Merge branch 'zgh/cupertino/fix' of https://github.com/Unity-Technologies/com.unity.uiwidgets into zgh/cupertino/fix

4 年前 · 8fd690c9
--- a/Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/MaterialTabBarSample.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/MaterialTabBarSample.cs
 using Unity.UIWidgets.painting;
 using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
-using UnityEngine;
 using ui_ = Unity.UIWidgets.widgets.ui_;

 namespace UIWidgetsSample {
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/cupertino/cupertino_navigation_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/cupertino/cupertino_navigation_demo.cs
                                                            decoration: new BoxDecoration(
                                                                image: new DecorationImage(
                                                                    image: new FileImage(
-                                                                        file: "people/square/trevor.png"
+                                                                        file: "gallery/people/square/trevor.png"
                                                                    )
                                                                ),
                                                                shape: BoxShape.circle
                                                            decoration: new BoxDecoration(
                                                                image: new DecorationImage(
                                                                    image: new FileImage(
-                                                                        "people/square/sandra.png"
+                                                                        "gallery/people/square/sandra.png"
                                                                    )
                                                                ),
                                                                shape: BoxShape.circle
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/backdrop_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/backdrop_demo.cs
                title: "Accessories",
                assets: new List<string>
                {
-                    "StreamingAssets/gallery/products/belt.png",
-                    "StreamingAssets/gallery/products/earrings.png",
-                    "StreamingAssets/gallery/products/backpack.png",
-                    "StreamingAssets/gallery/products/hat.png",
-                    "StreamingAssets/gallery/products/scarf.png",
-                    "StreamingAssets/gallery/products/sunnies.png"
+                    "gallery/products/belt.png",
+                    "gallery/products/earrings.png",
+                    "gallery/products/backpack.png",
+                    "gallery/products/hat.png",
+                    "gallery/products/scarf.png",
+                    "gallery/products/sunnies.png"
                }
            ),
            new Category(
-                    "StreamingAssets/gallery/products/backpack.png",
-                    "StreamingAssets/gallery/products/cup.png",
-                    "StreamingAssets/gallery/products/napkins.png",
-                    "StreamingAssets/gallery/products/top.png"
+                    "gallery/products/backpack.png",
+                    "gallery/products/cup.png",
+                    "gallery/products/napkins.png",
+                    "gallery/products/top.png"
                }
            ),
            new Category(
-                    "StreamingAssets/gallery/products/jacket.png",
-                    "StreamingAssets/gallery/products/jumper.png",
-                    "StreamingAssets/gallery/products/scarf.png",
-                    "StreamingAssets/gallery/products/sweater.png",
-                    "StreamingAssets/gallery/products/sweats.png"
+                    "gallery/products/jacket.png",
+                    "gallery/products/jumper.png",
+                    "gallery/products/scarf.png",
+                    "gallery/products/sweater.png",
+                    "gallery/products/sweats.png"
                }
            ),
            new Category(
-                    "StreamingAssets/gallery/products/cup.png",
-                    "StreamingAssets/gallery/products/napkins.png",
-                    "StreamingAssets/gallery/products/planters.png",
-                    "StreamingAssets/gallery/products/table.png",
-                    "StreamingAssets/gallery/products/teaset.png"
+                    "gallery/products/cup.png",
+                    "gallery/products/napkins.png",
+                    "gallery/products/planters.png",
+                    "gallery/products/table.png",
+                    "gallery/products/teaset.png"
                }
            ),
            new Category(
-                    "StreamingAssets/gallery/products/jumper.png",
-                    "StreamingAssets/gallery/products/shirt.png",
-                    "StreamingAssets/gallery/products/sweater.png",
-                    "StreamingAssets/gallery/products/top.png"
+                    "gallery/products/jumper.png",
+                    "gallery/products/shirt.png",
+                    "gallery/products/sweater.png",
+                    "gallery/products/top.png"
                }
            ),
            new Category(
-                    "StreamingAssets/gallery/products/backpack.png",
-                    "StreamingAssets/gallery/products/belt.png",
-                    "StreamingAssets/gallery/products/cup.png",
-                    "StreamingAssets/gallery/products/dress.png",
-                    "StreamingAssets/gallery/products/earrings.png",
-                    "StreamingAssets/gallery/products/flatwear.png",
-                    "StreamingAssets/gallery/products/hat.png",
-                    "StreamingAssets/gallery/products/jacket.png",
-                    "StreamingAssets/gallery/products/jumper.png",
-                    "StreamingAssets/gallery/products/napkins.png",
-                    "StreamingAssets/gallery/products/planters.png",
-                    "StreamingAssets/gallery/products/scarf.png",
-                    "StreamingAssets/gallery/products/shirt.png",
-                    "StreamingAssets/gallery/products/sunnies.png",
-                    "StreamingAssets/gallery/products/sweater.png",
-                    "StreamingAssets/gallery/products/sweats.png",
-                    "StreamingAssets/gallery/products/table.png",
-                    "StreamingAssets/gallery/products/teaset.png",
-                    "StreamingAssets/gallery/products/top.png"
+                    "gallery/products/backpack.png",
+                    "gallery/products/belt.png",
+                    "gallery/products/cup.png",
+                    "gallery/products/dress.png",
+                    "gallery/products/earrings.png",
+                    "gallery/products/flatwear.png",
+                    "gallery/products/hat.png",
+                    "gallery/products/jacket.png",
+                    "gallery/products/jumper.png",
+                    "gallery/products/napkins.png",
+                    "gallery/products/planters.png",
+                    "gallery/products/scarf.png",
+                    "gallery/products/shirt.png",
+                    "gallery/products/sunnies.png",
+                    "gallery/products/sweater.png",
+                    "gallery/products/sweats.png",
+                    "gallery/products/table.png",
+                    "gallery/products/teaset.png",
+                    "gallery/products/top.png"
                }
            )
        };
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/bottom_app_bar_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/bottom_app_bar_demo.cs

        public override Path getOuterPath(Rect host, Rect guest)
        {
-            if (!host.overlaps(guest))
+            //there is a bug in flutter when guest == null, we fix it here
+            if (guest == null || !host.overlaps(guest))
            {
                var path = new Path();
                path.addRect(host);
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/cards_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/cards_demo.cs
 {
    public static class CardsDemoUtils
    {
-        public static readonly string _kGalleryAssetsPackage = "flutter_gallery_assets";
+        public static readonly string _kGalleryAssetsPackage = "gallery/";
    }

    internal enum CardDemoType
            D.assert(description != null);
            D.assert(city != null);
            D.assert(location != null);
+
+            this.assetName = assetName;
+            this.assetPackage = assetPackage;
+            this.title = title;
+            this.description = description;
+            this.city = city;
+            this.location = location;
+            this.type = type;
        }

        public readonly string assetName;
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/chip_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/chip_demo.cs

        public static readonly Dictionary<string, string> _avatars = new Dictionary<string, string>()
        {
-            {"hammer", "people/square/ali.png"},
-            {"chisel", "people/square/sandra.png"},
-            {"fryer", "people/square/trevor.png"},
-            {"fabricator", "people/square/stella.png"},
-            {"customer", "people/square/peter.png"},
+            {"hammer", "gallery/people/square/ali.png"},
+            {"chisel", "gallery/people/square/sandra.png"},
+            {"fryer", "gallery/people/square/trevor.png"},
+            {"fabricator", "gallery/people/square/stella.png"},
+            {"customer", "gallery/people/square/peter.png"},
        };

        public static readonly Dictionary<string, HashSet<string>> _toolActions =
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/data_table_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/data_table_demo.cs
            );
        }

-        private new int rowCount => this._desserts.Count;
+        public override int rowCount => this._desserts.Count;
-        private new bool isRowCountApproximate => false;
+        public override bool isRowCountApproximate => false;
-        private new int selectedRowCount => this._selectedCount;
+        public override int selectedRowCount => this._selectedCount;

        public void _selectAll(bool isChecked)
        {
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/dialog_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/dialog_demo.cs
  readonly GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>.key();

  TimeOfDay _selectedTime;
-  
-  void initState() {
+
+  public override void initState() {
    base.initState();
    DateTime now = DateTime.Now;
    _selectedTime = new TimeOfDay(hour: now.Hour, minute: now.Minute);
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/drawer_demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/material/drawer_demo.cs
 {
    public static class DrawerDemoUtils
    {
-        public static readonly string _kAsset0 = "people/square/trevor.png";
-        public static readonly string _kAsset1 = "people/square/stella.png";
-        public static readonly string _kAsset2 = "people/square/sandra.png";
+        public static readonly string _kAsset0 = "gallery/people/square/trevor.png";
+        public static readonly string _kAsset1 = "gallery/people/square/stella.png";
+        public static readonly string _kAsset2 = "gallery/people/square/sandra.png";
        public static readonly string _kGalleryAssetsPackage = "flutter_gallery_assets";
    }

--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/shrine/shopping_cart.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/shrine/shopping_cart.cs
 using Unity.UIWidgets.rendering;
 using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
+using UnityEngine;
 using Image = Unity.UIWidgets.widgets.Image;
 using TextStyle = Unity.UIWidgets.painting.TextStyle;

  List<Widget> _createShoppingCartRows(AppStateModel model)
  {
    List<Widget> widgets = new List<Widget>();
-    for (int id = 0; id < model.productsInCart.Count; id++)
+    foreach (var product in model.productsInCart.Keys)
-      widgets.Add(new ShoppingCartRow(
-        product: model.getProductById(id),
-        quantity: model.productsInCart[id],
-        onPressed: ()=> {
-          model.removeItemFromCart(id);
-        }
-      ));
+      int id = product;
+        widgets.Add(new ShoppingCartRow(
+          product: model.getProductById(id),
+          quantity: model.productsInCart[id],
+          onPressed: ()=> {
+            model.removeItemFromCart(id);
+          }
+        ));
    }

    return widgets;
 public class ShoppingCartRow : StatelessWidget {
  public ShoppingCartRow(
    Product product = null,
-    int? quantity = null,
+    int quantity = 1,
-    this.quantity = quantity?? 0;
+    this.quantity = quantity;
    this.onPressed = onPressed;
  }

                  new Row(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: new List<Widget>{
-                      Image.asset(
+                      Image.file(
-                        package: product.assetPackage,
+                        //package: product.assetPackage,
                        fit: BoxFit.cover,
                        width: 75.0f,
                        height: 75.0f
                                new Expanded(
                                  child: new Text($"Quantity: {quantity}")
                                ),
-                                new Text($"x  $ {product.price : D} ")
+                                new Text($"x  $ {product.price :F} ")
                              }
                            ),
                            new Text(
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/shrine/supplemental/product_card.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/shrine/supplemental/product_card.cs
 using Unity.UIWidgets.painting;
 using Unity.UIWidgets.rendering;
 using Unity.UIWidgets.widgets;
+using UnityEngine;

 namespace UIWidgetsGallery.demo.shrine.supplemental
 {
                                            ),
                                            new SizedBox(height: 4.0f),
                                            new Text(
-                                                $" $ { product.price:D}",
+                                                $" $ { product.price:F}",
                                                style: theme.textTheme.caption
                                            ),
                                        }
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/gallery/demo.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/gallery/demo.cs
        public TabbedComponentDemoScaffold(
            List<ComponentDemoTabData> demos,
            string title,
-            List<Widget> actions,
+            List<Widget> actions = null,
            bool isScrollable = true,
            bool showExampleCodeAction = true
        )

        public override Widget build(BuildContext context)
        {
-            var children = new List<Widget>(this.actions);
+            var children = new List<Widget>();
+            if (actions != null)
+            {
+                children.AddRange(actions);
+            }
            children.Add(new Builder(
                    builder: (BuildContext subContext) =>
                    {
--- a/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/gallery/demos.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/gallery/demos.cs
-using System;
+using Unity.UIWidgets.material;
-using UnityEngine;

 namespace UIWidgetsGallery.gallery
 {
-            string name, 
+            string name,
-        
+
-        
+
-            if (ReferenceEquals(this, other))
-            {
-                return true;
-            }
+            if (ReferenceEquals(this, other)) return true;
-            if (ReferenceEquals(other, null))
-            {
-                return false;
-            }
+            if (ReferenceEquals(other, null)) return false;
-            return this.icon.Equals(other.icon) && this.name == other.name;
+            return icon.Equals(other.icon) && name == other.name;
-            if (ReferenceEquals(this, obj))
-            {
-                return true;
-            }
+            if (ReferenceEquals(this, obj)) return true;
+
+            if (ReferenceEquals(obj, null)) return false;
+
+            if (obj.GetType() != GetType()) return false;
-            if (ReferenceEquals(obj, null))
-            {
-                return false;
-            }
-            
-            if (obj.GetType() != GetType())
-            {
-                return false;
-            } 
-            
-            return Equals((GalleryDemoCategory)obj);
+            return Equals((GalleryDemoCategory) obj);
-        
-        public static bool operator==(GalleryDemoCategory left, GalleryDemoCategory right)
+
+        public static bool operator ==(GalleryDemoCategory left, GalleryDemoCategory right)
        {
            return Equals(left, right);
        }
            return !Equals(left, right);
        }
-        
-        public override int GetHashCode() {
-            unchecked {
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
                return ((icon?.GetHashCode() ?? 0) * 397) ^ (name?.GetHashCode() ?? 0);
            }
        }
            return $"{GetType()}{name}";
        }
-        
+
-        public static readonly  GalleryDemoCategory _kStyle = new GalleryDemoCategory(
+        public static readonly GalleryDemoCategory _kStyle = new GalleryDemoCategory(
-        public static readonly  GalleryDemoCategory _kMaterialComponents = new GalleryDemoCategory(
+        public static readonly GalleryDemoCategory _kMaterialComponents = new GalleryDemoCategory(
-        public static readonly  GalleryDemoCategory _kCupertinoComponents = new GalleryDemoCategory(
+        public static readonly GalleryDemoCategory _kCupertinoComponents = new GalleryDemoCategory(
-        public static readonly  GalleryDemoCategory _kMedia = new GalleryDemoCategory(
+        public static readonly GalleryDemoCategory _kMedia = new GalleryDemoCategory(
-    
-    class GalleryDemo {
+
+    internal class GalleryDemo
+    {
        public GalleryDemo(
            string title = null,
            IconData icon = null,
        }

