editable render object

Assets/UIWidgets/Tests/Menu.cs

         public static void gestures() {
             EditorWindow.GetWindow(typeof(Gestures));
         }
+        
+        [MenuItem("UIWidgetsTests/RenderEditable")]
+        public static void renderEditable() {
+            EditorWindow.GetWindow(typeof(RenderEditable));
+        }
     }
 }

Assets/UIWidgets/painting/text_painter.cs

 using System;
-using System.Runtime.ConstrainedExecution;
-using UIWidgets.math;
+using System.Collections.Generic;
+using UIWidgets.foundation;
+using UIWidgets.service;
+using Rect = UIWidgets.ui.Rect;
 
 namespace UIWidgets.painting
 {
   
             if (minWidth != maxWidth)
             {
-                var newWidth = MathUtil.Clamp(maxIntrinsicWidth, minWidth, maxWidth);
+                var newWidth = MathUtils.clamp(maxIntrinsicWidth, minWidth, maxWidth);
                 if (newWidth != width)
                 {
                     _paragraph.layout(new ParagraphConstraints(newWidth));
             _paragraph.paint(canvas, offset.dx, offset.dy);
         }
 
+        public Offset getOffsetForCaret(TextPosition position, Rect caretPrototype)
+        {
+            D.assert(!_needsLayout);
+            var offset = position.offset;
+            switch (position.affinity)
+            {
+                    case TextAffinity.upstream:
+                        return _getOffsetFromUpstream(offset, caretPrototype) ??
+                               _getOffsetFromDownstream(offset, caretPrototype) ?? _emptyOffset;  
+                    case TextAffinity.downstream:
+                        return _getOffsetFromDownstream(offset, caretPrototype) ??
+                               _getOffsetFromUpstream(offset, caretPrototype) ?? _emptyOffset;
+            }
+
+            return null;
+        }
+
+        public List<TextBox> getBoxesForSelection(TextSelection selection)
+        {
+            D.assert(!_needsLayout);
+            var results =  _paragraph.getRectsForRange(selection.start, selection.end);
+            if (results.Count > 0)
+            {
+                Debug.Log(string.Format(" getBoxesForSelection {0}", results[0]));
+            }
+            return results;
+        }
+        
+        public TextPosition getPositionForOffset(Offset offset) {
+            D.assert(!_needsLayout);
+            var result = _paragraph.getGlyphPositionAtCoordinate(offset.dx, offset.dy);
+            return new TextPosition(result.position, result.affinity);
+        }
+
+        public TextRange getWordBoundary(TextPosition position)
+        {
+            D.assert(!_needsLayout);
+            var range = _paragraph.getWordBoundary(position.offset);
+            return new TextRange(range.start, range.end);
+        }
+
         private ParagraphStyle _createParagraphStyle(TextDirection defaultTextDirection = TextDirection.ltr)
         {
             if (_text.style == null)
         {
             return Math.Ceiling(layoutValue);
         }
+        
+        
+        private Offset _getOffsetFromUpstream(int offset, Rect caretPrototype) {
+            var prevCodeUnit = _text.codeUnitAt(offset - 1);
+            if (prevCodeUnit == null)
+                return null;
+            var  prevRuneOffset = _isUtf16Surrogate((int)prevCodeUnit) ? offset - 2 : offset - 1;
+            var boxes = _paragraph.getRectsForRange(prevRuneOffset, offset);
+            if (boxes.Count == 0)
+                return null;
+            var box = boxes[0];
+            var caretEnd = box.end;
+            var dx = box.direction == TextDirection.rtl ? caretEnd : caretEnd - caretPrototype.width;
+            return new Offset(dx, box.top);
+        }
+
+        private Offset _getOffsetFromDownstream(int offset, Rect caretPrototype) {
+            var nextCodeUnit = _text.codeUnitAt(offset);
+            if (nextCodeUnit == null)
+                return null;
+            var nextRuneOffset = _isUtf16Surrogate((int)nextCodeUnit) ? offset + 2 : offset + 1;
+            var boxes = _paragraph.getRectsForRange(offset, nextRuneOffset);
+            if (boxes.Count == 0)
+                return null;
+            var box = boxes[0];
+            var caretStart = box.start;
+            var dx = box.direction == TextDirection.rtl ? caretStart - caretPrototype.width : caretStart;
+            return new Offset(dx, box.top);
+        }
+
+        private Offset _emptyOffset
+        {
+            get
+            {
+                D.assert(!_needsLayout);
+                switch (textAlign)
+                {
+                        case TextAlign.left:
+                            return Offset.zero;
+                        case TextAlign.right:
+                            return new Offset(width, 0.0);
+                        case TextAlign.center:
+                            return new Offset(width / 2.0, 0.0);
+                        case TextAlign.justify:
+                            if (textDirection == TextDirection.rtl)
+                            {
+                                return new Offset(width, 0.0);
+                            }
+                            return Offset.zero;
+                }
+                return null;
+            }
+        }
+        private static bool _isUtf16Surrogate(int value)
+        {
+            return (value & 0xF800) == 0xD800;
+        }
+
     }
 }

Assets/UIWidgets/painting/text_span.cs

             return sb.ToString();
         }
 
-        public int codeUnitAt(int index)
+        public int? codeUnitAt(int index)
-                return -1;
+                return null;
             }
 
             var offset = 0;
             if (ReferenceEquals(this, other)) return true;
             return Equals(style, other.style) && string.Equals(text, other.text) && childEquals(children, other.children);
         }
+        
+        public static bool operator ==(TextSpan left, TextSpan right)
+        {
+            return Equals(left, right);
+        }
+        public static bool operator !=(TextSpan left, TextSpan right)
+        {
+            return !Equals(left, right);
+        }
         private int childHash()
         {
             unchecked

Assets/UIWidgets/rendering/box.cs

             return false;
         }
 
-        protected bool hitTestChildren(HitTestResult result, Offset position = null) {
+        protected virtual bool hitTestChildren(HitTestResult result, Offset position = null) {
             return false;
         }
 

