Merge branch 'yczhang' into match_flutter12

Runtime/Plugins/platform/ios/UIWidgetsViewController.mm

     CGFloat bottom = CGRectGetHeight([[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue]);
     CGFloat scale = [UIScreen mainScreen].scale;
 
+    // scale == 3 => screen is 1242 * 2208 => we have to perform down-sampling to obtain the real length
+    // 0.8696 = 1920 / 2208, the vertical down-sampling ratio
+    if (scale == 3) {
+        bottom = bottom * 0.8696;
+    }
+
     viewInsets.bottom = bottom * scale;
     padding.bottom = 0;
 

Runtime/animation/animation_controller.cs

             this._direction = _AnimationDirection.forward;
             return this._animateToInternal(target, duration: duration, curve: curve);
         }
-        
-        TickerFuture animateBack(float target, TimeSpan? duration, Curve curve = null) {
+
+        public TickerFuture animateBack(float target, TimeSpan? duration, Curve curve = null) {
             D.assert(
                 this._ticker != null,
                 "AnimationController.animateBack() called after AnimationController.dispose()\n" +
                 new _InterpolationSimulation(this._value, target, simulationDuration.Value, curve));
         }
 
-        public TickerFuture repeat(float? min = null, float? max = null, bool reverse = false, TimeSpan? period = null) {
+        public TickerFuture repeat(float? min = null, float? max = null, bool reverse = false,
+            TimeSpan? period = null) {
             min = min ?? this.lowerBound;
             max = max ?? this.upperBound;
             period = period ?? this.duration;
 
                 return true;
             });
-            
+
             D.assert(max >= min);
             D.assert(max <= this.upperBound && min >= this.lowerBound);
             return this.animateWith(new _RepeatingSimulation(this._value, min.Value, max.Value, reverse, period.Value));
             this._min = min;
             this._max = max;
             this._periodInSeconds = (float) period.Ticks / TimeSpan.TicksPerSecond;
-            this._initialT = (max == min) ? 0.0f : (initialValue / (max - min)) * (period.Ticks / TimeSpan.TicksPerSecond);
+            this._initialT =
+                (max == min) ? 0.0f : (initialValue / (max - min)) * (period.Ticks / TimeSpan.TicksPerSecond);
             this._reverse = reverse;
             D.assert(this._periodInSeconds > 0.0f);
             D.assert(this._initialT >= 0.0f);
             D.assert(timeInSeconds >= 0.0f);
             float totalTimeInSeconds = timeInSeconds + this._initialT;
             float t = (totalTimeInSeconds / this._periodInSeconds) % 1.0f;
-            bool _isPlayingReverse = ((int)(totalTimeInSeconds / this._periodInSeconds)) % 2 == 1;
+            bool _isPlayingReverse = ((int) (totalTimeInSeconds / this._periodInSeconds)) % 2 == 1;
-            } else {
+            }
+            else {
                 return MathUtils.lerpFloat(this._min, this._max, t);
             }
         }

Runtime/animation/curves.cs

         public static readonly Curve linear = new _Linear();
 
         public static readonly Curve decelerate = new _DecelerateCurve();
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
-        
+
         public static readonly Cubic easeInOutBack = new Cubic(0.68f, -0.55f, 0.265f, 1.55f);
 
         public static readonly Curve fastOutSlowIn = new Cubic(0.4f, 0.0f, 0.2f, 1.0f);

Runtime/animation/listener_helpers.mixin.gen.cs

 
         public override void removeListener(VoidCallback listener) {
             bool removed = this._listeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }
 
         public override void removeListener(VoidCallback listener) {
             bool removed = this._listeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }
 
         public override void removeStatusListener(AnimationStatusListener listener) {
             bool removed = this._statusListeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }
 
         public override void removeStatusListener(AnimationStatusListener listener) {
             bool removed = this._statusListeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }
 
         public override void removeStatusListener(AnimationStatusListener listener) {
             bool removed = this._statusListeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }

Runtime/animation/listener_helpers.mixin.njk

 
         public override void removeListener(VoidCallback listener) {
             bool removed = this._listeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }
 
         public override void removeStatusListener(AnimationStatusListener listener) {
             bool removed = this._statusListeners.Remove(listener);
-            if(removed) {
+            if (removed) {
                 this.didUnregisterListener();
             }
         }

Runtime/animation/tween.cs

         }
     }
 
+    class ConstantTween<T> : Tween<T> {
+        public ConstantTween(T value) : base(begin: value, end: value) {
+        }
+
+        public override T lerp(float t) {
+            return this.begin;
+        }
+
+        public override string ToString() {
+            return $"{this.GetType()}(value: {this.begin})";
+        }
+    }
+
     public class CurveTween : Animatable<float> {
         public CurveTween(Curve curve = null) {
             D.assert(curve != null);

Runtime/engine/UIWidgetsPanel.cs

         protected virtual void Update() {
             this._displayMetrics.Update();
             UIWidgetsMessageManager.ensureUIWidgetsMessageManagerIfNeeded();
+            
+#if UNITY_ANDROID
+            if (Input.GetKeyDown(KeyCode.Escape)) {
+                this._windowAdapter.withBinding(() => {
+                    WidgetsBinding.instance.handlePopRoute();
+                });
+            }
+#endif
 
             if (!this._viewMetricsCallbackRegistered) {
                 this._viewMetricsCallbackRegistered = true;

Runtime/foundation/debug.cs

 using Unity.UIWidgets.editor;
 using Unity.UIWidgets.painting;
 using Unity.UIWidgets.ui;
+using Canvas = Unity.UIWidgets.ui.Canvas;
+using Color = Unity.UIWidgets.ui.Color;
+using Rect = Unity.UIWidgets.ui.Rect;
-
         public static void logError(string message, Exception ex = null) {
             Debug.LogException(new AssertionError(message, ex));
         }
 #endif
             }
         }
-        
+
         [Conditional("UIWidgets_DEBUG")]
         public static void assert(Func<bool> result, string message = null) {
             if (!result()) {
 
         public static bool debugCheckIntrinsicSizes = false;
 
-        public static HSVColor debugCurrentRepaintColor = 
+        public static bool debugPrintMouseHoverEvents = false;
+
+        public static HSVColor debugCurrentRepaintColor =
             HSVColor.fromAHSV(0.4f, 60.0f, 1.0f, 1.0f);
 
         public static void _debugDrawDoubleRect(Canvas canvas, Rect outerRect, Rect innerRect, Color color) {
                 return true;
             });
         }
-        
+
-            bool? debugPaintPointersEnabled= null,
+            bool? debugPaintPointersEnabled = null,
-            bool? debugRepaintRainbowEnabled = null ) {
-
+            bool? debugRepaintRainbowEnabled = null) {
-            
+
-            
+
-            
-            if (debugPaintLayerBordersEnabled != null && debugPaintLayerBordersEnabled != D.debugPaintLayerBordersEnabled) {
+
+            if (debugPaintLayerBordersEnabled != null &&
+                debugPaintLayerBordersEnabled != D.debugPaintLayerBordersEnabled) {
-            
+
             if (debugRepaintRainbowEnabled != null && debugRepaintRainbowEnabled != D.debugRepaintRainbowEnabled) {
                 D.debugRepaintRainbowEnabled = debugRepaintRainbowEnabled.Value;
                 needRepaint = true;
     [Serializable]
     public class AssertionError : Exception {
         readonly Exception innerException;
-        
+
         public AssertionError(string message) : base(message) {
         }
 
                 if (this.innerException != null) {
                     return this.innerException.StackTrace;
                 }
-                
+
                 var stackTrace = base.StackTrace;
                 var lines = stackTrace.Split('\n');
                 var strippedLines = lines.Skip(1);

Runtime/gestures/binding.cs

                 this._handlePointerHoverEvent(evt);
             }
 
-            HitTestResult result;
+            HitTestResult result = null;
             if (evt is PointerDownEvent) {
                 D.assert(!this._hitTests.ContainsKey(evt.pointer));
                 result = new HitTestResult();
             else if (evt.down) {
                 result = this._hitTests.getOrDefault(evt.pointer);
             }
-            else {
-                return;
-            }
+
+            D.assert(() => {
+                if (D.debugPrintMouseHoverEvents && evt is PointerHoverEvent) {
+                    Debug.LogFormat("{0}", evt);
+                }
+
+                return true;
+            });
-            if (result != null) {
+            if (result != null ||
+                evt is PointerHoverEvent ||
+                evt is PointerAddedEvent ||
+                evt is PointerRemovedEvent
+            ) {
                 this.dispatchEvent(evt, result);
             }
         }
         }
 
         public void dispatchEvent(PointerEvent evt, HitTestResult result) {
+            if (result == null) {
+                D.assert(evt is PointerHoverEvent || evt is PointerAddedEvent || evt is PointerRemovedEvent);
+                try {
+                    this.pointerRouter.route(evt);
+                }
+                catch (Exception ex) {
+                    UIWidgetsError.reportError(new UIWidgetsErrorDetails(
+                            exception: ex,
+                            library: "gesture library",
+                            context: "while dispatching a non-hit-tested pointer event",
+                            informationCollector: information => {
+                                information.AppendLine("Event: ");
+                                information.AppendFormat(" {0}", evt);
+                            }
+                        )
+                    );
+                }
+
+                return;
+            }
+
             foreach (HitTestEntry entry in result.path) {
                 try {
                     entry.target.handleEvent(evt, entry);

Runtime/gestures/converter.cs

     public static class PointerEventConverter {
         static readonly Dictionary<int, _PointerState> _pointers = new Dictionary<int, _PointerState>();
 
+        static void clearPointers() {
+            _pointers.Clear();
+        }
+
         static _PointerState _ensureStateForPointer(PointerData datum, Offset position) {
             return _pointers.putIfAbsent(
                 datum.device,
                         if (state == null || !state.down) {
                             break;
                         }
-                        
+
                         D.assert(state.down);
                         if (position != state.lastPosition) {
                             Offset offset = position - state.lastPosition;

Runtime/gestures/monodrag.cs

         public DragGestureRecognizer(
             object debugOwner = null,
             PointerDeviceKind? kind = null,
-            DragStartBehavior dragStartBehavior = DragStartBehavior.start)
+            DragStartBehavior dragStartBehavior = DragStartBehavior.down)
             : base(debugOwner: debugOwner, kind: kind) {
             this.dragStartBehavior = dragStartBehavior;
         }
         public override void dispose() {
             this._velocityTrackers.Clear();
             base.dispose();
+        }
+
+        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            properties.add(new EnumProperty<DragStartBehavior>("start behavior", this.dragStartBehavior));
         }
     }
 

Runtime/gestures/recognizer.cs

     public enum GestureRecognizerState {
         ready,
         possible,
+        accepted,
         defunct,
     }
 
             object debugOwner = null,
-            PointerDeviceKind? kind = null
+            PointerDeviceKind? kind = null,
+            float? preAcceptSlotTolerance = Constants.kTouchSlop,
+            float? postAcceptSlotTolerance = Constants.kTouchSlop
+            D.assert(preAcceptSlotTolerance == null || preAcceptSlotTolerance >= 0,
+                "The preAcceptSlopTolerance must be positive or null");
+
+            D.assert(postAcceptSlotTolerance == null || postAcceptSlotTolerance >= 0,
+                "The postAcceptSlopTolerance must be positive or null");
+
+            this.preAcceptSlotTolerance = preAcceptSlotTolerance;
+            this.postAcceptSlotTolerance = postAcceptSlotTolerance;
+
+        public readonly float? preAcceptSlotTolerance;
+
+        public readonly float? postAcceptSlotTolerance;
 
         public GestureRecognizerState state = GestureRecognizerState.ready;
 
 
         protected override void handleEvent(PointerEvent evt) {
             D.assert(this.state != GestureRecognizerState.ready);
-            if (this.state == GestureRecognizerState.possible && evt.pointer == this.primaryPointer) {
-                if (evt is PointerMoveEvent && this._getDistance(evt) > Constants.kTouchSlop) {
+
+            if (evt.pointer == this.primaryPointer) {
+                bool isPreAcceptSlopPastTolerance = this.state == GestureRecognizerState.possible &&
+                                                    this.preAcceptSlotTolerance != null &&
+                                                    this._getDistance(evt) > this.preAcceptSlotTolerance;
+                bool isPostAcceptSlopPastTolerance = this.state == GestureRecognizerState.accepted &&
+                                                     this.postAcceptSlotTolerance != null &&
+                                                     this._getDistance(evt) > this.postAcceptSlotTolerance;
+
+                if (evt is PointerMoveEvent && (isPreAcceptSlopPastTolerance || isPostAcceptSlopPastTolerance)) {
                     this.resolve(GestureDisposition.rejected);
                     this.stopTrackingPointer(this.primaryPointer);
                 }
             D.assert(this.deadline == null);
         }
 
+        public override void acceptGesture(int pointer) {
+            if (pointer == this.primaryPointer && this.state == GestureRecognizerState.possible) {
+                this.state = GestureRecognizerState.accepted;
+            }
+        }
+
-            if (pointer == this.primaryPointer && this.state == GestureRecognizerState.possible) {
+            if (pointer == this.primaryPointer && (this.state == GestureRecognizerState.possible ||
+                                                   this.state == GestureRecognizerState.accepted)) {
                 this._stopTimer();
                 this.state = GestureRecognizerState.defunct;
             }

Runtime/material/list_tile.cs

 
         public readonly bool selected;
 
+        public static IEnumerable<Widget> divideTiles(BuildContext context = null, IEnumerable<Widget> tiles = null,
+            Color color = null) {
+            D.assert(tiles != null);
+            D.assert(color != null || context != null);
+
+            IEnumerator<Widget> enumerator = tiles.GetEnumerator();
+            List<Widget> result = new List<Widget> { };
+
+            Decoration decoration = new BoxDecoration(
+                border: new Border(
+                    bottom: Divider.createBorderSide(context, color: color)
+                )
+            );
+
+            Widget tile = enumerator.Current;
+            while (enumerator.MoveNext()) {
+                result.Add(new DecoratedBox(
+                    position: DecorationPosition.foreground,
+                    decoration: decoration,
+                    child: tile
+                ));
+                tile = enumerator.Current;
+            }
+
+            return result;
+        }
 