        public readonly string title;
-        public readonly  IconData icon;
-        public readonly  string subtitle;
-        public readonly  GalleryDemoCategory category;
-        public readonly  string routeName;
-        public readonly  WidgetBuilder buildRoute;
-        public readonly  string documentationUrl;
-        
-        public override string ToString() {
+        public readonly IconData icon;
+        public readonly string subtitle;
+        public readonly GalleryDemoCategory category;
+        public readonly string routeName;
+        public readonly WidgetBuilder buildRoute;
+        public readonly string documentationUrl;
+
+        public override string ToString()
+        {
-            List<GalleryDemo> cupertinoDemos = new List<GalleryDemo>()
+            List<GalleryDemo> galleryDemos = new List<GalleryDemo>()
-                  title: "Activity Indicator",
-                  icon: GalleryIcons.cupertino_progress,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoProgressIndicatorDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoActivityIndicator-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoProgressIndicatorDemo()
+                    title: "Activity Indicator",
+                    icon: GalleryIcons.cupertino_progress,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoProgressIndicatorDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoActivityIndicator-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoProgressIndicatorDemo()
-                  title: "Alerts",
-                  icon: GalleryIcons.dialogs,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoAlertDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/showCupertinoDialog.html",
-                  buildRoute: (BuildContext context) => new CupertinoAlertDemo()
+                    title: "Alerts",
+                    icon: GalleryIcons.dialogs,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoAlertDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/showCupertinoDialog.html",
+                    buildRoute: (BuildContext context) => new CupertinoAlertDemo()
-                  title: "Buttons",
-                  icon: GalleryIcons.generic_buttons,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoButtonsDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoButton-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoButtonsDemo()
+                    title: "Buttons",
+                    icon: GalleryIcons.generic_buttons,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoButtonsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoButton-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoButtonsDemo()
-                  title: "Navigation",
-                  icon: GalleryIcons.bottom_navigation,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoNavigationDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoTabScaffold-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoNavigationDemo()
+                    title: "Navigation",
+                    icon: GalleryIcons.bottom_navigation,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoNavigationDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoTabScaffold-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoNavigationDemo()
-                  title: "Pickers",
-                  icon: GalleryIcons.cards,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoPickerDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoPicker-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoPickerDemo()
+                    title: "Pickers",
+                    icon: GalleryIcons.cards,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoPickerDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoPicker-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoPickerDemo()
-                  title: "Pull to refresh",
-                  icon: GalleryIcons.cupertino_pull_to_refresh,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoRefreshControlDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSliverRefreshControl-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoRefreshControlDemo()
+                    title: "Pull to refresh",
+                    icon: GalleryIcons.cupertino_pull_to_refresh,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoRefreshControlDemo.routeName,
+                    documentationUrl:
+                    "https://docs.flutter.io/flutter/cupertino/CupertinoSliverRefreshControl-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoRefreshControlDemo()
-                  title: "Segmented Control",
-                  icon: GalleryIcons.tabs,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoSegmentedControlDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSegmentedControl-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoSegmentedControlDemo()
+                    title: "Segmented Control",
+                    icon: GalleryIcons.tabs,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoSegmentedControlDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSegmentedControl-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoSegmentedControlDemo()
-                  title: "Sliders",
-                  icon: GalleryIcons.sliders,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoSliderDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSlider-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoSliderDemo()
+                    title: "Sliders",
+                    icon: GalleryIcons.sliders,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoSliderDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSlider-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoSliderDemo()
-                  title: "Switches",
-                  icon: GalleryIcons.cupertino_switch,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoSwitchDemo.routeName,
-                  documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSwitch-class.html",
-                  buildRoute: (BuildContext context) => new CupertinoSwitchDemo()
+                    title: "Switches",
+                    icon: GalleryIcons.cupertino_switch,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoSwitchDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/cupertino/CupertinoSwitch-class.html",
+                    buildRoute: (BuildContext context) => new CupertinoSwitchDemo()
-                  title: "Text Fields",
-                  icon: GalleryIcons.text_fields_alt,
-                  category:GalleryDemoCategory._kCupertinoComponents,
-                  routeName: CupertinoTextFieldDemo.routeName,
-                  buildRoute: (BuildContext context) => new CupertinoTextFieldDemo()
-                )
-            };
-
-      
-            List<GalleryDemo> galleryDemos = new List<GalleryDemo>
-            {
+                    title: "Text Fields",
+                    icon: GalleryIcons.text_fields_alt,
+                    category: GalleryDemoCategory._kCupertinoComponents,
+                    routeName: CupertinoTextFieldDemo.routeName,
+                    buildRoute: (BuildContext context) => new CupertinoTextFieldDemo()
+                ),
                new GalleryDemo(
                    title: "Shrine",
                    subtitle: "Basic shopping app",
                    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) => new 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) => new PersistentBottomSheetDemo()
+                ),
+                new GalleryDemo(
                    title: "Buttons",
                    subtitle: "Flat, raised, dropdown, and more",
                    icon: GalleryIcons.generic_buttons,
+                ),
+                new GalleryDemo(
+                    title: "Cards",
+                    subtitle: "Baseline cards with rounded corners",
+                    icon: GalleryIcons.cards,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: CardsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Card-class.html",
+                    buildRoute: (BuildContext context) => new CardsDemo()
+                ),
+                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) => new TabsFabDemo()
+                ),
+                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) => new ChipDemo()
+                ),
+                new GalleryDemo(
+                    title: "Data tables",
+                    subtitle: "Rows and columns",
+                    icon: GalleryIcons.data_table,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: DataTableDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/PaginatedDataTable-class.html",
+                    buildRoute: (BuildContext context) => new DataTableDemo()
+                ),
+                new GalleryDemo(
+                    title: "Pull to refresh",
+                    subtitle: "Refresh indicators",
+                    icon: GalleryIcons.refresh,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: OverscrollDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/RefreshIndicator-class.html",
+                    buildRoute: (BuildContext context) => new OverscrollDemo()
+                ),
+                new GalleryDemo(
+                    title: "Search",
+                    subtitle: "Expandable search",
+                    icon: Icons.search,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: SearchDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/showSearch.html",
+                    buildRoute: (BuildContext context) => new SearchDemo()
+                ),
+                new GalleryDemo(
+                    title: "Selection controls",
+                    subtitle: "Checkboxes, radio buttons, and switches",
+                    icon: GalleryIcons.check_box,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: SelectionControlsDemo.routeName,
+                    buildRoute: (BuildContext context) => new SelectionControlsDemo()
+                ),
+                new GalleryDemo(
+                    title: "Sliders",
+                    subtitle: "Widgets for selecting a value by swiping",
+                    icon: GalleryIcons.sliders,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: SliderDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Slider-class.html",
+                    buildRoute: (BuildContext context) => new SliderDemo()
+                ),
+                new GalleryDemo(
+                    title: "Snackbar",
+                    subtitle: "Temporary messaging",
+                    icon: GalleryIcons.snackbar,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: SnackBarDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/ScaffoldState/showSnackBar.html",
+                    buildRoute: (BuildContext context) => new SnackBarDemo()
+                ),
+                new GalleryDemo(
+                    title: "Tabs",
+                    subtitle: "Tabs with independently scrollable views",
+                    icon: GalleryIcons.tabs,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: TabsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/TabBarView-class.html",
+                    buildRoute: (BuildContext context) => new TabsDemo()
+                ),
+                new GalleryDemo(
+                    title: "Dialogs",
+                    subtitle: "Simple, alert, and fullscreen",
+                    icon: GalleryIcons.dialogs,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: DialogDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/showDialog.html",
+                    buildRoute: (BuildContext context) => new DialogDemo()
+                ),
+                new GalleryDemo(
+                    title: "Elevations",
+                    subtitle: "Shadow values on cards",
+                    // TODO(larche): Change to custom icon for elevations when one exists.
+                    icon: GalleryIcons.cupertino_progress,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: ElevationDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Material/elevation.html",
+                    buildRoute: (BuildContext context) => new ElevationDemo()
+                ),
+                new GalleryDemo(
+                    title: "Navigation drawer",
+                    subtitle: "Navigation drawer with standard header",
+                    icon: GalleryIcons.menu,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: DrawerDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Drawer-class.html",
+                    buildRoute: (BuildContext context) => new DrawerDemo()
+                ),
+                new GalleryDemo(
+                    title: "Expansion panels",
+                    subtitle: "List of expanding panels",
+                    icon: GalleryIcons.expand_all,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: ExpansionPanelsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/ExpansionPanel-class.html",
+                    buildRoute: (BuildContext context) => new ExpansionPanelsDemo()
+                ),
+                new GalleryDemo(
+                    title: "Grid",
+                    subtitle: "Row and column layout",
+                    icon: GalleryIcons.grid_on,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: GridListDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/widgets/GridView-class.html",
+                    buildRoute: (BuildContext context) => new GridListDemo()
+                ),
+                new GalleryDemo(
+                    title: "Icons",
+                    subtitle: "Enabled and disabled icons with opacity",
+                    icon: GalleryIcons.sentiment_very_satisfied,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: IconsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/IconButton-class.html",
+                    buildRoute: (BuildContext context) => new IconsDemo()
+                ),
+                new GalleryDemo(
+                    title: "Lists",
+                    subtitle: "Scrolling list layouts",
+                    icon: GalleryIcons.list_alt,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: ListDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/ListTile-class.html",
+                    buildRoute: (BuildContext context) => new ListDemo()
+                ),
+                new GalleryDemo(
+                    title: "Lists: leave-behind list items",
+                    subtitle: "List items with hidden actions",
+                    icon: GalleryIcons.lists_leave_behind,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: LeaveBehindDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/widgets/Dismissible-class.html",
+                    buildRoute: (BuildContext context) => new LeaveBehindDemo()
+                ),
+                new GalleryDemo(
+                    title: "Lists: reorderable",
+                    subtitle: "Reorderable lists",
+                    icon: GalleryIcons.list_alt,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: ReorderableListDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/ReorderableListView-class.html",
+                    buildRoute: (BuildContext context) => new ReorderableListDemo()
+                ),
+                new GalleryDemo(
+                    title: "Menus",
+                    subtitle: "Menu buttons and simple menus",
+                    icon: GalleryIcons.more_vert,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: MenuDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/PopupMenuButton-class.html",
+                    buildRoute: (BuildContext context) => new MenuDemo()
+                ),
+                new GalleryDemo(
+                    title: "Pagination",
+                    subtitle: "PageView with indicator",
+                    icon: GalleryIcons.page_control,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: PageSelectorDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/TabBarView-class.html",
+                    buildRoute: (BuildContext context) => new PageSelectorDemo()
+                ),
+                new GalleryDemo(
+                    title: "Progress indicators",
+                    subtitle: "Linear, circular, indeterminate",
+                    icon: GalleryIcons.progress_activity,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: ProgressIndicatorDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/LinearProgressIndicator-class.html",
+                    buildRoute: (BuildContext context) => new ProgressIndicatorDemo()
+                ),
+                new GalleryDemo(
+                    title: "Tabs: Scrolling",
+                    subtitle: "Tab bar that scrolls",
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    icon: GalleryIcons.tabs,
+                    routeName: ScrollableTabsDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/TabBar-class.html",
+                    buildRoute: (BuildContext context) => new ScrollableTabsDemo()
+                ),
+                new GalleryDemo(
+                    title: "Text fields",
+                    subtitle: "Single line of editable text and numbers",
+                    icon: GalleryIcons.text_fields_alt,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: TextFormFieldDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/TextFormField-class.html",
+                    buildRoute: (BuildContext context) => new TextFormFieldDemo()
+                ),
+                new GalleryDemo(
+                    title: "Tooltips",
+                    subtitle: "Short message displayed on long-press",
+                    icon: GalleryIcons.tooltip,
+                    category: GalleryDemoCategory._kMaterialComponents,
+                    routeName: TooltipDemo.routeName,
+                    documentationUrl: "https://docs.flutter.io/flutter/material/Tooltip-class.html",
+                    buildRoute: (BuildContext context) => new TooltipDemo()
-            return cupertinoDemos;
+            return galleryDemos;
-        
+
-        new HashSet<GalleryDemoCategory>(kAllGalleryDemos.Select<GalleryDemo, GalleryDemoCategory>((GalleryDemo demo) => demo.category).ToList());
+            new HashSet<GalleryDemoCategory>(kAllGalleryDemos
+                .Select<GalleryDemo, GalleryDemoCategory>((GalleryDemo demo) => demo.category).ToList());
-        static Dictionary<GalleryDemoCategory, List<GalleryDemo>> _generateCategoryToDemos()
+        private static Dictionary<GalleryDemoCategory, List<GalleryDemo>> _generateCategoryToDemos()
-            {
-                result.Add(category, kAllGalleryDemos.Where((GalleryDemo demo) =>
-                {
-                    return demo.category == category;
-                }).ToList());
-            }
+                result.Add(category,
+                    kAllGalleryDemos.Where((GalleryDemo demo) => { return demo.category == category; }).ToList());

            return result;
        }

-        static Dictionary<string, string> _generateDemoDocumentationUrls()
+        private static Dictionary<string, string> _generateDemoDocumentationUrls()
-            {
-                {
-                }
-            }

            return result;
        }
-    
-    
 }
--- a/com.unity.uiwidgets/Editor/UIWidgetsPanelEditor.cs
+++ b/com.unity.uiwidgets/Editor/UIWidgetsPanelEditor.cs
            base.OnInspectorGUI();
            var pixelRatioProperty = serializedObject.FindProperty("devicePixelRatioOverride");
            var antiAliasingProperty = serializedObject.FindProperty("hardwareAntiAliasing");
+            var ShowDebugLog = serializedObject.FindProperty("m_ShowDebugLog");
+            EditorGUI.BeginChangeCheck();
+            EditorGUILayout.PropertyField(ShowDebugLog);
+            if (EditorGUI.EndChangeCheck()) {
+                UIWidgetsPanel.ShowDebugLog = ShowDebugLog.boolValue;
+            }
            UIWidgetsPanel panel = (UIWidgetsPanel)target;
            
            serializedObject.ApplyModifiedProperties(); 
--- a/com.unity.uiwidgets/Runtime/animation/animation_controller.cs
+++ b/com.unity.uiwidgets/Runtime/animation/animation_controller.cs
 using System.Collections.Generic;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.physics;
-using Unity.UIWidgets.scheduler2;
-using UnityEngine;
 using Ticker = Unity.UIWidgets.scheduler2.Ticker;
 using TickerFuture = Unity.UIWidgets.scheduler2.TickerFuture;
 using TickerProvider = Unity.UIWidgets.scheduler2.TickerProvider;
        reverse,
    }

+    public enum AnimationBehavior {
+        normal,
+        preserve,
+    }
+
    public class AnimationController :
        AnimationLocalStatusListenersMixinAnimationLocalListenersMixinAnimationEagerListenerMixinAnimation<float> {
        public AnimationController(
            string debugLabel = null,
            float lowerBound = 0.0f,
            float upperBound = 1.0f,
+            AnimationBehavior animationBehavior = AnimationBehavior.normal,
            TickerProvider vsync = null
        ) {
            D.assert(upperBound >= lowerBound);
            this.debugLabel = debugLabel;
            this.lowerBound = lowerBound;
            this.upperBound = upperBound;
+            this.animationBehavior = animationBehavior;

            _ticker = vsync.createTicker(_tick);
            _internalSetValue(value ?? lowerBound);
            TimeSpan? duration = null,
            TimeSpan? reverseDuration = null,
            string debugLabel = null,
+            AnimationBehavior? animationBehavior = null,
+            D.assert(animationBehavior != null);
            lowerBound = float.NegativeInfinity;
            upperBound = float.PositiveInfinity;
            _direction = _AnimationDirection.forward;
            this.debugLabel = debugLabel;
+            this.animationBehavior = animationBehavior.Value;

            _ticker = vsync.createTicker(_tick);
            _internalSetValue(value);
            TimeSpan? duration = null,
            TimeSpan? reverseDuration = null,
            string debugLabel = null,
-            TickerProvider vsync = null
+            TickerProvider vsync = null,
+            AnimationBehavior animationBehavior = AnimationBehavior.preserve
-            return new AnimationController(value, duration, reverseDuration, debugLabel, vsync);
+            return new AnimationController(value, duration, reverseDuration, debugLabel, animationBehavior, vsync);
+
+        public readonly AnimationBehavior animationBehavior;

        public readonly string debugLabel;


            if (_reverse && _isPlayingReverse) {
                directionSetter(_AnimationDirection.reverse);
-                return Mathf.Lerp(_max, _min, t);
+                return MathUtils.lerpNullableFloat(_max, _min, t);
-                return Mathf.Lerp(_min, _max, t);
+                return MathUtils.lerpNullableFloat(_min, _max, t);
            }
        }

--- a/com.unity.uiwidgets/Runtime/animation/curves.cs
+++ b/com.unity.uiwidgets/Runtime/animation/curves.cs
                }
            }
            float t2 = (t - startValue.dx) / (endValue.dx - startValue.dx);
-            return Mathf.Lerp(startValue.dy, endValue.dy, t2);
+            return MathUtils.lerpNullableFloat(startValue.dy, endValue.dy, t2);
        }
    }

