Scrollable TabBar Version 0

sky/sdk/lib/widgets/scrollable.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // 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';
 import '../animation/mechanics.dart';
 import '../animation/scroll_behavior.dart';
 import '../theme/view_configuration.dart' as config;
 import 'basic.dart';
 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;
   double get scrollOffset => _scrollOffset;
 
   ScrollBehavior _scrollBehavior;
   ScrollBehavior createScrollBehavior();
   ScrollBehavior get scrollBehavior {
     if (_scrollBehavior == null)
       _scrollBehavior = createScrollBehavior();
@@ skipping 93 matching lines @@
   void _handlePointerDown(_) {
     _stopSimulation();
   }
 
   void _handlePointerUpOrCancel(_) {
     if (_simulation == null)
       _startSimulation(_createParticle());
   }
 
   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) {
     _startSimulation(_createParticle());
   }
 
   void _handleWheel(sky.WheelEvent event) {
     scrollBy(-event.offsetY);
   }
 
 }