Use screen buffer for terminal rendering

app/src/main/java/com/neatstudio/tmuxandroid/MainActivity.java

@@ -19,12 +19,7 @@ import android.net.Uri;
 import android.os.Build;
 import android.os.Bundle;
 import android.provider.Settings;
-import android.text.SpannableStringBuilder;
-import android.text.Spanned;
 import android.text.InputType;
-import android.text.style.BackgroundColorSpan;
-import android.text.style.ForegroundColorSpan;
-import android.text.style.StyleSpan;
 import android.view.Gravity;
 import android.view.HapticFeedbackConstants;
 import android.view.View;
@@ -62,7 +57,6 @@ public final class MainActivity extends Activity {
     private static final int MAX_TERMINAL_COLS = 140;
     private static final int MIN_TERMINAL_ROWS = 8;
     private static final int MAX_TERMINAL_ROWS = 80;
-    private static final int MAX_TERMINAL_CHARS = 40_000;
     private static final int STATUS_NORMAL = 0;
     private static final int STATUS_BUSY = 1;
     private static final int STATUS_SUCCESS = 2;
@@ -102,7 +96,7 @@ public final class MainActivity extends Activity {
     private String activeSessionName;
     private String activeMainPage = PAGE_SESSIONS;
     private String pendingImageUploadSession;
-    private final StringBuilder terminalBuffer = new StringBuilder();
+    private TerminalScreenBuffer terminalScreen = new TerminalScreenBuffer(DEFAULT_TERMINAL_COLS, DEFAULT_TERMINAL_ROWS);
     private final StringBuilder queuedTerminalInput = new StringBuilder();
     private boolean terminalConnected;
     private boolean terminalRenderPending;
@@ -971,7 +965,7 @@ public final class MainActivity extends Activity {
 
     private void openTerminal(String sessionName) {
         activeSessionName = sessionName;
-        terminalBuffer.setLength(0);
+        terminalScreen = new TerminalScreenBuffer(DEFAULT_TERMINAL_COLS, DEFAULT_TERMINAL_ROWS);
         queuedTerminalInput.setLength(0);
         terminalConnected = false;
         terminalRenderPending = false;
@@ -1132,7 +1126,7 @@ public final class MainActivity extends Activity {
                 .setItems(items, (dialog, which) -> {
                     switch (which) {
                         case 0:
-                            terminalBuffer.setLength(0);
+                            terminalScreen.clear();
                             terminalText.setText("");
                             if (terminalSocket != null) {
                                 terminalSocket.clearHistory();
@@ -1829,13 +1823,15 @@ public final class MainActivity extends Activity {
         if (lineHeight <= 0) {
             lineHeight = dp(16);
         }
-        int cols = clamp((int) Math.floor((width - horizontalPadding) / charWidth), MIN_TERMINAL_COLS, MAX_TERMINAL_COLS);
+        int cols = clamp((int) Math.floor((width - horizontalPadding) / charWidth) - 1, MIN_TERMINAL_COLS, MAX_TERMINAL_COLS);
         int rows = clamp((height - verticalPadding) / lineHeight, MIN_TERMINAL_ROWS, MAX_TERMINAL_ROWS);
         if (cols == terminalCols && rows == terminalRows && !forceSend) {
             return;
         }
         terminalCols = cols;
         terminalRows = rows;
+        terminalScreen.resize(cols, rows);
+        scheduleTerminalRender();
         TerminalSocketClient socket = terminalSocket;
         if (socket != null && !socket.isClosed() && terminalConnected) {
             socket.resize(cols, rows);
@@ -1911,10 +1907,7 @@ public final class MainActivity extends Activity {
     }
 
     private void appendTerminal(String data) {
-        terminalBuffer.append(data);
+        terminalScreen.write(data);
-        if (terminalBuffer.length() > MAX_TERMINAL_CHARS) {
-            terminalBuffer.delete(0, terminalBuffer.length() - MAX_TERMINAL_CHARS);
-        }
         scheduleTerminalRender();
     }
 
@@ -1936,194 +1929,10 @@ public final class MainActivity extends Activity {
             return;
         }
         lastTerminalRenderMs = System.currentTimeMillis();
-        terminalText.setText(renderAnsiForTerminal(terminalBuffer.toString()));
+        terminalText.setText(terminalScreen.render());
         terminalScroll.post(() -> terminalScroll.fullScroll(View.FOCUS_DOWN));
     }
 
-    private CharSequence renderAnsiForTerminal(String text) {
-        SpannableStringBuilder output = new SpannableStringBuilder();
-        int fg = Color.rgb(230, 235, 242);
-        int bg = Color.TRANSPARENT;
-        boolean bold = false;
-        int index = 0;
-        while (index < text.length()) {
-            char item = text.charAt(index);
