Remove some textbuff and replace with direct text.

Runtime/ui/txt/layout.cs

 
         static float _x, _y, _maxX, _maxY; // Used to pass bounds from static to non-static doLayout
 
-        public static float measureText(float offset, TextBuff buff, int start, int count, TextStyle style,
+        public static float measureText(float offset, string text, int start, int count, TextStyle style,
-            return _doLayout(offset, buff, start, count, style, advances, null, advanceOffset, tabStops);
+            return _doLayout(offset, text, start, count, style, advances, null, advanceOffset, tabStops);
-        public void doLayout(float offset, TextBuff buff, int start, int count, TextStyle style, TabStops tabStops) {
+        public void doLayout(float offset, string text, int start, int count, TextStyle style, TabStops tabStops) {
-            this._advance = _doLayout(offset, buff, start, count, style, this._advances, this._positions, 0,
+            this._advance = _doLayout(offset, text, start, count, style, this._advances, this._positions, 0,
-        public static void computeCharWidths(TextBuff buff, int start, int count, TextStyle style, List<float> advances, int advanceOffset) {
-            char startingChar = buff.charAt(start);
+        public static void computeCharWidths(string text, int start, int count, TextStyle style, List<float> advances, int advanceOffset) {
+            char startingChar = text[start];
-                    char ch = buff.charAt(start + i);
+                    char ch = text[start + i];
                     if (char.IsHighSurrogate(ch) || EmojiUtils.isSingleCharNonEmptyEmoji(ch)) {
                         advances[i + advanceOffset] = advance;
                     }
             }
             else {
                 Font font = FontManager.instance.getOrCreate(style.fontFamily, style.fontWeight, style.fontStyle).font;
-                font.RequestCharactersInTextureSafe(buff.subString(start, count), style.UnityFontSize, style.UnityFontStyle);
+                font.RequestCharactersInTextureSafe(text.Substring(start, count), style.UnityFontSize, style.UnityFontStyle);
-                    char ch = buff.charAt(start + i);
+                    char ch = text[start + i];
                     if (font.getGlyphInfo(ch, out var glyphInfo, style.UnityFontSize, style.UnityFontStyle)) {
                         advances[i + advanceOffset] = glyphInfo.advance + style.letterSpacing;
                     }
             }
         }
 
-        static float _doLayout(float offset, TextBuff buff, int start, int count, TextStyle style,
+        static float _doLayout(float offset, string text, int start, int count, TextStyle style,
-            char startingChar = buff.charAt(start);
+            char startingChar = text[start];
-                advance = _layoutEmoji(buff.text, buff.offset + start, style, font, count,
+                advance = _layoutEmoji(text, start, style, font, count,
                     advances, positions, advanceOffset, advance);
             }
             else {
 //                    : LayoutUtils.getPrevWordBreakForCache(buff, start + 1);
                 int wordend;
                 for (int iter = start; iter < start + count; iter = wordend) {
-                    wordend = LayoutUtils.getNextWordBreak(buff.text, buff.offset + iter, start + count);
-                    advance = _layoutWord(offset, iter - start, buff.text, iter + buff.offset, 
+                    wordend = LayoutUtils.getNextWordBreak(text, iter, start + count);
+                    advance = _layoutWord(offset, iter - start, text, iter, 
                         wordend - iter, style, font, advances, positions, advanceOffset, advance,
                         tabStops);
                 }

Runtime/ui/txt/linebreaker.cs

 //                Layout.measureText(this._width - this._preBreak, this._textBuf,
 //                    start, end - start, style,
 //                    this._charWidths, start, this._tabStops);
-                Layout.computeCharWidths(this._textBuf, start, end - start, style, this._charWidths, start);
+                Layout.computeCharWidths(this._textBuf.text, this._textBuf.offset + start, end - start, style, this._charWidths, start);
             }
 
             int current = this._wordBreaker.current();

Runtime/ui/txt/paragraph.cs

                 }
             }
 
-            layout.doLayout(runXOffset, new TextBuff(text), textStart, textCount, run.style, this._tabStops);
+            layout.doLayout(runXOffset, text, textStart, textCount, run.style, this._tabStops);
 
             builder.allocRunPos(run.style, text, textStart, textCount);
             // bounds relative to first character
             // performance, and the ellipsis is handled here
             Layout.requireEllipsisInTexture(this._paragraphStyle.ellipsis, style);
 
-            TextBuff ellipsisTextBuff = new TextBuff(this._paragraphStyle.ellipsis);
-            float ellipsisWidth = Layout.measureText(runXOffset, ellipsisTextBuff, 0,
+            float ellipsisWidth = Layout.measureText(runXOffset, this._paragraphStyle.ellipsis, 0,
-            float textWidth = Layout.measureText(runXOffset, new TextBuff(text), textStart, textCount, style,
+            float textWidth = Layout.measureText(runXOffset, text, textStart, textCount, style,
                 textAdvances, 0, this._tabStops);
 
             // Find the minimum number of characters to truncate, so that the truncated text appended with ellipsis