Merge pull request microsoft#163836 from microsoft/tyriar/161622_editorStatus

Defer editorStatus model content and cursor position updates

Author: Tyriar

src/vs/base/common/event.ts

@@ -53,6 +53,39 @@ export namespace Event {
 		}
 	}
 
+	/**
+	 * Given an event, returns another event which debounces calls and defers the listeners to a later task via a shared
+	 * `setTimeout`. The event is converted into a signal (`Event<void>`) to avoid additional object creation as a
+	 * result of merging events and to try prevent race conditions that could arise when using related deferred and
+	 * non-deferred events.
+	 *
+	 * This is useful for deferring non-critical work (eg. general UI updates) to ensure it does not block critical work
+	 * (eg. latency of keypress to text rendered).
+	 *
+	 * *NOTE* that this function returns an `Event` and it MUST be called with a `DisposableStore` whenever the returned
+	 * event is accessible to "third parties", e.g the event is a public property. Otherwise a leaked listener on the
+	 * returned event causes this utility to leak a listener on the original event.
+	 */
+	export function defer(event: Event<unknown>, disposable?: DisposableStore): Event<void> {
+		return debounce<unknown, void>(event, () => void 0, 0, undefined, undefined, disposable);
+	}
+
+	/**
+	 * Debounces an event, firing after some delay (default=0) with an array of all event original objects.
+	 *
+	 * *NOTE* that this function returns an `Event` and it MUST be called with a `DisposableStore` whenever the returned
+	 * event is accessible to "third parties", e.g the event is a public property. Otherwise a leaked listener on the
+	 * returned event causes this utility to leak a listener on the original event.
+	 */
+	export function accumulate<T>(event: Event<T>, delay: number = 0, disposable?: DisposableStore): Event<T[]> {
+		return Event.debounce<T, T[]>(event, (last, e) => {
+			if (!last) {
+				return [e];
+			}
+			last.push(e);
+			return last;
+		}, delay, undefined, undefined, disposable);
+	}
 
 	/**
 	 * Given an event, returns another event which only fires once.

src/vs/workbench/browser/parts/editor/editorStatus.ts

@@ -671,7 +671,7 @@ export class EditorStatus extends Disposable implements IWorkbenchContribution {
 			}));
 
 			// Hook Listener for Selection changes
-			this.activeEditorListeners.add(activeCodeEditor.onDidChangeCursorPosition(() => {
+			this.activeEditorListeners.add(Event.defer(activeCodeEditor.onDidChangeCursorPosition)(() => {
 				this.onSelectionChange(activeCodeEditor);
 				this.currentProblemStatus.update(activeCodeEditor);
 			}));
@@ -682,16 +682,18 @@ export class EditorStatus extends Disposable implements IWorkbenchContribution {
 			}));
 
 			// Hook Listener for content changes
-			this.activeEditorListeners.add(activeCodeEditor.onDidChangeModelContent(e => {
+			this.activeEditorListeners.add(Event.accumulate(activeCodeEditor.onDidChangeModelContent)(e => {
 				this.onEOLChange(activeCodeEditor);
 				this.currentProblemStatus.update(activeCodeEditor);
 
 				const selections = activeCodeEditor.getSelections();
 				if (selections) {
-					for (const change of e.changes) {
-						if (selections.some(selection => Range.areIntersecting(selection, change.range))) {
-							this.onSelectionChange(activeCodeEditor);
-							break;
+					for (const inner of e) {
+						for (const change of inner.changes) {
+							if (selections.some(selection => Range.areIntersecting(selection, change.range))) {
+								this.onSelectionChange(activeCodeEditor);
+								break;
+							}
 						}
 					}
 				}