-            if (item == '\r') {
-                deleteCurrentTerminalLine(output);
-                index++;
-                continue;
-            }
-            if (item == '\b') {
-                if (output.length() > 0 && output.charAt(output.length() - 1) != '\n') {
-                    output.delete(output.length() - 1, output.length());
-                }
-                index++;
-                continue;
-            }
-            if (item == '\u001b' && index + 1 < text.length() && text.charAt(index + 1) == '[') {
-                int end = findAnsiEnd(text, index + 2);
-                if (end == -1) {
-                    break;
-                }
-                char command = text.charAt(end);
-                if (command == 'm') {
-                    int[] state = applySgr(text.substring(index + 2, end), fg, bg, bold);
-                    fg = state[0];
-                    bg = state[1];
-                    bold = state[2] == 1;
-                } else if (command == 'K') {
-                    String params = text.substring(index + 2, end);
-                    if (params.startsWith("2")) {
-                        deleteCurrentTerminalLine(output);
-                    }
-                } else if (command == 'J') {
-                    String params = text.substring(index + 2, end);
-                    if (params.startsWith("2") || params.startsWith("3")) {
-                        output.clear();
-                    }
-                }
-                index = end + 1;
-                continue;
-            }
-            if (item == '\u001b') {
-                int skipped = skipNonCsiEscape(text, index);
-                if (skipped > index) {
-                    index = skipped;
-                    continue;
-                }
-            }
-
-            int runStart = index;
-            while (index < text.length()) {
-                char runItem = text.charAt(index);
-                if (runItem == '\r' || runItem == '\b' || runItem == '\u001b') {
-                    break;
-                }
-                index++;
-            }
-            appendTerminalRun(output, text.substring(runStart, index), fg, bg, bold);
-        }
-        return output;
-    }
-
-    private void deleteCurrentTerminalLine(SpannableStringBuilder output) {
-        int start = output.length();
-        while (start > 0 && output.charAt(start - 1) != '\n') {
-            start--;
-        }
-        if (start < output.length()) {
-            output.delete(start, output.length());
-        }
-    }
-
-    private int skipNonCsiEscape(String text, int index) {
-        if (index + 1 >= text.length()) {
-            return index + 1;
-        }
-        char next = text.charAt(index + 1);
-        if (next == ']' || next == 'P' || next == '^' || next == '_') {
-            int cursor = index + 2;
-            while (cursor < text.length()) {
-                char item = text.charAt(cursor);
-                if (item == '\u0007') {
-                    return cursor + 1;
-                }
-                if (item == '\u001b' && cursor + 1 < text.length() && text.charAt(cursor + 1) == '\\') {
-                    return cursor + 2;
-                }
-                cursor++;
-            }
-            return text.length();
-        }
-        if (next == '(' || next == ')' || next == '*' || next == '+' || next == '-' || next == '.') {
-            return Math.min(index + 3, text.length());
-        }
-        return Math.min(index + 2, text.length());
-    }
-
-    private void appendTerminalRun(SpannableStringBuilder output, String text, int fg, int bg, boolean bold) {
-        if (text.isEmpty()) {
-            return;
-        }
-        int start = output.length();
-        output.append(text);
-        int finish = output.length();
-        output.setSpan(new ForegroundColorSpan(fg), start, finish, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-        if (bg != Color.TRANSPARENT) {
-            output.setSpan(new BackgroundColorSpan(bg), start, finish, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-        }
-        if (bold) {
-            output.setSpan(new StyleSpan(Typeface.BOLD), start, finish, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
-        }
-    }
-
-    private int findAnsiEnd(String text, int start) {
-        for (int index = start; index < text.length(); index++) {
-            char item = text.charAt(index);
-            if (item >= '@' && item <= '~') {
-                return index;
-            }
-        }
-        return -1;
-    }
-
