add markdown-language-features to sqlops (#2338)

extensions/markdown-language-features/preview-src/activeLineMarker.ts

@@ -0,0 +1,34 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import { getElementsForSourceLine } from './scroll-sync';
+
+export class ActiveLineMarker {
+	private _current: any;
+
+	onDidChangeTextEditorSelection(line: number) {
+		const { previous } = getElementsForSourceLine(line);
+		this._update(previous && previous.element);
+	}
+
+	_update(before: HTMLElement | undefined) {
+		this._unmarkActiveElement(this._current);
+		this._markActiveElement(before);
+		this._current = before;
+	}
+
+	_unmarkActiveElement(element: HTMLElement | undefined) {
+		if (!element) {
+			return;
+		}
+		element.className = element.className.replace(/\bcode-active-line\b/g, '');
+	}
+
+	_markActiveElement(element: HTMLElement | undefined) {
+		if (!element) {
+			return;
+		}
+		element.className += ' code-active-line';
+	}
+}