Fix editable trailing space problem.

Runtime/ui/txt/layout.cs

             return 0;
         }
 
-        public static void computeCharWidths(string text, int start, int count, TextStyle style, float[] advances,
-            int advanceOffset) {
+        public static float computeCharWidths(float offset, string text, int start, int count, TextStyle style,
+            float[] advances, int advanceOffset, TabStops tabStops) {
+            float totalWidths = 0;
             if (char.IsHighSurrogate(startingChar) || EmojiUtils.isSingleCharEmoji(startingChar)) {
                 float advance = style.fontSize + style.letterSpacing;
                 for (int i = 0; i < count; i++) {
+                        totalWidths += advance;
                     }
                     else {
                         advances[i + advanceOffset] = 0;
                 font.RequestCharactersInTextureSafe(text, style.UnityFontSize, style.UnityFontStyle);
                 for (int i = 0; i < count; i++) {
                     char ch = text[start + i];
-                    if (font.getGlyphInfo(ch, out var glyphInfo, style.UnityFontSize, style.UnityFontStyle)) {
+                    if (ch == '\t') {
+                        advances[i + advanceOffset] = tabStops.nextTab(offset + totalWidths) - (offset + totalWidths);
+                    }
+                    else if (font.getGlyphInfo(ch, out var glyphInfo, style.UnityFontSize, style.UnityFontStyle)) {
                         advances[i + advanceOffset] = glyphInfo.advance + style.letterSpacing;
                     }
                     else {
                     if (LayoutUtils.isWordSpace(ch)) {
                         advances[i + advanceOffset] += style.wordSpacing;
                     }
+
+                    totalWidths += advances[i + advanceOffset];
+
+            return totalWidths;
         }
 
         public static float doLayout(float offset, string text, int start, int count, TextStyle style,

Runtime/ui/txt/linebreaker.cs

             this._lineWidth = lineWidth;
         }
 
-        public void addStyleRun(TextStyle style, int start, int end) {
+        public float addStyleRun(TextStyle style, int start, int end) {
+            float width = 0;
-                Layout.computeCharWidths(this._textBuf.text, this._textBuf.offset + start, end - start, style,
-                    this._charWidths, start);
+                width = Layout.computeCharWidths(this._width - this._preBreak, this._textBuf.text,
+                    this._textBuf.offset + start, end - start, style,
+                    this._charWidths, start, this._tabStops);
             }
 
             int current = this._wordBreaker.current();
                     current = this._wordBreaker.next();
                 }
             }
+
+            return width;
         }
 
         public void finish() {

Runtime/ui/txt/paragraph.cs

 
             this._lineCount = lineLimit;
 
-            // Compute max intrinsic width and min intrinsic width
-            // max intrinsic width := maximum width this paragraph could possibly expand, without any constraints,
-            //                        which equals the length of the maximum hard-break line
-            this._maxIntrinsicWidth = 0;
-            float lineBlockWidth = 0;
-            for (int i = 0; i < this._lineWidthCount; ++i) {
-                lineBlockWidth += this._lineWidths[i];
-                if (this._lineRanges[i].hardBreak) {
-                    this._maxIntrinsicWidth = Mathf.Max(lineBlockWidth, this._maxIntrinsicWidth);
-                    lineBlockWidth = 0;
-                }
-            }
-
-            this._maxIntrinsicWidth = Mathf.Max(lineBlockWidth, this._maxIntrinsicWidth);
-
             if (this._paragraphStyle.maxLines == 1 || (this._paragraphStyle.maxLines == null &&
                                                        this._paragraphStyle.ellipsized())) {
                 this._minIntrinsicWidth = this.maxIntrinsicWidth;
 
         int _addStyleRuns(LineBreaker lineBreaker, ref int runIndex, int blockStart, int blockEnd) {
             int countRuns = 0;
+            float lineBlockWidth = 0;
             while (runIndex < this._runs.size) {
                 var run = this._runs.getRun(runIndex);
                 if (run.start >= blockEnd) {
 
                 int runStart = Mathf.Max(run.start, blockStart) - blockStart;
                 int runEnd = Mathf.Min(run.end, blockEnd) - blockStart;
-                lineBreaker.addStyleRun(run.style, runStart, runEnd);
+                lineBlockWidth += lineBreaker.addStyleRun(run.style, runStart, runEnd);
+
                 countRuns++;
 
                 if (run.end > blockEnd) {
                 runIndex++;
             }
+            this._maxIntrinsicWidth = Mathf.Max(lineBlockWidth, this._maxIntrinsicWidth);
 
             return countRuns;
         }