-    private int[] applySgr(String params, int fg, int bg, boolean bold) {
-        if (params.isEmpty()) {
-            params = "0";
-        }
-        String[] parts = params.split(";");
-        for (String part : parts) {
-            int value;
-            try {
-                value = part.isEmpty() ? 0 : Integer.parseInt(part);
-            } catch (NumberFormatException ignored) {
-                continue;
-            }
-            if (value == 0) {
-                fg = Color.rgb(230, 235, 242);
-                bg = Color.TRANSPARENT;
-                bold = false;
-            } else if (value == 1) {
-                bold = true;
-            } else if (value == 22) {
-                bold = false;
-            } else if (value == 39) {
-                fg = Color.rgb(230, 235, 242);
-            } else if (value == 49) {
-                bg = Color.TRANSPARENT;
-            } else if ((value >= 30 && value <= 37) || (value >= 90 && value <= 97)) {
-                fg = ansiColor(value, false);
-            } else if ((value >= 40 && value <= 47) || (value >= 100 && value <= 107)) {
-                bg = ansiColor(value, true);
-            }
-        }
-        return new int[]{fg, bg, bold ? 1 : 0};
-    }
-
-    private int ansiColor(int code, boolean background) {
-        int base = background ? (code >= 100 ? code - 100 : code - 40) : (code >= 90 ? code - 90 : code - 30);
-        boolean bright = code >= 90;
-        switch (base) {
-            case 0:
-                return bright ? Color.rgb(80, 88, 100) : Color.rgb(33, 38, 45);
-            case 1:
-                return bright ? Color.rgb(255, 123, 114) : Color.rgb(248, 81, 73);
-            case 2:
-                return bright ? Color.rgb(86, 211, 100) : Color.rgb(63, 185, 80);
-            case 3:
-                return bright ? Color.rgb(234, 179, 8) : Color.rgb(210, 153, 34);
-            case 4:
-                return bright ? Color.rgb(121, 192, 255) : Color.rgb(88, 166, 255);
-            case 5:
-                return bright ? Color.rgb(210, 168, 255) : Color.rgb(188, 140, 255);
-            case 6:
-                return bright ? Color.rgb(86, 211, 219) : Color.rgb(57, 197, 187);
-            case 7:
-            default:
-                return bright ? Color.rgb(240, 246, 252) : Color.rgb(201, 209, 217);
-        }
-    }
-
     private void saveServerAndRefresh() {
         String url = normalizeServerUrl(urlField.getText().toString());
         prefs.edit().putString("server_url", url).apply();

app/src/main/java/com/neatstudio/tmuxandroid/TerminalScreenBuffer.java

@@ -0,0 +1,615 @@
+package com.neatstudio.tmuxandroid;
+
+import android.graphics.Color;
+import android.graphics.Typeface;
+import android.text.SpannableStringBuilder;
+import android.text.Spanned;
+import android.text.style.BackgroundColorSpan;
+import android.text.style.ForegroundColorSpan;
+import android.text.style.StyleSpan;
+
+import java.util.ArrayList;
+import java.util.List;
+
+final class TerminalScreenBuffer {
+    private static final int DEFAULT_FG = 0xffe6ebf2;
+    private static final int DEFAULT_BG = Color.TRANSPARENT;
+
+    private int cols;
+    private int rows;
+    private Cell[][] cells;
+    private int cursorRow;
+    private int cursorCol;
+    private int savedRow;
+    private int savedCol;
+    private String pendingControl = "";
+    private boolean wrapPending;
+    private int fg = DEFAULT_FG;
+    private int bg = DEFAULT_BG;
+    private boolean bold;
+
+    TerminalScreenBuffer(int cols, int rows) {
+        resize(cols, rows);
+    }
+
+    void resize(int nextCols, int nextRows) {
+        nextCols = Math.max(1, nextCols);
+        nextRows = Math.max(1, nextRows);
+        Cell[][] previous = cells;
+        int previousRows = rows;
+        int previousCols = cols;
+        cols = nextCols;
+        rows = nextRows;
+        cells = new Cell[rows][cols];
+        for (int row = 0; row < rows; row++) {
+            for (int col = 0; col < cols; col++) {
+                cells[row][col] = new Cell();
+            }
+        }
+        if (previous != null) {
+            int copyRows = Math.min(previousRows, rows);
+            int copyCols = Math.min(previousCols, cols);
+            int previousStart = Math.max(0, previousRows - copyRows);
+            int nextStart = Math.max(0, rows - copyRows);
+            for (int row = 0; row < copyRows; row++) {
+                for (int col = 0; col < copyCols; col++) {
+                    cells[nextStart + row][col].copyFrom(previous[previousStart + row][col]);