Assets/UIWidgets/rendering/box.mixin.gen.cs

 using System;
 using System.Collections.Generic;
+using UIWidgets.gestures;
 using UIWidgets.ui;
 
 namespace UIWidgets.rendering {
                 context.paintChild(child, childParentData.offset + offset);
                 child = childParentData.nextSibling;
             }
+        }
+        
+        public bool defaultHitTestChildren(HitTestResult result, Offset position) {
+            // the x, y parameters have the top left of the node's box as the origin
+            ChildType child = lastChild;
+            while (child != null)
+            {
+                ParentDataType childParentData = (ParentDataType) child.parentData;
+                if (child.hitTest(result, position: position - childParentData.offset))
+                    return true;
+                child = childParentData.previousSibling;
+            }
+            return false;
         }
 
         public List<ChildType> getChildrenAsList() {

Assets/UIWidgets/rendering/flex.cs

 using System;
 using System.Collections.Generic;
+using UIWidgets.gestures;
 using UIWidgets.painting;
 using UIWidgets.ui;
 
                 return;
 
             context.pushClipRect(this.needsCompositing, offset, Offset.zero & this.size, this.defaultPaint);
+        }
+
+        protected override bool  hitTestChildren(HitTestResult result, Offset position = null) {
+            return defaultHitTestChildren(result, position: position);
         }
     }
 }

Assets/UIWidgets/rendering/proxy_box.mixin.gen.cs

 using UIWidgets.ui;
+using UIWidgets.gestures;
 using UnityEngine;
 
 namespace UIWidgets.rendering {
             if (this.child != null) {
                 context.paintChild(this.child, offset);
             }
+        }
+        
+        protected override bool hitTestChildren(HitTestResult result, Offset position = null) {
+            if (this.child != null) {
+                return this.child.hitTest(result, position);
+            }
+
+            return false;
         }
     }
 

Assets/UIWidgets/rendering/proxy_box.mixin.njk

 using UIWidgets.ui;
+using UIWidgets.gestures;
 using UnityEngine;
 
 namespace UIWidgets.rendering {
             if (this.child != null) {
                 context.paintChild(this.child, offset);
             }
+        }
+        
+        protected override bool hitTestChildren(HitTestResult result, Offset position = null) {
+            if (this.child != null) {
+                return this.child.hitTest(result, position);
+            }
+
+            return false;
         }
     }
 {% endmacro %}

Assets/UIWidgets/rendering/shifted_box.cs

 using System;
+using UIWidgets.gestures;
 using UIWidgets.painting;
 using UIWidgets.ui;
 
                 var childParentData = (BoxParentData) this.child.parentData;
                 context.paintChild(this.child, childParentData.offset + offset);
             }
+        }
+
+        protected override bool hitTestChildren(HitTestResult result, Offset position = null)
+        {
+            if (child != null)
+            {
+                var childParentData = child.parentData as BoxParentData;
+                if (childParentData != null)
+                {
+                    position = position - childParentData.offset;
+                }
+
+                return child.hitTest(result, position);
+            }
+            return false;
         }
     }
 

Assets/UIWidgets/ui/text.cs

             }
         }
     }
+
+    public class TextBox: IEquatable<TextBox>
+    {
+        public readonly double left;
+        
+        public readonly double top;
+        
+        public readonly double right;
+        
+        public readonly double bottom;
+
+        public readonly TextDirection direction;
+
+        private TextBox(double left, double top, double right, double bottom, TextDirection direction)
+        {
+            this.left = left;
+            this.top = top;
+            this.right = right;
+            this.bottom = bottom;
+            this.direction = direction;
+        }
+        
+        public static TextBox fromLTBD(double left, double top, double right, double bottom, TextDirection direction)
+        {
+            return new TextBox(left, top, right, bottom, direction);
+        }
+
+        public Rect toRect()
+        {
+            return Rect.fromLTRB(left, top, right, bottom);
+        }
+
+        public double start
+        {
+            get { return direction == TextDirection.ltr ? left : right; }
+        }
+        
+        public double end
+        {
+            get { return direction == TextDirection.ltr ? right : left; }
+        }
+
+        public bool Equals(TextBox other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+            return left.Equals(other.left) && top.Equals(other.top) && right.Equals(other.right) && bottom.Equals(other.bottom) && direction == other.direction;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != this.GetType()) return false;
+            return Equals((TextBox) obj);
+        }
+
+        public override string ToString()
+        {
+            return string.Format("Left: {0}, Top: {1}, Right: {2}, Bottom: {3}, Direction: {4}", left, top, right, bottom, direction);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                var hashCode = left.GetHashCode();
+                hashCode = (hashCode * 397) ^ top.GetHashCode();
+                hashCode = (hashCode * 397) ^ right.GetHashCode();
+                hashCode = (hashCode * 397) ^ bottom.GetHashCode();
+                hashCode = (hashCode * 397) ^ (int) direction;
+                return hashCode;
+            }
+        }
+
+        public static bool operator ==(TextBox left, TextBox right)
+        {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(TextBox left, TextBox right)
+        {
+            return !Equals(left, right);
+        }
+    }
 }

Assets/UIWidgets/ui/txt/paragraph.cs

 using System;
 using System.Collections.Generic;
+using UIWidgets.painting;
 using UIWidgets.ui.txt;
 using UnityEngine;
 
             return new Vector2d(a.x - b.x, a.y - b.y);
         }
     }
+
+    public class CodeUnitRun
+    {
+        public int lineNumber;
+        public TextDirection direction;
+        public IndexRange codeUnits;
+        public FontMetrics fontMetrics;
+
+        public CodeUnitRun(IndexRange cu, int line, FontMetrics fontMetrics, TextDirection direction)
+        {
+            this.lineNumber = line;
+            this.codeUnits = cu;
+            this.fontMetrics = fontMetrics;
+            this.direction = direction;
+        }
+    }
+
+    public class FontMetrics
+    {
+        public readonly double ascent;
+        public readonly double descent;
+
+        public FontMetrics(double ascent, double descent)
+        {
+            this.ascent = ascent;
+            this.descent = descent;
+        }
+    }
+
+    public struct IndexRange :IEquatable<IndexRange>
+    {
+        public int start, end;
+
+        public IndexRange(int s, int e)
+        {
+            start = s;
+            end = e;
+        }
+
+        int width()
+        {
+            return end - start;
+        }
+
+        void shift(int delta)
+        {
+            start += delta;
+            end += delta;
+        }
+
+        public bool Equals(IndexRange other)
+        {
+            return start == other.start && end == other.end;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            return obj is IndexRange && Equals((IndexRange) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return (start * 397) ^ end;
+            }
+        }
+
+        public static bool operator ==(IndexRange left, IndexRange right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(IndexRange left, IndexRange right)
+        {
+            return !left.Equals(right);
+        }
+    }
+
+    public class PositionWithAffinity
+    {
+        public readonly int position;
+        public readonly TextAffinity affinity;
+
+        public PositionWithAffinity(int p, TextAffinity a)
+        {
+            position = p;
+            affinity = a;
+        }
+    }
     
     public class Paragraph
     {
         private ParagraphStyle _paragraphStyle;
         private List<LineRange> _lineRanges = new List<LineRange>();
         private List<double> _lineWidths = new List<double>();
+        private List<double> _lineBaseLines = new List<double>();
         private Vector2d[] _characterPositions;
         private double _maxIntrinsicWidth;
         private double _minIntrinsicWidth;
         private List<double> _lineHeights = new List<double>();
         private List<PaintRecord> _paintRecords = new List<PaintRecord>();
+        private List<CodeUnitRun> _codeUnitRuns = new List<CodeUnitRun>();
         private bool _didExceedMaxLines;
       
