fix line break

Runtime/ui/txt/linebreaker.cs

             int candIndex = this._candidates.Count;
             this._candidates.Add(cand);
             if (cand.postBreak - this._preBreak > this._lineWidth) {
+                if (this._bestBreak == this._lastBreak) {
+                    this._bestBreak = candIndex;
+                }
+                this._pushGreedyBreak();
+            }
+
+            while (this._lastBreak != candIndex && cand.postBreak - this._preBreak > this._lineWidth) {
+                for (int i = this._lastBreak + 1; i < candIndex; i++) {
+                    float penalty = this._candidates[i].penalty;
+                    if (penalty <= this._bestScore) {
+                        this._bestBreak = i;
+                        this._bestScore = penalty;
+                    }
+                }
+                if (this._bestBreak == this._lastBreak) {
+                    this._bestBreak = candIndex;
+                }
                 this._pushGreedyBreak();
             }
 

Runtime/ui/txt/word_separate.cs

             Backward,
         }
 
-        enum characterType {
+        internal enum characterType {
             LetterLike,
             Symbol,
             WhiteSpace
                 return new Range<int>(0, 0);
             }
 
-            var t = this.classifyChar(index);
+            var t = classifyChar(this._text, index);
-                    if (this.classifyChar(i) != t) {
+                    if (classifyChar(this._text, i) != t) {
                         break;
                     }
 
             int end = index;
             for (int i = index; i < this._text.Length; ++i) {
                 if (!char.IsLowSurrogate(this._text[i])) {
-                    if (this.classifyChar(i) != t) {
+                    if (classifyChar(this._text, i) != t) {
                         break;
                     }
 
         }
 
 
-        characterType classifyChar(int index) {
-            if (char.IsWhiteSpace(this._text, index)) {
+        internal static characterType classifyChar(string text, int index) {
+            if (char.IsWhiteSpace(text, index)) {
-            if (char.IsLetterOrDigit(this._text, index) || this._text[index] == '\'') {
+            if (char.IsLetterOrDigit(text, index) || text[index] == '\'') {
                 return characterType.LetterLike;
             }
 

Runtime/ui/txt/wordbreaker.cs

+
 namespace Unity.UIWidgets.ui {
     public class WordBreaker {
         public const uint U16_SURROGATE_OFFSET = ((0xd800 << 10) + 0xdc00 - 0x10000);
                 this._current = this._findNextBreakInEmailOrUrl();
             }
             else {
-                this._current = this._findNextBreakNormal();
+                this._current = this._findNextBoundaryNormal();
             }
 
             return this._current;
             this._current = 0;
             this._scanOffset = 0;
             this._inEmailOrUrl = false;
+            this.nextUntilCodePoint();
         }
 
         public int current() {
             return 0;
         }
 
-        int _findNextBreakNormal() {
+        int _findNextBoundaryNormal() {
+            WordSeparate.characterType preType = WordSeparate.classifyChar(this._text, this._current + this._offset);
-                char c = this._text[this._current + this._offset];
-                if (LayoutUtils.isWordSpace(c) || c == '\t') {
-                    return this._current;
+                this.nextUntilCodePoint();
+                if (this._current >= this._size) {
+                    break;
+                }
+                var currentType = WordSeparate.classifyChar(this._text, this._current + this._offset);
+                if (currentType != preType) {
+                    break;
+                preType = currentType;
-
-
+        
         void _detectEmailOrUrl() {
         }
 
 
         public static uint getSupplementary(uint lead, uint trail) {
             return (char) (((uint) (lead) << 10) + (uint) (trail - U16_SURROGATE_OFFSET));
+        }
+
+        void nextUntilCodePoint() {
+            while (this._current < this._size
+                   && (char.IsLowSurrogate(this._text[this._current + this._offset]) 
+                       ||  char.IsHighSurrogate(this._text[this._current + this._offset]))) {
+                this._current++;
+            }
         }
     }
 }

Samples/UIWidgetSample/TextInputCanvas.cs

             List<Widget> widgets = new List<Widget>();
             var style = new TextStyle();
             var cursorColor = new Color(0xFF000000);
+            var selectionColor = new Color(0xFF6F6F6F);
-                new EditableText(controller, node, style, cursorColor, onSubmitted: this.textSubmitted)))));
+                new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor,  onSubmitted: this.textSubmitted)))));
-                    new EditableText(controller, node, style, cursorColor, maxLines: 4,
+                    new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor,  maxLines: 4,
-                    new EditableText(controller, node, style, cursorColor, obscureText: true,
+                    new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor, obscureText: true,
-                new EditableText(controller, node, style, cursorColor, keyboardType: TextInputType.number,
+                new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor, keyboardType: TextInputType.number,
-                new EditableText(controller, node, style, cursorColor, keyboardType: TextInputType.phone,
+                new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor, keyboardType: TextInputType.phone,
-                new EditableText(controller, node, style, cursorColor, keyboardType: TextInputType.emailAddress,
+                new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor, keyboardType: TextInputType.emailAddress,
-                new EditableText(controller, node, style, cursorColor, keyboardType: TextInputType.url,
+                new EditableText(controller, node, style, cursorColor, selectionColor: selectionColor, keyboardType: TextInputType.url,
                     onSubmitted: this.textSubmitted)))));
 
             return new Column(