material/snack_bar.dart

@@ -77,7 +77,7 @@ class _SnackBar extends StatelessComponent {
           minHeight: kSnackBarHeight,
           maxHeight: kSnackBarHeight,
           child: new Material(
-            level: 2,
+            elevation: 6,
             color: _kSnackBackground,
             child: new Container(
               margin: const EdgeDims.symmetric(horizontal: _kSideMargins),

packages/flutter/lib/src/material/switch.dart

@@ -134,8 +134,8 @@ class _RenderSwitch extends RenderToggleable {
     // Draw the raised thumb with a shadow
     paint.color = thumbColor;
     ShadowDrawLooperBuilder builder = new ShadowDrawLooperBuilder();
-    for (BoxShadow boxShadow in shadows[1])
-      builder.addShadow(boxShadow.offset, boxShadow.color, boxShadow.blur);
+    for (BoxShadow boxShadow in elevationToShadow[1])
+      builder.addShadow(boxShadow.offset, boxShadow.color, boxShadow.blurRadius);
     paint.drawLooper = builder.build();
 
     // The thumb contracts slightly during the animation

packages/flutter/lib/src/material/tool_bar.dart

@@ -18,7 +18,7 @@ class ToolBar extends StatelessComponent {
     this.center,
     this.right,
     this.bottom,
-    this.level: 2,
+    this.elevation: 4,
     this.backgroundColor,
     this.textTheme,
     this.padding: EdgeDims.zero
@@ -28,7 +28,7 @@ class ToolBar extends StatelessComponent {
   final Widget center;
   final List<Widget> right;
   final Widget bottom;
-  final int level;
+  final int elevation;
   final Color backgroundColor;
   final TextTheme textTheme;
   final EdgeDims padding;
@@ -40,7 +40,7 @@ class ToolBar extends StatelessComponent {
       center: center,
       right: right,
       bottom: bottom,
-      level: level,
+      elevation: elevation,
       backgroundColor: backgroundColor,
       textTheme: textTheme,
       padding: newPadding
@@ -95,7 +95,7 @@ class ToolBar extends StatelessComponent {
       padding: new EdgeDims.symmetric(horizontal: 8.0),
       decoration: new BoxDecoration(
         backgroundColor: color,
-        boxShadow: level == 0 ? null : shadows[2]
+        boxShadow: elevationToShadow[elevation]
       ),
       child: new DefaultTextStyle(
         style: sideStyle,

packages/flutter/lib/src/painting/box_painter.dart

@@ -8,7 +8,6 @@ import 'dart:ui' as ui;
 import 'package:flutter/services.dart';
 
 import 'basic_types.dart';
-import 'shadows.dart';
 
 /// An immutable set of offsets in each of the four cardinal directions.
 ///
@@ -253,11 +252,13 @@ class Border {
 ///
 /// Note: BoxShadow can cast non-rectangular shadows if the box is
 /// non-rectangular (e.g., has a border radius or a circular shape).
+/// This class is similar to CSS box-shadow.
 class BoxShadow {
   const BoxShadow({
     this.color,
     this.offset,
-    this.blur
+    this.blurRadius,
+    this.spreadRadius: 0.0
   });
 
   /// The color of the shadow
@@ -267,14 +268,20 @@ class BoxShadow {
   final Offset offset;
 
   /// The standard deviation of the Gaussian to convolve with the box's shape
-  final double blur;
+  final double blurRadius;
 
-  /// Returns a new box shadow with its offset and blur scaled by the given factor
+  final double spreadRadius;
+
+  // See SkBlurMask::ConvertRadiusToSigma()
+  double get _blurSigma => blurRadius * 0.57735 + 0.5;
+
+  /// Returns a new box shadow with its offset, blurRadius, and spreadRadius scaled by the given factor
   BoxShadow scale(double factor) {
     return new BoxShadow(
       color: color,
       offset: offset * factor,
-      blur: blur * factor
+      blurRadius: blurRadius * factor,
+      spreadRadius: spreadRadius * factor
     );
   }
 
@@ -282,7 +289,7 @@ class BoxShadow {
   ///
   /// 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.
+  /// offset and a zero blurRadius.
   static BoxShadow lerp(BoxShadow a, BoxShadow b, double t) {
     if (a == null && b == null)
       return null;
@@ -293,7 +300,8 @@ class BoxShadow {
     return new BoxShadow(
       color: Color.lerp(a.color, b.color, t),
       offset: Offset.lerp(a.offset, b.offset, t),
-      blur: ui.lerpDouble(a.blur, b.blur, t)
+      blurRadius: ui.lerpDouble(a.blurRadius, b.blurRadius, t),
+      spreadRadius: ui.lerpDouble(a.spreadRadius, b.spreadRadius, t)
     );
   }
 
