From 9a7517d3ebb0c0692a45820a8ab183c4b0025445 Mon Sep 17 00:00:00 2001
From: Daniel Imms <2193314+Tyriar@users.noreply.github.com>
Date: Sun, 19 Oct 2025 01:15:30 -0700
Subject: [PATCH] Clear selection on vertical resize

Fixes #5300
---
 src/browser/services/SelectionService.ts |  8 ++++++++
 src/common/TestUtils.test.ts             |  4 ++--
 src/common/services/BufferService.ts     | 10 +++++-----
 src/common/services/Services.ts          |  9 ++++++++-
 4 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/src/browser/services/SelectionService.ts b/src/browser/services/SelectionService.ts
index 9da8ab5d..39d666de 100644
--- a/src/browser/services/SelectionService.ts
+++ b/src/browser/services/SelectionService.ts
@@ -152,6 +152,14 @@ export class SelectionService extends Disposable implements ISelectionService {
     this._register(toDisposable(() => {
       this._removeMouseDownListeners();
     }));
+
+    // Clear selection when resizing vertically. This experience could be improved, this is the
+    // simple option to fix the buggy behavior. https://github.com/xtermjs/xterm.js/issues/5300
+    this._register(this._bufferService.onResize(e => {
+      if (e.rowsChanged) {
+        this.clearSelection();
+      }
+    }));
   }
 
   public reset(): void {
diff --git a/src/common/TestUtils.test.ts b/src/common/TestUtils.test.ts
index 8e3d02f9..e12311ff 100644
--- a/src/common/TestUtils.test.ts
+++ b/src/common/TestUtils.test.ts
@@ -3,7 +3,7 @@
  * @license MIT
  */
 
-import { IBufferService, ICoreService, ILogService, IOptionsService, ITerminalOptions, ICoreMouseService, ICharsetService, UnicodeCharProperties, UnicodeCharWidth, IUnicodeService, IUnicodeVersionProvider, LogLevelEnum, IDecorationService, IInternalDecoration, IOscLinkService } from 'common/services/Services';
+import { IBufferService, ICoreService, ILogService, IOptionsService, ITerminalOptions, ICoreMouseService, ICharsetService, UnicodeCharProperties, UnicodeCharWidth, IUnicodeService, IUnicodeVersionProvider, LogLevelEnum, IDecorationService, IInternalDecoration, IOscLinkService, type IBufferResizeEvent } from 'common/services/Services';
 import { UnicodeService } from 'common/services/UnicodeService';
 import { clone } from 'common/Clone';
 import { DEFAULT_OPTIONS } from 'common/services/OptionsService';
@@ -18,7 +18,7 @@ export class MockBufferService implements IBufferService {
   public serviceBrand: any;
   public get buffer(): IBuffer { return this.buffers.active; }
   public buffers: IBufferSet = {} as any;
-  public onResize: Event<{ cols: number, rows: number }> = new Emitter<{ cols: number, rows: number }>().event;
+  public onResize: Event<IBufferResizeEvent> = new Emitter<IBufferResizeEvent>().event;
   public onScroll: Event<number> = new Emitter<number>().event;
   private readonly _onScroll = new Emitter<number>();
   public isUserScrolling: boolean = false;
diff --git a/src/common/services/BufferService.ts b/src/common/services/BufferService.ts
index d8d8d6b6..4cba3c15 100644
--- a/src/common/services/BufferService.ts
+++ b/src/common/services/BufferService.ts
@@ -7,7 +7,7 @@ import { Disposable } from 'vs/base/common/lifecycle';
 import { IAttributeData, IBufferLine } from 'common/Types';
 import { BufferSet } from 'common/buffer/BufferSet';
 import { IBuffer, IBufferSet } from 'common/buffer/Types';
-import { IBufferService, IOptionsService } from 'common/services/Services';
+import { IBufferService, IOptionsService, type IBufferResizeEvent } from 'common/services/Services';
 import { Emitter } from 'vs/base/common/event';
 
 export const MINIMUM_COLS = 2; // Less than 2 can mess with wide chars
@@ -22,7 +22,7 @@ export class BufferService extends Disposable implements IBufferService {
   /** Whether the user is scrolling (locks the scroll position) */
   public isUserScrolling: boolean = false;
 
-  private readonly _onResize = this._register(new Emitter<{ cols: number, rows: number }>());
+  private readonly _onResize = this._register(new Emitter<IBufferResizeEvent>());
   public readonly onResize = this._onResize.event;
   private readonly _onScroll = this._register(new Emitter<number>());
   public readonly onScroll = this._onScroll.event;
@@ -43,12 +43,12 @@ export class BufferService extends Disposable implements IBufferService {
   }
 
   public resize(cols: number, rows: number): void {
+    const colsChanged = this.cols !== cols;
+    const rowsChanged = this.rows !== rows;
     this.cols = cols;
     this.rows = rows;
     this.buffers.resize(cols, rows);
-    // TODO: This doesn't fire when scrollback changes - add a resize event to BufferSet and forward
-    //       event
-    this._onResize.fire({ cols, rows });
+    this._onResize.fire({ cols, rows, colsChanged, rowsChanged });
   }
 
   public reset(): void {
diff --git a/src/common/services/Services.ts b/src/common/services/Services.ts
index d47c3bbc..a2847f1b 100644
--- a/src/common/services/Services.ts
+++ b/src/common/services/Services.ts
@@ -18,7 +18,7 @@ export interface IBufferService {
   readonly buffer: IBuffer;
   readonly buffers: IBufferSet;
   isUserScrolling: boolean;
-  onResize: Event<{ cols: number, rows: number }>;
+  onResize: Event<IBufferResizeEvent>;
   onScroll: Event<number>;
   scroll(eraseAttr: IAttributeData, isWrapped?: boolean): void;
   scrollLines(disp: number, suppressScrollEvent?: boolean): void;
@@ -26,6 +26,13 @@ export interface IBufferService {
   reset(): void;
 }
 
+export interface IBufferResizeEvent {
+  cols: number;
+  rows: number;
+  colsChanged: boolean;
+  rowsChanged: boolean;
+}
+
 export const ICoreMouseService = createDecorator<ICoreMouseService>('CoreMouseService');
 export interface ICoreMouseService {
   serviceBrand: undefined;