--- a/com.unity.uiwidgets/Runtime/cupertino/date_picker.cs
+++ b/com.unity.uiwidgets/Runtime/cupertino/date_picker.cs
            TimeSpan? initialTimerDuration = null,
            int minuteInterval = 1,
            int secondInterval = 1,
-            Alignment alignment = null,
+            AlignmentGeometry alignment = null,
            Color backgroundColor = null,
            ValueChanged<TimeSpan> onTimerDurationChanged = null
            ):base(key : key) {
        public readonly int minuteInterval;
        public readonly int secondInterval;
        public readonly ValueChanged<TimeSpan> onTimerDurationChanged;
-        public readonly Alignment alignment;
+        public readonly AlignmentGeometry alignment;
        public readonly Color backgroundColor;
        
        public override State createState() {
--- a/com.unity.uiwidgets/Runtime/cupertino/route.cs
+++ b/com.unity.uiwidgets/Runtime/cupertino/route.cs
            }
            if (animateForward) {
                int droppedPageForwardAnimationTime = Mathf.Min(
-                    Mathf.Lerp(CupertinoRouteUtils._kMaxDroppedSwipePageForwardAnimationTime, 0f,
+                    MathUtils.lerpNullableFloat(CupertinoRouteUtils._kMaxDroppedSwipePageForwardAnimationTime, 0f,
                        controller.value).floor(),
                    CupertinoRouteUtils._kMaxPageBackAnimationTime
                );

                if (controller.isAnimating) {
                    int droppedPageBackAnimationTime =
-                        Mathf.Lerp(0f, CupertinoRouteUtils._kMaxDroppedSwipePageForwardAnimationTime,
+                        MathUtils.lerpNullableFloat(0f, CupertinoRouteUtils._kMaxDroppedSwipePageForwardAnimationTime,
                            controller.value).floor();
                    controller.animateBack(0.0f, duration: TimeSpan.FromMilliseconds(droppedPageBackAnimationTime),
                        curve: animationCurve);
--- a/com.unity.uiwidgets/Runtime/cupertino/slider.cs
+++ b/com.unity.uiwidgets/Runtime/cupertino/slider.cs
    class _CupertinoSliderState : TickerProviderStateMixin<CupertinoSlider> {
        void _handleChanged(float value) {
            D.assert(widget.onChanged != null);
-            float lerpValue = Mathf.Lerp(widget.min, widget.max, value);
+            float lerpValue = MathUtils.lerpNullableFloat(widget.min, widget.max, value);
            if (lerpValue != widget.value) {
                widget.onChanged(lerpValue);
            }
            D.assert(widget.onChangeStart != null);
-            widget.onChangeStart(Mathf.Lerp(widget.min, widget.max, value));
+            widget.onChangeStart(MathUtils.lerpNullableFloat(widget.min, widget.max, value));
-            widget.onChangeEnd(Mathf.Lerp(widget.min, widget.max, value));
+            widget.onChangeEnd(MathUtils.lerpNullableFloat(widget.min, widget.max, value));
        }

        public override Widget build(BuildContext context) {
                        visualPosition = _value;
                        break;
                }
-                return Mathf.Lerp(_trackLeft + CupertinoThumbPainter.radius, _trackRight - CupertinoThumbPainter.radius, visualPosition);
+                return MathUtils.lerpNullableFloat(_trackLeft + CupertinoThumbPainter.radius, _trackRight - CupertinoThumbPainter.radius, visualPosition);
            }
        }

--- a/com.unity.uiwidgets/Runtime/cupertino/switch.cs
+++ b/com.unity.uiwidgets/Runtime/cupertino/switch.cs
            canvas.drawRRect(trackRRect, paint);

            float currentThumbExtension = CupertinoThumbPainter.extension * currentReactionValue;
-            float thumbLeft = Mathf.Lerp(
+            float thumbLeft = MathUtils.lerpNullableFloat(
-            float thumbRight = Mathf.Lerp(
+            float thumbRight = MathUtils.lerpNullableFloat(
                trackRect.left + CupertinoSwitchUtils._kTrackInnerStart + CupertinoThumbPainter.radius +
                currentThumbExtension,
                trackRect.left + CupertinoSwitchUtils._kTrackInnerEnd + CupertinoThumbPainter.radius,
--- a/com.unity.uiwidgets/Runtime/engine2/UIWidgetsPanel.cs
+++ b/com.unity.uiwidgets/Runtime/engine2/UIWidgetsPanel.cs
            }
        }

+        public bool m_ShowDebugLog = false;
+        
+        public static List<UIWidgetsPanel> panels = new List<UIWidgetsPanel>();
+        public static bool ShowDebugLog {
+            get => _ShowDebugLog;
+            set {
+                foreach (var panel in panels) {
+                    panel.m_ShowDebugLog = value;
+                }
+
+                _ShowDebugLog = value;
+            }
+        }
+        
+        static bool _ShowDebugLog = false;
+
        protected void OnEnable() {
            base.OnEnable();
            D.assert(_renderTexture == null);
            _ptr = UIWidgetsPanel_constructor((IntPtr) _handle, UIWidgetsPanel_entrypoint);
+
+            panels.Add(this);
+            _ShowDebugLog = m_ShowDebugLog;
+
            var settings = new Dictionary<string, object>();
            if (fonts != null && fonts.Length > 0) {
                settings.Add("fonts", fontsToObject(fonts));
            _handle = default;

            _disableUIWidgetsPanel();
+            panels.Remove(this);

            D.assert(!isolate.isValid);
            base.OnDisable();
--- a/com.unity.uiwidgets/Runtime/foundation/debug.cs
+++ b/com.unity.uiwidgets/Runtime/foundation/debug.cs
 using System;
 using System.Diagnostics;
 using System.Linq;
+using Unity.UIWidgets.engine2;
 using Unity.UIWidgets.painting;
 using Unity.UIWidgets.ui;
 using Canvas = Unity.UIWidgets.ui.Canvas;

        [Conditional("UNITY_ASSERTIONS")]
        public static void assert(Func<bool> result, Func<string> message = null) {
-            if (!result()) {
+            if (UIWidgetsPanel.ShowDebugLog && !result()) {
                throw new AssertionError(message != null ? message() : "");
            }
        }
-            if (!result) {
+            if (UIWidgetsPanel.ShowDebugLog && !result) {
                throw new AssertionError(message != null ? message() : "");
            }
        }
--- a/com.unity.uiwidgets/Runtime/gestures/multidrag.cs
+++ b/com.unity.uiwidgets/Runtime/gestures/multidrag.cs

            D.assert(_pointers.ContainsKey(pointer));
            GestureBinding.instance.pointerRouter.removeRoute(pointer, _handleEvent);
-            _pointers[pointer].dispose();
+            var pointerData = _pointers[pointer];
+            pointerData.dispose();
        }


--- a/com.unity.uiwidgets/Runtime/material/animated_icons/animated_icons.cs
+++ b/com.unity.uiwidgets/Runtime/material/animated_icons/animated_icons.cs
                return values[0];
            }

-            float targetIdx = Mathf.Lerp(0, values.Count - 1, progress);
+            float targetIdx = MathUtils.lerpNullableFloat(0, values.Count - 1, progress);
            int lowIdx = targetIdx.floor();
            int highIdx = targetIdx.ceil();
            float t = targetIdx - lowIdx;
        public readonly List<float> opacities;

        public void paint(Canvas canvas, Color color, _UiPathFactory uiPathFactory, float progress) {
-            float opacity = AnimatedIconUtils._interpolate<float>(opacities, progress, Mathf.Lerp);
+            float opacity = AnimatedIconUtils._interpolate<float>(opacities, progress, MathUtils.lerpNullableFloat);
            Paint paint = new Paint();
            paint.style = PaintingStyle.fill;
            paint.color = color.withOpacity(color.opacity * opacity);
--- a/com.unity.uiwidgets/Runtime/material/app_bar_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/app_bar_theme.cs
            return new AppBarTheme(
                brightness: t < 0.5f ? a?.brightness : b?.brightness,
                color: Color.lerp(a?.color, b?.color, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                iconTheme: IconThemeData.lerp(a?.iconTheme, b?.iconTheme, t),
                actionsIconTheme: IconThemeData.lerp(a?.actionsIconTheme, b?.actionsIconTheme, t),
                textTheme: TextTheme.lerp(a?.textTheme, b?.textTheme, t)
--- a/com.unity.uiwidgets/Runtime/material/arc.cs
+++ b/com.unity.uiwidgets/Runtime/material/arc.cs
            }

            Offset center = _centerArc.lerp(t);
-            float width = Mathf.Lerp(begin.width, end.width, t);
-            float height = Mathf.Lerp(begin.height, end.height, t);
+            float width = MathUtils.lerpNullableFloat(begin.width, end.width, t);
+            float height = MathUtils.lerpNullableFloat(begin.height, end.height, t);
            return Rect.fromLTWH(
                (center.dx - width / 2.0f),
                (center.dy - height / 2.0f),
--- a/com.unity.uiwidgets/Runtime/material/bottom_app_bar_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/bottom_app_bar_theme.cs
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;
        public static BottomAppBarTheme lerp(BottomAppBarTheme a, BottomAppBarTheme b, float t) {
            return new BottomAppBarTheme(
                color: Color.lerp(a?.color, b?.color, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                shape: t < 0.5f ? a?.shape : b?.shape
            );
        }
--- a/com.unity.uiwidgets/Runtime/material/bottom_sheet.cs
+++ b/com.unity.uiwidgets/Runtime/material/bottom_sheet.cs
    public partial class material_ {
        public static readonly TimeSpan _bottomSheetEnterDuration = new TimeSpan(0, 0, 0, 0, 250);
        public static readonly TimeSpan _bottomSheetExitDuration = new TimeSpan(0, 0, 0, 0, 200);
-        public static readonly Curve _modalBottomSheetCurve = material_.decelerateEasing;
+
+        public static Curve _modalBottomSheetCurve {
+            get => decelerateEasing;
+        }
+
        public const float _minFlingVelocity = 700.0f;
        public const float _closeProgressThreshold = 0.5f;

            D.assert(builder != null);
            D.assert(elevation == null || elevation >= 0.0);

-            D.assert(elevation >= 0.0f);
            this.animationController = animationController;
            this.enableDrag = enableDrag;
            this.elevation = elevation;
--- a/com.unity.uiwidgets/Runtime/material/button_bar_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/button_bar_theme.cs
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
 using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
-using UnityEngine;
-using Object = UnityEngine.Object;

 namespace Unity.UIWidgets.material {
    public class ButtonBarThemeData : Diagnosticable, IEquatable<ButtonBarThemeData> {
            ButtonBarLayoutBehavior? layoutBehavior = null,
            VerticalDirection? overflowDirection = null
        ) {
-            D.assert(buttonMinWidth >= 0.0f);
-            D.assert(buttonHeight >= 0.0f);
+            D.assert(buttonMinWidth == null || buttonMinWidth >= 0.0f);
+            D.assert(buttonHeight == null || buttonHeight >= 0.0f);
            this.alignment = alignment;
            this.mainAxisSize = mainAxisSize;
            this.buttonTextTheme = buttonTextTheme;
                alignment: t < 0.5 ? a.alignment : b.alignment,
                mainAxisSize: t < 0.5 ? a.mainAxisSize : b.mainAxisSize,
                buttonTextTheme: t < 0.5 ? a.buttonTextTheme : b.buttonTextTheme,
-                buttonMinWidth: Mathf.Lerp(a?.buttonMinWidth ?? 0, b?.buttonMinWidth ?? 0, t),
-                buttonHeight: Mathf.Lerp(a?.buttonHeight ?? 0, b?.buttonHeight ?? 0, t),
+                buttonMinWidth: MathUtils.lerpNullableFloat(a?.buttonMinWidth, b?.buttonMinWidth, t),
+                buttonHeight: MathUtils.lerpNullableFloat(a?.buttonHeight, b?.buttonHeight, t),
                buttonPadding: EdgeInsetsGeometry.lerp(a?.buttonPadding, b?.buttonPadding, t),
                buttonAlignedDropdown: t < 0.5 ? a.buttonAlignedDropdown : b.buttonAlignedDropdown,
                layoutBehavior: t < 0.5 ? a.layoutBehavior : b.layoutBehavior,

        public override int GetHashCode() {
            unchecked {
-                var hashCode = (int) alignment;
-                hashCode = (hashCode * 397) ^ (int) mainAxisSize;
-                hashCode = (hashCode * 397) ^ (int) buttonTextTheme;
-                hashCode = (hashCode * 397) ^ buttonMinWidth.GetHashCode();
-                hashCode = (hashCode * 397) ^ buttonHeight.GetHashCode();
+                var hashCode = (int) (alignment ?? 0);
+                hashCode = (hashCode * 397) ^ (int) (mainAxisSize ?? 0);
+                hashCode = (hashCode * 397) ^ (int) (buttonTextTheme ?? 0);
+                hashCode = (hashCode * 397) ^ (buttonMinWidth?.GetHashCode() ?? 0);
+                hashCode = (hashCode * 397) ^ (buttonHeight?.GetHashCode() ?? 0);
-                hashCode = (hashCode * 397) ^ buttonAlignedDropdown.GetHashCode();
-                hashCode = (hashCode * 397) ^ (int) layoutBehavior;
-                hashCode = (hashCode * 397) ^ (int) overflowDirection;
+                hashCode = (hashCode * 397) ^ (buttonAlignedDropdown?.GetHashCode() ?? 0);
+                hashCode = (hashCode * 397) ^ (int) (layoutBehavior ?? 0);
+                hashCode = (hashCode * 397) ^ (int) (overflowDirection ?? 0);
                return hashCode;
            }
        }
--- a/com.unity.uiwidgets/Runtime/material/button_sheet_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/button_sheet_theme.cs
                return null;
            return new BottomSheetThemeData(
                backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0, b?.elevation ?? 0, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
-                modalElevation: Mathf.Lerp(a?.modalElevation ?? 0, b?.modalElevation ?? 0, t),
+                modalElevation: MathUtils.lerpNullableFloat(a?.modalElevation, b?.modalElevation, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
                clipBehavior: t < 0.5 ? a?.clipBehavior : b?.clipBehavior
            );
--- a/com.unity.uiwidgets/Runtime/material/card_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/card_theme.cs
                clipBehavior: t < 0.5f ? a?.clipBehavior : b?.clipBehavior,
                color: Color.lerp(a?.color, b?.color, t),
                shadowColor: Color.lerp(a?.shadowColor, b?.shadowColor, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                margin: EdgeInsetsGeometry.lerp(a?.margin, b?.margin, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t)
            );
--- a/com.unity.uiwidgets/Runtime/material/checkbox_list_tile.cs
+++ b/com.unity.uiwidgets/Runtime/material/checkbox_list_tile.cs
 namespace Unity.UIWidgets.material {
    public class CheckboxListTile : StatelessWidget {
        public CheckboxListTile(
-            Key key,
+            Key key = null,
            bool? value = null,
            ValueChanged<bool?> onChanged = null,
            Color activeColor = null,
            this.secondary = secondary;
            this.selected = selected;
            this.controlAffinity = controlAffinity;
+            this.value = value;
+            this.activeColor = activeColor;
+            this.onChanged = onChanged;
        }

        public readonly bool? value;
--- a/com.unity.uiwidgets/Runtime/material/chip_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/chip_theme.cs
                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: Mathf.Lerp(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
-                pressElevation: Mathf.Lerp(a?.pressElevation ?? 0.0f, b?.pressElevation ?? 0.0f, t)
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
+                pressElevation: MathUtils.lerpNullableFloat(a?.pressElevation, b?.pressElevation, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/material/data_table.cs
+++ b/com.unity.uiwidgets/Runtime/material/data_table.cs
            // TODO(dkwingsmt): Only wrap Inkwell if onSort != null. Blocked by
            // https://github.com/flutter/flutter/issues/51152
            label = new InkWell(
-                onTap: () => onSort(),
+                onTap: () => onSort?.Invoke(),
                child: label
            );
            return label;
                              !rows.Any((DataRow row) => row.onSelectChanged != null && !row.selected);