         // private double _characterWidth;
             _paragraphStyle = style;
         }
 
+        public List<TextBox> getRectsForRange(int start, int end)
+        {
+            var lineBoxes = new SortedDictionary<int, List<TextBox>>();
+            foreach (var run in _codeUnitRuns)
+            {
+                if (run.codeUnits.start >= end)
+                {
+                    break;
+                }
+
+                if (run.codeUnits.end <= start)
+                {
+                    continue;
+                }
+
+                var baseLine = _lineBaseLines[run.lineNumber];
+                double top = baseLine - run.fontMetrics.ascent;
+                double bottom = baseLine + run.fontMetrics.descent;
+
+                // double left, right;
+                var from = Math.Max(start, run.codeUnits.start);
+                var to = Math.Min(end, run.codeUnits.end);
+                if (from < to)
+                {
+                    List<TextBox> boxs;
+                    if (!lineBoxes.TryGetValue(run.lineNumber, out boxs))
+                    {
+                        boxs = new List<TextBox>();
+                        lineBoxes.Add(run.lineNumber, boxs);
+                    }
+
+                    double left = _characterPositions[from].x;
+                    double right = _characterPositions[to - 1].x + _characterWidths[to - 1];
+                    boxs.Add(TextBox.fromLTBD(left, top, right, bottom, run.direction));
+                }
+            }
+
+            for (int lineNumber = 0; lineNumber < _lineRanges.Count; ++lineNumber)
+            {
+                var line = _lineRanges[lineNumber];
+                if (line.start >= end)
+                {
+                    break;
+                }
+
+                if (line.endIncludingNewLine <= start)
+                {
+                    continue;
+                }
+
+                if (!lineBoxes.ContainsKey(lineNumber))
+                {
+                    if (line.end != line.endIncludingNewLine && line.end >= start && line.endIncludingNewLine <= end)
+                    {
+                        var x = _lineWidths[lineNumber];
+                        var top = (lineNumber > 0) ? _lineHeights[lineNumber - 1] : 0;
+                        var bottom = _lineHeights[lineNumber];
+                        lineBoxes.Add(lineNumber, new List<TextBox>(){TextBox.fromLTBD(
+                            x, top, x, bottom, TextDirection.ltr)});
+                    }
+                }
+                
+            }
+
+            var result = new List<TextBox>();
+            foreach (var keyValuePair in lineBoxes)
+            {
+                result.AddRange(keyValuePair.Value);
+            }
+
+            return result;
+        }
+
+        public PositionWithAffinity getGlyphPositionAtCoordinate(double dx, double dy)
+        {
+            if (_lineHeights.Count == 0)
+            {
+                return new PositionWithAffinity(0, TextAffinity.downstream);
+            }
+
+            int yIndex;
+            for (yIndex = 0; yIndex < _lineHeights.Count - 1; ++yIndex)
+            {
+                if (dy < _lineHeights[yIndex])
+                {
+                    break;
+                }
+            }
+
+            var line = _lineRanges[yIndex];
+            if (line.start >= line.end)
+            {
+                return new PositionWithAffinity(line.start, TextAffinity.downstream);
+            }
+
+            int index;
+            for (index = line.start; index < line.end; ++index)
+            {
+                if (dx < _characterPositions[index].x + _characterWidths[index])
+                {
+                    break;
+                }
+            }
+
+            if (index >= line.end)
+            {
+                return new PositionWithAffinity(line.end, TextAffinity.upstream);
+            }
+            
+            TextDirection direction = TextDirection.ltr;
+            var codeUnit = _codeUnitRuns.Find((u) => u.codeUnits.start >= index && index < u.codeUnits.end);
+            if (codeUnit != null)
+            {
+                direction = codeUnit.direction;
+            }
+
+            double glyphCenter = (_characterPositions[index].x + _characterPositions[index].x + _characterWidths[index]) / 2;
+            if ((direction == TextDirection.ltr && dx < glyphCenter) || (direction == TextDirection.rtl && dx >= glyphCenter))
+            {
+                return new PositionWithAffinity(index, TextAffinity.downstream);
+            } else
+            {
+                return new PositionWithAffinity(index, TextAffinity.upstream);
+            }
+        }
+
+        public IndexRange getWordBoundary(int offset)
+        {
+            WordSeparate s = new WordSeparate(_text);
+            return s.findWordRange(offset);
+        }
+
         public static void offsetCharacters(Vector2d offset, Vector2d[] characterPos, int start, int end)
         {
             if (characterPos != null)
                 }
             }
         }
+        
 
         private void computeWidthMetrics(double maxWordWidth)
         {
             _lineHeights.Clear();
             _lineRanges.Clear();
             _lineWidths.Clear();
+            _lineBaseLines.Clear();
+            _codeUnitRuns.Clear();
             _characterWidths = new double[_text.Length];
             for (int i = 0; i < _runs.size; ++i)
             {
                             _paintRecords.Add(new PaintRecord(run.style, new TextBlob(
                                     _text, start, end, _characterPositions, run.style, bounds), 
                                 lineNumber, width));
+                            _codeUnitRuns.Add(new CodeUnitRun(
+                                new IndexRange(start, end), lineNumber, new FontMetrics(ascent, descent), TextDirection.ltr));
                         }
                     }
 
                
                 _lineHeights.Add((_lineHeights.Count == 0 ? 0 : _lineHeights[_lineHeights.Count - 1]) + 
                                  Math.Round(maxAscent + maxDescent));
+                _lineBaseLines.Add(yOffset);
             }
         }
         

