Serialize scroll region

fixes #3433

addons/addon-serialize/src/SerializeAddon.test.ts

@@ -153,6 +153,43 @@ describe('SerializeAddon', () => {
         assert.ok(result.includes('58:5:46'), result);
       });
     });
+
+    describe('scroll region', () => {
+      let scrollTerminal: Terminal;
+      let scrollAddon: SerializeAddon;
+
+      beforeEach(() => {
+        scrollTerminal = new Terminal({ cols: 10, rows: 5, allowProposedApi: true });
+        scrollAddon = new SerializeAddon();
+        scrollTerminal.loadAddon(scrollAddon);
+      });
+
+      it('should serialize scroll region when margins are set', async () => {
+        await writeP(scrollTerminal, '\x1b[2;4r');
+        const buffer = (scrollTerminal as any)._core.buffer;
+        assert.equal(buffer.scrollTop, 1, 'scrollTop should be 1');
+        assert.equal(buffer.scrollBottom, 3, 'scrollBottom should be 3');
+        const result = scrollAddon.serialize();
+        assert.ok(result.includes('\x1b[2;4r'), result);
+      });
+
+      it('should not serialize scroll region when excludeModes is true', async () => {
+        await writeP(scrollTerminal, '\x1b[2;4r');
+        const result = scrollAddon.serialize({ excludeModes: true });
+        assert.ok(!result.includes('\x1b[2;4r'), result);
+      });
+
+      it('should restore scroll region correctly when deserialized', async () => {
+        await writeP(scrollTerminal, '\x1b[2;4r');
+        const serialized = scrollAddon.serialize();
+        const terminal2 = new Terminal({ cols: 10, rows: 5, allowProposedApi: true });
+        terminal2.loadAddon(new SerializeAddon());
+        await writeP(terminal2, serialized);
+        const buffer = (terminal2 as any)._core.buffer;
+        assert.equal(buffer.scrollTop, 1);
+        assert.equal(buffer.scrollBottom, 3);
+      });
+    });
   });
 
   describe('html', () => {

addons/addon-serialize/src/SerializeAddon.ts

@@ -513,6 +513,25 @@ export class SerializeAddon implements ITerminalAddon , ISerializeApi {
     return '';
   }
 
+  /**
+   * Serializes the scroll region (DECSTBM) if it's not set to the full terminal size.
+   * Uses internal API access since scroll region is not exposed in the public API.
+   */
+  private _serializeScrollRegion(terminal: Terminal): string {
+    // HACK: Internal API access since scroll region is not exposed in the public API
+    const buffer = (terminal as any)._core.buffer;
+    const scrollTop: number = buffer.scrollTop;
+    const scrollBottom: number = buffer.scrollBottom;
+
+    // Only serialize if scroll region is not the default (full terminal size)
+    if (scrollTop !== 0 || scrollBottom !== terminal.rows - 1) {
+      // DECSTBM uses 1-based indices: CSI Ps ; Ps r
+      return `\x1b[${scrollTop + 1};${scrollBottom + 1}r`;
+    }
+
+    return '';
+  }
+
   private _serializeModes(terminal: Terminal): string {
     let content = '';
     const modes = terminal.modes;
@@ -562,9 +581,10 @@ export class SerializeAddon implements ITerminalAddon , ISerializeApi {
       }
     }
 
-    // Modes
+    // Modes and scroll region
     if (!options?.excludeModes) {
       content += this._serializeModes(this._terminal);
+      content += this._serializeScrollRegion(this._terminal);
     }
 
     return content;