fixes #17722

src/vs/workbench/services/viewlet/browser/viewletService.ts

@@ -13,6 +13,11 @@ import { Registry } from 'vs/platform/registry/common/platform';
 import { ViewletDescriptor, ViewletRegistry, Extensions as ViewletExtensions } from 'vs/workbench/browser/viewlet';
 import { IExtensionService } from 'vs/platform/extensions/common/extensions';
 import { IProgressService } from 'vs/platform/progress/common/progress';
+import { IContextKeyService, RawContextKey, IContextKey } from 'vs/platform/contextkey/common/contextkey';
+import { dispose, IDisposable } from 'vs/base/common/lifecycle';
+
+const ActiveViewletContextId = 'activeViewlet';
+export const ActiveViewletContext = new RawContextKey<string>(ActiveViewletContextId, '');
 
 export class ViewletService implements IViewletService {
 
@@ -24,20 +29,40 @@ export class ViewletService implements IViewletService {
 	private extensionViewlets: ViewletDescriptor[];
 	private extensionViewletsLoaded: TPromise<void>;
 	private extensionViewletsLoadedPromiseComplete: ValueCallback;
+	private activeViewletContextKey: IContextKey<string>;
+	private disposables: IDisposable[] = [];
 
 	public get onDidViewletOpen(): Event<IViewlet> { return this.sidebarPart.onDidViewletOpen; }
 	public get onDidViewletClose(): Event<IViewlet> { return this.sidebarPart.onDidViewletClose; }
 
 	constructor(
 		sidebarPart: SidebarPart,
-		@IExtensionService private extensionService: IExtensionService
+		@IExtensionService private extensionService: IExtensionService,
+		@IContextKeyService contextKeyService: IContextKeyService
 	) {
 		this.sidebarPart = sidebarPart;
 		this.viewletRegistry = Registry.as<ViewletRegistry>(ViewletExtensions.Viewlets);
 
+		this.activeViewletContextKey = ActiveViewletContext.bindTo(contextKeyService);
+
+		this.onDidViewletOpen(this._onDidViewletOpen, this, this.disposables);
+		this.onDidViewletClose(this._onDidViewletClose, this, this.disposables);
+
 		this.loadExtensionViewlets();
 	}
 
+	private _onDidViewletOpen(viewlet: IViewlet): void {
+		this.activeViewletContextKey.set(viewlet.getId());
+	}
+
+	private _onDidViewletClose(viewlet: IViewlet): void {
+		const id = viewlet.getId();
+
+		if (this.activeViewletContextKey.get() === id) {
+			this.activeViewletContextKey.set('');
+		}
+	}
+
 	private loadExtensionViewlets(): void {
 		this.extensionViewlets = [];
 
@@ -104,4 +129,8 @@ export class ViewletService implements IViewletService {
 	public getProgressIndicator(id: string): IProgressService {
 		return this.sidebarPart.getProgressIndicator(id);
 	}
+
+	dispose(): void {
+		this.disposables = dispose(this.disposables);
+	}
 }