context keys introduce "listMultiSelection"

fixes #43319

src/vs/platform/list/browser/listService.ts

@@ -83,6 +83,7 @@ const RawWorkbenchListFocusContextKey = new RawContextKey<boolean>('listFocus',
 export const WorkbenchListSupportsMultiSelectContextKey = new RawContextKey<boolean>('listSupportsMultiselect', true);
 export const WorkbenchListFocusContextKey = ContextKeyExpr.and(RawWorkbenchListFocusContextKey, ContextKeyExpr.not(InputFocusedContextKey));
 export const WorkbenchListDoubleSelection = new RawContextKey<boolean>('listDoubleSelection', false);
+export const WorkbenchListMultiSelection = new RawContextKey<boolean>('listMultiSelection', false);
 
 export type Widget = List<any> | PagedList<any> | ITree;
 
@@ -166,6 +167,7 @@ export class WorkbenchList<T> extends List<T> {
 	readonly contextKeyService: IContextKeyService;
 
 	private listDoubleSelection: IContextKey<boolean>;
+	private listMultiSelection: IContextKey<boolean>;
 
 	private _useAltAsMultipleSelectionModifier: boolean;
 
@@ -183,6 +185,7 @@ export class WorkbenchList<T> extends List<T> {
 
 		this.contextKeyService = createScopedContextKeyService(contextKeyService, this);
 		this.listDoubleSelection = WorkbenchListDoubleSelection.bindTo(this.contextKeyService);
+		this.listMultiSelection = WorkbenchListMultiSelection.bindTo(this.contextKeyService);
 
 		this._useAltAsMultipleSelectionModifier = useAltAsMultipleSelectionModifier(configurationService);
 
@@ -190,7 +193,11 @@ export class WorkbenchList<T> extends List<T> {
 			this.contextKeyService,
 			(listService as ListService).register(this),
 			attachListStyler(this, themeService),
-			this.onSelectionChange(() => this.listDoubleSelection.set(this.getSelection().length === 2))
+			this.onSelectionChange(() => {
+				const selection = this.getSelection();
+				this.listMultiSelection.set(selection.length > 1);
+				this.listDoubleSelection.set(selection.length === 2);
+			})
 		]));
 
 		this.registerListeners();
@@ -266,6 +273,7 @@ export class WorkbenchTree extends Tree {
 	protected disposables: IDisposable[] = [];
 
 	private listDoubleSelection: IContextKey<boolean>;
+	private listMultiSelection: IContextKey<boolean>;
 
 	private _openOnSingleClick: boolean;
 	private _useAltAsMultipleSelectionModifier: boolean;
@@ -284,6 +292,7 @@ export class WorkbenchTree extends Tree {
 
 		this.contextKeyService = createScopedContextKeyService(contextKeyService, this);
 		this.listDoubleSelection = WorkbenchListDoubleSelection.bindTo(this.contextKeyService);
+		this.listMultiSelection = WorkbenchListMultiSelection.bindTo(this.contextKeyService);
 
 		this._openOnSingleClick = useSingleClickToOpen(configurationService);
 		this._useAltAsMultipleSelectionModifier = useAltAsMultipleSelectionModifier(configurationService);
@@ -309,6 +318,7 @@ export class WorkbenchTree extends Tree {
 		this.disposables.push(this.onDidChangeSelection(() => {
 			const selection = this.getSelection();
 			this.listDoubleSelection.set(selection && selection.length === 2);
+			this.listMultiSelection.set(selection && selection.length > 1);
 		}));
 
 		this.disposables.push(this.configurationService.onDidChangeConfiguration(e => {