+                }
+            }
+        }
+        cursorRow = clamp(cursorRow, 0, rows - 1);
+        cursorCol = clamp(cursorCol, 0, cols - 1);
+        savedRow = clamp(savedRow, 0, rows - 1);
+        savedCol = clamp(savedCol, 0, cols - 1);
+    }
+
+    void clear() {
+        clearScreen();
+        cursorRow = 0;
+        cursorCol = 0;
+        savedRow = 0;
+        savedCol = 0;
+        pendingControl = "";
+        wrapPending = false;
+        fg = DEFAULT_FG;
+        bg = DEFAULT_BG;
+        bold = false;
+    }
+
+    void write(String text) {
+        if (!pendingControl.isEmpty()) {
+            text = pendingControl + text;
+            pendingControl = "";
+        }
+        int index = 0;
+        while (index < text.length()) {
+            char item = text.charAt(index);
+            if (item == '\u001b') {
+                int next = handleEscape(text, index);
+                if (next < 0) {
+                    pendingControl = text.substring(index);
+                    return;
+                }
+                index = next;
+            } else if (item == '\r') {
+                wrapPending = false;
+                cursorCol = 0;
+                index++;
+            } else if (item == '\n') {
+                wrapPending = false;
+                newLine();
+                index++;
+            } else if (item == '\b') {
+                wrapPending = false;
+                cursorCol = Math.max(0, cursorCol - 1);
+                index++;
+            } else if (item == '\t') {
+                int nextTab = ((cursorCol / 8) + 1) * 8;
+                while (cursorCol < Math.min(nextTab, cols)) {
+                    putChar(' ');
+                }
+                index++;
+            } else if (item >= 0x20 && item != 0x7f) {
+                putChar(item);
+                index++;
+            } else {
+                index++;
+            }
+        }
+    }
+
+    CharSequence render() {
+        SpannableStringBuilder output = new SpannableStringBuilder();
+        for (int row = 0; row < rows; row++) {
+            appendRow(output, row);
+            if (row + 1 < rows) {
+                output.append('\n');
+            }
+        }
+        return output;
+    }
+
+    private int handleEscape(String text, int index) {
+        if (index + 1 >= text.length()) {
+            return -1;
+        }
+        char next = text.charAt(index + 1);
+        wrapPending = false;
+        if (next == '[') {
+            int end = findAnsiEnd(text, index + 2);
+            if (end == -1) {
+                return -1;
+            }
+            applyCsi(text.substring(index + 2, end), text.charAt(end));
+            return end + 1;
+        }
+        if (next == ']') {
+            return skipStringEscape(text, index + 2);
+        }
+        if (next == 'P' || next == '^' || next == '_') {
+            return skipStringEscape(text, index + 2);
+        }
+        if (next == '(' || next == ')' || next == '*' || next == '+' || next == '-' || next == '.') {
+            if (index + 2 >= text.length()) {
+                return -1;
+            }
+            return Math.min(index + 3, text.length());
+        }
+        if (next == '7') {
+            saveCursor();
+        } else if (next == '8') {
+            restoreCursor();
+        } else if (next == 'D') {
+            newLine();
+        } else if (next == 'E') {
+            cursorCol = 0;
+            newLine();
+        } else if (next == 'M') {
+            reverseIndex();
+        } else if (next == 'c') {
+            clear();
+        }
+        return Math.min(index + 2, text.length());
+    }
+
+    private void applyCsi(String rawParams, char command) {
+        wrapPending = false;
+        String params = rawParams;
+        while (!params.isEmpty()) {
+            char first = params.charAt(0);
+            if (first == '?' || first == '>' || first == '!' || first == '=') {
+                params = params.substring(1);
+            } else {
+                break;
+            }
+        }
+        List<Integer> values = parseParams(params);
+        switch (command) {
+            case 'm':
+                applySgr(values);
+                break;
+            case 'H':
+            case 'f':
+                cursorRow = clamp(param(values, 0, 1) - 1, 0, rows - 1);
+                cursorCol = clamp(param(values, 1, 1) - 1, 0, cols - 1);
+                break;
+            case 'A':
+                cursorRow = clamp(cursorRow - param(values, 0, 1), 0, rows - 1);
+                break;