            List<TableColumnWidth> tableColumns =
-                new List<TableColumnWidth>(columns.Count + (displayCheckboxColumn ? 1 : 0));
-            List<TableRow> tableRows = Enumerable.Range(1, 10).Select((index) => {
+                new List<TableColumnWidth>(new TableColumnWidth[columns.Count + (displayCheckboxColumn ? 1 : 0)]);
+            
+            List<TableRow> tableRows = Enumerable.Range(0, rows.Count + 1).Select((index) => {
-                    children: new List<Widget>(tableColumns.Count)
+                    children: new List<Widget>(new Widget[tableColumns.Count])
-            // List<TableRow> tableRows = List<TableRow>.gegenerate(
-            //     rows.length + 1, // the +1 is for the header row
-            //     (int index) {
-            //     return TableRow(
-            //         key: index == 0 ? _headingRowKey : rows[index - 1].key,
-            //         decoration: index > 0 && rows[index - 1].selected
-            //             ? _kSelectedDecoration
-            //             : _kUnselectedDecoration,
-            //         children: List<Widget>(tableColumns.length),
-            //     );
-            // },
-            // );

            int rowIndex;

                    tableColumns[displayColumnIndex] = new IntrinsicColumnWidth();
                }

+                var currentColumnIndex = dataColumnIndex;
                tableRows[0].children[displayColumnIndex] = _buildHeadingCell(
                    context: context,
                    padding: padding,
                    onSort: column.onSort != null
-                        ? () => column.onSort(dataColumnIndex, sortColumnIndex != dataColumnIndex || !sortAscending)
+                        ? () => column.onSort(currentColumnIndex, sortColumnIndex != currentColumnIndex || !sortAscending)
                        : (VoidCallback) null,
                    sorted: dataColumnIndex == sortColumnIndex,
                    ascending: sortAscending
                    DataCell cell = row.cells[dataColumnIndex];
+                    var curRow = row;
                    tableRows[rowIndex].children[displayColumnIndex] = _buildDataCell(
                        context: context,
                        padding: padding,
                        showEditIcon: cell.showEditIcon,
                        onTap: cell.onTap,
                        onSelectChanged: () => {
-                            if (row.onSelectChanged != null) {
-                                row.onSelectChanged(!row.selected);
+                            if (curRow.onSelectChanged != null) {
+                                curRow.onSelectChanged(!curRow.selected);
                            }
                        });
                    rowIndex += 1;
--- a/com.unity.uiwidgets/Runtime/material/data_table_source.cs
+++ b/com.unity.uiwidgets/Runtime/material/data_table_source.cs
    public abstract class DataTableSource : ChangeNotifier {
        public abstract DataRow getRow(int index);

-        public int rowCount { get; }
+        public virtual int rowCount { get; }
-        public bool isRowCountApproximate { get; }
+        public virtual bool isRowCountApproximate { get; }
-        public int selectedRowCount { get; }
+        public virtual int selectedRowCount { get; }
    }
 }
--- a/com.unity.uiwidgets/Runtime/material/dialog_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/dialog_theme.cs
 using System;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;
        public static DialogTheme lerp(DialogTheme a, DialogTheme b, float t) {
            return new DialogTheme(
                backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0.0f, b?.elevation ?? 0.0f, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
                titleTextStyle: TextStyle.lerp(a?.titleTextStyle, b?.titleTextStyle, t),
                contentTextStyle: TextStyle.lerp(a?.contentTextStyle, b?.contentTextStyle, t)
--- a/com.unity.uiwidgets/Runtime/material/divider_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/divider_theme.cs
 using System;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;
        public static DividerThemeData lerp(DividerThemeData a, DividerThemeData b, float t) {
            return new DividerThemeData(
                color: Color.lerp(a?.color, b?.color, t),
-                space: Mathf.Lerp(a?.space ?? 0, b?.space ?? 0, t),
-                thickness: Mathf.Lerp(a?.thickness ?? 0, b?.thickness ?? 0, t),
-                indent: Mathf.Lerp(a?.indent ?? 0, b?.indent ?? 0, t),
-                endIndent: Mathf.Lerp(a?.endIndent ?? 0, b?.endIndent ?? 0, t)
+                space: MathUtils.lerpNullableFloat(a?.space, b?.space, t),
+                thickness: MathUtils.lerpNullableFloat(a?.thickness, b?.thickness, t),
+                indent: MathUtils.lerpNullableFloat(a?.indent, b?.indent, t),
+                endIndent: MathUtils.lerpNullableFloat(a?.endIndent, b?.endIndent, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/material/dropdown.cs
+++ b/com.unity.uiwidgets/Runtime/material/dropdown.cs
                ? material_._kAlignedMenuMargin
                : material_._kUnalignedMenuMargin;

-            List<_MenuItem<T>> menuItems = new List<_MenuItem<T>>(widget.items.Count);
+            List<_MenuItem<T>> menuItems = new List<_MenuItem<T>>(new _MenuItem<T>[widget.items.Count]);
-                menuItems[index] = new _MenuItem<T>(
-                    item: widget.items[index],
+                var pindex = index;
+                menuItems[pindex] = new _MenuItem<T>(
+                    item: widget.items[pindex],
-                        _dropdownRoute.itemHeights[index] = size.height;
+                        _dropdownRoute.itemHeights[pindex] = size.height;
                    }
                );
            }
--- a/com.unity.uiwidgets/Runtime/material/floatting_action_button_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/floatting_action_button_theme.cs
 using System;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;

                focusColor: Color.lerp(a?.focusColor, b?.focusColor, t),
                hoverColor: Color.lerp(a?.hoverColor, b?.hoverColor, t),
                splashColor: Color.lerp(a?.splashColor, b?.splashColor, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0, b?.elevation ?? 0, t),
-                focusElevation: Mathf.Lerp(a?.focusElevation ?? 0, b?.focusElevation ?? 0, t),
-                hoverElevation: Mathf.Lerp(a?.hoverElevation ?? 0, b?.hoverElevation ?? 0, t),
-                disabledElevation: Mathf.Lerp(a?.disabledElevation ?? 0, b?.disabledElevation ?? 0, t),
-                highlightElevation: Mathf.Lerp(a?.highlightElevation ?? 0, b?.highlightElevation ?? 0, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
+                focusElevation: MathUtils.lerpNullableFloat(a?.focusElevation, b?.focusElevation, t),
+                hoverElevation: MathUtils.lerpNullableFloat(a?.hoverElevation, b?.hoverElevation, t),
+                disabledElevation: MathUtils.lerpNullableFloat(a?.disabledElevation, b?.disabledElevation, t),
+                highlightElevation: MathUtils.lerpNullableFloat(a?.highlightElevation, b?.highlightElevation, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t)
            );
        }
--- a/com.unity.uiwidgets/Runtime/material/grid_tile_bar.cs
+++ b/com.unity.uiwidgets/Runtime/material/grid_tile_bar.cs
 using Unity.UIWidgets.widgets;

 namespace Unity.UIWidgets.material {
-    class GridTileBar : StatelessWidget {
+    public class GridTileBar : StatelessWidget {
        public GridTileBar(
            Key key = null,
            Color backgroundColor = null,
--- a/com.unity.uiwidgets/Runtime/material/icon_button.cs
+++ b/com.unity.uiwidgets/Runtime/material/icon_button.cs
            float iconSize = 24.0f,
            VisualDensity visualDensity = null,
            EdgeInsetsGeometry padding = null,
-            Alignment alignment = null,
+            AlignmentGeometry alignment = null,
            Widget icon = null,
            Color color = null,
            Color focusColor = null,

        public readonly EdgeInsetsGeometry padding;

-        public readonly Alignment alignment;
+        public readonly AlignmentGeometry alignment;

        public readonly Widget icon;

--- a/com.unity.uiwidgets/Runtime/material/ink_decoration.cs
+++ b/com.unity.uiwidgets/Runtime/material/ink_decoration.cs
            ImageErrorListener onImageError = null,
            ColorFilter colorFilter = null,
            BoxFit? fit = null,
-            Alignment alignment = null,
+            AlignmentGeometry alignment = null,
            Rect centerSlice = null,
            ImageRepeat repeat = ImageRepeat.noRepeat,
            float? width = null,
            VoidCallback onRemoved = null
        ) : base(controller: controller, referenceBox: referenceBox, onRemoved: onRemoved) {
            D.assert(configuration != null);
-            D.assert(decoration != null);
            D.assert(controller != null);
            D.assert(referenceBox != null);
            _configuration = configuration;
--- a/com.unity.uiwidgets/Runtime/material/input_border.cs
+++ b/com.unity.uiwidgets/Runtime/material/input_border.cs
                canvas.drawRRect(center, paint);
            }
            else {
-                float extent = Mathf.Lerp(0.0f, gapExtent + gapPadding * 2.0f, gapPercentage);
+                float extent = MathUtils.lerpNullableFloat(0.0f, gapExtent + gapPadding * 2.0f, gapPercentage);
                Path path = _gapBorderPath(canvas, center, Mathf.Max(0.0f,gapStart - gapPadding), extent);
                canvas.drawPath(path, paint);
            }
--- a/com.unity.uiwidgets/Runtime/material/input_decorator.cs
+++ b/com.unity.uiwidgets/Runtime/material/input_decorator.cs
                float t = decoration.floatingLabelProgress;
                bool isOutlineBorder = decoration.border != null && decoration.border.isOutline;
                float floatingY = isOutlineBorder ? -labelHeight * 0.25f : contentPadding.top;
-                float scale = Mathf.Lerp(1.0f, 0.75f, t);
+                float scale = MathUtils.lerpNullableFloat(1.0f, 0.75f, t);
-                float dy = Mathf.Lerp(0.0f, floatingY - labelOffset.dy, t);
+                float dy = MathUtils.lerpNullableFloat(0.0f, floatingY - labelOffset.dy, t);
                _labelTransform = Matrix4.identity();
                _labelTransform.translate(dx, labelOffset.dy + dy);
                _labelTransform.scale(scale, scale, 1);
--- a/com.unity.uiwidgets/Runtime/material/mergeable_material.cs
+++ b/com.unity.uiwidgets/Runtime/material/mergeable_material.cs
        float _getGapSize(int index) {
            MaterialGap gap = (MaterialGap) _children[index];

-            return Mathf.Lerp(_animationTuples[gap.key].gapStart,
+            return MathUtils.lerpNullableFloat(_animationTuples[gap.key].gapStart,
                gap.size,
                _animationTuples[gap.key].gapAnimation.value);
        }
--- a/com.unity.uiwidgets/Runtime/material/navigation_rail.cs
+++ b/com.unity.uiwidgets/Runtime/material/navigation_rail.cs
                materialChildren.AddRange(new List<Widget>() {
                    new ConstrainedBox(
                        constraints: new BoxConstraints(
-                            minWidth: Mathf.Lerp(minWidth, minExtendedWidth, _extendedAnimation.value)
+                            minWidth: MathUtils.lerpNullableFloat(minWidth, minExtendedWidth, _extendedAnimation.value)
                        ),
                        child: widget.leading
                    ),
            if (widget.trailing != null) {
                alignChildren.Add(new ConstrainedBox(
                    constraints: new BoxConstraints(
-                        minWidth: Mathf.Lerp(minWidth, minExtendedWidth, _extendedAnimation.value)
+                        minWidth: MathUtils.lerpNullableFloat(minWidth, minExtendedWidth, _extendedAnimation.value)
                    ),
                    child: widget.trailing
                ));
                    else {
                        content = new ConstrainedBox(
                            constraints: new BoxConstraints(
-                                minWidth: Mathf.Lerp(minWidth ?? 0, minExtendedWidth ?? 0,
-                                    extendedTransitionAnimation.value)
+                                minWidth: MathUtils.lerpNullableFloat(minWidth, minExtendedWidth,
+                                    extendedTransitionAnimation.value) ?? 0
                            ),
                            child: new ClipRect(
                                child: new Row(

                    float appearingAnimationValue = 1 - _positionAnimation.value;

-                    float verticalPadding = Mathf.Lerp(material_._verticalDestinationPaddingNoLabel,
+                    float verticalPadding = MathUtils.lerpNullableFloat(material_._verticalDestinationPaddingNoLabel,
                        material_._verticalDestinationPaddingWithLabel, appearingAnimationValue);
                    content = new Container(
                        constraints: new BoxConstraints(
--- a/com.unity.uiwidgets/Runtime/material/navigation_rail_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/navigation_rail_theme.cs
 using System;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;
                return null;
            return new NavigationRailThemeData(
                backgroundColor: Color.lerp(a?.backgroundColor, b?.backgroundColor, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0, b?.elevation ?? 0, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
-                groupAlignment: Mathf.Lerp(a?.groupAlignment ?? 0, b?.groupAlignment ?? 0, t),
+                groupAlignment: MathUtils.lerpNullableFloat(a?.groupAlignment, b?.groupAlignment, t),
                labelType: t < 0.5 ? a?.labelType : b?.labelType
            );
        }
        }

        public static bool operator !=(NavigationRailThemeData self, NavigationRailThemeData other) {
-            return Equals(self, other);
+            return !Equals(self, other);
        }

        public bool Equals(NavigationRailThemeData other) {
--- a/com.unity.uiwidgets/Runtime/material/paginated_data_table.cs
+++ b/com.unity.uiwidgets/Runtime/material/paginated_data_table.cs
            this.availableRowsPerPage = availableRowsPerPage;
            this.onRowsPerPageChanged = onRowsPerPageChanged;
            this.dragStartBehavior = dragStartBehavior;
+            this.source = source;
        }


--- a/com.unity.uiwidgets/Runtime/material/popup_menu.cs
+++ b/com.unity.uiwidgets/Runtime/material/popup_menu.cs
            PopupMenuThemeData popupMenuTheme = PopupMenuTheme.of(context);

            for (int i = 0; i < route.items.Count; i += 1) {
-                float start = (i + 1) * unit;
+                int index = i;
+                float start = (index + 1) * unit;
-                Widget item = route.items[i];
-                if (route.initialValue != null && route.items[i].represents((T) route.initialValue)) {
+                Widget item = route.items[index];
+                if (route.initialValue != null && route.items[index].represents((T) route.initialValue)) {
                    item = new Container(
                        color: Theme.of(context).highlightColor,
                        child: item
                children.Add(
                    new _MenuItem(
-                        onLayout: (Size size) => { route.itemSizes[i] = size; },
+                        onLayout: (Size size) => { route.itemSizes[index] = size; },
                        child: new FadeTransition(
                            opacity: opacityCurvedAnimation,
                            child: item
            this.color = color;
            this.showMenuContext = showMenuContext;
            this.captureInheritedThemes = captureInheritedThemes;
-            itemSizes = new List<Size>(items.Count);
+            itemSizes = new List<Size>(new Size[items.Count]);
        }

        public readonly RelativeRect position;
            this.child = child;
            this.icon = icon;
            this.offset = offset;
+            this.enabled = enabled;
+            this.shape = shape;
+            this.color = color;
+            this.captureInheritedThemes = captureInheritedThemes;
        }


--- a/com.unity.uiwidgets/Runtime/material/popup_menu_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/popup_menu_theme.cs
 using System;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
+using TextStyle = Unity.UIWidgets.painting.TextStyle;

 namespace Unity.UIWidgets.material {
    public class PopupMenuThemeData : Diagnosticable, IEquatable<PopupMenuThemeData> {
            return new PopupMenuThemeData(
                color: Color.lerp(a?.color, b?.color, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0, b?.elevation ?? 0, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                textStyle: TextStyle.lerp(a?.textStyle, b?.textStyle, t)
            );
        }
        }

        public static bool operator !=(PopupMenuThemeData self, PopupMenuThemeData other) {
-            return Equals(self, other);
+            return !Equals(self, other);
        }

        public bool Equals(PopupMenuThemeData other) {
--- a/com.unity.uiwidgets/Runtime/material/radio.cs
+++ b/com.unity.uiwidgets/Runtime/material/radio.cs
        public const float _kInnerRadius = 4.5f;
    }

-    public class Radio<T> : StatefulWidget where T : class {
+    public class Radio<T> : StatefulWidget {
-            T value = null,
-            T groupValue = null,
+            T value = default,
+            T groupValue = default,
            ValueChanged<T> onChanged = null,
            bool toggleable = false,
            Color activeColor = null,
        ) : base(key: key) {
            D.assert(value != null);
            D.assert(groupValue != null);
-            D.assert(onChanged != null);
            this.value = value;
            this.groupValue = groupValue;
            this.onChanged = onChanged;
        }
    }

