From 8f2392cf9fc7ad33bfef53bf4c6d51539402c7ca Mon Sep 17 00:00:00 2001
From: OS-josesoares <jose.soares@outsystems.com>
Date: Fri, 23 Oct 2026 15:33:42 +0100
Subject: [PATCH] RDEV-9911 - shadow dom mouse leave

---
 build/monaco/package.json                     |  2 +-
 .../editor/browser/controller/mouseHandler.ts |  2 +-
 .../browser/controller/mouseHandler.test.ts   | 71 +++++++++++++++++++
 3 files changed, 73 insertions(+), 2 deletions(-)
 create mode 100644 src/vs/editor/test/browser/controller/mouseHandler.test.ts

diff --git a/build/monaco/package.json b/build/monaco/package.json
index 91ed0c1c9a1b06..7eefe26b92dab9 100644
--- a/build/monaco/package.json
+++ b/build/monaco/package.json
@@ -1,7 +1,7 @@
 {
   "name": "monaco-editor-core",
   "private": true,
-  "version": "0.55.1-os1",
+  "version": "0.55.1-os2",
   "description": "A browser based code editor",
   "author": "Microsoft Corporation",
   "license": "MIT",
diff --git a/src/vs/editor/browser/controller/mouseHandler.ts b/src/vs/editor/browser/controller/mouseHandler.ts
index 4ad4ca9d817e57..6c5f6de87c174c 100644
--- a/src/vs/editor/browser/controller/mouseHandler.ts
+++ b/src/vs/editor/browser/controller/mouseHandler.ts
@@ -103,7 +103,7 @@ export class MouseHandler extends ViewEventHandler {
 
 			if (!this._mouseLeaveMonitor) {
 				this._mouseLeaveMonitor = dom.addDisposableListener(this.viewHelper.viewDomNode.ownerDocument, 'mousemove', (e) => {
-					if (!this.viewHelper.viewDomNode.contains(e.target as Node | null)) {
+					if (!this.viewHelper.viewDomNode.contains(e.composedPath()[0] as Node | null)) {
 						// went outside the editor!
 						this._onMouseLeave(new EditorMouseEvent(e, false, this.viewHelper.viewDomNode));
 					}
diff --git a/src/vs/editor/test/browser/controller/mouseHandler.test.ts b/src/vs/editor/test/browser/controller/mouseHandler.test.ts
new file mode 100644
index 00000000000000..71b33c345294f7
--- /dev/null
+++ b/src/vs/editor/test/browser/controller/mouseHandler.test.ts
@@ -0,0 +1,71 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import assert from 'assert';
+import { mainWindow } from '../../../../base/browser/window.js';
+import { Color } from '../../../../base/common/color.js';
+import { toDisposable } from '../../../../base/common/lifecycle.js';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../base/test/common/utils.js';
+import { CodeEditorWidget } from '../../../browser/widget/codeEditor/codeEditorWidget.js';
+import { TokenizationRegistry } from '../../../common/languages.js';
+import { instantiateTextModel } from '../../common/testTextModel.js';
+import { createCodeEditorServices } from '../testCodeEditor.js';
+
+suite('MouseHandler', () => {
+
+	const disposables = ensureNoDisposablesAreLeakedInTestSuite();
+
+	let previousColorMap: Color[] | null;
+
+	suiteSetup(() => {
+		// Without a token color map, the minimap of a real editor view reports unexpected errors
+		previousColorMap = TokenizationRegistry.getColorMap();
+		TokenizationRegistry.setColorMap([null!, Color.black, Color.white]);
+	});
+
+	suiteTeardown(() => {
+		TokenizationRegistry.setColorMap(previousColorMap!);
+	});
+
+	function dispatchMouseMove(target: EventTarget, clientX: number, clientY: number): void {
+		target.dispatchEvent(new MouseEvent('mousemove', { bubbles: true, composed: true, clientX, clientY }));
+	}
+
+	test('in an open shadow root, moving inside the editor does not fire onMouseLeave and moving outside does', () => {
+		// Arrange
+		const shadowHost = mainWindow.document.createElement('div');
+		mainWindow.document.body.appendChild(shadowHost);
+		disposables.add(toDisposable(() => shadowHost.remove()));
+		const container = mainWindow.document.createElement('div');
+		shadowHost.attachShadow({ mode: 'open' }).appendChild(container);
+
+		const instantiationService = createCodeEditorServices(disposables);
+		const model = disposables.add(instantiateTextModel(instantiationService, 'hello world'));
+		const editor = disposables.add(instantiationService.createInstance(CodeEditorWidget, container, {}, { contributions: [] }));
+		editor.setModel(model);
+		editor.layout({ width: 400, height: 200 });
+
+		const editorDomNode = editor.getDomNode()!;
+		const editorRect = editorDomNode.getBoundingClientRect();
+		const log: string[] = [];
+		disposables.add(editor.onMouseMove(() => log.push('onMouseMove')));
+		disposables.add(editor.onMouseLeave(() => log.push('onMouseLeave')));
+
+		// Act
+		log.push('move inside');
+		dispatchMouseMove(editorDomNode, editorRect.left + 10, editorRect.top + 10);
+		log.push('move inside');
+		dispatchMouseMove(editorDomNode, editorRect.left + 20, editorRect.top + 10);
+		log.push('move outside');
+		dispatchMouseMove(mainWindow.document.body, editorRect.left + 10, editorRect.bottom + 10);
+
+		// Assert
+		assert.deepStrictEqual(log, [
+			'move inside', 'onMouseMove',
+			'move inside', 'onMouseMove',
+			'move outside', 'onMouseLeave',
+		]);
+	});
+});