Assets/UIWidgets/Tests/RenderEditable.cs

+using UnityEditor;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UIWidgets.editor;
+using UIWidgets.foundation;
+using UIWidgets.painting;
+using UIWidgets.rendering;
+using UIWidgets.service;
+using UIWidgets.ui;
+using UnityEditor;
+using UnityEngine;
+using Color = UIWidgets.ui.Color;
+using FontStyle = UIWidgets.ui.FontStyle;
+
+namespace UIWidgets.Tests
+{
+    public class RenderEditable: EditorWindow
+    {
+        private readonly Func<RenderBox>[] _options;
+
+        private readonly string[] _optionStrings;
+
+        private int _selected;
+
+        
+        RenderEditable() {
+            this._options = new Func<RenderBox>[] {
+                this.textEditable,
+            };
+            this._optionStrings = this._options.Select(x => x.Method.Name).ToArray();
+            this._selected = 0;
+            this.titleContent = new GUIContent("RenderEditable");
+        }
+
+        private WindowAdapter windowAdapter;
+
+        private RendererBindings rendererBindings;
+
+        [NonSerialized] private bool hasInvoked = false;
+
+        void OnGUI() {
+            var selected = EditorGUILayout.Popup("test case", this._selected, this._optionStrings);
+            if (selected != this._selected || !this.hasInvoked) {
+                this._selected = selected;
+                this.hasInvoked = true;
+
+                var renderBox = this._options[this._selected]();
+                this.rendererBindings.setRoot(renderBox);
+            }
+
+            if (this.windowAdapter != null) {
+                this.windowAdapter.OnGUI();
+            }
+        }
+
+        void Update() {
+            if (this.windowAdapter != null) {
+                this.windowAdapter.Update();
+            }
+        }
+
+        private void OnEnable() {
+            this.windowAdapter = new WindowAdapter(this);
+            this.rendererBindings = new RendererBindings(this.windowAdapter);
+        }
+
+        void OnDestroy() {
+            this.windowAdapter = null;
+            this.rendererBindings = null;
+        }
+
+        private RenderBox box(RenderBox p, int width = 400, int height = 400)
+        {
+            return new RenderConstrainedOverflowBox(
+                minWidth: width,
+                maxWidth: width,
+                minHeight: height,
+                maxHeight: height,
+                alignment: Alignment.center,
+                child: p
+                )
+                ;
+        }
+        
+        private RenderBox flexItemBox(RenderBox p, int width = 200, int height = 100)
+        {
+            return new RenderConstrainedBox(
+                additionalConstraints: new BoxConstraints(minWidth: width, maxWidth: width, minHeight: height,
+                    maxHeight: height),
+                child: new RenderDecoratedBox(
+                    decoration: new BoxDecoration(
+                        color: new Color(0xFFFFFFFF),
+                        borderRadius: BorderRadius.all(3),
+                        border: Border.all(Color.fromARGB(255, 255, 0, 0), 1)
+                    ),
+                    child: new RenderPadding(EdgeInsets.all(10), p
+                    )
+                ));
+        }
+        
+        RenderBox textEditable()
+        {
+            var span = new TextSpan("", children:
+                new List<TextSpan>
+                {
+                    new TextSpan("Word Wrap:The ascent of the font is the distance from the baseline to the top line of the font, as defined in the font's original data file.", null),
+                }, style:new painting.TextStyle(height:1.0));
+            
+            var flexbox = new RenderFlex(
+                direction: Axis.vertical,
+                mainAxisAlignment: MainAxisAlignment.spaceAround,
+                crossAxisAlignment: CrossAxisAlignment.center);
+
+            flexbox.add(flexItemBox(
+                new rendering.RenderEditable(span, TextDirection.ltr, 
+                    new _FixedViewportOffset(0.0), new ValueNotifier<bool>(true), this.rendererBindings.rendererBinding,
+                    onSelectionChanged: selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0), 
+                    maxLines: 100,
+                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+            ));
+            
+            span = new TextSpan("", children:
+                new List<TextSpan>
+                {
+                    new TextSpan("Hard Break:The ascent of the font is the distance\nfrom the baseline to the top \nline of the font,\nas defined in", null),
+                }, style:new painting.TextStyle(height:1.0));
+            flexbox.add(flexItemBox(
+                new rendering.RenderEditable(span, TextDirection.ltr, 
+                    new _FixedViewportOffset(0.0), new ValueNotifier<bool>(true), this.rendererBindings.rendererBinding,
+                    onSelectionChanged: selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0), 
+                    maxLines: 100,
+                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+            ));
+            
+            span = new TextSpan("", children:
+                new List<TextSpan>
+                {
+                    new TextSpan("Single Line:How to create mixin", null),
+                }, style:new painting.TextStyle(height:1.0));
+            flexbox.add(flexItemBox(
+                new rendering.RenderEditable(span, TextDirection.ltr, 
+                    new _FixedViewportOffset(0.0), new ValueNotifier<bool>(true), this.rendererBindings.rendererBinding,
+                    onSelectionChanged: selectionChanged, cursorColor: Color.fromARGB(255, 0, 0, 0), 
+                    selectionColor: Color.fromARGB(255, 255, 0, 0))
+            , width:300));
+            return flexbox;
+        }
+        
+
+        private void selectionChanged(TextSelection selection, rendering.RenderEditable renderObject,
+            SelectionChangedCause cause)
+        {
+            Debug.Log(string.Format("selection {0}", selection));
+            renderObject.selection = selection;
+        }
+        
+    }
+}

Assets/UIWidgets/Tests/RenderEditable.cs.meta

+fileFormatVersion: 2
+guid: 3133671f82dc4c0e93d4dbeb9e50b55d
+timeCreated: 1536660300