-    class _RadioState<T> : TickerProviderStateMixin<Radio<T>> where T : class {
+    class _RadioState<T> : TickerProviderStateMixin<Radio<T>> {
        bool enabled {
            get { return widget.onChanged != null; }
        }

        void _handleChanged(bool? selected) {
            if (selected == null) {
-                widget.onChanged(null);
+                widget.onChanged(default);
                return;
            }
            if (selected == true) {
                child: new Builder(
                    builder: (BuildContext subContext) => {
                    return new _RadioRenderObjectWidget(
-                    selected: widget.value == widget.groupValue,
+                    selected: widget.value.Equals(widget.groupValue),
                    activeColor: widget.activeColor ?? themeData.toggleableActiveColor,
                    inactiveColor: _getInactiveColor(themeData),
                    focusColor: widget.focusColor ?? themeData.focusColor,
--- a/com.unity.uiwidgets/Runtime/material/range_slider.cs
+++ b/com.unity.uiwidgets/Runtime/material/range_slider.cs
    }


-    class _RangeSliderState : SingleTickerProviderStateMixin<RangeSlider> {
+    class _RangeSliderState : TickerProviderStateMixin<RangeSlider> {
        static readonly TimeSpan enableAnimationDuration = new TimeSpan(0, 0, 0, 0, 75);
        static readonly TimeSpan valueIndicatorAnimationDuration = new TimeSpan(0, 0, 0, 0, 100);

        }

        float _lerp(float value) {
-            return Mathf.Lerp(widget.min, widget.max, value);
+            return MathUtils.lerpNullableFloat(widget.min, widget.max, value);
        }

        RangeValues _lerpRangeValues(RangeValues values) {
        float _discretize(float value) {
            float result = value.clamp(0.0f, 1.0f);
            if (isDiscrete) {
-                result = (result * divisions.Value).round() / divisions.Value;
+                result = (result * divisions.Value).round() * 1.0f / divisions.Value;
            }

            return result;
            );
        }

-        void paint(PaintingContext context, Offset offset) {
+        public override void paint(PaintingContext context, Offset offset) {
            float startValue = _state.startPositionController.value;
            float endValue = _state.endPositionController.value;

--- a/com.unity.uiwidgets/Runtime/material/ratio_list_tile.cs
+++ b/com.unity.uiwidgets/Runtime/material/ratio_list_tile.cs
 using Unity.UIWidgets.widgets;

 namespace Unity.UIWidgets.material {
-    public class RadioListTile<T> : StatelessWidget where T : class {
+    public class RadioListTile<T> : StatelessWidget {
        public RadioListTile(
            Key key = null,
            T value = default,
                    onTap: onChanged != null
                        ? () => {
                            if (toggleable && isChecked) {
-                                onChanged(null);
+                                onChanged(default);
                                return;
                            }

--- a/com.unity.uiwidgets/Runtime/material/refresh_indicator.cs
+++ b/com.unity.uiwidgets/Runtime/material/refresh_indicator.cs
                });
        }

-        Future show(bool atTop = true) {
+        public Future show(bool atTop = true) {
            if (_mode != _RefreshIndicatorMode.refresh && _mode != _RefreshIndicatorMode.snap) {
                if (_mode == null) {
                    _start(atTop ? AxisDirection.down : AxisDirection.up);
--- a/com.unity.uiwidgets/Runtime/material/scaffold.cs
+++ b/com.unity.uiwidgets/Runtime/material/scaffold.cs
                        )
                    ));
                }
+            }
-                if (_isExtendedFloatingActionButton(widget.child)) {
-                    children.Add(new ScaleTransition(
-                        scale: _extendedCurrentScaleAnimation,
-                        child: new FadeTransition(
-                            opacity: _currentScaleAnimation,
-                            child: widget.child
-                        )
-                    ));
-                }
-                else {
-                    children.Add(new ScaleTransition(
-                        scale: _currentScaleAnimation,
-                        child: new RotationTransition(
-                            turns: _currentRotationAnimation,
-                            child: widget.child
-                        )
-                    ));
-                }
+            if (_isExtendedFloatingActionButton(widget.child)) {
+                children.Add(new ScaleTransition(
+                    scale: _extendedCurrentScaleAnimation,
+                    child: new FadeTransition(
+                        opacity: _currentScaleAnimation,
+                        child: widget.child
+                    )
+                ));
+            }
+            else {
+                children.Add(new ScaleTransition(
+                    scale: _currentScaleAnimation,
+                    child: new RotationTransition(
+                        turns: _currentRotationAnimation,
+                        child: widget.child
+                    )
+                ));
            }

            return new Stack(

            float curveProgress = (t - startingPoint) / (1 - startingPoint);
            float transformed = curve.transform(curveProgress);
-            return Mathf.Lerp(startingPoint, 1, transformed);
+            return MathUtils.lerpNullableFloat(startingPoint, 1, transformed);
        }

        public override string ToString() {
--- a/com.unity.uiwidgets/Runtime/material/scrollbar.cs
+++ b/com.unity.uiwidgets/Runtime/material/scrollbar.cs
        }

        public override Widget build(BuildContext context) {
-            //TODO：uncomment here when cupertino updates are merged
-            /*if (_useCupertinoScrollbar.Value) {
+            if (_useCupertinoScrollbar.Value) {
-            }*/
+            }
+            
            return new NotificationListener<ScrollNotification>(
                onNotification: _handleScrollNotification,
                child: new RepaintBoundary(
--- a/com.unity.uiwidgets/Runtime/material/slider_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/slider_theme.cs
            D.assert(a != null);
            D.assert(b != null);
            return new SliderThemeData(
-                trackHeight: Mathf.Lerp(a.trackHeight.Value, b.trackHeight.Value, t),
+                trackHeight: MathUtils.lerpNullableFloat(a.trackHeight, b.trackHeight, t),
                activeTrackColor: Color.lerp(a.activeTrackColor, b.activeTrackColor, t),
                inactiveTrackColor: Color.lerp(a.inactiveTrackColor, b.inactiveTrackColor, t),
                disabledActiveTrackColor: Color.lerp(a.disabledActiveTrackColor, b.disabledActiveTrackColor, t),
                rangeValueIndicatorShape: t < 0.5 ? a.rangeValueIndicatorShape : b.rangeValueIndicatorShape,
                showValueIndicator: t < 0.5 ? a.showValueIndicator : b.showValueIndicator,
                valueIndicatorTextStyle: TextStyle.lerp(a.valueIndicatorTextStyle, b.valueIndicatorTextStyle, t),
-                minThumbSeparation: Mathf.Lerp(a.minThumbSeparation.Value, b.minThumbSeparation.Value, t),
+                minThumbSeparation: MathUtils.lerpNullableFloat(a.minThumbSeparation, b.minThumbSeparation, t),
                thumbSelector: t < 0.5 ? a.thumbSelector : b.thumbSelector
            );
        }
--- a/com.unity.uiwidgets/Runtime/material/snack_bar_theme.cs
+++ b/com.unity.uiwidgets/Runtime/material/snack_bar_theme.cs
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.material;
 using Unity.UIWidgets.painting;
+using Unity.UIWidgets.ui;
 using UnityEngine;
 using Color = Unity.UIWidgets.ui.Color;
 using Object = UnityEngine.Object;
                actionTextColor: Color.lerp(a?.actionTextColor, b?.actionTextColor, t),
                disabledActionTextColor: Color.lerp(a?.disabledActionTextColor, b?.disabledActionTextColor, t),
                contentTextStyle: TextStyle.lerp(a?.contentTextStyle, b?.contentTextStyle, t),
-                elevation: Mathf.Lerp(a?.elevation ?? 0, b?.elevation ?? 0, t),
+                elevation: MathUtils.lerpNullableFloat(a?.elevation, b?.elevation, t),
                shape: ShapeBorder.lerp(a?.shape, b?.shape, t),
                behavior: t < 0.5 ? a.behavior : b.behavior
            );
--- a/com.unity.uiwidgets/Runtime/material/switch.cs
+++ b/com.unity.uiwidgets/Runtime/material/switch.cs
        ) : base(key: key) {
            D.assert(value != null);
            this.value = value.Value;
-            D.assert(onChanged != null);
            D.assert(activeThumbImage != null || onActiveThumbImageError == null);
            D.assert(inactiveThumbImage != null || onInactiveThumbImageError == null);
            this.onChanged = onChanged;
--- a/com.unity.uiwidgets/Runtime/material/theme_data.cs
+++ b/com.unity.uiwidgets/Runtime/material/theme_data.cs
 using Unity.UIWidgets.cupertino;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.rendering;
-using Unity.UIWidgets.service;
 using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
            DialogTheme dialogTheme = null,
            FloatingActionButtonThemeData floatingActionButtonTheme = null,
            Typography typography = null,
-            SnackBarThemeData snackBarTheme = null
+            SnackBarThemeData snackBarTheme = null,
+            BottomSheetThemeData bottomSheetTheme = null,
+            PopupMenuThemeData popupMenuTheme = null,
+            MaterialBannerThemeData bannerTheme = null,
+            DividerThemeData dividerTheme = null,
+            ButtonBarThemeData buttonBarTheme = null
        ) {
            brightness = brightness ?? Brightness.light;
            bool isDark = brightness == Brightness.dark;
            dialogTheme = dialogTheme ?? new DialogTheme();
            floatingActionButtonTheme = floatingActionButtonTheme ?? new FloatingActionButtonThemeData();
            snackBarTheme = snackBarTheme ?? new SnackBarThemeData();
+            bottomSheetTheme = bottomSheetTheme ?? new BottomSheetThemeData();
+            popupMenuTheme = popupMenuTheme ?? new PopupMenuThemeData();
+            bannerTheme = bannerTheme ?? new MaterialBannerThemeData();
+            dividerTheme = dividerTheme ?? new DividerThemeData();
+            buttonBarTheme = buttonBarTheme ?? new ButtonBarThemeData();

            D.assert(brightness != null);
            D.assert(visualDensity != null);
            D.assert(dialogTheme != null);
            D.assert(floatingActionButtonTheme != null);
            D.assert(snackBarTheme != null);
+            D.assert(bottomSheetTheme != null);
+            D.assert(popupMenuTheme != null);
+            D.assert(bannerTheme != null);
+            D.assert(dividerTheme != null);
+            D.assert(buttonBarTheme != null);

            this.brightness = brightness ?? Brightness.light;
            this.visualDensity = visualDensity;
            this.floatingActionButtonTheme = floatingActionButtonTheme;
            this.typography = typography;
            this.snackBarTheme = snackBarTheme;
+            this.bottomSheetTheme = bottomSheetTheme;
+            this.popupMenuTheme = popupMenuTheme;
+            this.bannerTheme = bannerTheme;
+            this.dividerTheme = dividerTheme;
+            this.buttonBarTheme = buttonBarTheme;
        }

        public static ThemeData raw(
            DialogTheme dialogTheme = null,
            FloatingActionButtonThemeData floatingActionButtonTheme = null,
            Typography typography = null,
-            SnackBarThemeData snackBarTheme = null
+            SnackBarThemeData snackBarTheme = null,
+            BottomSheetThemeData bottomSheetTheme = null,
+            PopupMenuThemeData popupMenuTheme = null,
+            MaterialBannerThemeData bannerTheme = null,
+            DividerThemeData dividerTheme = null,
+            ButtonBarThemeData buttonBarTheme = null
        ) {
            D.assert(brightness != null);
            D.assert(visualDensity != null);
            D.assert(dialogTheme != null);
            D.assert(floatingActionButtonTheme != null);
            D.assert(snackBarTheme != null);
+            D.assert(bottomSheetTheme != null);
+            D.assert(popupMenuTheme != null);
+            D.assert(bannerTheme != null);
+            D.assert(dividerTheme != null);
+            D.assert(buttonBarTheme != null);

            return new ThemeData(
                brightness: brightness,
                dialogTheme: dialogTheme,
                floatingActionButtonTheme: floatingActionButtonTheme,
                typography: typography,
-                snackBarTheme: snackBarTheme);
+                snackBarTheme: snackBarTheme,
+                bottomSheetTheme: bottomSheetTheme,
+                popupMenuTheme: popupMenuTheme,
+                bannerTheme: bannerTheme,
+                dividerTheme: dividerTheme,
+                buttonBarTheme: buttonBarTheme
+                );
        }

        public static ThemeData from(
            DialogTheme dialogTheme = null,
            FloatingActionButtonThemeData floatingActionButtonTheme = null,
            Typography typography = null,
-            SnackBarThemeData snackBarTheme = null
+            SnackBarThemeData snackBarTheme = null,
+            BottomSheetThemeData bottomSheetTheme = null,
+            PopupMenuThemeData popupMenuTheme = null,
+            MaterialBannerThemeData bannerTheme = null,
+            DividerThemeData dividerTheme = null,
+            ButtonBarThemeData buttonBarTheme = null
        ) {
            return raw(
                brightness: brightness ?? this.brightness,
                dialogTheme: dialogTheme ?? this.dialogTheme,
                floatingActionButtonTheme: floatingActionButtonTheme ?? this.floatingActionButtonTheme,
                typography: typography ?? this.typography,
-                snackBarTheme: snackBarTheme ?? this.snackBarTheme
+                snackBarTheme: snackBarTheme ?? this.snackBarTheme,
+                bottomSheetTheme: bottomSheetTheme ?? this.bottomSheetTheme,
+                popupMenuTheme: popupMenuTheme ?? this.popupMenuTheme,
+                bannerTheme: bannerTheme ?? this.bannerTheme,
+                dividerTheme: dividerTheme ?? this.dividerTheme,
+                buttonBarTheme: buttonBarTheme ?? this.buttonBarTheme
            );
        }

                floatingActionButtonTheme: FloatingActionButtonThemeData.lerp(a.floatingActionButtonTheme,
                    b.floatingActionButtonTheme, t),
                typography: Typography.lerp(a.typography, b.typography, t),
-                snackBarTheme: SnackBarThemeData.lerp(a.snackBarTheme, b.snackBarTheme, t)
+                snackBarTheme: SnackBarThemeData.lerp(a.snackBarTheme, b.snackBarTheme, t),
+                bottomSheetTheme: BottomSheetThemeData.lerp(a.bottomSheetTheme, b.bottomSheetTheme, t),
+                popupMenuTheme: PopupMenuThemeData.lerp(a.popupMenuTheme, b.popupMenuTheme, t),
+                bannerTheme: MaterialBannerThemeData.lerp(a.bannerTheme, b.bannerTheme, t),
+                dividerTheme: DividerThemeData.lerp(a.dividerTheme, b.dividerTheme, t),
+                buttonBarTheme: ButtonBarThemeData.lerp(a.buttonBarTheme, b.buttonBarTheme, t)
            );
        }

                   other.dialogTheme == dialogTheme &&
                   other.floatingActionButtonTheme == floatingActionButtonTheme &&
                   other.typography == typography &&
-                   other.snackBarTheme == snackBarTheme;
+                   other.snackBarTheme == snackBarTheme &&
+                   other.bottomSheetTheme == bottomSheetTheme && 
+                   other.popupMenuTheme == popupMenuTheme &&
+                   other.bannerTheme == bannerTheme &&
+                   other.dividerTheme == dividerTheme &&
+                   other.buttonBarTheme == buttonBarTheme;
        }

        public override bool Equals(object obj) {
                hashCode = (hashCode * 397) ^ floatingActionButtonTheme.GetHashCode();
                hashCode = (hashCode * 397) ^ typography.GetHashCode();
                hashCode = (hashCode * 397) ^ snackBarTheme.GetHashCode(); 
+                hashCode = (hashCode * 397) ^ bottomSheetTheme.GetHashCode();
+                hashCode = (hashCode * 397) ^ popupMenuTheme.GetHashCode();
+                hashCode = (hashCode * 397) ^ bannerTheme.GetHashCode();
+                hashCode = (hashCode * 397) ^ dividerTheme.GetHashCode();
+                hashCode = (hashCode * 397) ^ buttonBarTheme.GetHashCode();

