Titlebar overlay is not enabled (fix microsoft#158203) (microsoft#158251)

Author: bpasero

src/vs/platform/window/common/window.ts

@@ -165,16 +165,20 @@ export function getTitleBarStyle(configurationService: IConfigurationService): '
 }
 
 export function useWindowControlsOverlay(configurationService: IConfigurationService, environmentService: IEnvironmentService): boolean {
-	// Window Controls Overlay are only configurable on Windows
 	if (!isWindows || isWeb || !environmentService.isBuilt) {
-		return false;
+		return false; // only supported on a built desktop windows instance
 	}
 
 	if (getTitleBarStyle(configurationService) === 'native') {
-		return false;
+		return false; // only supported when title bar is custom
 	}
 
-	return configurationService.getValue<boolean>('window.experimental.windowControlsOverlay.enabled');
+	const configuredUseWindowControlsOverlay = configurationService.getValue<boolean | undefined>('window.experimental.windowControlsOverlay.enabled');
+	if (typeof configuredUseWindowControlsOverlay === 'boolean') {
+		return configuredUseWindowControlsOverlay;
+	}
+
+	return true; // enabled by default
 }
 
 export interface IPath<T = IEditorOptions> extends IPathData<T> {

src/vs/platform/windows/electron-main/windowImpl.ts

@@ -143,6 +143,8 @@ export class CodeWindow extends Disposable implements ICodeWindow {
 	private representedFilename: string | undefined;
 	private documentEdited: boolean | undefined;
 
+	private readonly hasWindowControlOverlay: boolean = false;
+
 	private readonly whenReadyCallbacks: { (window: ICodeWindow): void }[] = [];
 
 	private readonly touchBarGroups: TouchBarSegmentedControl[] = [];
@@ -280,6 +282,8 @@ export class CodeWindow extends Disposable implements ICodeWindow {
 						color: titleBarColor,
 						symbolColor
 					};
+
+					this.hasWindowControlOverlay = true;
 				}
 			}
 
@@ -1072,7 +1076,7 @@ export class CodeWindow extends Disposable implements ICodeWindow {
 		}
 
 		// Windows: window control overlay (WCO)
-		if (isWindows && useWindowControlsOverlay(this.configurationService, this.environmentMainService)) {
+		if (isWindows && this.hasWindowControlOverlay) {
 			this._win.setTitleBarOverlay({
 				color: options.backgroundColor?.trim() === '' ? undefined : options.backgroundColor,
 				symbolColor: options.foregroundColor?.trim() === '' ? undefined : options.foregroundColor,