Scrollable TabBar Version 0

sky/sdk/lib/widgets/scrollable.dart

Index: sky/sdk/lib/widgets/scrollable.dart
diff --git a/sky/sdk/lib/widgets/scrollable.dart b/sky/sdk/lib/widgets/scrollable.dart
index a6c4023a356507f47251fd4354077a9ef3b1ee9c..34e1e07e1eafe0017bba18bea7301954a47a3f1a 100644
--- a/sky/sdk/lib/widgets/scrollable.dart
+++ b/sky/sdk/lib/widgets/scrollable.dart
@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:math' as math;
 import 'dart:sky' as sky;
 
 import '../animation/generators.dart';
@@ -14,24 +13,31 @@ import 'material.dart';
 
 const double _kMillisecondsPerSecond = 1000.0;
 
-double _velocityForFlingGesture(sky.GestureEvent event) {
-  return math.max(-config.kMaxFlingVelocity, math.min(config.kMaxFlingVelocity,
-      -event.velocityY)) / _kMillisecondsPerSecond;
+double _velocityForFlingGesture(double eventVelocity) {
+  return eventVelocity.clamp(-config.kMaxFlingVelocity, config.kMaxFlingVelocity) /
+    _kMillisecondsPerSecond;
 }
 
 abstract class ScrollClient {
   bool ancestorScrolled(Scrollable ancestor);
 }
 
+enum ScrollDirection { vertical, horizontal }
+
 abstract class Scrollable extends Component {
 
-  Scrollable({ String key, Color this.backgroundColor })
-    : super(key: key, stateful: true);
+  Scrollable({
+   String key,
+   this.backgroundColor,
+   this.direction: ScrollDirection.vertical
+  }) : super(key: key, stateful: true);
 
   Color backgroundColor;
+  ScrollDirection direction;
 
   void syncFields(Scrollable source) {
     backgroundColor = source.backgroundColor;
+    direction == source.direction;
   }
 
   double _scrollOffset = 0.0;
@@ -145,11 +151,14 @@ abstract class Scrollable extends Component {
   }
 
   void _handleScrollUpdate(sky.GestureEvent event) {
-    scrollBy(-event.dy);
+    scrollBy(direction == ScrollDirection.horizontal ? event.dx : -event.dy);
   }
 
   void _handleFlingStart(sky.GestureEvent event) {
-    _startSimulation(_createParticle(_velocityForFlingGesture(event)));
+    double eventVelocity = direction == ScrollDirection.horizontal
+      ? -event.velocityX
+      : -event.velocityY;
+    _startSimulation(_createParticle(_velocityForFlingGesture(eventVelocity)));
   }
 
   void _handleFlingCancel(sky.GestureEvent event) {