+            case 'B':
+                cursorRow = clamp(cursorRow + param(values, 0, 1), 0, rows - 1);
+                break;
+            case 'C':
+                cursorCol = clamp(cursorCol + param(values, 0, 1), 0, cols - 1);
+                break;
+            case 'D':
+                cursorCol = clamp(cursorCol - param(values, 0, 1), 0, cols - 1);
+                break;
+            case 'G':
+                cursorCol = clamp(param(values, 0, 1) - 1, 0, cols - 1);
+                break;
+            case 'd':
+                cursorRow = clamp(param(values, 0, 1) - 1, 0, rows - 1);
+                break;
+            case 'J':
+                eraseDisplay(param(values, 0, 0));
+                break;
+            case 'K':
+                eraseLine(param(values, 0, 0));
+                break;
+            case 'P':
+                deleteChars(param(values, 0, 1));
+                break;
+            case '@':
+                insertChars(param(values, 0, 1));
+                break;
+            case 'X':
+                eraseChars(param(values, 0, 1));
+                break;
+            case 'L':
+                insertLines(param(values, 0, 1));
+                break;
+            case 'M':
+                deleteLines(param(values, 0, 1));
+                break;
+            case 's':
+                saveCursor();
+                break;
+            case 'u':
+                restoreCursor();
+                break;
+            case 'c':
+                break;
+            default:
+                break;
+        }
+    }
+
+    private void applySgr(List<Integer> values) {
+        if (values.isEmpty()) {
+            values.add(0);
+        }
+        for (int index = 0; index < values.size(); index++) {
+            int value = values.get(index);
+            if (value == 0) {
+                fg = DEFAULT_FG;
+                bg = DEFAULT_BG;
+                bold = false;
+            } else if (value == 1) {
+                bold = true;
+            } else if (value == 22) {
+                bold = false;
+            } else if (value == 39) {
+                fg = DEFAULT_FG;
+            } else if (value == 49) {
+                bg = DEFAULT_BG;
+            } else if ((value >= 30 && value <= 37) || (value >= 90 && value <= 97)) {
+                fg = ansiColor(value, false);
+            } else if ((value >= 40 && value <= 47) || (value >= 100 && value <= 107)) {
+                bg = ansiColor(value, true);
+            } else if ((value == 38 || value == 48) && index + 2 < values.size()) {
+                boolean background = value == 48;
+                int mode = values.get(index + 1);
+                if (mode == 5) {
+                    int color = xtermColor(values.get(index + 2));
+                    if (background) {
+                        bg = color;
+                    } else {
+                        fg = color;
+                    }
+                    index += 2;
+                } else if (mode == 2 && index + 4 < values.size()) {
+                    int color = Color.rgb(
+                            clamp(values.get(index + 2), 0, 255),
+                            clamp(values.get(index + 3), 0, 255),
+                            clamp(values.get(index + 4), 0, 255)
+                    );
+                    if (background) {
+                        bg = color;
+                    } else {
+                        fg = color;
+                    }
+                    index += 4;
+                }
+            }
+        }
+    }
+
+    private void putChar(char value) {
+        if (wrapPending) {
+            wrapPending = false;
+            newLine();
+        }
+        cells[cursorRow][cursorCol].set(value, fg, bg, bold);
+        if (cursorCol == cols - 1) {
+            wrapPending = true;
+        } else {
+            cursorCol++;
+        }
+    }
+
+    private void newLine() {
+        wrapPending = false;
+        cursorRow++;
+        if (cursorRow >= rows) {
+            scrollUp(1);
+            cursorRow = rows - 1;
+        }
+        cursorCol = 0;
+    }
+
+    private void reverseIndex() {
+        if (cursorRow == 0) {
+            scrollDown(1);
+        } else {
+            cursorRow--;
+        }
+    }
+
+    private void eraseDisplay(int mode) {
+        if (mode == 2 || mode == 3) {
+            clearScreen();
+        } else if (mode == 1) {
+            for (int row = 0; row < cursorRow; row++) {
+                clearLine(row, 0, cols - 1);
+            }
+            clearLine(cursorRow, 0, cursorCol);