         Color _iconColor(ThemeData theme, ListTileTheme tileTheme) {
             if (!this.enabled) {

Runtime/material/theme_data.cs

             IconThemeData accentIconTheme = null,
             TabBarTheme tabBarTheme = null,
             CardTheme cardTheme = null,
+            ChipThemeData chipTheme = null,
             RuntimePlatform? platform = null,
             MaterialTapTargetSize? materialTapTargetSize = null,
             PageTransitionsTheme pageTransitionsTheme = null,
 
             tabBarTheme = tabBarTheme ?? new TabBarTheme();
             cardTheme = cardTheme ?? new CardTheme();
+            chipTheme = chipTheme ?? ChipThemeData.fromDefaults(
+                secondaryColor: primaryColor,
+                brightness: brightness,
+                labelStyle: textTheme.body2
+            );
             dialogTheme = dialogTheme ?? new DialogTheme();
 
             D.assert(brightness != null);
             D.assert(buttonColor != null);
             D.assert(tabBarTheme != null);
             D.assert(cardTheme != null);
+            D.assert(chipTheme != null);
             D.assert(dialogTheme != null);
 
             this.brightness = brightness ?? Brightness.light;
             this.accentIconTheme = accentIconTheme;
             this.tabBarTheme = tabBarTheme;
             this.cardTheme = cardTheme;
+            this.chipTheme = chipTheme;
             this.platform = platform.Value;
             this.materialTapTargetSize = materialTapTargetSize ?? MaterialTapTargetSize.padded;
             this.pageTransitionsTheme = pageTransitionsTheme;
             IconThemeData accentIconTheme = null,
             TabBarTheme tabBarTheme = null,
             CardTheme cardTheme = null,
+            ChipThemeData chipTheme = null,
             RuntimePlatform? platform = null,
             MaterialTapTargetSize? materialTapTargetSize = null,
             PageTransitionsTheme pageTransitionsTheme = null,
             D.assert(buttonColor != null);
             D.assert(tabBarTheme != null);
             D.assert(cardTheme != null);
+            D.assert(chipTheme != null);
             D.assert(dialogTheme != null);
 
             return new ThemeData(
                 accentIconTheme: accentIconTheme,
                 tabBarTheme: tabBarTheme,
                 cardTheme: cardTheme,
+                chipTheme: chipTheme,
                 platform: platform,
                 materialTapTargetSize: materialTapTargetSize,
                 pageTransitionsTheme: pageTransitionsTheme,
         public readonly TabBarTheme tabBarTheme;
         
         public readonly CardTheme cardTheme;
+        public readonly ChipThemeData chipTheme;
 
         public readonly RuntimePlatform platform;
 
             IconThemeData accentIconTheme = null,
             TabBarTheme tabBarTheme = null,
             CardTheme cardTheme = null,
+            ChipThemeData chipTheme = null,
             RuntimePlatform? platform = null,
             MaterialTapTargetSize? materialTapTargetSize = null,
             PageTransitionsTheme pageTransitionsTheme = null,
                 accentIconTheme: accentIconTheme ?? this.accentIconTheme,
                 tabBarTheme: tabBarTheme ?? this.tabBarTheme,
                 cardTheme: cardTheme ?? this.cardTheme,
+                chipTheme: chipTheme ?? this.chipTheme,
                 platform: platform ?? this.platform,
                 materialTapTargetSize: materialTapTargetSize ?? this.materialTapTargetSize,
                 pageTransitionsTheme: pageTransitionsTheme ?? this.pageTransitionsTheme,
                 accentIconTheme: IconThemeData.lerp(a.accentIconTheme, b.accentIconTheme, t),
                 tabBarTheme: TabBarTheme.lerp(a.tabBarTheme, b.tabBarTheme, t),
                 cardTheme: CardTheme.lerp(a.cardTheme, b.cardTheme, t),
+                chipTheme: ChipThemeData.lerp(a.chipTheme, b.chipTheme, t),
                 platform: t < 0.5 ? a.platform : b.platform,
                 materialTapTargetSize: t < 0.5 ? a.materialTapTargetSize : b.materialTapTargetSize,
                 pageTransitionsTheme: t < 0.5 ? a.pageTransitionsTheme : b.pageTransitionsTheme,
                    other.accentIconTheme == this.accentIconTheme &&
                    other.tabBarTheme == this.tabBarTheme &&
                    other.cardTheme == this.cardTheme &&
+                   other.chipTheme == this.chipTheme &&
                    other.platform == this.platform &&
                    other.materialTapTargetSize == this.materialTapTargetSize &&
                    other.pageTransitionsTheme == this.pageTransitionsTheme &&
                 hashCode = (hashCode * 397) ^ this.accentIconTheme.GetHashCode();
                 hashCode = (hashCode * 397) ^ this.tabBarTheme.GetHashCode();
                 hashCode = (hashCode * 397) ^ this.cardTheme.GetHashCode();
+                hashCode = (hashCode * 397) ^ this.chipTheme.GetHashCode();
                 hashCode = (hashCode * 397) ^ this.platform.GetHashCode();
                 hashCode = (hashCode * 397) ^ this.materialTapTargetSize.GetHashCode();
                 hashCode = (hashCode * 397) ^ this.pageTransitionsTheme.GetHashCode();
             properties.add(new DiagnosticsProperty<IconThemeData>("accentIconTheme", this.accentIconTheme));
             properties.add(new DiagnosticsProperty<TabBarTheme>("tabBarTheme", this.tabBarTheme));
             properties.add(new DiagnosticsProperty<CardTheme>("cardTheme", this.cardTheme));
+            properties.add(new DiagnosticsProperty<ChipThemeData>("chipTheme", this.chipTheme));
             properties.add(
                 new DiagnosticsProperty<MaterialTapTargetSize>("materialTapTargetSize", this.materialTapTargetSize));
             properties.add(

Runtime/painting/basic_types.cs

     public enum RenderComparison {
         identical,
         metadata,
+        function,
         paint,
         layout,
     }

Runtime/painting/text_span.cs

         public readonly string text;
         public readonly List<TextSpan> children;
         public readonly GestureRecognizer recognizer;
+        public readonly HoverRecognizer hoverRecognizer;
-            GestureRecognizer recognizer = null) {
+            GestureRecognizer recognizer = null, HoverRecognizer hoverRecognizer = null) {
+            this.hoverRecognizer = hoverRecognizer;
         }
 
         public void build(ParagraphBuilder builder, float textScaleFactor = 1.0f) {
 
             if (hasStyle) {
                 builder.pop();
+            }
+        }
+
+        public bool hasHoverRecognizer {
+            get {
+                bool need = false;
+                this.visitTextSpan((text) => {
+                    if (text.hoverRecognizer != null) {
+                        need = true;
+                        return false;
+                    }
+                    return true;
+                });
+                return need;
             }
         }
 
             RenderComparison result = Equals(this.recognizer, other.recognizer)
                 ? RenderComparison.identical
                 : RenderComparison.metadata;
+
+            if (!Equals(this.hoverRecognizer, other.hoverRecognizer)) {
+                result = RenderComparison.function > result ? RenderComparison.function : result;
+            }
+            
             if (this.style != null) {
                 var candidate = this.style.compareTo(other.style);
                 if (candidate > result) {

Runtime/rendering/image.cs

                 this.markNeedsLayout();
             }
         }
+        
+        
+        ColorFilter _colorFilter;
+
+        void _updateColorFilter() {
+            if (this._color == null)
+                this._colorFilter = null;
+            else
+                this._colorFilter = ColorFilter.mode(this._color, this._colorBlendMode);
+        }
 
         Color _color;
 
                 rect: offset & this.size,
                 image: this._image,
                 scale: this._scale,
-                // colorFilter: this._colorFilter,
+                colorFilter: this._colorFilter,
                 fit: this._fit,
                 alignment: this._alignment,
                 centerSlice: this._centerSlice,

Runtime/rendering/paragraph.cs

             this._selection = null;
             this.onSelectionChanged = onSelectionChanged;
             this.selectionColor = selectionColor;
+
+            this._resetHoverHandler();
         }
 
         public Action onSelectionChanged;
                     case RenderComparison.identical:
                     case RenderComparison.metadata:
                         return;
+                    case RenderComparison.function:
+                        this._textPainter.text = value;
+                        break;
                     case RenderComparison.paint:
                         this._textPainter.text = value;
                         this.markNeedsPaint();
                         this.markNeedsLayout();
                         break;
                 }
+
+                this._resetHoverHandler();
             }
         }
 
             }
         }
 
+        TextSpan _previousHoverSpan;
+        bool _pointerHoverInside;
+        bool _hasHoverRecognizer;
+
+        void _resetHoverHandler() {
+            this._hasHoverRecognizer = this._textPainter.text.hasHoverRecognizer;
+            this._previousHoverSpan = null;
+            this._pointerHoverInside = false;
+        }
+
         void _handleKeyEvent(RawKeyEvent keyEvent) {
             //only allow KCommand.copy
             if (keyEvent is RawKeyUpEvent) {
             this.onSelectionChanged?.Invoke();
         }
 
+
+        void _handlePointerHover(PointerEvent evt) {
+            if (!this._hasHoverRecognizer) {
+                return;
+            }
+
+            if (evt is PointerEnterEvent) {
+                this._pointerHoverInside = true;
+            }
+            else if (evt is PointerLeaveEvent) {
+                this._pointerHoverInside = false;
+                this._previousHoverSpan?.hoverRecognizer?.OnPointerLeave?.Invoke();
+                this._previousHoverSpan = null;
+            }
+            else if (evt is PointerHoverEvent && this._pointerHoverInside) {
+                this._layoutTextWithConstraints(this.constraints);
+                Offset offset = this.globalToLocal(evt.position);
+                TextPosition position = this._textPainter.getPositionForOffset(offset);
+                TextSpan span = this._textPainter.text.getSpanForPosition(position);
+
+                if (this._previousHoverSpan != span) {
+                    this._previousHoverSpan?.hoverRecognizer?.OnPointerLeave?.Invoke();
+                    span?.hoverRecognizer?.OnPointerEnter?.Invoke((PointerHoverEvent) evt);
+                    this._previousHoverSpan = span;
+                }
+            }
+        }
+
-            if (!(evt is PointerDownEvent)) {
+            if (evt is PointerDownEvent) {
+                this._layoutTextWithConstraints(this.constraints);
+                Offset offset = ((BoxHitTestEntry) entry).localPosition;
+                TextPosition position = this._textPainter.getPositionForOffset(offset);
+                TextSpan span = this._textPainter.text.getSpanForPosition(position);
+                span?.recognizer?.addPointer((PointerDownEvent) evt);
-            this._layoutTextWithConstraints(this.constraints);
-            Offset offset = ((BoxHitTestEntry) entry).localPosition;
-            TextPosition position = this._textPainter.getPositionForOffset(offset);
-            TextSpan span = this._textPainter.text.getSpanForPosition(position);
-            span?.recognizer?.addPointer((PointerDownEvent) evt);
+            this._handlePointerHover(evt);
         }
 
         protected override void performLayout() {
             foreach (var box in this._selectionRects) {
                 barPath.addRect(box.toRect().shift(effectiveOffset));
             }
+
             canvas.drawPath(barPath, paint);
         }
 

Runtime/widgets/binding.cs

 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.rendering;
 using Unity.UIWidgets.ui;
+using UnityEngine;
 
 namespace Unity.UIWidgets.widgets {
     public interface WidgetsBindingObserver {
 
         public bool removeObserver(WidgetsBindingObserver observer) {
             return this._observers.Remove(observer);
+        }
+
+        public void handlePopRoute() {
+            var idx = -1;
+            
+            void _handlePopRouteSub(bool result) {
+                if (!result) {
+                    idx++;
+                    if (idx >= this._observers.Count) {
+                        Application.Quit();
+                        return;
+                    }
+                    this._observers[idx].didPopRoute().Then(_handlePopRouteSub);
+                }
+            }
+            
+            _handlePopRouteSub(false);
         }
 
         public readonly WidgetInspectorService widgetInspectorService;

Samples/UIWidgetSample/txt/TextSpanGesture.cs

                                 color: Colors.green,
                                 decoration: TextDecoration.underline
                             )
-                          //  recognizer: this._longPressRecognizer
+                            //recognizer: this._longPressRecognizer
                         ),
                         new TextSpan(
                             text: " secret?"