Assets/UIWidgets/rendering/editable.cs

+using System;
+using System.Collections.Generic;
+using UIWidgets.foundation;
+using UIWidgets.gestures;
+using UIWidgets.painting;
+using UIWidgets.service;
+using UIWidgets.ui;
+using UnityEngine;
+using Canvas = UIWidgets.ui.Canvas;
+using Color = UIWidgets.ui.Color;
+using Rect = UIWidgets.ui.Rect;
+
+namespace UIWidgets.rendering
+{
+    public delegate void SelectionChangedHandler(TextSelection selection, RenderEditable renderObject,
+        SelectionChangedCause cause);
+
+    public delegate void CaretChangedHandler(Rect caretRect);
+
+    public enum SelectionChangedCause
+    {
+        tap,
+        doubleTap,
+        longPress,
+        keyboard,
+    }
+
+    public class TextSelectionPoint
+    {
+        public readonly Offset point;
+        public readonly TextDirection? direction;
+
+        public TextSelectionPoint(Offset point, TextDirection? direction)
+        {
+            D.assert(point != null);
+            this.point = point;
+            this.direction = direction;
+        }
+
+        public override string ToString()
+        {
+            return string.Format("Point: {0}, Direction: {1}", point, direction);
+        }
+    }
+/*
+    this._doubleTapGesture = new DoubleTapGestureRecognizer(this.rendererBindings.rendererBinding);
+    this._doubleTapGesture.onDoubleTap = () => { Debug.Log("onDoubleTap"); };*/
+
+    public class RenderEditable : RenderBox
+    {
+        public static readonly string obscuringCharacter = "•";
+        private static readonly double _kCaretGap = 1.0;
+        private static readonly double _kCaretHeightOffset = 2.0;
+        private static readonly double _kCaretWidth = 1.0;
+
+        private TextPainter _textPainter;
+        private Color _cursorColor;
+        private bool _hasFocus;
+        private int _maxLines;
+        private Color _selectionColor;
+        private ViewportOffset _offset;
+        private ValueNotifier<bool> _showCursor;
+        private TextSelection _selection;
+        private bool _obscureText;
+        private TapGestureRecognizer _tap;
+        private DoubleTapGestureRecognizer _doubleTap;
+        private bool ignorePointer;
+        private SelectionChangedHandler onSelectionChanged;
+        private CaretChangedHandler onCaretChanged;
+        private Rect _lastCaretRect;
+        private double? _textLayoutLastWidth;
+        private List<TextBox> _selectionRects;
+        private Rect _caretPrototype;
+        private bool _hasVisualOverflow = false;
+        private Offset _lastTapDownPosition;
+
+        public RenderEditable(TextSpan text, TextDirection textDirection, ViewportOffset offset,
+            ValueNotifier<bool> showCursor,
+            GestureBinding binding,
+            TextAlign textAlign = TextAlign.left, double textScaleFactor = 1.0, Color cursorColor = null,
+            bool? hasFocus = null, int maxLines = 1, Color selectionColor = null,
+            TextSelection selection = null, bool obscureText = false, SelectionChangedHandler onSelectionChanged = null,
+            CaretChangedHandler onCaretChanged = null, bool ignorePointer = false)
+        {
+            _textPainter = new TextPainter(text: text, textAlign: textAlign, textDirection: textDirection,
+                textScaleFactor: textScaleFactor);
+            _cursorColor = cursorColor;
+            _showCursor = showCursor ?? new ValueNotifier<bool>(false);
+            _hasFocus = hasFocus ?? false;
+            _maxLines = maxLines;
+            _selectionColor = selectionColor;
+            _selection = selection;
+            _obscureText = obscureText;
+            _offset = offset;
+            this.ignorePointer = ignorePointer;
+            this.onCaretChanged = onCaretChanged;
+            this.onSelectionChanged = onSelectionChanged;
+
+            D.assert(_showCursor != null);
+            D.assert(!_showCursor.value || cursorColor != null);
+
+            _tap = new TapGestureRecognizer(binding, this);
+            _doubleTap = new DoubleTapGestureRecognizer(binding, this);
+            _tap.onTapDown = this._handleTapDown;
+            _tap.onTap = this._handleTap;
+            _doubleTap.onDoubleTap = this._handleDoubleTap;
+        }
+
+        public bool obscureText
+        {
+            get { return _obscureText; }
+            set
+            {
+                if (_obscureText == value)
+                    return;
+                _obscureText = value;
+                markNeedsSemanticsUpdate();
+            }
+        }
+
+        public TextSpan text
+        {
+            get { return _textPainter.text; }
+            set
+            {
+                if (_textPainter.text == value)
+                {
+                    return;
+                }
+
+                _textPainter.text = value;
+                markNeedsTextLayout();
+                markNeedsSemanticsUpdate();
+            }
+        }
+
+        public TextAlign textAlign
+        {
+            get { return _textPainter.textAlign; }
+            set
+            {
+                if (_textPainter.textAlign == value)
+                {
+                    return;
+                }
+
+                _textPainter.textAlign = value;
+                markNeedsPaint();
+            }
+        }
+
+        public TextDirection? textDirection
+        {
+            get { return _textPainter.textDirection; }
+            set
+            {
+                if (_textPainter.textDirection == value)
+                {
+                    return;
+                }
+
+                _textPainter.textDirection = value;
+                markNeedsTextLayout();
+                markNeedsSemanticsUpdate();
+            }
+        }
+
+        public Color cursorColor
+        {
+            get { return _cursorColor; }
+            set
+            {
+                if (_cursorColor == value)
+                {
+                    return;
+                }
+
+                _cursorColor = value;
+                markNeedsPaint();
+            }
+        }
+
+        public ValueNotifier<bool> ShowCursor
+        {
+            get { return _showCursor; }
+            set
+            {
+                D.assert(value != null);
+                if (_showCursor == value)
+                {
+                    return;
+                }
+
+                if (attached)
+                {
+                    _showCursor.removeListener(markNeedsPaint);
+                }
+
+                _showCursor = value;
+                if (attached)
+                {
+                    _showCursor.addListener(markNeedsPaint);
+                }
+
+                markNeedsPaint();
+            }
+        }
+
+        public bool hasFocus
+        {
+            get { return _hasFocus; }
+            set
+            {
+                if (_hasFocus == value)
+                {
+                    return;
+                }
+
+                hasFocus = value;
+                markNeedsSemanticsUpdate();
+            }
+        }
+
+        public int maxLines
+        {
+            get { return _maxLines; }
+            set
+            {
+                D.assert(value > 0);
+                if (_maxLines == value)
+                {
+                    return;
+                }
+
+                _maxLines = value;
+                markNeedsTextLayout();
+            }
+        }
+
+        public Color selectionColor
+        {
+            get { return _selectionColor; }
+            set
+            {
+                if (_selectionColor == value)
+                {
+                    return;
+                }
+
+                _selectionColor = value;
+                markNeedsPaint();
+            }
+        }
+
+        public double textScaleFactor
+        {
+            get { return _textPainter.textScaleFactor; }
