Merge pull request #2724 from jerch/reverse_wraparound

Reverse wraparound

src/browser/Terminal.test.ts

@@ -1484,6 +1484,54 @@ describe('Terminal', () => {
         assert.deepEqual(getLines(term, term.rows + 1), ['12345', '125', '125', '125', '125', '125']);
       });
     });
+
+    describe('BS with reverseWraparound set/unset', () => {
+      const ttyBS = '\x08 \x08';  // tty ICANON sends <BS SP BS> on pressing BS
+
+      beforeEach(() => {
+        term = new TestTerminal({cols: 5, rows: 5, scrollback: 1});
+      });
+
+      describe('reverseWraparound set', () => {
+        it('should not reverse outside of scroll margins', () => {
+          // prepare buffer content
+          term.writeSync('#####abcdefghijklmnopqrstuvwxy');
+          assert.deepEqual(getLines(term, 6), ['#####', 'abcde', 'fghij', 'klmno', 'pqrst', 'uvwxy']);
+          assert.equal(term.buffer.ydisp, 1);
+          assert.equal(term.buffer.x, 5);
+          assert.equal(term.buffer.y, 4);
+          term.writeSync(ttyBS.repeat(100));
+          assert.deepEqual(getLines(term, 6), ['#####', 'abcde', 'fghij', 'klmno', 'pqrst', '    y']);
+
+          term.writeSync('\x1b[?45h');
+          term.writeSync('uvwxy');
+
+          // set top/bottom to 1/3 (0-based)
+          term.writeSync('\x1b[2;4r');
+          // place cursor below scroll bottom
+          term.buffer.x = 5;
+          term.buffer.y = 4;
+          term.writeSync(ttyBS.repeat(100));
+          assert.deepEqual(getLines(term, 6), ['#####', 'abcde', 'fghij', 'klmno', 'pqrst', '     ']);
+
+          term.writeSync('uvwxy');
+          // place cursor within scroll margins
+          term.buffer.x = 5;
+          term.buffer.y = 3;
+          term.writeSync(ttyBS.repeat(100));
+          assert.deepEqual(getLines(term, 6), ['#####', 'abcde', '     ', '     ', '     ', 'uvwxy']);
+          assert.equal(term.buffer.x, 0);
+          assert.equal(term.buffer.y, term.buffer.scrollTop);  // stops at 0, scrollTop
+
+          term.writeSync('fghijklmnopqrst');
+          // place cursor above scroll top
+          term.buffer.x = 5;
+          term.buffer.y = 0;
+          term.writeSync(ttyBS.repeat(100));
+          assert.deepEqual(getLines(term, 6), ['#####', '     ', 'fghij', 'klmno', 'pqrst', 'uvwxy']);
+        });
+      });
+    });
   });
 });
 

src/browser/Terminal2.test.ts

@@ -19,7 +19,7 @@ const TESTFILES = glob.sync('**/escape_sequence_files/*.in', { cwd: path.join(__
 const SKIP_FILES = [
   't0084-CBT.in',
   't0101-NLM.in',
-  't0103-reverse_wrap.in',
+  't0103-reverse_wrap.in',  // not comparable, we deviate from xterm reverse wrap on purpose
   't0504-vim.in'
 ];
 if (os.platform() === 'darwin') {

src/common/InputHandler.test.ts

@@ -28,7 +28,10 @@ function getCursor(bufferService: IBufferService): number[] {
 function getLines(bufferService: IBufferService, limit: number = bufferService.rows): string[] {
   const res: string[] = [];
   for (let i = 0; i < limit; ++i) {
-    res.push(bufferService.buffer.lines.get(i)!.translateToString(true));
+    const line = bufferService.buffer.lines.get(i);
+    if (line) {
+      res.push(line.translateToString(true));
+    }
   }
   return res;
 }
@@ -359,6 +362,14 @@ describe('InputHandler', () => {
       container[0] = 0x200B;
       inputHandler.print(container, 0, 1);
     });
+    it('should clear cells to the right on early wrap-around', () => {
+      bufferService.resize(5, 5);
+      optionsService.options.scrollback = 1;
+      inputHandler.parse('12345');
+      bufferService.buffer.x = 0;
+      inputHandler.parse('￥￥￥');
+      assert.deepEqual(getLines(bufferService, 2), ['￥￥', '￥']);
+    });
   });
 