Samples/UIWidgetsGallery/gallery/demos.cs

                     routeName: ContactsDemo.routeName,
                     buildRoute: (BuildContext context) => new ContactsDemo()
                 ),
-//                new GalleryDemo(
-//                    title: "Animation",
-//                    subtitle: "Section organizer",
-//                    icon: GalleryIcons.animation,
-//                    category: GalleryDemoCategory._kDemos,
-//                    routeName: AnimationDemo.routeName,
-//                    buildRoute: (BuildContext context) => new AnimationDemo()
-//                ),
-//
-//                // Style
+                new GalleryDemo(
+                    title: "Animation",
+                    subtitle: "Section organizer",
+                    icon: GalleryIcons.animation,
+                    category: DemoUtils._kDemos,
+                    routeName: AnimationDemo.routeName,
+                    buildRoute: (BuildContext context) => new AnimationDemo()
+                ),
+
+                // Style
                 new GalleryDemo(
                     title: "Colors",
                     subtitle: "All of the predefined colors",
                     documentationUrl: "https://docs.flutter.io/flutter/material/BottomNavigationBar-class.html",
                     buildRoute: (BuildContext context) => new BottomNavigationDemo()
                 ),
-//                new GalleryDemo(
-//                    title: "Bottom sheet: Modal",
-//                    subtitle: "A dismissable bottom sheet",
-//                    icon: GalleryIcons.bottom_sheets,
-//                    category: GalleryDemoCategory._kMaterialComponents,
-//                    routeName: ModalBottomSheetDemo.routeName,
-//                    documentationUrl: "https://docs.flutter.io/flutter/material/showModalBottomSheet.html",
-//                    buildRoute: (BuildContext context) => ModalBottomSheetDemo()
-//                ),
-//                new GalleryDemo(
-//                    title: "Bottom sheet: Persistent",
-//                    subtitle: "A bottom sheet that sticks around",
-//                    icon: GalleryIcons.bottom_sheet_persistent,
-//                    category: GalleryDemoCategory._kMaterialComponents,
-//                    routeName: PersistentBottomSheetDemo.routeName,
-//                    documentationUrl: "https://docs.flutter.io/flutter/material/ScaffoldState/showBottomSheet.html",
-//                    buildRoute: (BuildContext context) => PersistentBottomSheetDemo()
-//                ),
+                new GalleryDemo(
+                    title: "Bottom sheet: Modal",
+                    subtitle: "A dismissable bottom sheet",
+                    icon: GalleryIcons.bottom_sheets,
+                    category: _kMaterialComponents,
+                    routeName: ModalBottomSheetDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/showModalBottomSheet.html",
+                    buildRoute: (BuildContext context) => new ModalBottomSheetDemo()
+                ),
+                new GalleryDemo(
+                    title: "Bottom sheet: Persistent",
+                    subtitle: "A bottom sheet that sticks around",
+                    icon: GalleryIcons.bottom_sheet_persistent,
+                    category: _kMaterialComponents,
+                    routeName: PersistentBottomSheetDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/ScaffoldState/showBottomSheet.html",
+                    buildRoute: (BuildContext context) => new PersistentBottomSheetDemo()
+                ),
                 new GalleryDemo(
                     title: "Buttons",
                     subtitle: "Flat, raised, dropdown, and more",
                     buildRoute: (BuildContext context) => new ButtonsDemo()
                 ),
-//                new GalleryDemo(
-//                    title: "Buttons: Floating Action Button",
-//                    subtitle: "FAB with transitions",
-//                    icon: GalleryIcons.buttons,
-//                    category: GalleryDemoCategory._kMaterialComponents,
-//                    routeName: TabsFabDemo.routeName,
-//                    documentationUrl: "https://docs.flutter.io/flutter/material/FloatingActionButton-class.html",
-//                    buildRoute: (BuildContext context) => TabsFabDemo()
-//                ),
+                new GalleryDemo(
+                    title: "Buttons: Floating Action Button",
+                    subtitle: "FAB with transitions",
+                    icon: GalleryIcons.buttons,
+                    category: _kMaterialComponents,
+                    routeName: TabsFabDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/FloatingActionButton-class.html",
+                    buildRoute: (BuildContext context) => new TabsFabDemo()
+                ),
                 new GalleryDemo(
                     title: "Cards",
                     subtitle: "Baseline cards with rounded corners",
                     documentationUrl: "https://docs.flutter.io/flutter/material/Card-class.html",
                     buildRoute: (BuildContext context) => new CardsDemo()
                 ),
-//                new GalleryDemo(
-//                    title: "Chips",
-//                    subtitle: "Labeled with delete buttons and avatars",
-//                    icon: GalleryIcons.chips,
-//                    category: GalleryDemoCategory._kMaterialComponents,
-//                    routeName: ChipDemo.routeName,
-//                    documentationUrl: "https://docs.flutter.io/flutter/material/Chip-class.html",
-//                    buildRoute: (BuildContext context) => ChipDemo()
-//                ),
+                new GalleryDemo(
+                    title: "Chips",
+                    subtitle: "Labeled with delete buttons and avatars",
+                    icon: GalleryIcons.chips,
+                    category: _kMaterialComponents,
+                    routeName: ChipDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Chip-class.html",
+                    buildRoute: (BuildContext context) => new ChipDemo()
+                ),
 //                new GalleryDemo(
 //                    title: "Data tables",
 //                    subtitle: "Rows and columns",

Runtime/gestures/hover.cs

+using Unity.UIWidgets.foundation;
+
+namespace Unity.UIWidgets.gestures {
+    
+    public delegate void PointerHoverEnterCallback(PointerHoverEvent evt);
+
+    public delegate void PointerHoverLeaveCallback();
+    
+    public class HoverRecognizer : DiagnosticableTree {
+        public HoverRecognizer(object debugOwner = null) {
+            this.debugOwner = debugOwner;
+        }
+
+        readonly object debugOwner;
+
+        public PointerHoverEnterCallback OnPointerEnter;
+
+        public PointerHoverLeaveCallback OnPointerLeave;
+        
+        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            properties.add(new DiagnosticsProperty<object>("debugOwner", this.debugOwner,
+                defaultValue: Diagnostics.kNullDefaultValue));
+        }
+    }
+}

Runtime/gestures/hover.cs.meta

+fileFormatVersion: 2
+guid: 0482dd5944bd647da9d8a1a32a86801b
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Runtime/material/chip.cs.meta

+fileFormatVersion: 2
+guid: d4ca6b86209d4615b9aba98d6d112673
+timeCreated: 1555477997

Runtime/material/chip_theme.cs

+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.service;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using TextStyle = Unity.UIWidgets.painting.TextStyle;
+
+namespace Unity.UIWidgets.material {
+    public class ChipTheme : InheritedWidget {
+        public ChipTheme(
+            Key key = null,
+            ChipThemeData data = null,
+            Widget child = null
+        ) : base(key: key, child: child) {
+            D.assert(child != null);
+            D.assert(data != null);
+            this.data = data;
+        }
+
+        public readonly ChipThemeData data;
+
+        public static ChipThemeData of(BuildContext context) {
+            ChipTheme inheritedTheme = (ChipTheme) context.inheritFromWidgetOfExactType(typeof(ChipTheme));
+            return inheritedTheme?.data ?? Theme.of(context).chipTheme;
+        }
+
+        public override bool updateShouldNotify(InheritedWidget _oldWidget) {
+            ChipTheme oldWidget = _oldWidget as ChipTheme;
+            return this.data != oldWidget.data;
+        }
+    }
+
+    public class ChipThemeData : Diagnosticable {
+        public ChipThemeData(
+            Color backgroundColor = null,
+            Color deleteIconColor = null,
+            Color disabledColor = null,
+            Color selectedColor = null,
+            Color secondarySelectedColor = null,
+            EdgeInsets labelPadding = null,
+            EdgeInsets padding = null,
+            ShapeBorder shape = null,
+            TextStyle labelStyle = null,
+            TextStyle secondaryLabelStyle = null,
+            Brightness? brightness = null,
+            float? elevation = null,
+            float? pressElevation = null
+        ) {
+            D.assert(backgroundColor != null);
+            D.assert(disabledColor != null);
+            D.assert(selectedColor != null);
+            D.assert(secondarySelectedColor != null);
+            D.assert(labelPadding != null);
+            D.assert(padding != null);
+            D.assert(shape != null);
+            D.assert(labelStyle != null);
+            D.assert(secondaryLabelStyle != null);
+            D.assert(brightness != null);
+            this.backgroundColor = backgroundColor;
+            this.deleteIconColor = deleteIconColor;
+            this.disabledColor = disabledColor;
+            this.selectedColor = selectedColor;
+            this.secondarySelectedColor = secondarySelectedColor;
+            this.labelPadding = labelPadding;
+            this.padding = padding;
+            this.shape = shape;
+            this.labelStyle = labelStyle;
+            this.secondaryLabelStyle = secondaryLabelStyle;
+            this.brightness = brightness;
+            this.elevation = elevation;
+            this.pressElevation = pressElevation;
+        }
+
+        public static ChipThemeData fromDefaults(
+            Brightness? brightness = null,
+            Color primaryColor = null,
+            Color secondaryColor = null,
+            TextStyle labelStyle = null
+        ) {
+            D.assert(primaryColor != null || brightness != null,
+                "One of primaryColor or brightness must be specified");
+            D.assert(primaryColor == null || brightness == null,
+                "Only one of primaryColor or brightness may be specified");
+            D.assert(secondaryColor != null);
+            D.assert(labelStyle != null);
+
+            if (primaryColor != null) {
+                brightness = ThemeData.estimateBrightnessForColor(primaryColor);
+            }
+
+            const int backgroundAlpha = 0x1f; // 12%
+            const int deleteIconAlpha = 0xde; // 87%
+            const int disabledAlpha = 0x0c; // 38% * 12% = 5%
+            const int selectAlpha = 0x3d; // 12% + 12% = 24%
+            const int textLabelAlpha = 0xde; // 87%
+            ShapeBorder shape = new StadiumBorder();
+            EdgeInsets labelPadding = EdgeInsets.symmetric(horizontal: 8.0f);
+            EdgeInsets padding = EdgeInsets.all(4.0f);
+
+            primaryColor = primaryColor ?? (brightness == Brightness.light ? Colors.black : Colors.white);
+            Color backgroundColor = primaryColor.withAlpha(backgroundAlpha);
+            Color deleteIconColor = primaryColor.withAlpha(deleteIconAlpha);
+            Color disabledColor = primaryColor.withAlpha(disabledAlpha);
+            Color selectedColor = primaryColor.withAlpha(selectAlpha);
+            Color secondarySelectedColor = secondaryColor.withAlpha(selectAlpha);
+            TextStyle secondaryLabelStyle = labelStyle.copyWith(
+                color: secondaryColor.withAlpha(textLabelAlpha)
+            );
+            labelStyle = labelStyle.copyWith(color: primaryColor.withAlpha(textLabelAlpha));
+
+            return new ChipThemeData(
+                backgroundColor: backgroundColor,
+                deleteIconColor: deleteIconColor,
+                disabledColor: disabledColor,
+                selectedColor: selectedColor,
+                secondarySelectedColor: secondarySelectedColor,
+                labelPadding: labelPadding,
+                padding: padding,
+                shape: shape,
+                labelStyle: labelStyle,
+                secondaryLabelStyle: secondaryLabelStyle,
+                brightness: brightness
+            );
+        }
+
+        public readonly Color backgroundColor;
+
+        public readonly Color deleteIconColor;
+
+        public readonly Color disabledColor;
+
+        public readonly Color selectedColor;
+
+        public readonly Color secondarySelectedColor;
+
+        public readonly EdgeInsets labelPadding;
+
+        public readonly EdgeInsets padding;
+
+        public readonly ShapeBorder shape;
+
+        public readonly TextStyle labelStyle;
+
+        public readonly TextStyle secondaryLabelStyle;
+
+        public readonly Brightness? brightness;
+
+        public readonly float? elevation;
+
+        public readonly float? pressElevation;
+
+        public ChipThemeData copyWith(
+            Color backgroundColor = null,
+            Color deleteIconColor = null,
+            Color disabledColor = null,
+            Color selectedColor = null,
+            Color secondarySelectedColor = null,
+            EdgeInsets labelPadding = null,
+            EdgeInsets padding = null,
+            ShapeBorder shape = null,
+            TextStyle labelStyle = null,
+            TextStyle secondaryLabelStyle = null,
+            Brightness? brightness = null,
+            float? elevation = null,
+            float? pressElevation = null
+        ) {
+            return new ChipThemeData(
+                backgroundColor: backgroundColor ?? this.backgroundColor,
+                deleteIconColor: deleteIconColor ?? this.deleteIconColor,
+                disabledColor: disabledColor ?? this.disabledColor,
+                selectedColor: selectedColor ?? this.selectedColor,
+                secondarySelectedColor: secondarySelectedColor ?? this.secondarySelectedColor,
+                labelPadding: labelPadding ?? this.labelPadding,
+                padding: padding ?? this.padding,
+                shape: shape ?? this.shape,
+                labelStyle: labelStyle ?? this.labelStyle,
+                secondaryLabelStyle: secondaryLabelStyle ?? this.secondaryLabelStyle,
+                brightness: brightness ?? this.brightness,
+                elevation: elevation ?? this.elevation,
+                pressElevation: pressElevation ?? this.pressElevation
+            );
+        }
+
+        public static ChipThemeData lerp(ChipThemeData a, ChipThemeData b, float t) {
+            D.assert(t != null);
+            if (a == null && b == null) {
+                return null;
+            }
+
+            return new ChipThemeData(
+                backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
+                deleteIconColor: Color.lerp(a?.deleteIconColor, b?.deleteIconColor, t),
+                disabledColor: Color.lerp(a?.disabledColor, b?.disabledColor, t),
+                selectedColor: Color.lerp(a?.selectedColor, b?.selectedColor, t),
+                secondarySelectedColor: Color.lerp(a?.secondarySelectedColor, b?.secondarySelectedColor, t),
+                labelPadding: EdgeInsets.lerp(a?.labelPadding, b?.labelPadding, t),
+                padding: EdgeInsets.lerp(a?.padding, b?.padding, t),
+                shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
+                labelStyle: TextStyle.lerp(a?.labelStyle, b?.labelStyle, t),
+                secondaryLabelStyle: TextStyle.lerp(a?.secondaryLabelStyle, b?.secondaryLabelStyle, t),
+                brightness: t < 0.5f ? a?.brightness ?? Brightness.light : b?.brightness ?? Brightness.light,
+                elevation: MathUtils.lerpFloat(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                pressElevation: MathUtils.lerpFloat(a?.pressElevation ?? 0.0f, b?.pressElevation ?? 0.0f, t)
+            );
+        }
+
+        public override int GetHashCode() {
+            var hashCode = this.backgroundColor.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.deleteIconColor.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.disabledColor.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.selectedColor.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.secondarySelectedColor.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.labelPadding.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.padding.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.shape.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.labelStyle.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.secondaryLabelStyle.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.brightness.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.elevation.GetHashCode();
+            hashCode = (hashCode * 397) ^ this.pressElevation.GetHashCode();
+            return hashCode;
+        }
+
+        public bool Equals(ChipThemeData other) {
+            return other.backgroundColor == this.backgroundColor
+                   && other.deleteIconColor == this.deleteIconColor
+                   && other.disabledColor == this.disabledColor
+                   && other.selectedColor == this.selectedColor
+                   && other.secondarySelectedColor == this.secondarySelectedColor
+                   && other.labelPadding == this.labelPadding
+                   && other.padding == this.padding
+                   && other.shape == this.shape
+                   && other.labelStyle == this.labelStyle
+                   && other.secondaryLabelStyle == this.secondaryLabelStyle
+                   && other.brightness == this.brightness
+                   && other.elevation == this.elevation
+                   && other.pressElevation == this.pressElevation;
+        }
+
+        public override bool Equals(object obj) {
+            if (ReferenceEquals(null, obj)) {
+                return false;
+            }
+
+            if (ReferenceEquals(this, obj)) {
+                return true;
+            }
+
+            if (obj.GetType() != this.GetType()) {
+                return false;
+            }
+
+            return this.Equals((ChipThemeData) obj);
+        }
+
+        public static bool operator ==(ChipThemeData left, ChipThemeData right) {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(ChipThemeData left, ChipThemeData right) {
+            return !Equals(left, right);
+        }
+
+        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            ThemeData defaultTheme = ThemeData.fallback();
+            ChipThemeData defaultData = fromDefaults(
+                secondaryColor: defaultTheme.primaryColor,
+                brightness: defaultTheme.brightness,
+                labelStyle: defaultTheme.textTheme.body2
+            );
+            properties.add(new DiagnosticsProperty<Color>("backgroundColor", this.backgroundColor,
+                defaultValue: defaultData.backgroundColor));
+            properties.add(new DiagnosticsProperty<Color>("deleteIconColor", this.deleteIconColor,
+                defaultValue: defaultData.deleteIconColor));
+            properties.add(new DiagnosticsProperty<Color>("disabledColor", this.disabledColor,
+                defaultValue: defaultData.disabledColor));
+            properties.add(new DiagnosticsProperty<Color>("selectedColor", this.selectedColor,
+                defaultValue: defaultData.selectedColor));
+            properties.add(new DiagnosticsProperty<Color>("secondarySelectedColor", this.secondarySelectedColor,
+                defaultValue: defaultData.secondarySelectedColor));
+            properties.add(new DiagnosticsProperty<EdgeInsets>("labelPadding", this.labelPadding,
+                defaultValue: defaultData.labelPadding));
+            properties.add(
+                new DiagnosticsProperty<EdgeInsets>("padding", this.padding, defaultValue: defaultData.padding));
+            properties.add(new DiagnosticsProperty<ShapeBorder>("shape", this.shape, defaultValue: defaultData.shape));
+            properties.add(new DiagnosticsProperty<TextStyle>("labelStyle", this.labelStyle,
+                defaultValue: defaultData.labelStyle));
+            properties.add(new DiagnosticsProperty<TextStyle>("secondaryLabelStyle", this.secondaryLabelStyle,
+                defaultValue: defaultData.secondaryLabelStyle));
+            properties.add(new EnumProperty<Brightness?>("brightness", this.brightness,
+                defaultValue: defaultData.brightness));
+            properties.add(new FloatProperty("elevation", this.elevation, defaultValue: defaultData.elevation));
+            properties.add(new FloatProperty("pressElevation", this.pressElevation,
+                defaultValue: defaultData.pressElevation));
+        }
+    }
+}