+            set
+            {
+                if (_textPainter.textScaleFactor == value)
+                {
+                    return;
+                }
+
+                _textPainter.textScaleFactor = value;
+                markNeedsTextLayout();
+            }
+        }
+
+        public TextSelection selection
+        {
+            get { return _selection; }
+            set
+            {
+                if (_selection == value)
+                {
+                    return;
+                }
+
+                _selection = value;
+                _selectionRects = null;
+                markNeedsPaint();
+                markNeedsSemanticsUpdate();
+            }
+        }
+
+        public ViewportOffset offset
+        {
+            get { return _offset; }
+            set
+            {
+                D.assert(offset != null);
+                if (_offset == value)
+                {
+                    return;
+                }
+
+                if (attached)
+                {
+                    _offset.removeListener(markNeedsPaint);
+                }
+
+                _offset = value;
+                if (attached)
+                {
+                    _offset.addListener(markNeedsPaint);
+                }
+
+                markNeedsLayout();
+            }
+        }
+
+        public ValueNotifier<bool> showCursor
+        {
+            get { return _showCursor; }
+            set
+            {
+                D.assert(value != null);
+                if (_showCursor == value)
+                {
+                    return;
+                }
+
+                if (attached)
+                {
+                    _showCursor.removeListener(markNeedsPaint);
+                }
+                _showCursor = value;
+                if (attached)
+                {
+                    _showCursor.addListener(markNeedsPaint);
+                }
+
+                markNeedsPaint();
+            }
+        }
+
+        public double preferredLineHeight
+        {
+            get { return _textPainter.preferredLineHeight; }
+        }
+
+
+        public override void attach(object ownerObject)
+        {
+            base.attach(ownerObject);
+            _offset.addListener(markNeedsLayout);
+            _showCursor.addListener(markNeedsPaint);
+        }
+
+        public override void detach()
+        {
+            _offset.removeListener(markNeedsLayout);
+            _showCursor.removeListener(markNeedsPaint);
+            base.detach();
+        }
+
+        /// Returns the local coordinates of the endpoints of the given selection.
+        ///
+        /// If the selection is collapsed (and therefore occupies a single point), the
+        /// returned list is of length one. Otherwise, the selection is not collapsed
+        /// and the returned list is of length two. In this case, however, the two
+        /// points might actually be co-located (e.g., because of a bidirectional
+        /// selection that contains some text but whose ends meet in the middle).
+        ///
+        public List<TextSelectionPoint> getEndpointsForSelection(TextSelection selection)
+        {
+            D.assert(constraints != null);
+            _layoutText(constraints.maxWidth);
+            var paintOffset = _paintOffset;
+            if (selection.isCollapsed)
+            {
+                var caretOffset = _textPainter.getOffsetForCaret(selection.extendPos, _caretPrototype);
+                var start = new Offset(0.0, preferredLineHeight) + caretOffset + paintOffset;
+                return new List<TextSelectionPoint>{new TextSelectionPoint(start, null)};
+            }
+            else
+            {
+                var boxes = _textPainter.getBoxesForSelection(selection);
+                var start = new Offset(boxes[0].start, boxes[0].bottom) + paintOffset;
+                var last = boxes.Count - 1;
+                var end = new Offset(boxes[last].end, boxes[last].bottom) + paintOffset;
+                return new List<TextSelectionPoint>
+                    {
+                        new TextSelectionPoint(start, boxes[0].direction),
+                        new TextSelectionPoint(end, boxes[last].direction),
+                    };
+            }
+        }
+
+        public TextPosition getPositionForPoint(Offset globalPosition)
+        {
+            _layoutText(constraints.maxWidth);
+            globalPosition -= _paintOffset;
+            return _textPainter.getPositionForOffset(globalPosition);
+        }
+
+        public Rect getLocalRectForCaret(TextPosition caretPosition)
+        {
+            _layoutText(constraints.maxWidth);
+            var caretOffset = _textPainter.getOffsetForCaret(caretPosition, _caretPrototype);
+            return Rect.fromLTWH(0.0, 0.0, _kCaretWidth, preferredLineHeight).shift(caretOffset + _paintOffset);
+        }
+        
+        public override double computeMinIntrinsicWidth(double height) {
+            _layoutText(double.PositiveInfinity);
+            return _textPainter.minIntrinsicWidth;
+        }
+        
+        public override double computeMaxIntrinsicWidth(double height) {
+            _layoutText(double.PositiveInfinity);
+            return _textPainter.maxIntrinsicWidth;
+        }
+
+        public override double computeMinIntrinsicHeight(double width) {
+            return _preferredHeight(width);
+        }
+
+        public override double computeMaxIntrinsicHeight(double width) {
+            return _preferredHeight(width);
+        }
+
+        public override double? computeDistanceToActualBaseline(TextBaseline baseline) {
+            _layoutText(constraints.maxWidth);
+            return _textPainter.computeDistanceToActualBaseline(baseline);
+        }
+        
+        public override void handleEvent(PointerEvent evt, HitTestEntry entry) {
+            if (ignorePointer)
+                return;
+            D.assert(debugHandleEvent(evt, entry));
+            if (evt is PointerDownEvent && onSelectionChanged != null) {
+                _tap.addPointer((PointerDownEvent)evt);
+                _doubleTap.addPointer((PointerDownEvent)evt);
+                // todo long press
+            }
+        }
+
+        public void handleTapDown(TapDownDetails details)
+        {
+            _lastTapDownPosition = details.globalPosition - _paintOffset;
+        }
+
+        public void handleTap()
+        {
+            _layoutText(constraints.maxWidth);
+            D.assert(_lastTapDownPosition != null);
+            if (onSelectionChanged != null)
+            {
+                var position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
+                onSelectionChanged(TextSelection.fromPosition(position), this, SelectionChangedCause.tap);
+            }
+        }
+        
+        public void handleDoubleTap()
+        {
+            _layoutText(constraints.maxWidth);
+            D.assert(_lastTapDownPosition != null);
+            if (onSelectionChanged != null)
+            {
+                var position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
+                onSelectionChanged(_selectWordAtOffset(position), this, SelectionChangedCause.doubleTap);
+            }
+        }
+        
+        
+        public override void performLayout() {
+            _layoutText(constraints.maxWidth);
+            _caretPrototype = Rect.fromLTWH(0.0, _kCaretHeightOffset, _kCaretWidth,
+                preferredLineHeight - 2.0 * _kCaretHeightOffset);
+            _selectionRects = null;
+
+            var textPainterSize = _textPainter.size;
+            size = new Size(constraints.maxWidth, constraints.constrainHeight(_preferredHeight(constraints.maxWidth)));
+            var contentSize = new Size(textPainterSize.width + _kCaretGap + _kCaretWidth, textPainterSize.height);