   describe('alt screen', () => {
@@ -1375,6 +1386,88 @@ describe('InputHandler', () => {
       assert.deepEqual(getLines(bufferService), ['￥￥  ￥￥', '￥￥    ￥', '￥￥    ￥', '￥￥￥￥￥', '']);
     });
   });
+
+  describe('BS with reverseWraparound set/unset', () => {
+    const ttyBS = '\x08 \x08';  // tty ICANON sends <BS SP BS> on pressing BS
+    beforeEach(() => {
+      bufferService.resize(5, 5);
+      optionsService.options.scrollback = 1;
+    });
+    describe('reverseWraparound unset (default)', () => {
+      it('cannot delete last cell', () => {
+        inputHandler.parse('12345');
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 1), ['123 5']);
+        inputHandler.parse(ttyBS.repeat(10));
+        assert.deepEqual(getLines(bufferService, 1), ['    5']);
+      });
+      it('cannot access prev line', () => {
+        inputHandler.parse('12345'.repeat(2));
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['12345', '123 5']);
+        inputHandler.parse(ttyBS.repeat(10));
+        assert.deepEqual(getLines(bufferService, 2), ['12345', '    5']);
+      });
+    });
+    describe('reverseWraparound set', () => {
+      it('can delete last cell', () => {
+        inputHandler.parse('\x1b[?45h');
+        inputHandler.parse('12345');
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 1), ['1234 ']);
+        inputHandler.parse(ttyBS.repeat(7));
+        assert.deepEqual(getLines(bufferService, 1), ['     ']);
+      });
+      it('can access prev line if wrapped', () => {
+        inputHandler.parse('\x1b[?45h');
+        inputHandler.parse('12345'.repeat(2));
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['12345', '1234 ']);
+        inputHandler.parse(ttyBS.repeat(7));
+        assert.deepEqual(getLines(bufferService, 2), ['12   ', '     ']);
+      });
+      it('should lift isWrapped', () => {
+        inputHandler.parse('\x1b[?45h');
+        inputHandler.parse('12345'.repeat(2));
+        assert.equal(bufferService.buffer.lines.get(1)?.isWrapped, true);
+        inputHandler.parse(ttyBS.repeat(7));
+        assert.equal(bufferService.buffer.lines.get(1)?.isWrapped, false);
+      });
+      it('stops at hard NLs', () => {
+        inputHandler.parse('\x1b[?45h');
+        inputHandler.parse('12345\r\n');
+        inputHandler.parse('12345'.repeat(2));
+        inputHandler.parse(ttyBS.repeat(50));
+        assert.deepEqual(getLines(bufferService, 3), ['12345', '     ', '     ']);
+        assert.equal(bufferService.buffer.x, 0);
+        assert.equal(bufferService.buffer.y, 1);
+      });
+      it('handles wide chars correctly', () => {
+        inputHandler.parse('\x1b[?45h');
+        inputHandler.parse('￥￥￥');
+        assert.deepEqual(getLines(bufferService, 2), ['￥￥', '￥']);
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['￥￥', '  ']);
+        assert.equal(bufferService.buffer.x, 1);
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['￥￥', '  ']);
+        assert.equal(bufferService.buffer.x, 0);
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['￥  ', '  ']);
+        assert.equal(bufferService.buffer.x, 3);  // x=4 skipped due to early wrap-around
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['￥  ', '  ']);
+        assert.equal(bufferService.buffer.x, 2);
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['    ', '  ']);
+        assert.equal(bufferService.buffer.x, 1);
+        inputHandler.parse(ttyBS);
+        assert.deepEqual(getLines(bufferService, 2), ['    ', '  ']);
+        assert.equal(bufferService.buffer.x, 0);
+      });
+    });
+  });
+
   describe('DECSTR', () => {
     beforeEach(() => {
       bufferService.resize(10, 5);