Runtime/material/chip_theme.cs.meta

+fileFormatVersion: 2
+guid: 4d46bfb5d5bb492e92f07114849df905
+timeCreated: 1556165564

Runtime/material/circle_avatar.cs

+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.service;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using TextStyle = Unity.UIWidgets.painting.TextStyle;
+
+namespace UIWidgetsGallery.gallery {
+    public class CircleAvatar : StatelessWidget {
+        public CircleAvatar(
+            Key key = null,
+            Widget child = null,
+            Color backgroundColor = null,
+            ImageProvider backgroundImage = null,
+            Color foregroundColor = null,
+            float? radius = null,
+            float? minRadius = null,
+            float? maxRadius = null
+        ) : base(key: key) {
+            D.assert(radius == null || (minRadius == null && maxRadius == null));
+            this.child = child;
+            this.backgroundColor = backgroundColor;
+            this.backgroundImage = backgroundImage;
+            this.foregroundColor = foregroundColor;
+            this.radius = radius;
+            this.minRadius = minRadius;
+            this.maxRadius = maxRadius;
+        }
+
+        public readonly Widget child;
+
+        public readonly Color backgroundColor;
+
+        public readonly Color foregroundColor;
+
+        public readonly ImageProvider backgroundImage;
+
+        public readonly float? radius;
+
+        public readonly float? minRadius;
+
+        public readonly float? maxRadius;
+
+        const float _defaultRadius = 20.0f;
+
+        const float _defaultMinRadius = 0.0f;
+
+        const float _defaultMaxRadius = float.PositiveInfinity;
+
+        float _minDiameter {
+            get {
+                if (this.radius == null && this.minRadius == null && this.maxRadius == null) {
+                    return _defaultRadius * 2.0f;
+                }
+
+                return 2.0f * (this.radius ?? this.minRadius ?? _defaultMinRadius);
+            }
+        }
+
+        float _maxDiameter {
+            get {
+                if (this.radius == null && this.minRadius == null && this.maxRadius == null) {
+                    return _defaultRadius * 2.0f;
+                }
+
+                return 2.0f * (this.radius ?? this.maxRadius ?? _defaultMaxRadius);
+            }
+        }
+
+        public override Widget build(BuildContext context) {
+            D.assert(WidgetsD.debugCheckHasMediaQuery(context));
+            ThemeData theme = Theme.of(context);
+            TextStyle textStyle = theme.primaryTextTheme.subhead.copyWith(color: this.foregroundColor);
+            Color effectiveBackgroundColor = this.backgroundColor;
+            if (effectiveBackgroundColor == null) {
+                switch (ThemeData.estimateBrightnessForColor(textStyle.color)) {
+                    case Brightness.dark:
+                        effectiveBackgroundColor = theme.primaryColorLight;
+                        break;
+                    case Brightness.light:
+                        effectiveBackgroundColor = theme.primaryColorDark;
+                        break;
+                }
+            }
+            else if (this.foregroundColor == null) {
+                switch (ThemeData.estimateBrightnessForColor(this.backgroundColor)) {
+                    case Brightness.dark:
+                        textStyle = textStyle.copyWith(color: theme.primaryColorLight);
+                        break;
+                    case Brightness.light:
+                        textStyle = textStyle.copyWith(color: theme.primaryColorDark);
+                        break;
+                }
+            }
+
+            float minDiameter = this._minDiameter;
+            float maxDiameter = this._maxDiameter;
+            return new AnimatedContainer(
+                constraints: new BoxConstraints(
+                    minHeight: minDiameter,
+                    minWidth: minDiameter,
+                    maxWidth: maxDiameter,
+                    maxHeight: maxDiameter
+                ),
+                duration: Constants.kThemeChangeDuration,
+                decoration: new BoxDecoration(
+                    color: effectiveBackgroundColor,
+                    image: this.backgroundImage != null
+                        ? new DecorationImage(image: this.backgroundImage, fit: BoxFit.cover)
+                        : null,
+                    shape: BoxShape.circle
+                ),
+                child: this.child == null
+                    ? null
+                    : new Center(
+                        child: new MediaQuery(
+                            data: MediaQuery.of(context).copyWith(textScaleFactor: 1.0f),
+                            child: new IconTheme(
+                                data: theme.iconTheme.copyWith(color: textStyle.color),
+                                child: new DefaultTextStyle(
+                                    style: textStyle,
+                                    child: this.child
+                                )
+                            )
+                        )
+                    )
+            );
+        }
+    }
+}

Runtime/material/circle_avatar.cs.meta

+fileFormatVersion: 2
+guid: 32591e65e11049cab124c86bc8fe573c
+timeCreated: 1556169017

Samples/UIWidgetSample/HoverRecognizerSample.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.gestures;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using UnityEngine;
+
+namespace UIWidgetsSample {
+    public class HoverRecognizerSample : UIWidgetsSamplePanel {
+        protected override Widget createWidget() {
+            return new MaterialApp(
+                showPerformanceOverlay: false,
+                home: new HoverMainPanel()
+                );
+        }
+
+        protected override void OnEnable() {
+            FontManager.instance.addFont(Resources.Load<Font>(path: "MaterialIcons-Regular"), "Material Icons");
+            base.OnEnable();
+        }
+    }
+
+    class HoverMainPanel : StatefulWidget {
+        public override State createState() {
+            return new HoverMainPanelState();
+        }
+    }
+
+    class HoverMainPanelState : State<HoverMainPanel> {
+        bool hoverActivated = false;
+        
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                appBar: new AppBar(
+                    title: new Center(
+                        child: new Text("Test Hover Widget")
+                    )
+                ),
+                body: new Card(
+                    color: Colors.white,
+                    child: new Center(
+                        child: new Column(
+                            mainAxisSize: MainAxisSize.min,
+                            crossAxisAlignment: CrossAxisAlignment.center,
+                            children: new List<Widget> {
+                                new Icon(this.hoverActivated ? Unity.UIWidgets.material.Icons.pool : Unity.UIWidgets.material.Icons.directions_walk, size: 128.0f),
+                                new RichText(
+                                    text: new TextSpan(
+                                        text: "Test <",
+                                        style: new TextStyle(color: Colors.black),
+                                        children: new List<TextSpan>() {
+                                            new TextSpan(
+                                                text: "Hover Me",
+                                                style: new TextStyle(
+                                                    color: Colors.green,
+                                                    decoration: TextDecoration.underline
+                                                ),
+                                                hoverRecognizer: new HoverRecognizer {
+                                                    OnPointerEnter = evt => {
+                                                        this.setState(() => { this.hoverActivated = true; });
+                                                    },
+                                                    OnPointerLeave = () => {
+                                                        this.setState(() => { this.hoverActivated = false;});
+                                                    }
+                                                }
+                                            ),
+                                            new TextSpan(
+                                                text: ">"
+                                            )
+                                        }
+                                    )
+                                )
+                            }
+                        )
+                    )
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetSample/HoverRecognizerSample.cs.meta

+fileFormatVersion: 2
+guid: aeab7b6e566d741a8a11a4400d52e708
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

Samples/UIWidgetsGallery/demo/animation.meta

+fileFormatVersion: 2
+guid: 4861503ddfc74b9ba36f159521c79b65
+timeCreated: 1554970886

Samples/UIWidgetsGallery/demo/animation_demo.cs

+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.widgets;
+
+namespace UIWidgetsGallery.gallery {
+    public class AnimationDemo : StatelessWidget {
+        public AnimationDemo(Key key = null) : base(key: key) {
+        }
+
+        public const string routeName = "/animation";
+
+        public override Widget build(BuildContext context) {
+            return new AnimationDemoHome();
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/animation_demo.cs.meta

+fileFormatVersion: 2
+guid: f13faff4d2b84ce0935236f3b953849f
+timeCreated: 1554969121

