turn openFoldersInNewWindow and openFilesInNewWindow into an enum and explain behaviour

src/vs/code/electron-main/windows.ts

@@ -374,8 +374,8 @@ export class WindowsManager implements IWindowsMainService {
 
 		// let the user settings override how folders are open in a new window or same window unless we are forced
 		let openFolderInNewWindow = (openConfig.preferNewWindow || openConfig.forceNewWindow) && !openConfig.forceReuseWindow;
-		if (!openConfig.forceNewWindow && !openConfig.forceReuseWindow && windowConfig && typeof windowConfig.openFoldersInNewWindow === 'boolean') {
-			openFolderInNewWindow = windowConfig.openFoldersInNewWindow;
+		if (!openConfig.forceNewWindow && !openConfig.forceReuseWindow && windowConfig && (windowConfig.openFoldersInNewWindow === 'on' || windowConfig.openFoldersInNewWindow === 'off')) {
+			openFolderInNewWindow = (windowConfig.openFoldersInNewWindow === 'on');
 		}
 
 		// Handle files to open/diff or to create when we dont open a folder
@@ -390,8 +390,8 @@ export class WindowsManager implements IWindowsMainService {
 					openFilesInNewWindow = true; // only on macOS do we allow to open files in a new window if this is triggered via DOCK context
 				}
 
-				if (!openConfig.cli.extensionDevelopmentPath && windowConfig && typeof windowConfig.openFilesInNewWindow === 'boolean') {
-					openFilesInNewWindow = windowConfig.openFilesInNewWindow;
+				if (!openConfig.cli.extensionDevelopmentPath && windowConfig && (windowConfig.openFilesInNewWindow === 'on' || windowConfig.openFilesInNewWindow === 'off')) {
+					openFilesInNewWindow = (windowConfig.openFilesInNewWindow === 'on');
 				}
 			}
 

src/vs/platform/windows/common/windows.ts

@@ -87,8 +87,8 @@ export interface IWindowService {
 }
 
 export interface IWindowSettings {
-	openFilesInNewWindow: boolean;
-	openFoldersInNewWindow: boolean;
+	openFilesInNewWindow: 'on' | 'off' | 'default';
+	openFoldersInNewWindow: 'on' | 'off' | 'default';
 	reopenFolders: 'all' | 'one' | 'none';
 	restoreFullscreen: boolean;
 	zoomLevel: number;

src/vs/workbench/electron-browser/main.contribution.ts

@@ -171,14 +171,36 @@ configurationRegistry.registerConfiguration({
 // Configuration: Window
 let properties: { [path: string]: IJSONSchema; } = {
 	'window.openFilesInNewWindow': {
-		'type': 'boolean',
-		'default': false,
-		'description': nls.localize('openFilesInNewWindow', "When enabled, will prefer to open files in a new window instead of reusing an existing instance. Note that there can still be cases where this setting is ignored (e.g. when using the -n command line option).")
+		'type': 'string',
+		'enum': ['on', 'off', 'default'],
+		'default': 'default',
+		'description': platform.isMacintosh ?
+			nls.localize('openFilesInNewWindowMac',
+				`Controls if files should open in a new window or the last active window.
+- default: files will open in the last active window unless opened via the dock or from finder
+- on: files will open in a new window
+- off: files will open in the last active window
+Note that there can still be cases where this setting is ignored (e.g. when using the -new-window or -reuse-window command line option).`
+			) :
+			nls.localize('openFilesInNewWindow',
+				`Controls if files should open in a new window or the last active window.
+- default: files will open in the last active window
+- on: files will open in a new window
+- off: files will open in the last active window
+Note that there can still be cases where this setting is ignored (e.g. when using the -new-window or -reuse-window command line option).`
+			)
 	},
 	'window.openFoldersInNewWindow': {
-		'type': 'boolean',
-		'default': false,
-		'description': nls.localize('openFoldersInNewWindow', "When enabled, will prefer to open folders in a new window instead of reusing an existing instance. Note that there can still be cases where this setting is ignored (e.g. when using the -n command line option).")
+		'type': 'string',
+		'enum': ['on', 'off', 'default'],
+		'default': 'default',
+		'description': nls.localize('openFoldersInNewWindow',
+			`Controls if folders should open in a new window or the last active window.
+- default: folders will open in a new window unless a folder is picked from within the application (e.g. via the File menu)
+- on: folders will open in a new window
+- off: folders will open in the last active window
+Note that there can still be cases where this setting is ignored (e.g. when using the -new-window or -reuse-window command line option).`
+		)
 	},
 	'window.reopenFolders': {
 		'type': 'string',