#134: added support for terminal Save/Restore Position command (s/u)

Author: bugy

web-src/js/components/terminal/terminal_model.js

@@ -41,8 +41,6 @@ export class TerminalModel {
         this.listeners = [];
 
         this.clear();
-
-        this.changedLines = [];
     }
 
     addListener(listener) {
@@ -140,6 +138,10 @@ export class TerminalModel {
 
         this.currentStyle = null;
 
+        this.changedLines = [];
+
+        this.savedCursorPosition = null;
+
         for (const listener of this.listeners) {
             listener.cleared();
         }
@@ -504,6 +506,23 @@ class MoveCursorToPositionHandler extends CommandHandler {
     }
 }
 
+class SaveCursorPositionHandler extends CommandHandler {
+    handle(args, terminal) {
+        terminal.savedCursorPosition = [terminal.currentLine, terminal.currentPosition];
+    }
+}
+
+class RestoreCursorPositionHandler extends CommandHandler {
+    handle(args, terminal) {
+        if (isNull(terminal.savedCursorPosition)) {
+            console.log('WARN! trying to restore cursor position, but nothing is saved');
+            return;
+        }
+        const [line, position] = terminal.savedCursorPosition;
+        terminal.setCursorPosition(line, position);
+    }
+}
+
 class ClearLineHandler extends CommandHandler {
     constructor() {
         super();
@@ -534,8 +553,8 @@ COMMAND_HANDLERS.set('A', new MoveCursorVerticallyHandler(true));
 COMMAND_HANDLERS.set('B', new MoveCursorVerticallyHandler(false));
 COMMAND_HANDLERS.set('C', new MoveCursorHorizontallyHandler(true));
 COMMAND_HANDLERS.set('D', new MoveCursorHorizontallyHandler(false));
-COMMAND_HANDLERS.set('s', null);
-COMMAND_HANDLERS.set('u', null);
+COMMAND_HANDLERS.set('s', new SaveCursorPositionHandler());
+COMMAND_HANDLERS.set('u', new RestoreCursorPositionHandler());
 
 const TEXT_COLOR_DICT = new Map();
 TEXT_COLOR_DICT.set(39, null);

web-src/tests/terminal_model_test.js

@@ -15,7 +15,9 @@ import {
     moveCursorLeft,
     moveCursorRight,
     moveCursorUp,
-    moveToPosition
+    moveToPosition,
+    restorePosition,
+    savePosition
 } from './terminal_test_utils';
 
 chaiConfig.truncateThreshold = 0;
@@ -970,4 +972,49 @@ describe('Test terminal model', function () {
             assert.deepEqual([[0, 1, 2], [2]], this.changedLines);
         });
     });
+
+    describe('Save/restore cursor position', function () {
+        beforeEach(function () {
+            sinon.stub(console, 'log').returns(void 0);
+        });
+
+        afterEach(function () {
+            console.log.restore();
+        });
+
+        it('Test restore in the first line', function () {
+            this.model.write('1234' + savePosition() + '5678' + restorePosition() + 'abc');
+
+            assert.deepEqual(['1234abc8'], this.model.lines);
+        });
+
+        it('Test restore in the first line, when 3 lines', function () {
+            this.model.write('123' + savePosition() + '45\n678\n90' + restorePosition() + 'abc');
+
+            assert.deepEqual(['123abc', '678', '90'], this.model.lines);
+        });
+
+        it('Test restore in the last line, when 3 lines', function () {
+            this.model.write('123\n4567\n8' + savePosition() + '90' + moveCursorUp(2) + 'X'
+                + restorePosition() + 'abc');
+
+            assert.deepEqual(['123X', '4567', '8abc'], this.model.lines);
+        });
+
+        it('Test restore position without save', function () {
+            this.model.write('1234' + restorePosition() + 'abc');
+
+            assert.deepEqual(['1234abc'], this.model.lines);
+            expect(console.log.args[0][0]).to.equal('WARN! trying to restore cursor position, but nothing is saved');
+        });
+
+        it('Test restore position after clear', function () {
+            this.model.write('1234' + savePosition());
+            this.model.clear();
+            this.model.write('abc' + restorePosition() + 'XYZ');
+
+            assert.deepEqual(['abcXYZ'], this.model.lines);
+            expect(console.log.args[0][0]).to.equal('WARN! trying to restore cursor position, but nothing is saved');
+        });
+    })
 });

web-src/tests/terminal_test_utils.js

@@ -28,6 +28,14 @@ export function moveToPosition(line, column, command = 'H') {
     return escapePrefix + line + ';' + column + command;
 }
 
+export function savePosition() {
+    return escapePrefix + 's';
+}
+
+export function restorePosition() {
+    return escapePrefix + 'u';
+}
+
 export function clearLineToRight() {
     return clearLine('');
 }