Samples/UIWidgetsGallery/demo/material/chip_demo.cs

+using System.Collections.Generic;
+using System.Linq;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+
+namespace UIWidgetsGallery.gallery {
+    class ChipDemoUtils {
+        public static readonly List<string> _defaultMaterials = new List<string> {
+            "poker",
+            "tortilla",
+            "fish and",
+            "micro",
+            "wood"
+        };
+
+        public static readonly List<string> _defaultActions = new List<string> {
+            "flake",
+            "cut",
+            "fragment",
+            "splinter",
+            "nick",
+            "fry",
+            "solder",
+            "cash in",
+            "eat"
+        };
+
+        public static readonly Dictionary<string, string> _results = new Dictionary<string, string> {
+            {"flake", "flaking"},
+            {"cut", "cutting"},
+            {"fragment", "fragmenting"},
+            {"splinter", "splintering"},
+            {"nick", "nicking"},
+            {"fry", "frying"},
+            {"solder", "soldering"},
+            {"cash in", "cashing in"},
+            {"eat", "eating"}
+        };
+
+        public static readonly List<string> _defaultTools = new List<string> {
+            "hammer",
+            "chisel",
+            "fryer",
+            "fabricator",
+            "customer"
+        };
+
+        public static readonly Dictionary<string, string> _avatars = new Dictionary<string, string> {
+            {"hammer", "people/square/ali"},
+            {"chisel", "people/square/sandra"},
+            {"fryer", "people/square/trevor"},
+            {"fabricator", "people/square/stella"},
+            {"customer", "people/square/peter"}
+        };
+
+        public static readonly Dictionary<string, HashSet<string>> _toolActions =
+            new Dictionary<string, HashSet<string>> {
+                {"hammer", new HashSet<string>(new List<string> {"flake", "fragment", "splinter"})},
+                {"chisel", new HashSet<string>(new List<string> {"flake", "nick", "splinter"})},
+                {"fryer", new HashSet<string>(new List<string> {"fry"})},
+                {"fabricator", new HashSet<string>(new List<string> {"solder"})},
+                {"customer", new HashSet<string>(new List<string> {"cash in", "eat"})}
+            };
+
+        public static readonly Dictionary<string, HashSet<string>> _materialActions =
+            new Dictionary<string, HashSet<string>> {
+                {"poker", new HashSet<string>(new List<string> {"cash in"})},
+                {"tortilla", new HashSet<string>(new List<string> {"fry", "eat"})},
+                {"fish and", new HashSet<string>(new List<string> {"fry", "eat"})},
+                {"micro", new HashSet<string>(new List<string> {"solder", "fragment"})},
+                {"wood", new HashSet<string>(new List<string> {"flake", "cut", "splinter", "nick"})}
+            };
+    }
+
+
+    class _ChipsTile : StatelessWidget {
+        public _ChipsTile(
+            Key key = null,
+            string label = null,
+            List<Widget> children = null
+        ) : base(key: key) {
+            this.label = label;
+            this.children = children;
+        }
+
+        public readonly string label;
+        public readonly List<Widget> children;
+
+        public override Widget build(BuildContext context) {
+            List<Widget> cardChildren = new List<Widget> {
+                new Container(
+                    padding: EdgeInsets.only(top: 16.0f, bottom: 4.0f),
+                    alignment: Alignment.center,
+                    child: new Text(this.label, textAlign: TextAlign.left)
+                )
+            };
+            if (this.children.isNotEmpty()) {
+                cardChildren.Add(new Wrap(
+                    children: this.children.Select<Widget, Widget>((Widget chip) => {
+                        return new Padding(
+                            padding: EdgeInsets.all(2.0f),
+                            child: chip
+                        );
+                    }).ToList()));
+            }
+            else {
+                TextStyle textStyle = Theme.of(context).textTheme.caption.copyWith(fontStyle: FontStyle.italic);
+                cardChildren.Add(
+                    new Container(
+                        alignment: Alignment.center,
+                        constraints: new BoxConstraints(minWidth: 48.0f, minHeight: 48.0f),
+                        padding: EdgeInsets.all(8.0f),
+                        child: new Text("None", style: textStyle)
+                    )
+                );
+            }
+
+            return new Card(
+                child: new Column(
+                    mainAxisSize: MainAxisSize.min,
+                    children: cardChildren
+                )
+            );
+        }
+    }
+
+    public class ChipDemo : StatefulWidget {
+        public const string routeName = "/material/chip";
+
+        public override State createState() {
+            return new _ChipDemoState();
+        }
+    }
+
+    class _ChipDemoState : State<ChipDemo> {
+        public _ChipDemoState() {
+            this._reset();
+        }
+
+        HashSet<string> _materials = new HashSet<string>(new List<string> { });
+        string _selectedMaterial = "";
+        string _selectedAction = "";
+        HashSet<string> _tools = new HashSet<string>(new List<string> { });
+        HashSet<string> _selectedTools = new HashSet<string>(new List<string> { });
+        HashSet<string> _actions = new HashSet<string>(new List<string> { });
+        bool _showShapeBorder = false;
+
+        void _reset() {
+            this._materials.Clear();
+            this._materials.UnionWith(ChipDemoUtils._defaultMaterials);
+            this._actions.Clear();
+            this._actions.UnionWith(ChipDemoUtils._defaultActions);
+            this._tools.Clear();
+            this._tools.UnionWith(ChipDemoUtils._defaultTools);
+            this._selectedMaterial = "";
+            this._selectedAction = "";
+            this._selectedTools.Clear();
+        }
+
+        void _removeMaterial(string name) {
+            this._materials.Remove(name);
+            if (this._selectedMaterial == name) {
+                this._selectedMaterial = "";
+            }
+        }
+
+        void _removeTool(string name) {
+            this._tools.Remove(name);
+            this._selectedTools.Remove(name);
+        }
+
+        string _capitalize(string name) {
+            D.assert(name != null && name.isNotEmpty());
+            return name.Substring(0, 1).ToUpper() + name.Substring(1);
+        }
+
+        Color _nameToColor(string name) {
+            D.assert(name.Length > 1);
+            int hash = name.GetHashCode() & 0xffff;
+            float hue = (360.0f * hash / (1 << 15)) % 360.0f;
+            return HSVColor.fromAHSV(1.0f, hue, 0.4f, 0.90f).toColor();
+        }
+
+        AssetImage _nameToAvatar(string name) {
+            D.assert(ChipDemoUtils._avatars.ContainsKey(name));
+            return new AssetImage(
+                ChipDemoUtils._avatars[name]
+            );
+        }
+
+        string _createResult() {
+            if (this._selectedAction.isEmpty()) {
+                return "";
+            }
+
+            return this._capitalize(ChipDemoUtils._results[this._selectedAction]) + "!";
+        }
+
+        public override Widget build(BuildContext context) {
+            List<Widget> chips = this._materials.Select<string, Widget>((string name) => {
+                return new Chip(
+                    key: Key.key(name),
+                    backgroundColor: this._nameToColor(name),
+                    label: new Text(this._capitalize(name)),
+                    onDeleted: () => { this.setState(() => { this._removeMaterial(name); }); }
+                );
+            }).ToList();
+
+            List<Widget> inputChips = this._tools.Select<string, Widget>((string name) => {
+                return new InputChip(
+                    key: ValueKey<string>.key(name),
+                    avatar: new CircleAvatar(
+                        backgroundImage: this._nameToAvatar(name)
+                    ),
+                    label: new Text(this._capitalize(name)),
+                    onDeleted: () => { this.setState(() => { this._removeTool(name); }); });
+            }).ToList();
+
+            List<Widget> choiceChips = this._materials.Select<string, Widget>((string name) => {
+                return new ChoiceChip(
+                    key: ValueKey<string>.key(name),
+                    backgroundColor: this._nameToColor(name),
+                    label: new Text(this._capitalize(name)),
+                    selected: this._selectedMaterial == name,
+                    onSelected: (bool value) => {
+                        this.setState(() => { this._selectedMaterial = value ? name : ""; });
+                    }
+                );
+            }).ToList();
+
+            List<Widget> filterChips = ChipDemoUtils._defaultTools.Select<string, Widget>((string name) => {
+                return new FilterChip(
+                    key: ValueKey<string>.key(name),
+                    label: new Text(this._capitalize(name)),
+                    selected: this._tools.Contains(name) ? this._selectedTools.Contains(name) : false,
+                    onSelected: !this._tools.Contains(name)
+                        ? (ValueChanged<bool>) null
+                        : (bool value) => {
+                            this.setState(() => {
+                                if (!value) {
+                                    this._selectedTools.Remove(name);
+                                }
+                                else {
+                                    this._selectedTools.Add(name);
+                                }
+                            });
+                        }
+                );
+            }).ToList();
+
+            HashSet<string> allowedActions = new HashSet<string>(new List<string> { });
+            if (this._selectedMaterial != null && this._selectedMaterial.isNotEmpty()) {
+                foreach (string tool in this._selectedTools) {
+                    allowedActions.UnionWith(ChipDemoUtils._toolActions[tool]);
+                }
+
+                allowedActions =
+                    new HashSet<string>(
+                        allowedActions.Intersect(ChipDemoUtils._materialActions[this._selectedMaterial]));
+            }
+
+            List<Widget> actionChips = allowedActions.Select<string, Widget>((string name) => {
+                return new ActionChip(
+                    label: new Text(this._capitalize(name)),
+                    onPressed: () => { this.setState(() => { this._selectedAction = name; }); }
+                );
+            }).ToList();
+
+            ThemeData theme = Theme.of(context);
+            List<Widget> tiles = new List<Widget> {
+                new SizedBox(height: 8.0f, width: 0.0f),
+                new _ChipsTile(label: "Available Materials (Chip)", children: chips),
+                new _ChipsTile(label: "Available Tools (InputChip)", children: inputChips),
+                new _ChipsTile(label: "Choose a Material (ChoiceChip)", children: choiceChips),
+                new _ChipsTile(label: "Choose Tools (FilterChip)", children: filterChips),
+                new _ChipsTile(label: "Perform Allowed Action (ActionChip)", children: actionChips),
+                new Divider(),
+                new Padding(
+                    padding: EdgeInsets.all(8.0f),
+                    child: new Center(
+                        child: new Text(this._createResult(),
+                            style: theme.textTheme.title
+                        )
+                    )
+                )
+            };
+
+            return new Scaffold(
+                appBar: new AppBar(
+                    title: new Text("Chips"),
+                    actions: new List<Widget> {
+                        new MaterialDemoDocumentationButton(ChipDemo.routeName),
+                        new IconButton(
+                            onPressed: () => {
+                                this.setState(() => { this._showShapeBorder = !this._showShapeBorder; });
+                            },
+                            icon: new Icon(Icons.vignette)
+                        )
+                    }
+                ),
+                body: new ChipTheme(
+                    data: this._showShapeBorder
+                        ? theme.chipTheme.copyWith(
+                            shape: new BeveledRectangleBorder(
+                                side: new BorderSide(width: 0.66f, style: BorderStyle.solid, color: Colors.grey),
+                                borderRadius: BorderRadius.circular(10.0f)
+                            ))
+                        : theme.chipTheme,
+                    child: new ListView(children: tiles)
+                ),
+                floatingActionButton: new FloatingActionButton(
+                    onPressed: () => this.setState(this._reset),
+                    child: new Icon(Icons.refresh)
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/material/chip_demo.cs.meta

+fileFormatVersion: 2
+guid: c65920c8c4b64c709b62586d0bde9579
+timeCreated: 1555411023

Samples/UIWidgetsGallery/demo/material/modal_bottom_sheet_demo.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+
+namespace UIWidgetsGallery.gallery {
+    public class ModalBottomSheetDemo : StatelessWidget {
+        public const string routeName = "/material/modal-bottom-sheet";
+
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                appBar: new AppBar(
+                    title: new Text("Modal bottom sheet"),
+                    actions: new List<Widget> {new MaterialDemoDocumentationButton(routeName)}
+                ),
+                body: new Center(
+                    child: new RaisedButton(
+                        child: new Text("SHOW BOTTOM SHEET"),
+                        onPressed: () => {
+                            BottomSheetUtils.showModalBottomSheet<object>(context: context,
+                                builder: (BuildContext _context) => {
+                                    return new Container(
+                                        child: new Padding(
+                                            padding: EdgeInsets.all(32.0f),
+                                            child: new Text("This is the modal bottom sheet. Tap anywhere to dismiss.",
+                                                textAlign: TextAlign.center,
+                                                style: new TextStyle(
+                                                    color: Theme.of(_context).accentColor,
+                                                    fontSize: 24.0f
+                                                )
+                                            )
+                                        )
+                                    );
+                                });
+                        }
+                    )
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/material/modal_bottom_sheet_demo.cs.meta

+fileFormatVersion: 2
+guid: 3c47b9e1a46e47858145acbe84590d05
+timeCreated: 1555059325

Samples/UIWidgetsGallery/demo/material/persistent_bottom_sheet_demo.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using DialogUtils = Unity.UIWidgets.material.DialogUtils;
+
+namespace UIWidgetsGallery.gallery {
+    public class PersistentBottomSheetDemo : StatefulWidget {
+        public const string routeName = "/material/persistent-bottom-sheet";
+
+        public override State createState() {
+            return new _PersistentBottomSheetDemoState();
+        }
+    }
+
+    class _PersistentBottomSheetDemoState : State<PersistentBottomSheetDemo> {
+        GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>.key();
+
+        VoidCallback _showBottomSheetCallback;
+
+        public override void initState() {
+            base.initState();
+            this._showBottomSheetCallback = this._showBottomSheet;
+        }
+
+        void _showBottomSheet() {
+            this.setState(() => {
+                // disable the button
+                this._showBottomSheetCallback = null;
+            });
+            this._scaffoldKey.currentState.showBottomSheet((BuildContext context) => {
+                    ThemeData themeData = Theme.of(this.context);
+                    return new Container(
+                        decoration: new BoxDecoration(
+                            border: new Border(top: new BorderSide(color: themeData.disabledColor))
+                        ),
+                        child: new Padding(
+                            padding: EdgeInsets.all(32.0f),
+                            child: new Text("This is a Material persistent bottom sheet. Drag downwards to dismiss it.",
+                                textAlign: TextAlign.center,
+                                style: new TextStyle(
+                                    color: themeData.accentColor,
+                                    fontSize: 24.0f
+                                )
+                            )
+                        )
+                    );
+                })
+                .closed.Then((value) => {
+                    if (this.mounted) {
+                        this.setState(() => {
+                            // re-enable the button
+                            this._showBottomSheetCallback = this._showBottomSheet;
+                        });
+                    }
+                });
+        }
+
+        void _showMessage() {
+            DialogUtils.showDialog(
+                context: this.context,
+                builder: (BuildContext context) => {
+                    return new AlertDialog(
+                        content: new Text("You tapped the floating action button."),
+                        actions: new List<Widget> {
+                            new FlatButton(
+                                onPressed: () => { Navigator.pop(context); },
+                                child: new Text("OK")
+                            )
+                        }
+                    );
+                }
+            );
+        }
+
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                key: this._scaffoldKey,
+                appBar: new AppBar(
+                    title: new Text("Persistent bottom sheet"),
+                    actions: new List<Widget> {
+                        new MaterialDemoDocumentationButton(PersistentBottomSheetDemo.routeName)
+                    }
+                ),
+                floatingActionButton: new FloatingActionButton(
+                    onPressed: this._showMessage,
+                    backgroundColor: Colors.redAccent,
+                    child: new Icon(
+                        Icons.add
+                    )
+                ),
+                body: new Center(
+                    child: new RaisedButton(
+                        onPressed: this._showBottomSheetCallback,
+                        child: new Text("SHOW BOTTOM SHEET")
+                    )
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/material/persistent_bottom_sheet_demo.cs.meta

+fileFormatVersion: 2
+guid: afb410d95c524a18b8761713f1335427
+timeCreated: 1555059936