+        } else {
+            clearLine(cursorRow, cursorCol, cols - 1);
+            for (int row = cursorRow + 1; row < rows; row++) {
+                clearLine(row, 0, cols - 1);
+            }
+        }
+    }
+
+    private void eraseLine(int mode) {
+        if (mode == 2) {
+            clearLine(cursorRow, 0, cols - 1);
+        } else if (mode == 1) {
+            clearLine(cursorRow, 0, cursorCol);
+        } else {
+            clearLine(cursorRow, cursorCol, cols - 1);
+        }
+    }
+
+    private void eraseChars(int count) {
+        int end = Math.min(cols - 1, cursorCol + Math.max(1, count) - 1);
+        clearLine(cursorRow, cursorCol, end);
+    }
+
+    private void deleteChars(int count) {
+        count = Math.max(1, count);
+        Cell[] line = cells[cursorRow];
+        for (int col = cursorCol; col < cols; col++) {
+            int source = col + count;
+            if (source < cols) {
+                line[col].copyFrom(line[source]);
+            } else {
+                line[col].clear();
+            }
+        }
+    }
+
+    private void insertChars(int count) {
+        count = Math.max(1, count);
+        Cell[] line = cells[cursorRow];
+        for (int col = cols - 1; col >= cursorCol; col--) {
+            int source = col - count;
+            if (source >= cursorCol) {
+                line[col].copyFrom(line[source]);
+            } else {
+                line[col].clear();
+            }
+        }
+    }
+
+    private void insertLines(int count) {
+        count = Math.min(Math.max(1, count), rows - cursorRow);
+        for (int row = rows - 1; row >= cursorRow + count; row--) {
+            copyLine(row, row - count);
+        }
+        for (int row = cursorRow; row < cursorRow + count; row++) {
+            clearLine(row, 0, cols - 1);
+        }
+    }
+
+    private void deleteLines(int count) {
+        count = Math.min(Math.max(1, count), rows - cursorRow);
+        for (int row = cursorRow; row + count < rows; row++) {
+            copyLine(row, row + count);
+        }
+        for (int row = rows - count; row < rows; row++) {
+            clearLine(row, 0, cols - 1);
+        }
+    }
+
+    private void clearScreen() {
+        for (int row = 0; row < rows; row++) {
+            clearLine(row, 0, cols - 1);
+        }
+    }
+
+    private void clearLine(int row, int start, int end) {
+        start = clamp(start, 0, cols - 1);
+        end = clamp(end, 0, cols - 1);
+        for (int col = start; col <= end; col++) {
+            cells[row][col].clear();
+        }
+    }
+
+    private void scrollUp(int count) {
+        count = Math.min(Math.max(1, count), rows);
+        for (int row = 0; row + count < rows; row++) {
+            copyLine(row, row + count);
+        }
+        for (int row = rows - count; row < rows; row++) {
+            clearLine(row, 0, cols - 1);
+        }
+    }
+
+    private void scrollDown(int count) {
+        count = Math.min(Math.max(1, count), rows);
+        for (int row = rows - 1; row - count >= 0; row--) {
+            copyLine(row, row - count);
+        }
+        for (int row = 0; row < count; row++) {
+            clearLine(row, 0, cols - 1);
+        }
+    }
+
+    private void copyLine(int target, int source) {
+        for (int col = 0; col < cols; col++) {
+            cells[target][col].copyFrom(cells[source][col]);
+        }
+    }
+
+    private void appendRow(SpannableStringBuilder output, int row) {
+        int col = 0;
+        while (col < cols) {
+            Cell first = cells[row][col];
+            int start = output.length();
+            int fgColor = first.fg;
+            int bgColor = first.bg;
+            boolean isBold = first.bold;
+            while (col < cols) {
+                Cell cell = cells[row][col];
+                if (cell.fg != fgColor || cell.bg != bgColor || cell.bold != isBold) {
+                    break;
+                }
+                output.append(cell.value);
+                col++;
+            }
+            int end = output.length();
+            output.setSpan(new ForegroundColorSpan(fgColor), start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+            if (bgColor != DEFAULT_BG) {
+                output.setSpan(new BackgroundColorSpan(bgColor), start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+            }
+            if (isBold) {
+                output.setSpan(new StyleSpan(Typeface.BOLD), start, end, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
+            }
+        }
+    }
+