+            var _maxScrollExtent = _getMaxScrollExtend(contentSize);
+            _hasVisualOverflow = _maxScrollExtent > 0.0;
+            offset.applyViewportDimension(_viewportExtend);
+            offset.applyContentDimensions(0.0, _maxScrollExtent);
+        }
+
+        public override void paint(PaintingContext context, Offset offset)
+        {
+            _layoutText(constraints.maxWidth);
+            if (_hasVisualOverflow)
+            {
+                context.pushClipRect(needsCompositing, offset, Offset.zero & size, _paintContents);
+            }
+            else
+            {
+                _paintContents(context, offset);
+            }
+        }
+        
+        protected override bool hitTestSelf(Offset position)
+        {
+            return true;
+        }
+
+        protected void markNeedsTextLayout()
+        {
+            _textLayoutLastWidth = null;
+            markNeedsLayout();
+        }
+
+        // describeSemanticsConfiguration todo
+        
+        
+        protected internal override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            properties.add(new DiagnosticsProperty<Color>("cursorColor", cursorColor));
+            properties.add(new DiagnosticsProperty<ValueNotifier<bool>>("showCursor", showCursor));
+            properties.add(new DiagnosticsProperty<int>("maxLines", maxLines));
+            properties.add(new DiagnosticsProperty<Color>("selectionColor", selectionColor));
+            properties.add(new DiagnosticsProperty<double>("textScaleFactor", textScaleFactor));
+            properties.add(new DiagnosticsProperty<TextSelection>("selection", selection));
+            properties.add(new DiagnosticsProperty<ViewportOffset>("offset", offset));
+        }
+
+        private void _paintCaret(Canvas canvas, Offset effectiveOffset)
+        {
+            D.assert(_textLayoutLastWidth == constraints.maxWidth);
+            var caretOffset = _textPainter.getOffsetForCaret(_selection.extendPos, _caretPrototype);
+            var paint = new Paint() {color = _cursorColor};
+            var caretRec = _caretPrototype.shift(caretOffset + effectiveOffset);
+            canvas.drawRect(caretRec, BorderWidth.zero, BorderRadius.zero, paint);
+            if (!caretRec.Equals(_lastCaretRect))
+            {
+                _lastCaretRect = caretRec;
+                if (onCaretChanged != null)
+                {
+                    onCaretChanged(caretRec);
+                }
+            }
+        }
+
+        void _paintSelection(Canvas canvas, Offset effectiveOffset)
+        {
+            D.assert(_textLayoutLastWidth == constraints.maxWidth);
+            D.assert(_selectionRects != null);
+            var paint = new Paint() {color = _selectionColor};
+            
+            foreach (var box in _selectionRects)
+            {
+                Debug.Log(string.Format("draw box {0}", box.toRect().shift(effectiveOffset)));
+                canvas.drawRect(box.toRect().shift(effectiveOffset), BorderWidth.zero, BorderRadius.zero, paint);
+            }
+        }
+
+        void _paintContents(PaintingContext context, Offset offset)
+        {
+            D.assert(_textLayoutLastWidth == constraints.maxWidth);
+            var effectiveOffset = offset + _paintOffset;
+            
+            if (_selection != null) {
+                if (_selection.isCollapsed && _showCursor.value && cursorColor != null) {
+                    _paintCaret(context.canvas, effectiveOffset);
+                } else if (!_selection.isCollapsed && _selectionColor != null) {
+                    _selectionRects = _selectionRects??_textPainter.getBoxesForSelection(_selection);
+                    _paintSelection(context.canvas, effectiveOffset);
+                }
+            }
+
+            _textPainter.paint(context.canvas, effectiveOffset);
+        }
+        
+        private void _handleSetSelection(TextSelection selection)
+        {
+            onSelectionChanged(selection, this, SelectionChangedCause.keyboard);
+        }
+
+        private void _handleTapDown(TapDownDetails details)
+        {
+            D.assert(!ignorePointer);
+            handleTapDown(details);
+        }
+
+        private void _handleTap()
+        {
+            D.assert(!ignorePointer);
+            handleTap();
+        }
+
+        private void _handleDoubleTap()
+        {
+            D.assert(!ignorePointer);
+            handleDoubleTap();
+        }
+
+        private void markNeedsSemanticsUpdate()
+        {
+            // todo
+        }
+
+        private double _preferredHeight(double width)
+        {
+            if (maxLines <= 0)
+            {
+                return preferredLineHeight * maxLines;
+            }
+
+            if (double.IsInfinity(width))
+            {
+                var text = _textPainter.text.text;
+                int lines = 1;
+                for (int index = 0; index < text.Length; ++index)
+                {
+                    if (text[index] == 0x0A)
+                    {
+                        lines += 1;
+                    }
+                }
+
+                return preferredLineHeight * lines;
+            }
+            
+            _layoutText(width);
+            return Math.Max(preferredLineHeight, _textPainter.height);
+        }
+
+        private void _layoutText(double constraintWidth)
+        {
+            if (_textLayoutLastWidth == constraintWidth)
+            {
+                return;
+            }
+
+            var caretMargin = _kCaretGap + _kCaretWidth;
+            var avialableWidth = Math.Max(0.0, constraintWidth - caretMargin);
+            var maxWidth = _isMultiline ? avialableWidth : double.PositiveInfinity;
+            _textPainter.layout(minWidth: avialableWidth, maxWidth: maxWidth);
+            _textLayoutLastWidth = constraintWidth;
+        }
+
+        TextSelection _selectWordAtOffset(TextPosition position)
+        {
+            D.assert(_textLayoutLastWidth == constraints.maxWidth);
+            var word = _textPainter.getWordBoundary(position);
+            if (position.offset >= word.end)
+            {
+                return TextSelection.fromPosition(position);
+            }
+            return new TextSelection(baseOffset: word.start, extendOffset: word.end);
+        }
+        
+        private bool _isMultiline
+        {
+            get { return _maxLines != 1; }
+        }
+
+        private Axis _viewportAxis
+        {
+            get { return _isMultiline ? Axis.vertical : Axis.horizontal; }
+        }
+
+        private Offset _paintOffset
+        {
+            get
+            {
+                switch (_viewportAxis)
+                {
+                    case Axis.horizontal:
+                        return new Offset(-offset.pixels, 0.0);
+                    case Axis.vertical:
+                        return new Offset(0.0, -offset.pixels);
+                }
+
+                return null;
+            }
+        }
+
+        private double _viewportExtend
+        {
+            get
+            {
+                D.assert(hasSize);
+                switch (_viewportAxis)
+                {
+                    case Axis.horizontal:
+                        return size.width;
+                    case Axis.vertical:
+                        return size.height;
+                }
+
+                return 0.0;
+            }
+        }
+
+        private double _getMaxScrollExtend(Size contentSize)
+        {
+            D.assert(hasSize);
+            switch (_viewportAxis)
+            {
+                case Axis.horizontal:
+                    return Math.Max(0.0, contentSize.width - size.width);
+                case Axis.vertical:
+                    return Math.Max(0.0, contentSize.height - size.height);
+            }
+
+            return 0.0;
+        }
+    }
+}