                _cachedHashCode = hashCode;
                return hashCode;
            properties.add(new DiagnosticsProperty<Typography>("typography", typography,
                defaultValue: defaultData.typography));
            properties.add(new DiagnosticsProperty<SnackBarThemeData>("snackBarTheme", snackBarTheme, defaultValue: defaultData.snackBarTheme, level: DiagnosticLevel.debug));
+            properties.add(new DiagnosticsProperty<BottomSheetThemeData>("bottomSheetTheme", bottomSheetTheme, defaultValue: defaultData.bottomSheetTheme, level: DiagnosticLevel.debug));
+            properties.add(new DiagnosticsProperty<PopupMenuThemeData>("popupMenuTheme", popupMenuTheme, defaultValue: defaultData.popupMenuTheme, level: DiagnosticLevel.debug));
+            properties.add(new DiagnosticsProperty<MaterialBannerThemeData>("bannerTheme", bannerTheme, defaultValue: defaultData.bannerTheme, level: DiagnosticLevel.debug));
+            properties.add(new DiagnosticsProperty<DividerThemeData>("dividerTheme", dividerTheme, defaultValue: defaultData.dividerTheme, level: DiagnosticLevel.debug));
+            properties.add(new DiagnosticsProperty<ButtonBarThemeData>("buttonBarTheme", buttonBarTheme, defaultValue: defaultData.buttonBarTheme, level: DiagnosticLevel.debug));
+
        }
    }


        internal static VisualDensity lerp(VisualDensity a, VisualDensity b, float t) {
            return new VisualDensity(
-                horizontal: Mathf.Lerp(a.horizontal, b.horizontal, t),
-                vertical: Mathf.Lerp(a.horizontal, b.horizontal, t)
+                horizontal: MathUtils.lerpNullableFloat(a.horizontal, b.horizontal, t),
+                vertical: MathUtils.lerpNullableFloat(a.horizontal, b.horizontal, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/material/time_picker.cs
+++ b/com.unity.uiwidgets/Runtime/material/time_picker.cs
            );
            string formattedNextMinute = localizations.formatMinute(nextMinute);
            TimeOfDay previousMinute = fragmentContext.selectedTime.replacing(
-                minute: (fragmentContext.selectedTime.minute - 1) % TimeOfDay.minutesPerHour
+                minute: (fragmentContext.selectedTime.minute - 1 + TimeOfDay.minutesPerHour) % TimeOfDay.minutesPerHour
            );
            string formattedPreviousMinute = localizations.formatMinute(previousMinute);

--- a/com.unity.uiwidgets/Runtime/painting/alignment.cs
+++ b/com.unity.uiwidgets/Runtime/painting/alignment.cs
            if (a is AlignmentDirectional && b is AlignmentDirectional)
                return AlignmentDirectional.lerp(a, b, t);
            return new _MixedAlignment(
-                Mathf.Lerp(a._x, b._x, t),
-                Mathf.Lerp(a._start, b._start, t),
-                Mathf.Lerp(a._y, b._y, t)
+                MathUtils.lerpNullableFloat(a._x, b._x, t),
+                MathUtils.lerpNullableFloat(a._start, b._start, t),
+                MathUtils.lerpNullableFloat(a._y, b._y, t)
            );
        }

            }

            if (a == null) {
-                return new Alignment(Mathf.Lerp(0.0f, b.x, t), Mathf.Lerp(0.0f, b.y, t));
+                return new Alignment(MathUtils.lerpNullableFloat(0.0f, b.x, t), MathUtils.lerpNullableFloat(0.0f, b.y, t));
-                return new Alignment(Mathf.Lerp(a.x, 0.0f, t), Mathf.Lerp(a.y, 0.0f, t));
+                return new Alignment(MathUtils.lerpNullableFloat(a.x, 0.0f, t), MathUtils.lerpNullableFloat(a.y, 0.0f, t));
-            return new Alignment(Mathf.Lerp(a.x, b.x, t), Mathf.Lerp(a.y, b.y, t));
+            return new Alignment(MathUtils.lerpNullableFloat(a.x, b.x, t), MathUtils.lerpNullableFloat(a.y, b.y, t));
        }

        public bool Equals(Alignment other) {
            if (a == null && b == null)
                return null;
            if (a == null)
-                return new AlignmentDirectional(Mathf.Lerp(0.0f, b.start, t),
-                    Mathf.Lerp(0.0f, b.y, t));
+                return new AlignmentDirectional(MathUtils.lerpNullableFloat(0.0f, b.start, t),
+                    MathUtils.lerpNullableFloat(0.0f, b.y, t));
-                return new AlignmentDirectional(Mathf.Lerp(a.start, 0.0f, t),
-                    Mathf.Lerp(a.y, 0.0f, t));
-            return new AlignmentDirectional(Mathf.Lerp(a.start, b.start, t), Mathf.Lerp(a.y, b.y, t));
+                return new AlignmentDirectional(MathUtils.lerpNullableFloat(a.start, 0.0f, t),
+                    MathUtils.lerpNullableFloat(a.y, 0.0f, t));
+            return new AlignmentDirectional(MathUtils.lerpNullableFloat(a.start, b.start, t), MathUtils.lerpNullableFloat(a.y, b.y, t));
        }

        public override Alignment resolve(TextDirection? direction) {
--- a/com.unity.uiwidgets/Runtime/painting/borders.cs
+++ b/com.unity.uiwidgets/Runtime/painting/borders.cs
                return b;
            }

-            float width = Mathf.Lerp(a.width, b.width, t);
+            float width = MathUtils.lerpNullableFloat(a.width, b.width, t);
            if (width < 0.0) {
                return none;
            }
--- a/com.unity.uiwidgets/Runtime/painting/box_shadow.cs
+++ b/com.unity.uiwidgets/Runtime/painting/box_shadow.cs
            return new BoxShadow(
                color: Color.lerp(a.color, b.color, t),
                offset: Offset.lerp(a.offset, b.offset, t),
-                blurRadius: Mathf.Lerp(a.blurRadius, b.blurRadius, t),
-                spreadRadius: Mathf.Lerp(a.spreadRadius, b.spreadRadius, t)
+                blurRadius: MathUtils.lerpNullableFloat(a.blurRadius, b.blurRadius, t),
+                spreadRadius: MathUtils.lerpNullableFloat(a.spreadRadius, b.spreadRadius, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/painting/colors.cs
+++ b/com.unity.uiwidgets/Runtime/painting/colors.cs
            if (b == null)
                return a._scaleAlpha(1.0f - t);
            return HSLColor.fromAHSL(
-                Mathf.Lerp(a.alpha, b.alpha, t).clamp(0.0f, 1.0f),
-                Mathf.Lerp(a.hue, b.hue, t) % 360.0f,
-                Mathf.Lerp(a.saturation, b.saturation, t).clamp(0.0f, 1.0f),
-                Mathf.Lerp(a.lightness, b.lightness, t).clamp(0.0f, 1.0f)
+                MathUtils.lerpNullableFloat(a.alpha, b.alpha, t).clamp(0.0f, 1.0f),
+                MathUtils.lerpNullableFloat(a.hue, b.hue, t) % 360.0f,
+                MathUtils.lerpNullableFloat(a.saturation, b.saturation, t).clamp(0.0f, 1.0f),
+                MathUtils.lerpNullableFloat(a.lightness, b.lightness, t).clamp(0.0f, 1.0f)
            );
        }

--- a/com.unity.uiwidgets/Runtime/painting/decoration_image.cs
+++ b/com.unity.uiwidgets/Runtime/painting/decoration_image.cs
            ImageErrorListener onError = null,
            ColorFilter colorFilter = null,
            BoxFit? fit = null,
-            Alignment alignment = null,
+            AlignmentGeometry alignment = null,
            Rect centerSlice = null,
            ImageRepeat repeat = ImageRepeat.noRepeat,
            bool matchTextDirection = false
        public readonly ImageErrorListener onError;
        public readonly ColorFilter colorFilter;
        public readonly BoxFit? fit;
-        public readonly Alignment alignment;
+        public readonly AlignmentGeometry alignment;
        public readonly Rect centerSlice;
        public readonly ImageRepeat repeat;
        public readonly bool matchTextDirection;
                scale: _image.scale,
                colorFilter: _details.colorFilter,
                fit: _details.fit,
-                alignment: _details.alignment,
+                alignment: _details.alignment.resolve(configuration.textDirection),
                centerSlice: _details.centerSlice,
                repeat: _details.repeat,
                flipHorizontally: flipHorizontally,
--- a/com.unity.uiwidgets/Runtime/painting/edge_insets.cs
+++ b/com.unity.uiwidgets/Runtime/painting/edge_insets.cs
                return EdgeInsetsDirectional.lerp(a, b, t);

            return _MixedEdgeInsets.fromLRSETB(
-                Mathf.Lerp(a._left, b._left, t),
-                Mathf.Lerp(a._right, b._right, t),
-                Mathf.Lerp(a._start, b._start, t),
-                Mathf.Lerp(a._end, b._end, t),
-                Mathf.Lerp(a._top, b._top, t),
-                Mathf.Lerp(a._bottom, b._bottom, t)
+                MathUtils.lerpNullableFloat(a._left, b._left, t),
+                MathUtils.lerpNullableFloat(a._right, b._right, t),
+                MathUtils.lerpNullableFloat(a._start, b._start, t),
+                MathUtils.lerpNullableFloat(a._end, b._end, t),
+                MathUtils.lerpNullableFloat(a._top, b._top, t),
+                MathUtils.lerpNullableFloat(a._bottom, b._bottom, t)
            );
        }

            if (b == null)
                return a * (1.0f - t);
            return fromSTEB(
-                Mathf.Lerp(a.start, b.start, t),
-                Mathf.Lerp(a.top, b.top, t),
-                Mathf.Lerp(a.end, b.end, t),
-                Mathf.Lerp(a.bottom, b.bottom, t)
+                MathUtils.lerpNullableFloat(a.start, b.start, t),
+                MathUtils.lerpNullableFloat(a.top, b.top, t),
+                MathUtils.lerpNullableFloat(a.end, b.end, t),
+                MathUtils.lerpNullableFloat(a.bottom, b.bottom, t)
            );
        }

            }

            return fromLTRB(
-                Mathf.Lerp(a.left, b.left, t),
-                Mathf.Lerp(a.top, b.top, t),
-                Mathf.Lerp(a.right, b.right, t),
-                Mathf.Lerp(a.bottom, b.bottom, t)
+                MathUtils.lerpNullableFloat(a.left, b.left, t),
+                MathUtils.lerpNullableFloat(a.top, b.top, t),
+                MathUtils.lerpNullableFloat(a.right, b.right, t),
+                MathUtils.lerpNullableFloat(a.bottom, b.bottom, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/painting/fractional_offset.cs
+++ b/com.unity.uiwidgets/Runtime/painting/fractional_offset.cs
            }

            if (a == null) {
-                return new FractionalOffset(Mathf.Lerp(0.5f, b.dx, t), Mathf.Lerp(0.5f, b.dy, t));
+                return new FractionalOffset(MathUtils.lerpNullableFloat(0.5f, b.dx, t), MathUtils.lerpNullableFloat(0.5f, b.dy, t));
-                return new FractionalOffset(Mathf.Lerp(a.dx, 0.5f, t), Mathf.Lerp(a.dy, 0.5f, t));
+                return new FractionalOffset(MathUtils.lerpNullableFloat(a.dx, 0.5f, t), MathUtils.lerpNullableFloat(a.dy, 0.5f, t));
-            return new FractionalOffset(Mathf.Lerp(a.dx, b.dx, t), Mathf.Lerp(a.dy, b.dy, t));
+            return new FractionalOffset(MathUtils.lerpNullableFloat(a.dx, b.dx, t), MathUtils.lerpNullableFloat(a.dy, b.dy, t));
        }

        public override string ToString() {
--- a/com.unity.uiwidgets/Runtime/painting/gradient.cs
+++ b/com.unity.uiwidgets/Runtime/painting/gradient.cs

    public class LinearGradient : Gradient, IEquatable<LinearGradient> {
        public LinearGradient(
-            Alignment begin = null,
-            Alignment end = null,
+            AlignmentGeometry begin = null,
+            AlignmentGeometry end = null,
            List<Color> colors = null,
            List<float> stops = null,
            TileMode tileMode = TileMode.clamp,
            this.tileMode = tileMode;
        }

-        public readonly Alignment begin;
+        public readonly AlignmentGeometry begin;
-        public readonly Alignment end;
+        public readonly AlignmentGeometry end;
-                begin.withinRect(rect),
-                end.withinRect(rect),
+                begin.resolve(textDirection).withinRect(rect),
+                end.resolve(textDirection).withinRect(rect),
                colors, _impliedStops(),
                tileMode, _resolveTransform(rect, textDirection)
            );
                b._impliedStops(),
                t);
            return new LinearGradient(
-                begin: Alignment.lerp(a.begin, b.begin, t),
-                end: Alignment.lerp(a.end, b.end, t),
+                begin: AlignmentGeometry.lerp(a.begin, b.begin, t),
+                end: AlignmentGeometry.lerp(a.end, b.end, t),
                colors: interpolated.colors,
                stops: interpolated.stops,
                tileMode: t < 0.5 ? a.tileMode : b.tileMode

    public class RadialGradient : Gradient, IEquatable<RadialGradient> {
        public RadialGradient(
-            Alignment center = null,
+            AlignmentGeometry center = null,
+            AlignmentGeometry focal = null,
+            float focalRadius = 0.0f,
+            this.focal = focal;
+            this.focalRadius = focalRadius;
-        public readonly Alignment center;
+        public readonly AlignmentGeometry center;

        public readonly float radius;


        public override Shader createShader(Rect rect, TextDirection? textDirection = null) {
            return ui.Gradient.radial(
-                center.withinRect(rect),
+                center.resolve(textDirection).withinRect(rect),
                radius * rect.shortestSide,
                colors, _impliedStops(),
                tileMode,
                b._impliedStops(),
                t);
            return new RadialGradient(
-                center: Alignment.lerp(a.center, b.center, t),
-                radius: Mathf.Max(0.0f, Mathf.Lerp(a.radius, b.radius, t)),
+                center: AlignmentGeometry.lerp(a.center, b.center, t),
+                radius: Mathf.Max(0.0f, MathUtils.lerpNullableFloat(a.radius, b.radius, t)),
-                tileMode: t < 0.5 ? a.tileMode : b.tileMode
+                tileMode: t < 0.5 ? a.tileMode : b.tileMode,
+                focal: AlignmentGeometry.lerp(a.focal, b.focal, t),
+                focalRadius: Mathf.Max(0.0f, MathUtils.lerpNullableFloat(a.focalRadius, b.focalRadius, t))
            );
        }


    public class SweepGradient : Gradient, IEquatable<SweepGradient> {
        public SweepGradient(
-            Alignment center = null,
+            AlignmentGeometry center = null,
            float startAngle = 0.0f,
            float endAngle = Mathf.PI * 2,
            List<Color> colors = null,
            this.tileMode = tileMode;
        }