+    private void saveCursor() {
+        savedRow = cursorRow;
+        savedCol = cursorCol;
+    }
+
+    private void restoreCursor() {
+        cursorRow = clamp(savedRow, 0, rows - 1);
+        cursorCol = clamp(savedCol, 0, cols - 1);
+    }
+
+    private int skipStringEscape(String text, int start) {
+        int cursor = start;
+        while (cursor < text.length()) {
+            char item = text.charAt(cursor);
+            if (item == '\u0007') {
+                return cursor + 1;
+            }
+            if (item == '\u001b' && cursor + 1 < text.length() && text.charAt(cursor + 1) == '\\') {
+                return cursor + 2;
+            }
+            cursor++;
+        }
+        return -1;
+    }
+
+    private int findAnsiEnd(String text, int start) {
+        for (int index = start; index < text.length(); index++) {
+            char item = text.charAt(index);
+            if (item >= '@' && item <= '~') {
+                return index;
+            }
+        }
+        return -1;
+    }
+
+    private List<Integer> parseParams(String params) {
+        List<Integer> values = new ArrayList<>();
+        if (params.isEmpty()) {
+            return values;
+        }
+        String[] parts = params.split(";", -1);
+        for (String part : parts) {
+            String cleaned = part.trim();
+            if (cleaned.isEmpty()) {
+                values.add(0);
+                continue;
+            }
+            try {
+                values.add(Integer.parseInt(cleaned));
+            } catch (NumberFormatException ignored) {
+                values.add(0);
+            }
+        }
+        return values;
+    }
+
+    private int param(List<Integer> values, int index, int fallback) {
+        if (index >= values.size()) {
+            return fallback;
+        }
+        int value = values.get(index);
+        return value == 0 ? fallback : value;
+    }
+
+    private int ansiColor(int code, boolean background) {
+        int base = background ? (code >= 100 ? code - 100 : code - 40) : (code >= 90 ? code - 90 : code - 30);
+        boolean bright = code >= 90;
+        switch (base) {
+            case 0:
+                return bright ? Color.rgb(80, 88, 100) : Color.rgb(33, 38, 45);
+            case 1:
+                return bright ? Color.rgb(255, 123, 114) : Color.rgb(248, 81, 73);
+            case 2:
+                return bright ? Color.rgb(86, 211, 100) : Color.rgb(63, 185, 80);
+            case 3:
+                return bright ? Color.rgb(234, 179, 8) : Color.rgb(210, 153, 34);
+            case 4:
+                return bright ? Color.rgb(121, 192, 255) : Color.rgb(88, 166, 255);
+            case 5:
+                return bright ? Color.rgb(210, 168, 255) : Color.rgb(188, 140, 255);
+            case 6:
+                return bright ? Color.rgb(86, 211, 219) : Color.rgb(57, 197, 187);
+            case 7:
+            default:
+                return bright ? Color.rgb(240, 246, 252) : Color.rgb(201, 209, 217);
+        }
+    }
+
+    private int xtermColor(int value) {
+        value = clamp(value, 0, 255);
+        if (value < 16) {
+            if (value < 8) {
+                return ansiColor(30 + value, false);
+            }
+            return ansiColor(90 + value - 8, false);
+        }
+        if (value >= 232) {
+            int shade = 8 + (value - 232) * 10;
+            return Color.rgb(shade, shade, shade);
+        }
+        int index = value - 16;
+        int red = xtermComponent(index / 36);
+        int green = xtermComponent((index / 6) % 6);
+        int blue = xtermComponent(index % 6);
+        return Color.rgb(red, green, blue);
+    }
+
+    private int xtermComponent(int value) {
+        return value == 0 ? 0 : 55 + value * 40;
+    }
+
+    private static int clamp(int value, int min, int max) {
+        return Math.max(min, Math.min(max, value));
+    }
+
+    private static final class Cell {
+        char value = ' ';
+        int fg = DEFAULT_FG;
+        int bg = DEFAULT_BG;
+        boolean bold;
+
+        void clear() {
+            value = ' ';
+            fg = DEFAULT_FG;
+            bg = DEFAULT_BG;
+            bold = false;
+        }
+
+        void set(char nextValue, int nextFg, int nextBg, boolean nextBold) {
+            value = nextValue;
+            fg = nextFg;
+            bg = nextBg;
+            bold = nextBold;
+        }
+
+        void copyFrom(Cell other) {
+            value = other.value;
+            fg = other.fg;
+            bg = other.bg;
+            bold = other.bold;
+        }
+    }
+}