src/common/InputHandler.ts

@@ -556,6 +556,10 @@ export class InputHandler extends Disposable implements IInputHandler {
         // autowrap - DECAWM
         // automatically wraps to the beginning of the next line
         if (wraparoundMode) {
+          // clear left over cells to the right
+          while (buffer.x < cols) {
+            bufferRow.setCellFromCodePoint(buffer.x++, 0, 1, curAttr.fg, curAttr.bg);
+          }
           buffer.x = 0;
           buffer.y++;
           if (buffer.y === buffer.scrollBottom + 1) {
@@ -727,12 +731,62 @@ export class InputHandler extends Disposable implements IInputHandler {
    * Backspace (Ctrl-H).
    *
    * @vt: #Y   C0    BS   "Backspace"  "\b, \x08"  "Move the cursor one position to the left."
+   * By default it is not possible to move the cursor past the leftmost position.
+   * If `reverse wrap-around` (`CSI ? 45 h`) is set, a previous soft line wrap (DECAWM)
+   * can be undone with BS within the scroll margins. In that case the cursor will wrap back
+   * to the end of the previous row. Note that it is not possible to peek back into the scrollbuffer
+   * with the cursor, thus at the home position (top-leftmost cell) this has no effect.
    */
   public backspace(): void {
-    this._restrictCursor();
-    if (this._bufferService.buffer.x > 0) {
-      this._bufferService.buffer.x--;
+    const buffer = this._bufferService.buffer;
+
+    // reverse wrap-around is disabled
+    if (!this._coreService.decPrivateModes.reverseWraparound) {
+      this._restrictCursor();
+      if (buffer.x > 0) {
+        buffer.x--;
+      }
+      return;
+    }
+
+    // reverse wrap-around is enabled
+    // other than for normal operation mode, reverse wrap-around allows the cursor
+    // to be at x=cols to be able to address the last cell of a row by BS
+    this._restrictCursor(this._bufferService.cols);
+
+    if (buffer.x > 0) {
+      buffer.x--;
+    } else {
+      /**
+       * reverse wrap-around handling:
+       * Our implementation deviates from xterm on purpose. Details:
+       * - only previous soft NLs can be reversed (isWrapped=true)
+       * - only works within scrollborders (top/bottom, left/right not yet supported)
+       * - cannot peek into scrollbuffer
+       * - any cursor movement sequence keeps working as expected
+       */
+      if (buffer.x === 0
+          && buffer.y > buffer.scrollTop
+          && buffer.y <= buffer.scrollBottom
+          && buffer.lines.get(buffer.ybase + buffer.y)?.isWrapped)
+      {
+        buffer.lines.get(buffer.ybase + buffer.y)!.isWrapped = false;
+        buffer.y--;
+        buffer.x = this._bufferService.cols - 1;
+        // find last taken cell - last cell can have 3 different states:
+        // - hasContent(true) + hasWidth(1): narrow char - we are done
+        // - hasWidth(0): second part of wide char - we are done
+        // - hasContent(false) + hasWidth(1): empty cell due to early wrapping wide char, go one cell further back
+        const line = buffer.lines.get(buffer.ybase + buffer.y)!;
+        if (line.hasWidth(buffer.x) && !line.hasContent(buffer.x)) {
+          buffer.x--;
+          // We do this only once, since width=1 + hasContent=false currently happens only once before
+          // early wrapping of a wide char.
+          // This needs to be fixed once we support graphemes taking more than 2 cells.
+        }
+      }
     }
+    this._restrictCursor();
   }
 
