better way of finding out active list (for #11517)

src/vs/base/browser/ui/list/listWidget.ts

@@ -286,7 +286,7 @@ export class List<T> implements IDisposable {
 		this.disposables = [this.focus, this.selection, this.view, this._onDispose];
 
 		const tracker = DOM.trackFocus(this.view.domNode);
-		this.disposables.push(tracker.addFocusListener(() => setTimeout(() => this._onDOMFocus.fire())));
+		this.disposables.push(tracker.addFocusListener(() => this._onDOMFocus.fire()));
 		this.disposables.push(tracker.addBlurListener(() => this._onDOMBlur.fire()));
 
 		if (typeof options.keyboardSupport !== 'boolean' || options.keyboardSupport) {
@@ -469,6 +469,10 @@ export class List<T> implements IDisposable {
 		return this.view.domNode === document.activeElement;
 	}
 
+	getHTMLElement(): HTMLElement {
+		return this.view.domNode;
+	}
+
 	private toListEvent({ indexes }: ITraitChangeEvent) {
 		return { indexes, elements: indexes.map(i => this.view.element(i)) };
 	}

src/vs/base/parts/tree/browser/treeImpl.ts

@@ -93,7 +93,7 @@ export class Tree extends Events.EventEmitter implements _.ITree {
 		this.addEmitter2(this.model);
 		this.addEmitter2(this.view);
 
-		this.toDispose.push(this.model.addListener2('highlight', () => setTimeout(() => this._onHighlightChange.fire())));
+		this.toDispose.push(this.model.addListener2('highlight', () => this._onHighlightChange.fire()));
 	}
 
 	get onDOMFocus(): Event<void> {

src/vs/base/parts/tree/browser/treeView.ts

@@ -1523,7 +1523,7 @@ export class TreeView extends HeightMap {
 			DOM.addClass(this.domNode, 'focused');
 		}
 
-		setTimeout(() => this._onDOMFocus.fire());
+		this._onDOMFocus.fire();
 	}
 
 	private onBlur(): void {

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

@@ -9,6 +9,7 @@ import { List } from 'vs/base/browser/ui/list/listWidget';
 import { createDecorator } from 'vs/platform/instantiation/common/instantiation';
 import { dispose, IDisposable } from 'vs/base/common/lifecycle';
 import { IContextKeyService, IContextKey, RawContextKey } from 'vs/platform/contextkey/common/contextkey';
+import { RunOnceScheduler } from 'vs/base/common/async';
 
 export const IListService = createDecorator<IListService>('listService');
 
@@ -29,53 +30,75 @@ export class ListService implements IListService {
 	public _serviceBrand: any;
 
 	private focusedTreeOrList: ITree | List<any>;
+	private lists: (ITree | List<any>)[];
 
 	private listFocusContext: IContextKey<boolean>;
 
+	private focusChangeScheduler: RunOnceScheduler;
+
 	constructor(
 		@IContextKeyService contextKeyService: IContextKeyService
 	) {
 		this.listFocusContext = ListFocusContext.bindTo(contextKeyService);
+		this.lists = [];
+		this.focusChangeScheduler = new RunOnceScheduler(() => this.onFocusChange(), 50 /* delay until the focus/blur dust settles */);
 	}
 
 	public register(tree: ITree): IDisposable;
 	public register(list: List<any>): IDisposable;
 	public register(widget: ITree | List<any>): IDisposable {
+		if (this.lists.indexOf(widget) >= 0) {
+			throw new Error('Cannot register the same widget multiple times');
+		}
+
+		// Keep in our lists list
+		this.lists.push(widget);
 
 		// Check for currently being focused
 		if (widget.isDOMFocused()) {
-			this.onListDOMFocus(widget);
+			this.setFocusedList(widget);
 		}
 
 		const toDispose = [
-			widget.onDOMFocus(() => this.onListDOMFocus(widget)),
-			widget.onDOMBlur(() => this.onListDOMBlur(widget))
+			widget.onDOMFocus(() => this.focusChangeScheduler.schedule()),
+			widget.onDOMBlur(() => this.focusChangeScheduler.schedule())
 		];
 
 		// Special treatment for tree highlight mode
 		if (!(widget instanceof List)) {
-			toDispose.push(widget.onHighlightChange(() => {
-				if (this.focusedTreeOrList === widget && widget.getHighlight()) {
-					this.onListDOMBlur(widget);
-				} else if (widget.isDOMFocused()) {
-					this.onListDOMFocus(widget);
-				}
+			const tree = widget;
+
+			toDispose.push(tree.onHighlightChange(() => {
+				this.focusChangeScheduler.schedule();
 			}));
 		}
 
+		// Remove list once disposed
+		toDispose.push({
+			dispose: () => { this.lists.splice(this.lists.indexOf(widget), 1); }
+		});
+
 		return {
 			dispose: () => dispose(toDispose)
 		};
 	}
 
-	private onListDOMFocus(list: ITree | List<any>): void {
-		this.focusedTreeOrList = list;
-		this.listFocusContext.set(true);
+	private onFocusChange(): void {
+		let focusedList: ITree | List<any>;
+		for (let i = 0; i < this.lists.length; i++) {
+			const list = this.lists[i];
+			if (document.activeElement === list.getHTMLElement()) {
+				focusedList = list;
+				break;
+			}
+		}
+
+		this.setFocusedList(focusedList);
 	}
 
-	private onListDOMBlur(list: ITree | List<any>): void {
-		this.focusedTreeOrList = void 0;
-		this.listFocusContext.set(false);
+	private setFocusedList(focusedList: ITree | List<any>): void {
+		this.focusedTreeOrList = focusedList;
+		this.listFocusContext.set(!!focusedList);
 	}
 
 	public getFocused(): ITree | List<any> {

src/vs/workbench/parts/files/browser/views/explorerView.ts

@@ -370,8 +370,10 @@ export class ExplorerView extends CollapsibleViewletView {
 
 		// Update explorer focus context
 		this.toDispose.push(this.explorerViewer.onDOMFocus(() => {
-			this.filesExplorerFocussedContext.set(true);
-			this.explorerFocussedContext.set(true);
+			setTimeout(() => {
+				this.filesExplorerFocussedContext.set(true);
+				this.explorerFocussedContext.set(true);
+			}, 0 /* helps when focus jumps from one tree to another */);
 		}));
 
 		this.toDispose.push(this.explorerViewer.onDOMBlur(() => {

src/vs/workbench/parts/files/browser/views/openEditorsView.ts

@@ -126,8 +126,10 @@ export class OpenEditorsView extends AdaptiveCollapsibleViewletView {
 
 		// Update open editors focus context
 		this.toDispose.push(this.tree.onDOMFocus(() => {
-			this.openEditorsFocussedContext.set(true);
-			this.explorerFocussedContext.set(true);
+			setTimeout(() => {
+				this.openEditorsFocussedContext.set(true);
+				this.explorerFocussedContext.set(true);
+			}, 0 /* helps when focus jumps from one tree to another */);
 		}));
 
 		this.toDispose.push(this.tree.onDOMBlur(() => {