fix #107893

src/vs/base/browser/dom.ts

@@ -1229,7 +1229,6 @@ export function asCSSUrl(uri: URI): string {
 	return `url('${FileAccess.asBrowserUri(uri).toString(true).replace(/'/g, '%27')}')`;
 }
 
-
 export function triggerDownload(dataOrUri: Uint8Array | URI, name: string): void {
 
 	// If the data is provided as Buffer, we create a

src/vs/base/common/network.ts

@@ -135,6 +135,8 @@ class FileAccessImpl {
 	/**
 	 * Returns a URI to use in contexts where the browser is responsible
 	 * for loading (e.g. fetch()) or when used within the DOM.
+	 *
+	 * **Note:** use `dom.ts#asCSSUrl` whenever the URL is to be used in CSS context.
 	 */
 	asBrowserUri(uri: URI): URI;
 	asBrowserUri(moduleId: string, moduleIdToUrl: { toUrl(moduleId: string): string }): URI;

src/vs/workbench/browser/parts/editor/editorGroupView.ts

@@ -8,7 +8,7 @@ import { EditorGroup, IEditorOpenOptions, EditorCloseEvent, ISerializedEditorGro
 import { EditorInput, EditorOptions, GroupIdentifier, SideBySideEditorInput, CloseDirection, IEditorCloseEvent, ActiveEditorDirtyContext, IEditorPane, EditorGroupEditorsCountContext, SaveReason, IEditorPartOptionsChangeEvent, EditorsOrder, IVisibleEditorPane, ActiveEditorStickyContext, ActiveEditorPinnedContext, Deprecated_EditorPinnedContext, Deprecated_EditorDirtyContext, EditorResourceAccessor } from 'vs/workbench/common/editor';
 import { Event, Emitter, Relay } from 'vs/base/common/event';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
-import { Dimension, trackFocus, addDisposableListener, EventType, EventHelper, findParentWithClass, clearNode, isAncestor } from 'vs/base/browser/dom';
+import { Dimension, trackFocus, addDisposableListener, EventType, EventHelper, findParentWithClass, clearNode, isAncestor, asCSSUrl } from 'vs/base/browser/dom';
 import { ServiceCollection } from 'vs/platform/instantiation/common/serviceCollection';
 import { IContextKeyService } from 'vs/platform/contextkey/common/contextkey';
 import { ProgressBar } from 'vs/base/browser/ui/progressbar/progressbar';
@@ -1780,7 +1780,7 @@ registerThemingParticipant((theme, collector, environment) => {
 	const letterpress = `./media/letterpress${theme.type === 'dark' ? '-dark' : theme.type === 'hc' ? '-hc' : ''}.svg`;
 	collector.addRule(`
 		.monaco-workbench .part.editor > .content .editor-group-container.empty .editor-group-letterpress {
-			background-image: url('${FileAccess.asBrowserUri(letterpress, require).fsPath}')
+			background-image: ${asCSSUrl(FileAccess.asBrowserUri(letterpress, require))}
 		}
 	`);