@@ -326,18 +334,20 @@ class BoxShadow {
     final BoxShadow typedOther = other;
     return color == typedOther.color &&
            offset == typedOther.offset &&
-           blur == typedOther.blur;
+           blurRadius == typedOther.blurRadius &&
+           spreadRadius == typedOther.spreadRadius;
   }
 
   int get hashCode {
     int value = 373;
     value = 37 * value + color.hashCode;
     value = 37 * value + offset.hashCode;
-    value = 37 * value + blur.hashCode;
+    value = 37 * value + blurRadius.hashCode;
+    value = 37 * value + spreadRadius.hashCode;
     return value;
   }
 
-  String toString() => 'BoxShadow($color, $offset, $blur)';
+  String toString() => 'BoxShadow($color, $offset, $blurRadius, $spreadRadius)';
 }
 
 /// A 2D gradient
@@ -894,13 +904,6 @@ class BoxPainter {
       if (_decoration.backgroundColor != null)
         paint.color = _decoration.backgroundColor;
 
-      if (_decoration.boxShadow != null) {
-        var builder = new ShadowDrawLooperBuilder();
-        for (BoxShadow boxShadow in _decoration.boxShadow)
-          builder.addShadow(boxShadow.offset, boxShadow.color, boxShadow.blur);
-        paint.drawLooper = builder.build();
-      }
-
       if (_decoration.gradient != null)
         paint.shader = _decoration.gradient.createShader();
 
@@ -937,27 +940,40 @@ class BoxPainter {
     return _decoration.borderRadius > shortestSide ? shortestSide : _decoration.borderRadius;
   }
 
-  void _paintBackgroundColor(ui.Canvas canvas, Rect rect) {
-    if (_decoration.backgroundColor != null ||
-        _decoration.boxShadow != null ||
-        _decoration.gradient != null) {
+  void _paintBox(ui.Canvas canvas, Rect rect, Paint paint) {
     switch (_decoration.shape) {
       case Shape.circle:
         assert(_decoration.borderRadius == null);
         Point center = rect.center;
         double radius = rect.shortestSide / 2.0;
-          canvas.drawCircle(center, radius, _backgroundPaint);
+        canvas.drawCircle(center, radius, paint);
         break;
       case Shape.rectangle:
         if (_decoration.borderRadius == null) {
-            canvas.drawRect(rect, _backgroundPaint);
+          canvas.drawRect(rect, paint);
         } else {
           double radius = _getEffectiveBorderRadius(rect);
-            canvas.drawRRect(new ui.RRect.fromRectXY(rect, radius, radius), _backgroundPaint);
+          canvas.drawRRect(new ui.RRect.fromRectXY(rect, radius, radius), paint);
         }
         break;
     }
   }
+
+  void _paintShadows(ui.Canvas canvas, Rect rect) {
+    if (_decoration.boxShadow == null)
+      return;
+    for (BoxShadow boxShadow in _decoration.boxShadow) {
+      final Paint paint = new Paint()
+        ..color = boxShadow.color
+        ..maskFilter = new ui.MaskFilter.blur(ui.BlurStyle.normal, boxShadow._blurSigma);
+      final Rect bounds = rect.shift(boxShadow.offset).inflate(boxShadow.spreadRadius);
+      _paintBox(canvas, bounds, paint);
+    }
+  }
+
+  void _paintBackgroundColor(ui.Canvas canvas, Rect rect) {
+    if (_decoration.backgroundColor != null || _decoration.gradient != null)
+      _paintBox(canvas, rect, _backgroundPaint);
   }
 
   void _paintBackgroundImage(ui.Canvas canvas, Rect rect) {
@@ -1071,6 +1087,7 @@ class BoxPainter {
 
   /// Paint the box decoration into the given location on the given canvas
   void paint(ui.Canvas canvas, Rect rect) {
+    _paintShadows(canvas, rect);
     _paintBackgroundColor(canvas, rect);
     _paintBackgroundImage(canvas, rect);
     _paintBorder(canvas, rect);

packages/unit/test/rendering/box_test.dart

@@ -12,7 +12,7 @@ void main() {
         gradient: new RadialGradient(
           center: Point.origin, radius: 500.0,
           colors: <Color>[Colors.yellow[500], Colors.blue[500]]),
-        boxShadow: shadows[3])
+        boxShadow: elevationToShadow[3])
     );
     layout(root);
     expect(root.size.width, equals(800.0));