Samples/UIWidgetsGallery/demo/material/tabs_fab_demo.cs

+using System.Collections.Generic;
+using System.Linq;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+
+namespace UIWidgetsGallery.gallery {
+    class TabsFabDemoUtils {
+        public const string _explanatoryText =
+            "When the Scaffold's floating action button changes, the new button fades and " +
+            "turns into view. In this demo, changing tabs can cause the app to be rebuilt " +
+            "with a FloatingActionButton that the Scaffold distinguishes from the others " +
+            "by its key.";
+
+        public static readonly List<_Page> _allPages = new List<_Page> {
+            new _Page(label: "Blue", colors: Colors.indigo, icon: Icons.add),
+            new _Page(label: "Eco", colors: Colors.green, icon: Icons.create),
+            new _Page(label: "No"),
+            new _Page(label: "Teal", colors: Colors.teal, icon: Icons.add),
+            new _Page(label: "Red", colors: Colors.red, icon: Icons.create)
+        };
+    }
+
+    class _Page {
+        public _Page(
+            string label,
+            MaterialColor colors = null,
+            IconData icon = null
+        ) {
+            this.label = label;
+            this.colors = colors;
+            this.icon = icon;
+        }
+
+        public readonly string label;
+        public readonly MaterialColor colors;
+        public readonly IconData icon;
+
+        public Color labelColor {
+            get { return this.colors != null ? this.colors.shade300 : Colors.grey.shade300; }
+        }
+
+        public bool fabDefined {
+            get { return this.colors != null && this.icon != null; }
+        }
+
+        public Color fabColor {
+            get { return this.colors.shade400; }
+        }
+
+        public Icon fabIcon {
+            get { return new Icon(this.icon); }
+        }
+
+        public Key fabKey {
+            get { return new ValueKey<Color>(this.fabColor); }
+        }
+    }
+
+
+    public class TabsFabDemo : StatefulWidget {
+        public const string routeName = "/material/tabs-fab";
+
+        public override State createState() {
+            return new _TabsFabDemoState();
+        }
+    }
+
+    class _TabsFabDemoState : SingleTickerProviderStateMixin<TabsFabDemo> {
+        GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>.key();
+
+        TabController _controller;
+        _Page _selectedPage;
+        bool _extendedButtons = false;
+
+        public override void initState() {
+            base.initState();
+            this._controller = new TabController(vsync: this, length: TabsFabDemoUtils._allPages.Count);
+            this._controller.addListener(this._handleTabSelection);
+            this._selectedPage = TabsFabDemoUtils._allPages[0];
+        }
+
+        public override void dispose() {
+            this._controller.dispose();
+            base.dispose();
+        }
+
+        void _handleTabSelection() {
+            this.setState(() => { this._selectedPage = TabsFabDemoUtils._allPages[this._controller.index]; });
+        }
+
+        void _showExplanatoryText() {
+            this._scaffoldKey.currentState.showBottomSheet((BuildContext context) => {
+                return new Container(
+                    decoration: new BoxDecoration(
+                        border: new Border(top: new BorderSide(color: Theme.of(this.context).dividerColor))
+                    ),
+                    child: new Padding(
+                        padding: EdgeInsets.all(32.0f),
+                        child: new Text(TabsFabDemoUtils._explanatoryText,
+                            style: Theme.of(this.context).textTheme.subhead)
+                    )
+                );
+            });
+        }
+
+        Widget buildTabView(_Page page) {
+            return new Builder(
+                builder: (BuildContext context) => {
+                    return new Container(
+                        key: new ValueKey<string>(page.label),
+                        padding: EdgeInsets.fromLTRB(48.0f, 48.0f, 48.0f, 96.0f),
+                        child: new Card(
+                            child: new Center(
+                                child: new Text(page.label,
+                                    style: new TextStyle(
+                                        color: page.labelColor,
+                                        fontSize: 32.0f
+                                    ),
+                                    textAlign: TextAlign.center
+                                )
+                            )
+                        )
+                    );
+                }
+            );
+        }
+
+        Widget buildFloatingActionButton(_Page page) {
+            if (!page.fabDefined) {
+                return null;
+            }
+
+            if (this._extendedButtons) {
+                return FloatingActionButton.extended(
+                    key: new ValueKey<Key>(page.fabKey),
+                    tooltip: "Show explanation",
+                    backgroundColor: page.fabColor,
+                    icon: page.fabIcon,
+                    label: new Text(page.label.ToUpper()),
+                    onPressed: this._showExplanatoryText
+                );
+            }
+
+            return new FloatingActionButton(
+                key: page.fabKey,
+                tooltip: "Show explanation",
+                backgroundColor: page.fabColor,
+                child: page.fabIcon,
+                onPressed: this._showExplanatoryText
+            );
+        }
+
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                key: this._scaffoldKey,
+                appBar: new AppBar(
+                    title: new Text("FAB per tab"),
+                    bottom: new TabBar(
+                        controller: this._controller,
+                        tabs: TabsFabDemoUtils._allPages
+                            .Select<_Page, Widget>((_Page page) => new Tab(text: page.label.ToUpper())).ToList()
+                    ),
+                    actions: new List<Widget> {
+                        new MaterialDemoDocumentationButton(TabsFabDemo.routeName),
+                        new IconButton(
+                            icon: new Icon(Icons.sentiment_very_satisfied),
+                            onPressed: () => {
+                                this.setState(() => { this._extendedButtons = !this._extendedButtons; });
+                            }
+                        )
+                    }
+                ),
+                floatingActionButton: this.buildFloatingActionButton(this._selectedPage),
+                body: new TabBarView(
+                    controller: this._controller,
+                    children: TabsFabDemoUtils._allPages.Select<_Page, Widget>(this.buildTabView).ToList()
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/material/tabs_fab_demo.cs.meta

+fileFormatVersion: 2
+guid: 7c2dcb794cc84a458f028f3751cf08a7
+timeCreated: 1555060923

Samples/UIWidgetsGallery/demo/animation/home.cs.meta

+fileFormatVersion: 2
+guid: 628b4648bdda4c8d8c8fc6778c874067
+timeCreated: 1554970915

