rulers.css

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

.monaco-editor .view-ruler {
	position: absolute;
	top: 0;
	box-shadow: 1px 0 0 0 var(--vscode-editorRuler-foreground) inset;
}