Fixes microsoft#116483: Allow folding in the diff editor

Author: alexdima

src/vs/editor/browser/widget/codeEditorWidget.ts

@@ -207,6 +207,9 @@ export class CodeEditorWidget extends Disposable implements editorBrowser.ICodeE
 
 	private readonly _onDidChangeViewZones: Emitter<void> = this._register(new Emitter<void>());
 	public readonly onDidChangeViewZones: Event<void> = this._onDidChangeViewZones.event;
+
+	private readonly _onDidChangeHiddenAreas: Emitter<void> = this._register(new Emitter<void>());
+	public readonly onDidChangeHiddenAreas: Event<void> = this._onDidChangeHiddenAreas.event;
 	//#endregion
 
 	public readonly isSimpleWidget: boolean;
@@ -1535,6 +1538,9 @@ export class CodeEditorWidget extends Disposable implements editorBrowser.ICodeE
 				case OutgoingViewModelEventKind.ViewZonesChanged:
 					this._onDidChangeViewZones.fire();
 					break;
+				case OutgoingViewModelEventKind.HiddenAreasChanged:
+					this._onDidChangeHiddenAreas.fire();
+					break;
 				case OutgoingViewModelEventKind.ReadOnlyEditAttempt:
 					this._onDidAttemptReadOnlyEdit.fire();
 					break;

src/vs/editor/browser/widget/diffEditorWidget.ts

@@ -480,6 +480,11 @@ export class DiffEditorWidget extends Disposable implements editorBrowser.IDiffE
 			}
 		}));
 
+		this._register(editor.onDidChangeHiddenAreas(() => {
+			this._updateDecorationsRunner.cancel();
+			this._updateDecorations();
+		}));
+
 		this._register(editor.onDidChangeModelContent(() => {
 			if (this._isVisible) {
 				this._beginUpdateDecorationsSoon();
@@ -542,6 +547,11 @@ export class DiffEditorWidget extends Disposable implements editorBrowser.IDiffE
 			}
 		}));
 
+		this._register(editor.onDidChangeHiddenAreas(() => {
+			this._updateDecorationsRunner.cancel();
+			this._updateDecorations();
+		}));
+
 		this._register(editor.onDidChangeModelContent(() => {
 			if (this._isVisible) {
 				this._beginUpdateDecorationsSoon();
@@ -1064,7 +1074,6 @@ export class DiffEditorWidget extends Disposable implements editorBrowser.IDiffE
 		// Clone scrollbar options before changing them
 		clonedOptions.scrollbar = { ...(clonedOptions.scrollbar || {}) };
 		clonedOptions.scrollbar.vertical = 'visible';
-		clonedOptions.folding = false;
 		clonedOptions.codeLens = this._options.diffCodeLens;
 		clonedOptions.fixedOverflowWidgets = true;
 		// clonedOptions.lineDecorationsWidth = '2ch';

src/vs/editor/common/viewModel/viewModelEventDispatcher.ts

@@ -176,6 +176,7 @@ export const enum OutgoingViewModelEventKind {
 	FocusChanged,
 	ScrollChanged,
 	ViewZonesChanged,
+	HiddenAreasChanged,
 	ReadOnlyEditAttempt,
 	CursorStateChanged,
 }
@@ -308,6 +309,22 @@ export class ViewZonesChangedEvent {
 	}
 }
 
+export class HiddenAreasChangedEvent {
+
+	public readonly kind = OutgoingViewModelEventKind.HiddenAreasChanged;
+
+	constructor() {
+	}
+
+	public isNoOp(): boolean {
+		return false;
+	}
+
+	public merge(other: OutgoingViewModelEvent): HiddenAreasChangedEvent {
+		return this;
+	}
+}
+
 export class CursorStateChangedEvent {
 
 	public readonly kind = OutgoingViewModelEventKind.CursorStateChanged;
@@ -388,6 +405,7 @@ export type OutgoingViewModelEvent = (
 	| FocusChangedEvent
 	| ScrollChangedEvent
 	| ViewZonesChangedEvent
+	| HiddenAreasChangedEvent
 	| ReadOnlyEditAttemptEvent
 	| CursorStateChangedEvent
 );

src/vs/editor/common/viewModel/viewModelImpl.ts

@@ -442,9 +442,10 @@ export class ViewModel extends Disposable implements IViewModel {
 	}
 
 	public setHiddenAreas(ranges: Range[]): void {
+		let lineMappingChanged = false;
 		try {
 			const eventsCollector = this._eventDispatcher.beginEmitViewEvents();
-			let lineMappingChanged = this._lines.setHiddenAreas(ranges);
+			lineMappingChanged = this._lines.setHiddenAreas(ranges);
 			if (lineMappingChanged) {
 				eventsCollector.emitViewEvent(new viewEvents.ViewFlushedEvent());
 				eventsCollector.emitViewEvent(new viewEvents.ViewLineMappingChangedEvent());
@@ -458,6 +459,10 @@ export class ViewModel extends Disposable implements IViewModel {
 			this._eventDispatcher.endEmitViewEvents();
 		}
 		this._updateConfigurationViewLineCount.schedule();
+
+		if (lineMappingChanged) {
+			this._eventDispatcher.emitOutgoingEvent(new ViewZonesChangedEvent());
+		}
 	}
 
 	public getVisibleRangesPlusViewportAboveBelow(): Range[] {