fix alignment bug

add reorderable list sample

com.unity.uiwidgets/Runtime/painting/alignment.cs

         }
 
         public override Alignment resolve(TextDirection? direction) {
-            direction = direction ?? TextDirection.ltr;
-            switch (direction) {
-                case TextDirection.rtl:
-                    return new Alignment(_x - _start, _y);
-                case TextDirection.ltr:
-                    return new Alignment(_x + _start, _y);
-            }
-
-            return null;
+            return this;
         }
 
 

Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample.meta

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Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/ReorderableListSample.cs

+using System.Collections.Generic;
+using System.Linq;
+using uiwidgets;
+using Unity.UIWidgets.engine2;
+using Unity.UIWidgets.foundation;
+using Unity.UIWidgets.material;
+using Unity.UIWidgets.painting;
+using Unity.UIWidgets.rendering;
+using Unity.UIWidgets.ui;
+using Unity.UIWidgets.widgets;
+using UnityEngine;
+using Color = Unity.UIWidgets.ui.Color;
+using Material = Unity.UIWidgets.material.Material;
+using TextStyle = Unity.UIWidgets.painting.TextStyle;
+using ui_ = Unity.UIWidgets.widgets.ui_;
+
+namespace UIWidgetsSample {
+    public class ReorderableListSample : UIWidgetsPanel {
+        protected override void main() {
+            ui_.runApp(new MaterialApp(
+                showPerformanceOverlay: false,
+                home: new MaterialReorderableListViewWidget()));
+        }
+
+        protected new void OnEnable() {
+            base.OnEnable();
+        }
+    }
+
+    class MaterialReorderableListViewWidget : StatefulWidget {
+        public MaterialReorderableListViewWidget(Key key = null) : base(key) {
+        }
+
+        public override State createState() {
+            return new MaterialReorderableListViewWidgetState();
+        }
+    }
+
+    class MaterialReorderableListViewWidgetState : State<MaterialReorderableListViewWidget> {
+        List<string> _list = new List<string> {"Apple", "Ball", "Cat", "Dog", "Elephant"};
+
+        public override Widget build(BuildContext context) {
+            return new Scaffold(
+                body: new ReorderableListView(
+                    children: this._list.Select<string, Widget>((item) =>
+                    {
+                        return new ListTile(
+                            Key.key(item),
+                            title: new Text(item),
+                            trailing: new Icon(Icons.menu));
+                    }).ToList(),
+                    onReorder: (int start, int current) =>
+                    {
+                        if (start < current) {
+                            int end = current - 1;
+                            string startItem = _list[start];
+                            int i = 0;
+                            int local = start;
+                            do {
+                                _list[local] = _list[++local];
+                                i++;
+                            } while (i < end - start);
+                            _list[end] = startItem;
+                        }
+                        // dragging from bottom to top
+                        else if (start > current) {
+                            string startItem = _list[start];
+                            for (int i = start; i > current; i--) {
+                                _list[i] = _list[i - 1];
+                            }
+                            _list[current] = startItem;
+                        }
+                        setState(() => {});
+                    }
+                    )
+            );
+        }
+    }
+}

Samples/UIWidgetsSamples_2019_4/Assets/MaterialSample/ReorderableListSample.cs.meta

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