-        public readonly Alignment center;
+        public readonly AlignmentGeometry center;

        public readonly float startAngle;


        public override Shader createShader(Rect rect, TextDirection? textDirection = null) {
            return ui.Gradient.sweep(
-                center.withinRect(rect),
+                center.resolve(textDirection).withinRect(rect),
                colors, _impliedStops(),
                tileMode,
                startAngle, endAngle, _resolveTransform(rect, textDirection)
                _ColorsAndStops._interpolateColorsAndStops(a.colors, a.stops, b.colors, b.stops, t);
            return new SweepGradient(
                center: Alignment.lerp(a.center, b.center, t),
-                startAngle: Mathf.Max(0.0f, Mathf.Lerp(a.startAngle, b.startAngle, t)),
-                endAngle: Mathf.Max(0.0f, Mathf.Lerp(a.endAngle, b.endAngle, t)),
+                startAngle: Mathf.Max(0.0f, MathUtils.lerpNullableFloat(a.startAngle, b.startAngle, t)),
+                endAngle: Mathf.Max(0.0f, MathUtils.lerpNullableFloat(a.endAngle, b.endAngle, t)),
                colors: interpolated.colors,
                stops: interpolated.stops,
                tileMode: t < 0.5 ? a.tileMode : b.tileMode
--- a/com.unity.uiwidgets/Runtime/painting/matrix_utils.cs
+++ b/com.unity.uiwidgets/Runtime/painting/matrix_utils.cs

        public static Rect inverseTransformRect(Matrix4 transform, Rect rect) {
            D.assert(rect != null);
-            D.assert(transform.determinant() != 0.0);
+            
+            //FIXME: there is a bug here
+            //In flutter this assertion has been commented, but we cannot do it since the call of Matrix4.tryInvert will fail
+            //we need to find a better way to fix this issue here
+            // D.assert(transform.determinant() != 0.0);
-            transform = Matrix4.tryInvert(transform);
+            transform = Matrix4.copy(transform);
+            transform.invert();
+
            return transformRect(transform, rect);
        }

--- a/com.unity.uiwidgets/Runtime/painting/rounded_rectangle_border.cs
+++ b/com.unity.uiwidgets/Runtime/painting/rounded_rectangle_border.cs
                return new _RoundedRectangleToCircleBorder(
                    side: BorderSide.lerp(border.side, side, t),
                    borderRadius: BorderRadius.lerp(border.borderRadius, borderRadius, t),
-                    circleness: Mathf.Lerp(border.circleness, circleness, t)
+                    circleness: MathUtils.lerpNullableFloat(border.circleness, circleness, t)
                );
            }

                return new _RoundedRectangleToCircleBorder(
                    side: BorderSide.lerp(side, border.side, t),
                    borderRadius: BorderRadius.lerp(borderRadius, border.borderRadius, t),
-                    circleness: Mathf.Lerp(circleness, border.circleness, t)
+                    circleness: MathUtils.lerpNullableFloat(circleness, border.circleness, t)
                );
            }

--- a/com.unity.uiwidgets/Runtime/painting/stadium_border.cs
+++ b/com.unity.uiwidgets/Runtime/painting/stadium_border.cs
            if (a is _StadiumToCircleBorder border) {
                return new _StadiumToCircleBorder(
                    side: BorderSide.lerp(border.side, side, t),
-                    circleness: Mathf.Lerp(border.circleness, circleness, t)
+                    circleness: MathUtils.lerpNullableFloat(border.circleness, circleness, t)
                );
            }

            if (b is _StadiumToCircleBorder border) {
                return new _StadiumToCircleBorder(
                    side: BorderSide.lerp(side, border.side, t),
-                    circleness: Mathf.Lerp(circleness, border.circleness, t)
+                    circleness: MathUtils.lerpNullableFloat(circleness, border.circleness, t)
                );
            }

                return new _StadiumToRoundedRectangleBorder(
                    side: BorderSide.lerp(border.side, side, t),
                    borderRadius: BorderRadius.lerp(border.borderRadius, borderRadius, t),
-                    rectness: Mathf.Lerp(border.rectness, rectness, t)
+                    rectness: MathUtils.lerpNullableFloat(border.rectness, rectness, t)
                );
            }

                return new _StadiumToRoundedRectangleBorder(
                    side: BorderSide.lerp(side, border.side, t),
                    borderRadius: BorderRadius.lerp(borderRadius, border.borderRadius, t),
-                    rectness: Mathf.Lerp(rectness, border.rectness, t)
+                    rectness: MathUtils.lerpNullableFloat(rectness, border.rectness, t)
                );
            }

--- a/com.unity.uiwidgets/Runtime/painting/text_style.cs
+++ b/com.unity.uiwidgets/Runtime/painting/text_style.cs
                decoration: t < 0.5 ? a.decoration : b.decoration,
                decorationColor: Color.lerp(a.decorationColor, b.decorationColor, t),
                decorationStyle: t < 0.5 ? a.decorationStyle : b.decorationStyle,
-                decorationThickness: Mathf.Lerp(
+                decorationThickness: MathUtils.lerpNullableFloat(
                    a.decorationThickness ?? b.decorationThickness ?? 0.0f,
                    b.decorationThickness ?? a.decorationThickness ?? 0.0f, t),
                shadows: t < 0.5f ? a.shadows : b.shadows,
--- a/com.unity.uiwidgets/Runtime/rendering/box.cs
+++ b/com.unity.uiwidgets/Runtime/rendering/box.cs
                () => "Cannot interpolate between finite constraints and unbounded constraints.");
            return new BoxConstraints(
                minWidth: a.minWidth.isFinite()
-                    ? Mathf.Lerp(a.minWidth, b.minWidth, t)
+                    ? MathUtils.lerpNullableFloat(a.minWidth, b.minWidth, t)
-                    ? Mathf.Lerp(a.maxWidth, b.maxWidth, t)
+                    ? MathUtils.lerpNullableFloat(a.maxWidth, b.maxWidth, t)
-                    ? Mathf.Lerp(a.minHeight, b.minHeight, t)
+                    ? MathUtils.lerpNullableFloat(a.minHeight, b.minHeight, t)
-                    ? Mathf.Lerp(a.maxHeight, b.maxHeight, t)
+                    ? MathUtils.lerpNullableFloat(a.maxHeight, b.maxHeight, t)
                    : float.PositiveInfinity
            );
        }
--- a/com.unity.uiwidgets/Runtime/rendering/editable.cs
+++ b/com.unity.uiwidgets/Runtime/rendering/editable.cs

            if (_resetFloatingCursorAnimationValue != null) {
                sizeAdjustmentX =
-                    Mathf.Lerp(sizeAdjustmentX, 0f, _resetFloatingCursorAnimationValue.Value);
+                    MathUtils.lerpNullableFloat(sizeAdjustmentX, 0f, _resetFloatingCursorAnimationValue.Value);
-                    Mathf.Lerp(sizeAdjustmentY, 0f, _resetFloatingCursorAnimationValue.Value);
+                    MathUtils.lerpNullableFloat(sizeAdjustmentY, 0f, _resetFloatingCursorAnimationValue.Value);
            }

            Rect floatingCaretPrototype = Rect.fromLTRB(
--- a/com.unity.uiwidgets/Runtime/rendering/stack.cs
+++ b/com.unity.uiwidgets/Runtime/rendering/stack.cs
            }

            return fromLTRB(
-                Mathf.Lerp(a.left, b.left, t),
-                Mathf.Lerp(a.top, b.top, t),
-                Mathf.Lerp(a.right, b.right, t),
-                Mathf.Lerp(a.bottom, b.bottom, t)
+                MathUtils.lerpNullableFloat(a.left, b.left, t),
+                MathUtils.lerpNullableFloat(a.top, b.top, t),
+                MathUtils.lerpNullableFloat(a.right, b.right, t),
+                MathUtils.lerpNullableFloat(a.bottom, b.bottom, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/ui2/Matrix4.cs
+++ b/com.unity.uiwidgets/Runtime/ui2/Matrix4.cs
            return result;
        }

-        public Matrix4 copy(Matrix4 other) {
-            setFrom(other);
-            return this;
+        public static Matrix4 copy(Matrix4 other) {
+            var result = zero();
+            result.setFrom(other);
+            return result;
        }


            return r;
        }

-        public Matrix4 clone() => new Matrix4().copy(this);
+        public Matrix4 clone() => copy(this);

        public static Matrix4 operator *(Matrix4 a, Matrix4 b) {
            var result = a.clone();
            float invSY = 1.0f / sy;
            float invSZ = 1.0f / sz;

-            Matrix4 m = new Matrix4().copy(this);
+            Matrix4 m = copy(this);
            m._m4storage[0] *= invSX;
            m._m4storage[1] *= invSX;
            m._m4storage[2] *= invSX;
--- a/com.unity.uiwidgets/Runtime/ui2/geometry.cs
+++ b/com.unity.uiwidgets/Runtime/ui2/geometry.cs
            b = b ?? a;
            return a + (b - a) * t;
        }
+        
+        public static float lerpNullableFloat(float a, float b, float t) {
+            return a + (b - a) * t;
+        }

        public static int round(this float value) {
            return Mathf.RoundToInt(value);
                return a * (1.0f - t);
            }

-            return new Offset(Mathf.Lerp(a.dx, b.dx, t), Mathf.Lerp(a.dy, b.dy, t));
+            return new Offset(MathUtils.lerpNullableFloat(a.dx, b.dx, t), MathUtils.lerpNullableFloat(a.dy, b.dy, t));
        }

        public bool Equals(Offset other) {
                return a * (1.0f - t);
            }

-            return new Size(Mathf.Lerp(a.width, b.width, t), Mathf.Lerp(a.height, b.height, t));
+            return new Size(MathUtils.lerpNullableFloat(a.width, b.width, t), MathUtils.lerpNullableFloat(a.height, b.height, t));
        }

        public bool Equals(Size other) {
            }

            return fromLTRB(
-                Mathf.Lerp(a.left, b.left, t),
-                Mathf.Lerp(a.top, b.top, t),
-                Mathf.Lerp(a.right, b.right, t),
-                Mathf.Lerp(a.bottom, b.bottom, t)
+                MathUtils.lerpNullableFloat(a.left, b.left, t),
+                MathUtils.lerpNullableFloat(a.top, b.top, t),
+                MathUtils.lerpNullableFloat(a.right, b.right, t),
+                MathUtils.lerpNullableFloat(a.bottom, b.bottom, t)
            );
        }

            }

            return elliptical(
-                Mathf.Lerp(a.x, b.x, t),
-                Mathf.Lerp(a.y, b.y, t)
+                MathUtils.lerpNullableFloat(a.x, b.x, t),
+                MathUtils.lerpNullableFloat(a.y, b.y, t)
            );
        }

            }

            return fromLTRBAndCorners(
-                Mathf.Lerp(a.left, b.left, t),
-                Mathf.Lerp(a.top, b.top, t),
-                Mathf.Lerp(a.right, b.right, t),
-                Mathf.Lerp(a.bottom, b.bottom, t),
+                MathUtils.lerpNullableFloat(a.left, b.left, t),
+                MathUtils.lerpNullableFloat(a.top, b.top, t),
+                MathUtils.lerpNullableFloat(a.right, b.right, t),
+                MathUtils.lerpNullableFloat(a.bottom, b.bottom, t),
                Radius.lerp(a.tlRadius, b.tlRadius, t),
                Radius.lerp(a.trRadius, b.trRadius, t),
                Radius.lerp(a.brRadius, b.brRadius, t),
--- a/com.unity.uiwidgets/Runtime/ui2/painting.cs
+++ b/com.unity.uiwidgets/Runtime/ui2/painting.cs
            }

            return fromARGB(
-                ((int) Mathf.Lerp(a.alpha, b.alpha, t)).clamp(0, 255),
-                ((int) Mathf.Lerp(a.red, b.red, t)).clamp(0, 255),
-                ((int) Mathf.Lerp(a.green, b.green, t)).clamp(0, 255),
-                ((int) Mathf.Lerp(a.blue, b.blue, t)).clamp(0, 255)
+                ((int) MathUtils.lerpNullableFloat(a.alpha, b.alpha, t)).clamp(0, 255),
+                ((int) MathUtils.lerpNullableFloat(a.red, b.red, t)).clamp(0, 255),
+                ((int) MathUtils.lerpNullableFloat(a.green, b.green, t)).clamp(0, 255),
+                ((int) MathUtils.lerpNullableFloat(a.blue, b.blue, t)).clamp(0, 255)
            );
        }

            return new Shadow(
                color: Color.lerp(a.color, b.color, t),
                offset: Offset.lerp(a.offset, b.offset, t),
-                blurRadius: Mathf.Lerp(a.blurRadius, b.blurRadius, t)
+                blurRadius: MathUtils.lerpNullableFloat(a.blurRadius, b.blurRadius, t)
            );
        }

--- a/com.unity.uiwidgets/Runtime/ui2/text.cs
+++ b/com.unity.uiwidgets/Runtime/ui2/text.cs
        public static FontWeight lerp(FontWeight a, FontWeight b, float t) {
            if (a == null && b == null)
                return null;
-            return values[Mathf.Lerp(a?.index ?? normal.index, b?.index ?? normal.index, t).round().clamp(0, 8)];
+            return values[MathUtils.lerpNullableFloat(a?.index ?? normal.index, b?.index ?? normal.index, t).round().clamp(0, 8)];
        }

        public static readonly Dictionary<int, string> map = new Dictionary<int, string> {
--- a/com.unity.uiwidgets/Runtime/widgets/animated_cross_fade.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/animated_cross_fade.cs
            Curve firstCurve = null,
            Curve secondCurve = null,
            Curve sizeCurve = null,
-            Alignment alignment = null,
+            AlignmentGeometry alignment = null,
            CrossFadeState? crossFadeState = null,
            TimeSpan? duration = null,
            TimeSpan? reverseDuration = null,

        public readonly Curve sizeCurve;

-        public readonly Alignment alignment;
+        public readonly AlignmentGeometry alignment;

        public readonly AnimatedCrossFadeBuilder layoutBuilder;

        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
            base.debugFillProperties(properties);
            properties.add(new EnumProperty<CrossFadeState>("crossFadeState", crossFadeState));
-            properties.add(new DiagnosticsProperty<Alignment>("alignment", alignment,
+            properties.add(new DiagnosticsProperty<AlignmentGeometry>("alignment", alignment,
                defaultValue: Alignment.topCenter));
            properties.add(new IntProperty("duration", duration?.Milliseconds, unit: "ms"));
            properties.add(new IntProperty("reverseDuration", reverseDuration?.Milliseconds, unit: "ms", defaultValue: null));
            description.add(new EnumProperty<CrossFadeState>("crossFadeState", widget.crossFadeState));
            description.add(
                new DiagnosticsProperty<AnimationController>("controller", _controller, showName: false));
-            description.add(new DiagnosticsProperty<Alignment>("alignment", widget.alignment,
+            description.add(new DiagnosticsProperty<AlignmentGeometry>("alignment", widget.alignment,
                defaultValue: Alignment.topCenter));
        }
    }
--- a/com.unity.uiwidgets/Runtime/widgets/dismissible.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/dismissible.cs
            }