Samples/UIWidgetsGallery/demo/animation/home.cs

+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Unity.UIWidgets.animation;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.gestures;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.physics;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using UnityEngine;
+using Color = Unity.UIWidgets.ui.Color;
+using Rect = Unity.UIWidgets.ui.Rect;
+
+namespace UIWidgetsGallery.gallery {
+    class AnimationHomeUtils {
+        public static readonly Color _kAppBackgroundColor = new Color(0xFF353662);
+        public static readonly TimeSpan _kScrollDuration = new TimeSpan(0, 0, 0, 0, 400);
+        public static readonly Curve _kScrollCurve = Curves.fastOutSlowIn;
+        public const float _kAppBarMinHeight = 90.0f;
+        public const float _kAppBarMidHeight = 256.0f;
+    }
+
+    class _RenderStatusBarPaddingSliver : RenderSliver {
+        public _RenderStatusBarPaddingSliver(
+            float? maxHeight = null,
+            float? scrollFactor = null
+        ) {
+            D.assert(maxHeight >= 0.0f);
+            D.assert(scrollFactor >= 1.0f);
+            this._maxHeight = maxHeight;
+            this._scrollFactor = scrollFactor;
+        }
+
+        public float? maxHeight {
+            get { return this._maxHeight; }
+            set {
+                D.assert(this.maxHeight >= 0.0f);
+                if (this._maxHeight == value) {
+                    return;
+                }
+
+                this._maxHeight = value;
+                this.markNeedsLayout();
+            }
+        }
+
+        float? _maxHeight;
+
+        public float? scrollFactor {
+            get { return this._scrollFactor; }
+            set {
+                D.assert(this.scrollFactor >= 1.0f);
+                if (this._scrollFactor == value) {
+                    return;
+                }
+
+                this._scrollFactor = value;
+                this.markNeedsLayout();
+            }
+        }
+
+        float? _scrollFactor;
+
+        protected override void performLayout() {
+            float? height =
+                (this.maxHeight - this.constraints.scrollOffset / this.scrollFactor)?.clamp(0.0f,
+                    this.maxHeight ?? 0.0f);
+            this.geometry = new SliverGeometry(
+                paintExtent: Mathf.Min(height ?? 0.0f, this.constraints.remainingPaintExtent),
+                scrollExtent: this.maxHeight ?? 0.0f,
+                maxPaintExtent: this.maxHeight ?? 0.0f
+            );
+        }
+    }
+
+    class _StatusBarPaddingSliver : SingleChildRenderObjectWidget {
+        public _StatusBarPaddingSliver(
+            Key key = null,
+            float? maxHeight = null,
+            float scrollFactor = 5.0f
+        ) : base(key: key) {
+            D.assert(maxHeight != null && maxHeight >= 0.0f);
+            D.assert(scrollFactor != null && scrollFactor >= 1.0f);
+            this.maxHeight = maxHeight;
+            this.scrollFactor = scrollFactor;
+        }
+
+        public readonly float? maxHeight;
+        public readonly float scrollFactor;
+
+        public override RenderObject createRenderObject(BuildContext context) {
+            return new _RenderStatusBarPaddingSliver(
+                maxHeight: this.maxHeight,
+                scrollFactor: this.scrollFactor
+            );
+        }
+
+        public override void updateRenderObject(BuildContext context, RenderObject _renderObject) {
+            _RenderStatusBarPaddingSliver renderObject = _renderObject as _RenderStatusBarPaddingSliver;
+            renderObject.maxHeight = this.maxHeight;
+            renderObject.scrollFactor = this.scrollFactor;
+        }
+
+        public override void debugFillProperties(DiagnosticPropertiesBuilder description) {
+            base.debugFillProperties(description);
+            description.add(new FloatProperty("maxHeight", this.maxHeight));
+            description.add(new FloatProperty("scrollFactor", this.scrollFactor));
+        }
+    }
+
+    class _SliverAppBarDelegate : SliverPersistentHeaderDelegate {
+        public _SliverAppBarDelegate(
+            float minHeight,
+            float maxHeight,
+            Widget child
+        ) {
+            this.minHeight = minHeight;
+            this.maxHeight = maxHeight;
+            this.child = child;
+        }
+
+        public readonly float minHeight;
+        public readonly float maxHeight;
+        public readonly Widget child;
+
+        public override float? minExtent {
+            get { return this.minHeight; }
+        }
+
+        public override float? maxExtent {
+            get { return Mathf.Max(this.maxHeight, this.minHeight); }
+        }
+
+        public override Widget build(BuildContext context, float shrinkOffset, bool overlapsContent) {
+            return SizedBox.expand(child: this.child);
+        }
+
+        public override bool shouldRebuild(SliverPersistentHeaderDelegate _oldDelegate) {
+            _SliverAppBarDelegate oldDelegate = _oldDelegate as _SliverAppBarDelegate;
+            return this.maxHeight != oldDelegate.maxHeight
+                   || this.minHeight != oldDelegate.minHeight
+                   || this.child != oldDelegate.child;
+        }
+
+        public override string ToString() {
+            return "_SliverAppBarDelegate";
+        }
+    }
+
+    class _AllSectionsLayout : MultiChildLayoutDelegate {
+        public _AllSectionsLayout(
+            Alignment translation,
+            float tColumnToRow,
+            float tCollapsed,
+            int cardCount,
+            float selectedIndex
+        ) {
+            this.translation = translation;
+            this.tColumnToRow = tColumnToRow;
+            this.tCollapsed = tCollapsed;
+            this.cardCount = cardCount;
+            this.selectedIndex = selectedIndex;
+        }
+
+        public readonly Alignment translation;
+        public readonly float tColumnToRow;
+        public readonly float tCollapsed;
+        public readonly int cardCount;
+        public readonly float selectedIndex;
+
+        Rect _interpolateRect(Rect begin, Rect end) {
+            return Rect.lerp(begin, end, this.tColumnToRow);
+        }
+
+        Offset _interpolatePoint(Offset begin, Offset end) {
+            return Offset.lerp(begin, end, this.tColumnToRow);
+        }
+
+        public override void performLayout(Size size) {
+            float columnCardX = size.width / 5.0f;
+            float columnCardWidth = size.width - columnCardX;
+            float columnCardHeight = size.height / this.cardCount;
+            float rowCardWidth = size.width;
+            Offset offset = this.translation.alongSize(size);
+            float columnCardY = 0.0f;
+            float rowCardX = -(this.selectedIndex * rowCardWidth);
+
+            float columnTitleX = size.width / 10.0f;
+            float rowTitleWidth = size.width * ((1 + this.tCollapsed) / 2.25f);
+            float rowTitleX = (size.width - rowTitleWidth) / 2.0f - this.selectedIndex * rowTitleWidth;
+
+            const float paddedSectionIndicatorWidth = AnimationWidgetsUtils.kSectionIndicatorWidth + 8.0f;
+            float rowIndicatorWidth = paddedSectionIndicatorWidth +
+                                      (1.0f - this.tCollapsed) * (rowTitleWidth - paddedSectionIndicatorWidth);
+            float rowIndicatorX = (size.width - rowIndicatorWidth) / 2.0f - this.selectedIndex * rowIndicatorWidth;
+
+            for (int index = 0; index < this.cardCount; index++) {
+                Rect columnCardRect = Rect.fromLTWH(columnCardX, columnCardY, columnCardWidth, columnCardHeight);
+                Rect rowCardRect = Rect.fromLTWH(rowCardX, 0.0f, rowCardWidth, size.height);
+                Rect cardRect = this._interpolateRect(columnCardRect, rowCardRect).shift(offset);
+                string cardId = $"card{index}";
+                if (this.hasChild(cardId)) {
+                    this.layoutChild(cardId, BoxConstraints.tight(cardRect.size));
+                    this.positionChild(cardId, cardRect.topLeft);
+                }
+
+                Size titleSize = this.layoutChild($"title{index}", BoxConstraints.loose(cardRect.size));
+                float columnTitleY = columnCardRect.centerLeft.dy - titleSize.height / 2.0f;
+                float rowTitleY = rowCardRect.centerLeft.dy - titleSize.height / 2.0f;
+                float centeredRowTitleX = rowTitleX + (rowTitleWidth - titleSize.width) / 2.0f;
+                Offset columnTitleOrigin = new Offset(columnTitleX, columnTitleY);
+                Offset rowTitleOrigin = new Offset(centeredRowTitleX, rowTitleY);
+                Offset titleOrigin = this._interpolatePoint(columnTitleOrigin, rowTitleOrigin);
+                this.positionChild($"title{index}", titleOrigin + offset);
+
+                Size indicatorSize = this.layoutChild($"indicator{index}", BoxConstraints.loose(cardRect.size));
+                float columnIndicatorX = cardRect.centerRight.dx - indicatorSize.width - 16.0f;
+                float columnIndicatorY = cardRect.bottomRight.dy - indicatorSize.height - 16.0f;
+                Offset columnIndicatorOrigin = new Offset(columnIndicatorX, columnIndicatorY);
+                Rect titleRect = Rect.fromPoints(titleOrigin, titleSize.bottomRight(titleOrigin));
+                float centeredRowIndicatorX = rowIndicatorX + (rowIndicatorWidth - indicatorSize.width) / 2.0f;
+                float rowIndicatorY = titleRect.bottomCenter.dy + 16.0f;
+                Offset rowIndicatorOrigin = new Offset(centeredRowIndicatorX, rowIndicatorY);
+                Offset indicatorOrigin = this._interpolatePoint(columnIndicatorOrigin, rowIndicatorOrigin);
+                this.positionChild($"indicator{index}", indicatorOrigin + offset);
+
+                columnCardY += columnCardHeight;
+                rowCardX += rowCardWidth;
+                rowTitleX += rowTitleWidth;
+                rowIndicatorX += rowIndicatorWidth;
+            }
+        }
+
+        public override bool shouldRelayout(MultiChildLayoutDelegate _oldDelegate) {
+            _AllSectionsLayout oldDelegate = _oldDelegate as _AllSectionsLayout;
+            return this.tColumnToRow != oldDelegate.tColumnToRow
+                   || this.cardCount != oldDelegate.cardCount
+                   || this.selectedIndex != oldDelegate.selectedIndex;
+        }
+    }
+
+    class _AllSectionsView : AnimatedWidget {
+        public _AllSectionsView(
+            Key key = null,
+            int? sectionIndex = null,
+            List<Section> sections = null,
+            ValueNotifier<float> selectedIndex = null,
+            float? minHeight = null,
+            float? midHeight = null,
+            float? maxHeight = null,
+            List<Widget> sectionCards = null
+        ) : base(key: key, listenable: selectedIndex) {
+            sectionCards = sectionCards ?? new List<Widget>();
+            D.assert(sections != null);
+            D.assert(sectionCards.Count == sections.Count);
+            D.assert(sectionIndex >= 0 && sectionIndex < sections.Count);
+            D.assert(selectedIndex != null);
+            D.assert(selectedIndex.value >= 0.0f && (float) selectedIndex.value < sections.Count);
+            this.sectionIndex = sectionIndex;
+            this.sections = sections;
+            this.selectedIndex = selectedIndex;
+            this.minHeight = minHeight;
+            this.midHeight = midHeight;
+            this.maxHeight = maxHeight;
+            this.sectionCards = sectionCards;
+        }
+
+        public readonly int? sectionIndex;
+        public readonly List<Section> sections;
+        public readonly ValueNotifier<float> selectedIndex;
+        public readonly float? minHeight;
+        public readonly float? midHeight;
+        public readonly float? maxHeight;
+        public readonly List<Widget> sectionCards;
+
+        float _selectedIndexDelta(int index) {
+            return (index - this.selectedIndex.value).abs().clamp(0.0f, 1.0f);
+        }
+
+        Widget _build(BuildContext context, BoxConstraints constraints) {
+            Size size = constraints.biggest;
+
+            float? tColumnToRow =
+                1.0f - ((size.height - this.midHeight) /
+                        (this.maxHeight - this.midHeight))?.clamp(0.0f, 1.0f);
+
+
+            float? tCollapsed =
+                1.0f - ((size.height - this.minHeight) /
+                        (this.midHeight - this.minHeight))?.clamp(0.0f, 1.0f);
+
+            float _indicatorOpacity(int index) {
+                return 1.0f - this._selectedIndexDelta(index) * 0.5f;
+            }
+
+            float? _titleOpacity(int index) {
+                return 1.0f - this._selectedIndexDelta(index) * tColumnToRow * 0.5f;
+            }
+
+            float? _titleScale(int index) {
+                return 1.0f - this._selectedIndexDelta(index) * tColumnToRow * 0.15f;
+            }
+
+            List<Widget> children = new List<Widget>(this.sectionCards);
+
+            for (int index = 0; index < this.sections.Count; index++) {
+                Section section = this.sections[index];
+                children.Add(new LayoutId(
+                    id: $"title{index}",
+                    child: new SectionTitle(
+                        section: section,
+                        scale: _titleScale(index),
+                        opacity: _titleOpacity(index)
+                    )
+                ));
+            }
+
+            for (int index = 0; index < this.sections.Count; index++) {
+                children.Add(new LayoutId(
+                    id: $"indicator{index}",
+                    child: new SectionIndicator(
+                        opacity: _indicatorOpacity(index)
+                    )
+                ));
+            }
+
+            return new CustomMultiChildLayout(
+                layoutDelegate: new _AllSectionsLayout(
+                    translation: new Alignment((this.selectedIndex.value - this.sectionIndex) * 2.0f - 1.0f ?? 0.0f,
+                        -1.0f),
+                    tColumnToRow: tColumnToRow ?? 0.0f,
+                    tCollapsed: tCollapsed ?? 0.0f,
+                    cardCount: this.sections.Count,
+                    selectedIndex: this.selectedIndex.value
+                ),
+                children: children
+            );
+        }
+
+        protected override Widget build(BuildContext context) {
+            return new LayoutBuilder(builder: this._build);
+        }
+    }
+
+    class _SnappingScrollPhysics : ClampingScrollPhysics {
+        public _SnappingScrollPhysics(
+            ScrollPhysics parent = null,
+            float? midScrollOffset = null
+        ) : base(parent: parent) {
+            D.assert(midScrollOffset != null);
+        }
+
+        public readonly float midScrollOffset;
+
+        public override ScrollPhysics applyTo(ScrollPhysics ancestor) {
+            return new _SnappingScrollPhysics(parent: this.buildParent(ancestor),
+                midScrollOffset: this.midScrollOffset);
+        }
+
+        Simulation _toMidScrollOffsetSimulation(float offset, float dragVelocity) {
+            float velocity = Mathf.Max(dragVelocity, this.minFlingVelocity);
+            return new ScrollSpringSimulation(this.spring, offset, this.midScrollOffset, velocity,
+                tolerance: this.tolerance);
+        }
+
+        Simulation _toZeroScrollOffsetSimulation(float offset, float dragVelocity) {
+            float velocity = Mathf.Max(dragVelocity, this.minFlingVelocity);
+            return new ScrollSpringSimulation(this.spring, offset, 0.0f, velocity, tolerance: this.tolerance);
+        }
+
+        public override Simulation createBallisticSimulation(ScrollMetrics position, float dragVelocity) {
+            Simulation simulation = base.createBallisticSimulation(position, dragVelocity);
+            float offset = position.pixels;
+
+            if (simulation != null) {
+                float simulationEnd = simulation.x(float.PositiveInfinity);
+                if (simulationEnd >= this.midScrollOffset) {
+                    return simulation;
+                }
+
+                if (dragVelocity > 0.0f) {
+                    return this._toMidScrollOffsetSimulation(offset, dragVelocity);
+                }
+
+                if (dragVelocity < 0.0f) {
+                    return this._toZeroScrollOffsetSimulation(offset, dragVelocity);
+                }
+            }
+            else {
+                float snapThreshold = this.midScrollOffset / 2.0f;
+                if (offset >= snapThreshold && offset < this.midScrollOffset) {
+                    return this._toMidScrollOffsetSimulation(offset, dragVelocity);
+                }
+
+                if (offset > 0.0f && offset < snapThreshold) {
+                    return this._toZeroScrollOffsetSimulation(offset, dragVelocity);
+                }
+            }
+
+            return simulation;
+        }
+    }
+
+    public class AnimationDemoHome : StatefulWidget {
+        public AnimationDemoHome(Key key = null) : base(key: key) {
+        }
+
+        public const string routeName = "/animation";
+
+        public override State createState() {
+            return new _AnimationDemoHomeState();
+        }
+    }
+
+    class _AnimationDemoHomeState : State<AnimationDemoHome> {
+        ScrollController _scrollController = new ScrollController();
+        PageController _headingPageController = new PageController();
+        PageController _detailsPageController = new PageController();
+        ScrollPhysics _headingScrollPhysics = new NeverScrollableScrollPhysics();
+        ValueNotifier<float> selectedIndex = new ValueNotifier<float>(0.0f);
+
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                backgroundColor: AnimationHomeUtils._kAppBackgroundColor,
+                body: new Builder(
+                    builder: this._buildBody
+                )
+            );
+        }
+
+        void _handleBackButton(float midScrollOffset) {
+            if (this._scrollController.offset >= midScrollOffset) {
+                this._scrollController.animateTo(0.0f, curve: AnimationHomeUtils._kScrollCurve,
+                    duration: AnimationHomeUtils._kScrollDuration);
+            }
+            else {
+                Navigator.maybePop(this.context);
+            }
+        }
+
+        bool _handleScrollNotification(ScrollNotification notification, float midScrollOffset) {
+            if (notification.depth == 0 && notification is ScrollUpdateNotification) {
+                ScrollPhysics physics = this._scrollController.position.pixels >= midScrollOffset
+                    ? (ScrollPhysics) new PageScrollPhysics()
+                    : new NeverScrollableScrollPhysics();
+                if (physics != this._headingScrollPhysics) {
+                    this.setState(() => { this._headingScrollPhysics = physics; });
+                }
+            }
+
+            return false;
+        }
+
+        void _maybeScroll(float midScrollOffset, int pageIndex, float xOffset) {
+            if (this._scrollController.offset < midScrollOffset) {
+                this._headingPageController.animateToPage(pageIndex, curve: AnimationHomeUtils._kScrollCurve,
+                    duration: AnimationHomeUtils._kScrollDuration);
+                this._scrollController.animateTo(midScrollOffset, curve: AnimationHomeUtils._kScrollCurve,
+                    duration: AnimationHomeUtils._kScrollDuration);
+            }
+            else {
+                float centerX = this._headingPageController.position.viewportDimension / 2.0f;
+                int newPageIndex = xOffset > centerX ? pageIndex + 1 : pageIndex - 1;
+                this._headingPageController.animateToPage(newPageIndex, curve: AnimationHomeUtils._kScrollCurve,
+                    duration: AnimationHomeUtils._kScrollDuration);
+            }
+        }
+
+        bool _handlePageNotification(ScrollNotification notification, PageController leader, PageController follower) {
+            if (notification.depth == 0 && notification is ScrollUpdateNotification) {
+                this.selectedIndex.value = leader.page;
+                if (follower.page != leader.page) {
+                    follower.position.jumpTo(leader.position.pixels); // ignore: deprecated_member_use
+                }
+            }
+
+            return false;
+        }
+
+        IEnumerable<Widget> _detailItemsFor(Section section) {
+            IEnumerable<Widget> detailItems = section.details.Select<SectionDetail, Widget>((SectionDetail detail) => {
+                return new SectionDetailView(detail: detail);
+            });
+            return ListTile.divideTiles(context: this.context, tiles: detailItems);
+        }
+
+        List<Widget> _allHeadingItems(float maxHeight, float midScrollOffset) {
+            List<Widget> sectionCards = new List<Widget> { };
+            for (int index = 0; index < AnimationSectionsUtils.allSections.Count; index++) {
+                sectionCards.Add(new LayoutId(
+                    id: $"card{index}",
+                    child: new GestureDetector(
+                        behavior: HitTestBehavior.opaque,
+                        child: new SectionCard(section: AnimationSectionsUtils.allSections[index]),
+                        onTapUp: (TapUpDetails details) => {
+                            float xOffset = details.globalPosition.dx;
+                            this.setState(() => { this._maybeScroll(midScrollOffset, index, xOffset); });
+                        }
+                    )
+                ));
+            }
+
+            List<Widget> headings = new List<Widget> { };
+            for (int index = 0; index < AnimationSectionsUtils.allSections.Count; index++) {
+                headings.Add(new Container(
+                        color: AnimationHomeUtils._kAppBackgroundColor,
+                        child: new ClipRect(
+                            child: new _AllSectionsView(
+                                sectionIndex: index,
+                                sections: AnimationSectionsUtils.allSections,
+                                selectedIndex: this.selectedIndex,
+                                minHeight: AnimationHomeUtils._kAppBarMinHeight,
+                                midHeight: AnimationHomeUtils._kAppBarMidHeight,
+                                maxHeight: maxHeight,
+                                sectionCards: sectionCards
+                            )
+                        )
+                    )
+                );
+            }
+
+            return headings;
+        }
+
+        Widget _buildBody(BuildContext context) {
+            MediaQueryData mediaQueryData = MediaQuery.of(context);
+            float statusBarHeight = mediaQueryData.padding.top;
+            float screenHeight = mediaQueryData.size.height;
+            float appBarMaxHeight = screenHeight - statusBarHeight;
+
+            float appBarMidScrollOffset = statusBarHeight + appBarMaxHeight - AnimationHomeUtils._kAppBarMidHeight;
+
+            return SizedBox.expand(
+                child: new Stack(
+                    children: new List<Widget> {
+                        new NotificationListener<ScrollNotification>(
+                            onNotification: (ScrollNotification notification) => {
+                                return this._handleScrollNotification(notification, appBarMidScrollOffset);
+                            },
+                            child: new CustomScrollView(
+                                controller: this._scrollController,
+                                physics: new _SnappingScrollPhysics(midScrollOffset: appBarMidScrollOffset),
+                                slivers: new List<Widget> {
+                                    new _StatusBarPaddingSliver(
+                                        maxHeight: statusBarHeight,
+                                        scrollFactor: 7.0f
+                                    ),
+                                    new SliverPersistentHeader(
+                                        pinned: true,
+                                        del: new _SliverAppBarDelegate(
+                                            minHeight: AnimationHomeUtils._kAppBarMinHeight,
+                                            maxHeight: appBarMaxHeight,
+                                            child: new NotificationListener<ScrollNotification>(
+                                                onNotification: (ScrollNotification notification) => {
+                                                    return this._handlePageNotification(notification,
+                                                        this._headingPageController, this._detailsPageController);
+                                                },
+                                                child: new PageView(
+                                                    physics: this._headingScrollPhysics,
+                                                    controller: this._headingPageController,
+                                                    children: this._allHeadingItems(appBarMaxHeight,
+                                                        appBarMidScrollOffset)
+                                                )
+                                            )
+                                        )
+                                    ),
+                                    new SliverToBoxAdapter(
+                                        child: new SizedBox(
+                                            height: 610.0f,
+                                            child: new NotificationListener<ScrollNotification>(
+                                                onNotification: (ScrollNotification notification) => {
+                                                    return this._handlePageNotification(notification,
+                                                        this._detailsPageController, this._headingPageController);
+                                                },
+                                                child: new PageView(
+                                                    controller: this._detailsPageController,
+                                                    children: AnimationSectionsUtils.allSections
+                                                        .Select<Section, Widget>((Section section) => {
+                                                            return new Column(
+                                                                crossAxisAlignment: CrossAxisAlignment.stretch,
+                                                                children: this._detailItemsFor(section).ToList()
+                                                            );
+                                                        }).ToList()
+                                                )
+                                            )
+                                        )
+                                    )
+                                }
+                            )
+                        ),
+                        new Positioned(
+                            top: statusBarHeight,
+                            left: 0.0f,
+                            child: new IconTheme(
+                                data: new IconThemeData(color: Colors.white),
+                                child: new SafeArea(
+                                    top: false,
+                                    bottom: false,
+                                    child: new IconButton(
+                                        icon: new BackButtonIcon(),
+                                        tooltip: "Back",
+                                        onPressed: () => { this._handleBackButton(appBarMidScrollOffset); }
+                                    )
+                                )
+                            )
+                        )
+                    }
+                )
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/animation/sections.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.ui;
+
+namespace UIWidgetsGallery.gallery {
+    public class AnimationSectionsUtils {
+        public static readonly Color _mariner = new Color(0xFF3B5F8F);
+        public static readonly Color _mediumPurple = new Color(0xFF8266D4);
+        public static readonly Color _tomato = new Color(0xFFF95B57);
+        public static readonly Color _mySin = new Color(0xFFF3A646);
+        const string _kGalleryAssetsPackage = "flutter_gallery_assets";
+
+        public static readonly SectionDetail _eyeglassesDetail = new SectionDetail(
+            imageAsset: "products/sunnies",
+            imageAssetPackage: _kGalleryAssetsPackage,
+            title: "Flutter enables interactive animation",
+            subtitle: "3K views - 5 days"
+        );
+
+        public static readonly SectionDetail _eyeglassesImageDetail = new SectionDetail(
+            imageAsset: "products/sunnies",
+            imageAssetPackage: _kGalleryAssetsPackage
+        );
+
+        public static readonly SectionDetail _seatingDetail = new SectionDetail(
+            imageAsset: "products/table",
+            imageAssetPackage: _kGalleryAssetsPackage,
+            title: "Flutter enables interactive animation",
+            subtitle: "3K views - 5 days"
+        );
+
+        public static readonly SectionDetail _seatingImageDetail = new SectionDetail(
+            imageAsset: "products/table",
+            imageAssetPackage: _kGalleryAssetsPackage
+        );
+
+        public static readonly SectionDetail _decorationDetail = new SectionDetail(
+            imageAsset: "products/earrings",
+            imageAssetPackage: _kGalleryAssetsPackage,
+            title: "Flutter enables interactive animation",
+            subtitle: "3K views - 5 days"
+        );
+
+        public static readonly SectionDetail _decorationImageDetail = new SectionDetail(
+            imageAsset: "products/earrings",
+            imageAssetPackage: _kGalleryAssetsPackage
+        );
+
+        public static readonly SectionDetail _protectionDetail = new SectionDetail(
+            imageAsset: "products/hat",
+            imageAssetPackage: _kGalleryAssetsPackage,
+            title: "Flutter enables interactive animation",
+            subtitle: "3K views - 5 days"
+        );
+
+        public static readonly SectionDetail _protectionImageDetail = new SectionDetail(
+            imageAsset: "products/hat",
+            imageAssetPackage: _kGalleryAssetsPackage
+        );
+
+        public static List<Section> allSections = new List<Section> {
+            new Section(
+                title: "SUNGLASSES",
+                leftColor: _mediumPurple,
+                rightColor: _mariner,
+                backgroundAsset: "products/sunnies",
+                backgroundAssetPackage: _kGalleryAssetsPackage,
+                details: new List<SectionDetail> {
+                    _eyeglassesDetail,
+                    _eyeglassesImageDetail,
+                    _eyeglassesDetail,
+                    _eyeglassesDetail,
+                    _eyeglassesDetail,
+                    _eyeglassesDetail
+                }
+            ),
+            new Section(
+                title: "FURNITURE",
+                leftColor: _tomato,
+                rightColor: _mediumPurple,
+                backgroundAsset: "products/table",
+                backgroundAssetPackage: _kGalleryAssetsPackage,
+                details: new List<SectionDetail> {
+                    _seatingDetail,
+                    _seatingImageDetail,
+                    _seatingDetail,
+                    _seatingDetail,
+                    _seatingDetail,
+                    _seatingDetail
+                }
+            ),
+            new Section(
+                title: "JEWELRY",
+                leftColor: _mySin,
+                rightColor: _tomato,
+                backgroundAsset: "products/earrings",
+                backgroundAssetPackage: _kGalleryAssetsPackage,
+                details: new List<SectionDetail> {
+                    _decorationDetail,
+                    _decorationImageDetail,
+                    _decorationDetail,
+                    _decorationDetail,
+                    _decorationDetail,
+                    _decorationDetail
+                }
+            ),
+            new Section(
+                title: "HEADWEAR",
+                leftColor: Colors.white,
+                rightColor: _tomato,
+                backgroundAsset: "products/hat",
+                backgroundAssetPackage: _kGalleryAssetsPackage,
+                details: new List<SectionDetail> {
+                    _protectionDetail,
+                    _protectionImageDetail,
+                    _protectionDetail,
+                    _protectionDetail,
+                    _protectionDetail,
+                    _protectionDetail
+                }
+            )
+        };
+    }
+
+
+    public class SectionDetail {
+        public SectionDetail(
+            string title = null,
+            string subtitle = null,
+            string imageAsset = null,
+            string imageAssetPackage = null
+        ) {
+            this.title = title;
+            this.subtitle = subtitle;
+            this.imageAsset = imageAsset;
+            this.imageAssetPackage = imageAssetPackage;
+        }
+
+        public readonly string title;
+        public readonly string subtitle;
+        public readonly string imageAsset;
+        public readonly string imageAssetPackage;
+    }
+
+    public class Section {
+        public Section(
+            string title,
+            string backgroundAsset,
+            string backgroundAssetPackage,
+            Color leftColor,
+            Color rightColor,
+            List<SectionDetail> details
+        ) {
+            this.title = title;
+            this.backgroundAsset = backgroundAsset;
+            this.backgroundAssetPackage = backgroundAssetPackage;
+            this.leftColor = leftColor;
+            this.rightColor = rightColor;
+            this.details = details;
+        }
+
+        public readonly string title;
+        public readonly string backgroundAsset;
+        public readonly string backgroundAssetPackage;
+        public readonly Color leftColor;
+        public readonly Color rightColor;
+        public readonly List<SectionDetail> details;
+
+        public static bool operator ==(Section left, Section right) {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(Section left, Section right) {
+            return !Equals(left, right);
+        }
+
+        public bool Equals(Section other) {
+            return this.title == other.title;
+        }
+
+        public override bool Equals(object obj) {
+            if (ReferenceEquals(null, obj)) {
+                return false;
+            }
+
+            if (ReferenceEquals(this, obj)) {
+                return true;
+            }
+
+            if (obj.GetType() != this.GetType()) {
+                return false;
+            }
+
+            return this.Equals((Section) obj);
+        }
+
+        public override int GetHashCode() {
+            return this.title.GetHashCode();
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/animation/sections.cs.meta