   /**
@@ -777,8 +831,8 @@ export class InputHandler extends Disposable implements IInputHandler {
   /**
    * Restrict cursor to viewport size / scroll margin (origin mode).
    */
-  private _restrictCursor(): void {
-    this._bufferService.buffer.x = Math.min(this._bufferService.cols - 1, Math.max(0, this._bufferService.buffer.x));
+  private _restrictCursor(maxCol: number = this._bufferService.cols - 1): void {
+    this._bufferService.buffer.x = Math.min(maxCol, Math.max(0, this._bufferService.buffer.x));
     this._bufferService.buffer.y = this._coreService.decPrivateModes.origin
       ? Math.min(this._bufferService.buffer.scrollBottom, Math.max(this._bufferService.buffer.scrollTop, this._bufferService.buffer.y))
       : Math.min(this._bufferService.rows - 1, Math.max(0, this._bufferService.buffer.y));
@@ -1716,6 +1770,7 @@ export class InputHandler extends Disposable implements IInputHandler {
    * | 9     | X10 xterm mouse protocol.                               | #Y      |
    * | 12    | Start Blinking Cursor.                                  | #Y      |
    * | 25    | Show Cursor (DECTCEM).                                  | #Y      |
+   * | 45    | Reverse wrap-around.                                    | #Y      |
    * | 47    | Use Alternate Screen Buffer.                            | #Y      |
    * | 66    | Application keypad (DECNKM).                            | #Y      |
    * | 1000  | X11 xterm mouse protocol.                               | #Y      |
@@ -1767,6 +1822,9 @@ export class InputHandler extends Disposable implements IInputHandler {
         case 12:
           // this.cursorBlink = true;
           break;
+        case 45:
+          this._coreService.decPrivateModes.reverseWraparound = true;
+          break;
         case 66:
           this._logService.debug('Serial port requested application keypad.');
           this._coreService.decPrivateModes.applicationKeypad = true;
@@ -1950,6 +2008,7 @@ export class InputHandler extends Disposable implements IInputHandler {
    * | 9     | Don't send Mouse X & Y on button press.                 | #Y      |
    * | 12    | Stop Blinking Cursor.                                   | #Y      |
    * | 25    | Hide Cursor (DECTCEM).                                  | #Y      |
+   * | 45    | No reverse wrap-around.                                 | #Y      |
    * | 47    | Use Normal Screen Buffer.                               | #Y      |
    * | 66    | Numeric keypad (DECNKM).                                | #Y      |
    * | 1000  | Don't send Mouse reports.                               | #Y      |
@@ -1994,6 +2053,9 @@ export class InputHandler extends Disposable implements IInputHandler {
         case 12:
           // this.cursorBlink = false;
           break;
+        case 45:
+          this._coreService.decPrivateModes.reverseWraparound = false;
+          break;
         case 66:
           this._logService.debug('Switching back to normal keypad.');
           this._coreService.decPrivateModes.applicationKeypad = false;

src/common/TestUtils.test.ts

@@ -68,6 +68,7 @@ export class MockCoreService implements ICoreService {
     applicationKeypad: false,
     bracketedPasteMode: false,
     origin: false,
+    reverseWraparound: false,
     sendFocus: false,
     wraparound: true
   };

src/common/Types.d.ts

@@ -175,6 +175,7 @@ export interface IDecPrivateModes {
   applicationKeypad: boolean;
   bracketedPasteMode: boolean;
   origin: boolean;
+  reverseWraparound: boolean;
   sendFocus: boolean;
   wraparound: boolean; // defaults: xterm - true, vt100 - false
 }

src/common/services/CoreService.ts

@@ -17,6 +17,7 @@ const DEFAULT_DEC_PRIVATE_MODES: IDecPrivateModes = Object.freeze({
   applicationKeypad: false,
   bracketedPasteMode: false,
   origin: false,
+  reverseWraparound: false,
   sendFocus: false,
   wraparound: true // defaults: xterm - true, vt100 - false
 });