            _dragUnderway = false;
-            _confirmStartResizeAnimation().then_((value) => {
-                if (_moveController.isCompleted && value) {
-                    _startResizeAnimation();
-                }
-                else {
-                    float flingVelocity = _directionIsXAxis
-                        ? details.velocity.pixelsPerSecond.dx
-                        : details.velocity.pixelsPerSecond.dy;
-                    switch (_describeFlingGesture(details.velocity)) {
-                        case _FlingGestureKind.forward:
-                            D.assert(_dragExtent != 0.0f);
-                            D.assert(!_moveController.isDismissed);
-                            if ((widget.dismissThresholds.getOrDefault(_dismissDirection) ??
-                                 _kDismissThreshold) >= 1.0) {
-                                _moveController.reverse();
-                                break;
-                            }
+            if (_moveController.isCompleted) {
+                _confirmStartResizeAnimation().then_((value) => {
+                    if (value) {
+                        _startResizeAnimation();
+                        return;
+                    }
+                });
+            }
-                            _dragExtent = flingVelocity.sign();
-                            _moveController.fling(velocity: flingVelocity.abs() * _kFlingVelocityScale);
-                            break;
-                        case _FlingGestureKind.reverse:
-                            D.assert(_dragExtent != 0.0f);
-                            D.assert(!_moveController.isDismissed);
-                            _dragExtent = flingVelocity.sign();
-                            _moveController.fling(velocity: -flingVelocity.abs() * _kFlingVelocityScale);
-                            break;
-                        case _FlingGestureKind.none:
-                            if (!_moveController.isDismissed) {
-                                // we already know it's not completed, we check that above
-                                if (_moveController.value >
-                                    (widget.dismissThresholds.getOrDefault(_dismissDirection) ??
-                                     _kDismissThreshold)) {
-                                    _moveController.forward();
-                                }
-                                else {
-                                    _moveController.reverse();
-                                }
-                            }
+            float flingVelocity = _directionIsXAxis
+                ? details.velocity.pixelsPerSecond.dx
+                : details.velocity.pixelsPerSecond.dy;
+            switch (_describeFlingGesture(details.velocity)) {
+                case _FlingGestureKind.forward:
+                    D.assert(_dragExtent != 0.0f);
+                    D.assert(!_moveController.isDismissed);
+                    if ((widget.dismissThresholds.getOrDefault(_dismissDirection) ??
+                         _kDismissThreshold) >= 1.0) {
+                        _moveController.reverse();
+                        break;
+                    }
-                            break;
+                    _dragExtent = flingVelocity.sign();
+                    _moveController.fling(velocity: flingVelocity.abs() * _kFlingVelocityScale);
+                    break;
+                case _FlingGestureKind.reverse:
+                    D.assert(_dragExtent != 0.0f);
+                    D.assert(!_moveController.isDismissed);
+                    _dragExtent = flingVelocity.sign();
+                    _moveController.fling(velocity: -flingVelocity.abs() * _kFlingVelocityScale);
+                    break;
+                case _FlingGestureKind.none:
+                    if (!_moveController.isDismissed) {
+                        // we already know it's not completed, we check that above
+                        if (_moveController.value >
+                            (widget.dismissThresholds.getOrDefault(_dismissDirection) ??
+                             _kDismissThreshold)) {
+                            _moveController.forward();
+                        }
+                        else {
+                            _moveController.reverse();
+                        }
-                }
-            });
+
+                    break;
+            }
        }

        void _handleDismissStatusChanged(AnimationStatus status) {
                D.assert(() => {
                    if (_resizeAnimation.status != AnimationStatus.forward) {
                        D.assert(_resizeAnimation.status == AnimationStatus.completed);
-                        throw new UIWidgetsError(new List<DiagnosticsNode>{
+                        throw new UIWidgetsError(new List<DiagnosticsNode> {
                            new ErrorSummary("A dismissed Dismissible widget is still part of the tree."),
                            new ErrorHint(
                                "Make sure to implement the onDismissed handler and to immediately remove the Dismissible " +

                children.Add(content);
                content = new Stack(children: children);
-                
            }

            return new GestureDetector(
--- a/com.unity.uiwidgets/Runtime/widgets/editable_text.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/editable_text.cs
            }
            else {
                float lerpValue = _floatingCursorResetController.value;
-                float lerpX = Mathf.Lerp(_lastBoundedOffset.dx, finalPosition.dx, lerpValue);
-                float lerpY = Mathf.Lerp(_lastBoundedOffset.dy, finalPosition.dy, lerpValue);
+                float lerpX = MathUtils.lerpNullableFloat(_lastBoundedOffset.dx, finalPosition.dx, lerpValue);
+                float lerpY = MathUtils.lerpNullableFloat(_lastBoundedOffset.dy, finalPosition.dy, lerpValue);

                renderEditable.setFloatingCursor(FloatingCursorDragState.Update, new Offset(lerpX, lerpY),
                    _lastTextPosition, resetLerpValue: lerpValue);
--- a/com.unity.uiwidgets/Runtime/widgets/focus_manager.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/focus_manager.cs
            get { return FocusManager.instance.highlightMode; }
        }

-        public FocusScopeNode nearestScope {
+        public virtual FocusScopeNode nearestScope {
            get { return enclosingScope; }
        }

            skipTraversal: skipTraversal
        ) {}

-        public FocusScopeNode nearestScope {
+        public override FocusScopeNode nearestScope {
            get { return this; }
        }

--- a/com.unity.uiwidgets/Runtime/widgets/form.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/form.cs

    public delegate void FormFieldSetter<T>(T newValue);

-    public delegate Widget FormFieldBuilder<T>(FormFieldState<T> field) where T : class;
+    public delegate Widget FormFieldBuilder<T>(FormFieldState<T> field);
-    public class FormField<T> : StatefulWidget where T : class {
+    public class FormField<T> : StatefulWidget {
-            T initialValue = null,
+            T initialValue = default,
            bool autovalidate = false,
            bool enabled = true
        ) : base(key: key) {
        void reset();
    }

-    public class FormFieldState<T> : State<FormField<T>>, FormFieldState where T : class {
+    public class FormFieldState<T> : State<FormField<T>>, FormFieldState {
        T _value;
        string _errorText;

--- a/com.unity.uiwidgets/Runtime/widgets/framework.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/framework.cs
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
-using System.Text;
-using Unity.UIWidgets.cupertino;
 using Unity.UIWidgets.foundation;
 using Unity.UIWidgets.rendering;
 using Unity.UIWidgets.ui;

        public override void didChangeDependencies() {
            base.didChangeDependencies();
-            bool _didChangeDependencies = true;
+            _didChangeDependencies = true;
        }

        public override DiagnosticsNode toDiagnosticsNode(string name = null,
--- a/com.unity.uiwidgets/Runtime/widgets/navigator.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/navigator.cs
            }

            D.assert(entry != null);
-            _history.Remove(entry);
+            entry.remove();
            _flushHistoryUpdates(rearrangeOverlay: false);
            D.assert(() => {
                _debugLocked = false;
                _debugLocked = true;
                return true;
            });
-           // D.assert(_history.Where(_RouteEntry.isRoutePredicate(route)).Count() == 1);
+
            List<_RouteEntry> routeEntries = new List<_RouteEntry>();
            foreach (var historyEntry in _history) {
                if (_RouteEntry.isRoutePredicate(route)(historyEntry)) {
--- a/com.unity.uiwidgets/Runtime/widgets/nested_scroll_view.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/nested_scroll_view.cs
                            : new ClampingScrollPhysics(),
                        controller: _coordinator._outerController,
                        slivers: widget._buildSlivers(
-                            context,
+                            _context,
                            _coordinator._innerController,
                            _lastHasScrolledBody
                        ),
--- a/com.unity.uiwidgets/Runtime/widgets/routes.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/routes.cs
        public _ModalScope(
            Key key = null, 
            ModalRoute<T> route = null) 
-            : base(key) {
+            : base(key, route) {
-        public readonly new ModalRoute<T> route;
+        public new readonly ModalRoute<T> route;

        public override State createState() {
            return new _ModalScopeState<T>();
            _ModalScopeState scope = _scopeKey.currentState as _ModalScopeState ;
            D.assert(scope != null);

-            bool result = false;
-            foreach (WillPopCallback callback in _willPopCallbacks) {
-                callback.Invoke().then(v => result = !(bool)v);
-                if (result) {
-                    return  Future.value(RoutePopDisposition.doNotPop).to<RoutePopDisposition>();
+            Future InvokePopCallbacks(int index) {
+                if (index == _willPopCallbacks.Count) {
+                    return base.willPop();
+                var callback = _willPopCallbacks[index];
+                return callback.Invoke().then(v => {
+                    if (!(bool) v) {
+                        return Future.value(RoutePopDisposition.doNotPop);
+                    }
+
+                    return InvokePopCallbacks(index + 1);
+                });
-            return base.willPop();
-            
+
+            return InvokePopCallbacks(0).to<RoutePopDisposition>();
        }

        public void addScopedWillPopCallback(WillPopCallback callback) {
--- a/com.unity.uiwidgets/Runtime/widgets/scroll_position.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/scroll_position.cs
            this.keepScrollOffset = keepScrollOffset;
            this.debugLabel = debugLabel;
            _coordinator = coordinator;
-
            if (oldPosition != null) {
                absorb(oldPosition);
            }
        public bool hasMaxScrollExtent {
            get { return _maxScrollExtent != null; }
        }
-
+        
        public override float pixels {
            get {
                D.assert(_pixels != null);
--- a/com.unity.uiwidgets/Runtime/widgets/transitions.cs
+++ b/com.unity.uiwidgets/Runtime/widgets/transitions.cs

    public class AlignTransition : AnimatedWidget {
        public AlignTransition(
-            Animation<Alignment> alignment,
+            Animation<AlignmentGeometry> alignment,
            Widget child,
            Key key = null,
            float? widthFactor = null,
            this.heightFactor = heightFactor;
        }

-        Animation<Alignment> alignment {
-            get { return (Animation<Alignment>) listenable; }
+        Animation<AlignmentGeometry> alignment {
+            get { return (Animation<AlignmentGeometry>) listenable; }
        }

        public readonly float? widthFactor;
--- a/engine/src/shell/platform/unity/darwin/macos/uiwidgets_panel.h
+++ b/engine/src/shell/platform/unity/darwin/macos/uiwidgets_panel.h

  void VSyncCallback(intptr_t baton);

+  void OnKeyDown(int keyCode, bool isKeyDown);
+
  void OnMouseMove(float x, float y);

  void OnMouseDown(float x, float y, int button);
--- a/engine/src/shell/platform/unity/darwin/macos/uiwidgets_panel.mm
+++ b/engine/src/shell/platform/unity/darwin/macos/uiwidgets_panel.mm
  }
 }

+void UIWidgetsPanel::OnKeyDown(int keyCode, bool isKeyDown) {
+  if (process_events_) {
+    UIWidgetsPointerEvent event = {};
+    event.phase = isKeyDown ? UIWidgetsPointerPhase::kMouseDown : UIWidgetsPointerPhase::kMouseUp;
+    event.device_kind =
+        UIWidgetsPointerDeviceKind::kUIWidgetsPointerDeviceKindKeyboard;
+    event.buttons = keyCode;
+    event.struct_size = sizeof(event);
+    event.timestamp =
+        std::chrono::duration_cast<std::chrono::microseconds>(
+            std::chrono::high_resolution_clock::now().time_since_epoch())
+            .count();
+
+    UIWidgetsEngineSendPointerEvent(engine_, &event, 1);
+  }
+}
+
+
 void UIWidgetsPanel::OnMouseMove(float x, float y) {
  if (process_events_) {
    SendMouseMove(x, y);
 UIWIDGETS_API(void)
 UIWidgetsPanel_unregisterTexture(UIWidgetsPanel* panel, int texture_id) {
  panel->UnregisterTexture(texture_id);
+}
+
+
+UIWIDGETS_API(void)
+UIWidgetsPanel_onKey(UIWidgetsPanel* panel, int keyCode, bool isKeyDown) {
+  panel->OnKeyDown(keyCode, isKeyDown);
 }

 UIWIDGETS_API(void)
--- a/engine/src/shell/platform/unity/darwin/macos/unity_surface_manager.mm
+++ b/engine/src/shell/platform/unity/darwin/macos/unity_surface_manager.mm
  gl_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];
  gl_resource_context_ = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:gl_context_];

-  FML_DCHECK(gl_context_ != nullptr && gl_resource_context_ != nullptr);
+  FML_DCHECK(gl_context_ != nullptr);
 }

 UnitySurfaceManager::~UnitySurfaceManager() { ReleaseNativeRenderContext(); }
  const GLuint ConstGLType = GL_UNSIGNED_INT_8_8_8_8_REV;

  //render context must be available
-  FML_DCHECK(metal_device_ != nullptr && gl_context_ != nullptr && gl_resource_context_ != nullptr);
+  FML_DCHECK(metal_device_ != nullptr && gl_context_ != nullptr);

  //render textures must be released already
  FML_DCHECK(pixelbuffer_ref == nullptr && default_fbo_ == 0 && gl_tex_ == 0 && gl_tex_cache_ref_ == nullptr && gl_tex_ref_ == nullptr && metal_tex_ == nullptr && metal_tex_ref_ == nullptr && metal_tex_cache_ref_ == nullptr);

 bool UnitySurfaceManager::MakeCurrentResourceContext()
 {
-  [gl_resource_context_ makeCurrentContext];
+  if (gl_resource_context_ == nullptr)
+  {
+      [gl_context_ makeCurrentContext];
+  }
+  else
+  {
+      [gl_resource_context_ makeCurrentContext];
+  }
  return true;
 }


 void UnitySurfaceManager::ReleaseNativeRenderContext()
 {
-  FML_DCHECK(gl_resource_context_);
-  CGLReleaseContext(gl_resource_context_.CGLContextObj);
-  gl_resource_context_ = nullptr;
+  if (gl_resource_context_ != nullptr)
+  {
+      CGLReleaseContext(gl_resource_context_.CGLContextObj);
+      gl_resource_context_ = nullptr;
+  }

  FML_DCHECK(gl_context_);
  CGLReleaseContext(gl_context_.CGLContextObj);

  return true;
 }
-}  // namespace uiwidgets
+}  // namespace uiwidgets
--- a/Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/NavigatorPopSample.cs
+++ b/Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/NavigatorPopSample.cs
+using System.Collections.Generic;
+using Unity.UIWidgets.async2;
+using Unity.UIWidgets.engine2;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.widgets;
+
+namespace UIWidgetsSample
+{
+    public class NavigatorPopSample : UIWidgetsPanel
+    {
+        protected override void main()
+        {
+            ui_.runApp(new MaterialApp(
+                title: "Returning Data",
+                home: new PopDemo()));
+        }
+
+        protected new void OnEnable()
+        {
+            base.OnEnable();
+        }
+    }
+
+    public class PopDemo : StatelessWidget
+    {
+        public override Widget build(BuildContext context)
+        {
+            return new Scaffold(
+                appBar: new AppBar(
+                    title: new Text("Returning Data Demo")
+                ),
+                body: new Center(child: new SelectionButton())
+            );
+        }
+    }
+
+    internal class SelectionButton : StatelessWidget
+    {
+        public override Widget build(BuildContext context)
+        {
+            return new RaisedButton(
+                onPressed: () => { _navigateAndDisplaySelection(context); },
+                child: new Text("Pick an option, any option!")
+            );
+        }
+
+        // A method that launches the SelectionScreen and awaits the result from
+        // Navigator.pop!
+        private void _navigateAndDisplaySelection(BuildContext context)
+        {
+            // Navigator.push returns a Future that will complete after we call
+            // Navigator.pop on the Selection Screen!
+            Future<bool> result = Navigator.push<bool>(
+                context,
+                new MaterialPageRoute(builder: (subContext) => new SelectionScreen())
+            );
+
+            // After the Selection Screen returns a result, show it in a Snackbar!
+            result.then(value =>
+            {
+                bool res = (bool) value;
+                Scaffold
+                    .of(context)
+                    .showSnackBar(new SnackBar(content: new Text($"{res}")));
+            });
+        }
+    }
+
+    internal class SelectionScreen : StatelessWidget
+    {
+        public override Widget build(BuildContext context)
+        {
+            return new Scaffold(
+                appBar: new AppBar(
+                    title: new Text("Pick an option")
+                ),
+                body: new Center(
+                    child: new Column(
+                        mainAxisAlignment: MainAxisAlignment.center,
+                        children: new List<Widget>
+                        {
+                            new Padding(
+                                padding: EdgeInsets.all(8.0f),
+                                child: new RaisedButton(
+                                    onPressed: () =>
+                                    {
+                                        // Close the screen and return "Yep!" as the result
+                                        Navigator.pop(context, true);
+                                    },
+                                    child: new Text("Yep!")
+                                )
+                            ),
+                            new Padding(
+                                padding: EdgeInsets.all(8.0f),
+                                child: new RaisedButton(
+                                    onPressed: () =>
+                                    {
+                                        // Close the screen and return "Nope!" as the result
+                                        Navigator.pop(context, false);
+                                    },
+                                    child: new Text("Nope.")
+                                )
+                            )
+                        }
+                    )
+                )
+            );
+        }
+    }
+}
--- a/Samples/UIWidgetsSamples_2019_4/Assets/Scene/GalleryTest.unity
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