+fileFormatVersion: 2
+guid: 5180fb461b7448de8d4d084ff3f7c761
+timeCreated: 1555049317

Samples/UIWidgetsGallery/demo/animation/widgets.cs

+using System.Collections.Generic;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using Image = Unity.UIWidgets.widgets.Image;
+
+namespace UIWidgetsGallery.gallery {
+    class AnimationWidgetsUtils {
+        public const float kSectionIndicatorWidth = 32.0f;
+    }
+
+    public class SectionCard : StatelessWidget {
+        public SectionCard(
+            Key key = null,
+            Section section = null
+        ) : base(key: key) {
+            D.assert(section != null);
+            this.section = section;
+        }
+
+        public readonly Section section;
+
+        public override Widget build(BuildContext context) {
+            return new DecoratedBox(
+                decoration: new BoxDecoration(
+                    gradient: new LinearGradient(
+                        begin: Alignment.centerLeft,
+                        end: Alignment.centerRight,
+                        colors: new List<Color> {
+                            this.section.leftColor, this.section.rightColor
+                        }
+                    )
+                ),
+                child: Image.asset(this.section.backgroundAsset,
+                    color: Color.fromRGBO(255, 255, 255, 0.075f),
+                    colorBlendMode: BlendMode.modulate,
+                    fit: BoxFit.cover
+                )
+            );
+        }
+    }
+
+    public class SectionTitle : StatelessWidget {
+        public SectionTitle(
+            Key key = null,
+            Section section = null,
+            float? scale = null,
+            float? opacity = null
+        ) : base(key: key) {
+            D.assert(section != null);
+            D.assert(scale != null);
+            D.assert(opacity != null && opacity >= 0.0f && opacity <= 1.0f);
+            this.section = section;
+            this.scale = scale;
+            this.opacity = opacity;
+        }
+
+        public readonly Section section;
+        public readonly float? scale;
+        public readonly float? opacity;
+
+        public static readonly TextStyle sectionTitleStyle = new TextStyle(
+            fontFamily: "Raleway",
+            inherit: false,
+            fontSize: 24.0f,
+            fontWeight: FontWeight.w500,
+            color: Colors.white,
+            textBaseline: TextBaseline.alphabetic
+        );
+
+        public static readonly TextStyle sectionTitleShadowStyle = sectionTitleStyle.copyWith(
+            color: new Color(0x19000000)
+        );
+
+        public override Widget build(BuildContext context) {
+            return new IgnorePointer(
+                child: new Opacity(
+                    opacity: this.opacity ?? 1.0f,
+                    child: new Transform(
+                        transform: Matrix3.makeScale(this.scale ?? 1.0f),
+                        alignment: Alignment.center,
+                        child: new Stack(
+                            children: new List<Widget> {
+                                new Positioned(
+                                    top: 4.0f,
+                                    child: new Text(this.section.title, style: sectionTitleShadowStyle)
+                                ),
+                                new Text(this.section.title, style: sectionTitleStyle)
+                            }
+                        )
+                    )
+                )
+            );
+        }
+    }
+
+    public class SectionIndicator : StatelessWidget {
+        public SectionIndicator(Key key = null, float opacity = 1.0f) : base(key: key) {
+            this.opacity = opacity;
+        }
+
+        public readonly float opacity;
+
+        public override Widget build(BuildContext context) {
+            return new IgnorePointer(
+                child: new Container(
+                    width: AnimationWidgetsUtils.kSectionIndicatorWidth,
+                    height: 3.0f,
+                    color: Colors.white.withOpacity(this.opacity)
+                )
+            );
+        }
+    }
+
+    public class SectionDetailView : StatelessWidget {
+        public SectionDetailView(
+            Key key = null,
+            SectionDetail detail = null
+        ) : base(key: key) {
+            D.assert(detail != null && detail.imageAsset != null);
+            D.assert((detail.imageAsset ?? detail.title) != null);
+            this.detail = detail;
+        }
+
+        public readonly SectionDetail detail;
+
+        public override Widget build(BuildContext context) {
+            Widget image = new DecoratedBox(
+                decoration: new BoxDecoration(
+                    borderRadius: BorderRadius.circular(6.0f),
+                    image: new DecorationImage(
+                        image: new AssetImage(
+                            this.detail.imageAsset
+                        ),
+                        fit: BoxFit.cover,
+                        alignment: Alignment.center
+                    )
+                )
+            );
+
+            Widget item;
+            if (this.detail.title == null && this.detail.subtitle == null) {
+                item = new Container(
+                    height: 240.0f,
+                    padding: EdgeInsets.all(16.0f),
+                    child: new SafeArea(
+                        top: false,
+                        bottom: false,
+                        child: image
+                    )
+                );
+            }
+            else {
+                item = new ListTile(
+                    title: new Text(this.detail.title),
+                    subtitle: new Text(this.detail.subtitle),
+                    leading: new SizedBox(width: 32.0f, height: 32.0f, child: image)
+                );
+            }
+
+            return new DecoratedBox(
+                decoration: new BoxDecoration(color: Colors.grey.shade200),
+                child: item
+            );
+        }
+    }
+}

Samples/UIWidgetsGallery/demo/animation/widgets.cs.meta

+fileFormatVersion: 2
+guid: 4c84aedb64bf44338944d63be7c563ed
+timeCreated: 1555049115