Assets/UIWidgets/rendering/editable.cs.meta

+fileFormatVersion: 2
+guid: f171ccb5173340cf99e2ddd274a3cbd6
+timeCreated: 1536565172

Assets/UIWidgets/service.meta

+fileFormatVersion: 2
+guid: 355cc83db152457b8eb6da935c588fbc
+timeCreated: 1536566821

Assets/UIWidgets/ui/txt/word_separate.cs

+using System;
+
+namespace UIWidgets.ui
+{
+    public class WordSeparate
+    {
+        
+        enum Direction
+        {
+            Forward,
+            Backward,
+        }
+        
+        enum characterType
+        {
+            LetterLike,
+            Symbol,
+            WhiteSpace
+        }
+
+        private string _text;
+
+        public WordSeparate(string text)
+        {
+            this._text = text;
+        }
+        
+        public IndexRange findWordRange(int index)
+        {
+            var t = classifyChar(index);
+            int start = index;
+            for (int i = index; i >= 0; --i)
+            {
+                if (!char.IsLowSurrogate(_text[start]))
+                {
+                    if (classifyChar(i) != t)
+                    {
+                        break;
+                    }
+                    start = i;
+                }
+            }
+
+            int end = index;
+            for (int i = index; i < _text.Length; ++i)
+            {
+                if (!char.IsLowSurrogate(_text[i]))
+                {
+                    if (classifyChar(i) != t)
+                    {
+                        break;
+                    }
+                    end = i;
+                }
+            }
+            return new IndexRange(start, end + 1);
+        }
+
+        
+        private characterType classifyChar(int index)
+        {
+            if (char.IsWhiteSpace(_text, index))
+                return characterType.WhiteSpace;
+            if (char.IsLetterOrDigit(_text, index) || _text[index] == '\'')
+                return characterType.LetterLike;
+            return characterType.Symbol;
+        }
+
+    }
+}

Assets/UIWidgets/ui/txt/word_separate.cs.meta

+fileFormatVersion: 2
+guid: 1c8f1db7a67b4775942ad83def1ce873
+timeCreated: 1536654844

Assets/UIWidgets/service/text_editing.cs

+using System;
+using UIWidgets.foundation;
+using UIWidgets.ui;
+
+namespace UIWidgets.service
+{
+    public class TextRange: IEquatable<TextRange>
+    {
+        public readonly int start;
+        public readonly int end;
+
+        public static TextRange collapsed(int offset)
+        {
+            D.assert(offset >= -1);
+            return new TextRange(offset, offset);
+        }
+        
+        public static readonly TextRange empty = new TextRange(-1, -1);
+        
+        public TextRange(int start, int end)
+        {
+            D.assert(start >= -1);
+            D.assert(end >= -1);
+            this.start = start;
+            this.end = end;
+        }
+
+        public bool isValid
+        {
+            get { return start >= 0 && end >= 0; }
+        }
+        
+        public bool isCollapsed
+        {
+            get { return start == end; }
+        }
+
+        public bool isNormalized
+        {
+            get { return start <= end; }
+        }
+
+        public string textBefore(string text)
+        {
+            D.assert(isNormalized);
+            return text.Substring(0, start);
+        }
+        
+        public string textAfter(string text)
+        {
+            D.assert(isNormalized);
+            return text.Substring(end);
+        }
+
+        public string textInside(string text)
+        {
+            D.assert(isNormalized);
+            return text.Substring(start, end - start);
+        }
+
+        public bool Equals(TextRange other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+            return start == other.start && end == other.end;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != this.GetType()) return false;
+            return Equals((TextRange) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return (start * 397) ^ end;
+            }
+        }
+
+        public static bool operator ==(TextRange left, TextRange right)
+        {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(TextRange left, TextRange right)
+        {
+            return !Equals(left, right);
+        }
+
+        public override string ToString()
+        {
+            return string.Format("TextRange Start: {0}, End: {1}", start, end);
+        }
+    }
+
+    public class TextSelection : TextRange, IEquatable<TextSelection>
+    {
+        public readonly int baseOffset;
+        public readonly int extendOffset;
+        public readonly TextAffinity affinity;
+        public readonly bool isDirectional;
+
+        public TextSelection(int baseOffset, int extendOffset, TextAffinity affinity = TextAffinity.downstream,
+            bool isDirectional = false):base(baseOffset < extendOffset ? baseOffset: extendOffset, 
+            baseOffset < extendOffset ? extendOffset : baseOffset )
+        {
+            this.baseOffset = baseOffset;
+            this.extendOffset = extendOffset;
+            this.affinity = affinity;
+            this.isDirectional = isDirectional;
+        }
+
+        public static TextSelection collapsed(int offset, TextAffinity affinity = TextAffinity.downstream)
+        {
+            return new TextSelection(offset, offset, affinity, false);
+        }
+
+        public static TextSelection fromPosition(TextPosition position)
+        {
+            return collapsed(position.offset, position.affinity);
+        }
+        
+        public TextPosition basePos
+        {
+            get
+            {
+                return new TextPosition(offset: baseOffset, affinity: affinity);
+            }
+        }
+
+        public TextPosition extendPos
+        {
+            get
+            {
+                return new TextPosition(offset: extendOffset, affinity: affinity);
+            }
+        }
+
+        public bool Equals(TextSelection other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+            return baseOffset == other.baseOffset && extendOffset == other.extendOffset && 
+                   affinity == other.affinity && isDirectional == other.isDirectional;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != this.GetType()) return false;
+            return Equals((TextSelection) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                int hashCode = 0;
+                hashCode = (hashCode * 397) ^ baseOffset;
+                hashCode = (hashCode * 397) ^ extendOffset;
+                hashCode = (hashCode * 397) ^ (int) affinity;
+                hashCode = (hashCode * 397) ^ isDirectional.GetHashCode();
+                return hashCode;
+            }
+        }
+
+        public static bool operator ==(TextSelection left, TextSelection right)
+        {
+            return Equals(left, right);
+        }
+
+        public static bool operator !=(TextSelection left, TextSelection right)
+        {
+            return !Equals(left, right);
+        }
+
+        public TextSelection copyWith(int? baseOffset = null, int? extendOffset = null, TextAffinity? affinity = null,
+            bool? isDirectional = null)
+        {
+            return new TextSelection(
+                baseOffset??this.baseOffset, extendOffset??this.extendOffset, affinity??this.affinity,
+                isDirectional??this.isDirectional
+                );
+        }
+    }
+}

Assets/UIWidgets/service/text_editing.cs.meta

+fileFormatVersion: 2
+guid: 75983962965c4fd8bf21cc55ba91bde0
+timeCreated: 1536566838

Assets/UIWidgets/math.meta

-fileFormatVersion: 2
-guid: c53bae489a2f499ea5b9000edb31b0bb
-timeCreated: 1535421229