Hide markdown preview cells when they are folded

Fixes #116918

src/vs/workbench/contrib/notebook/browser/notebookBrowser.ts

@@ -467,6 +467,7 @@ export interface INotebookEditor extends IEditor, ICommonNotebookEditor {
 	layoutNotebookCell(cell: ICellViewModel, height: number): Promise<void>;
 
 	createMarkdownPreview(cell: ICellViewModel): Promise<void>;
+	unhideMarkdownPreview(cell: ICellViewModel): Promise<void>;
 	hideMarkdownPreview(cell: ICellViewModel): Promise<void>;
 	removeMarkdownPreview(cell: ICellViewModel): Promise<void>;
 

src/vs/workbench/contrib/notebook/browser/notebookEditorWidget.ts

@@ -1990,6 +1990,16 @@ export class NotebookEditorWidget extends Disposable implements INotebookEditor
 		}
 	}
 
+	async unhideMarkdownPreview(cell: MarkdownCellViewModel) {
+		if (!this._webview) {
+			return;
+		}
+
+		await this._resolveWebview();
+
+		await this._webview?.unhideMarkdownPreview(cell.id);
+	}
+
 	async hideMarkdownPreview(cell: MarkdownCellViewModel) {
 		if (!this._webview) {
 			return;

src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts

@@ -258,9 +258,13 @@ export interface IRemoveMarkdownMessage {
 	id: string;
 }
 
-
 export interface IHideMarkdownMessage {
-	type: 'hideMarkdownPreview',
+	type: 'hideMarkdownPreview';
+	id: string;
+}
+
+export interface IUnhideMarkdownMessage {
+	type: 'unhideMarkdownPreview';
 	id: string;
 }
 
@@ -311,6 +315,7 @@ export type ToWebviewMessage =
 	| IRemoveMarkdownMessage
 	| IShowMarkdownMessage
 	| IHideMarkdownMessage
+	| IUnhideMarkdownMessage
 	| IInitializeMarkdownMessage
 	| IViewScrollMarkdownRequestMessage;
 
@@ -1020,6 +1025,17 @@ var requirejs = (function() {
 		});
 	}
 
+	async unhideMarkdownPreview(cellId: string,) {
+		if (this._disposed) {
+			return;
+		}
+
+		this._sendMessageToWebview({
+			type: 'unhideMarkdownPreview',
+			id: cellId
+		});
+	}
+
 	async removeMarkdownPreview(cellId: string,) {
 		if (this._disposed) {
 			return;

src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts

@@ -52,6 +52,7 @@ import { CodiconActionViewItem, createAndFillInActionBarActionsWithVerticalSepar
 import { ThemeIcon } from 'vs/platform/theme/common/themeService';
 import { errorStateIcon, successStateIcon, unfoldIcon } from 'vs/workbench/contrib/notebook/browser/notebookIcons';
 import { syncing } from 'vs/platform/theme/common/iconRegistry';
+import { CellFoldingState } from 'vs/workbench/contrib/notebook/browser/contrib/fold/foldingModel';
 
 const $ = DOM.$;
 
@@ -539,6 +540,9 @@ export class MarkdownCellRenderer extends AbstractCellRenderer implements IListR
 			if (e.cellIsHoveredChanged) {
 				this.updateForHover(element, templateData);
 			}
+			if (e.foldingStateChanged) {
+				this.updateForFolding(element);
+			}
 		}));
 
 		// render toolbar first
@@ -575,6 +579,14 @@ export class MarkdownCellRenderer extends AbstractCellRenderer implements IListR
 		templateData.container.classList.toggle('markdown-cell-hover', element.cellIsHovered);
 	}
 
+	private updateForFolding(element: MarkdownCellViewModel) {
+		if (element.foldingState === CellFoldingState.Collapsed) {
+			this.notebookEditor.hideMarkdownPreview(element);
+		} else {
+			this.notebookEditor.unhideMarkdownPreview(element);
+		}
+	}
+
 	disposeTemplate(templateData: MarkdownCellRenderTemplate): void {
 		templateData.disposables.clear();
 	}

src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts

@@ -421,12 +421,21 @@ function webviewPreloads() {
 			case 'hideMarkdownPreview':
 				{
 					const data = event.data;
-					let cellContainer = document.getElementById(data.id);
+					const cellContainer = document.getElementById(data.id);
 					if (cellContainer) {
 						cellContainer.style.display = 'none';
 					}
 				}
 				break;
+			case 'unhideMarkdownPreview':
+				{
+					const data = event.data;
+					const cellContainer = document.getElementById(data.id);
+					if (cellContainer) {
+						cellContainer.style.display = '';
+					}
+				}
+				break;
 			case 'removeMarkdownPreview':
 				{
 					const data = event.data;

src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts

@@ -321,8 +321,11 @@ export class TestNotebookEditor implements INotebookEditor {
 	createMarkdownPreview(cell: ICellViewModel): Promise<void> {
 		return Promise.resolve();
 	}
-	hideMarkdownPreview(cell: ICellViewModel): Promise<void> {
-		return Promise.resolve();
+	async unhideMarkdownPreview(cell: ICellViewModel): Promise<void> {
+		// noop
+	}
+	async hideMarkdownPreview(cell: ICellViewModel): Promise<void> {
+		// noop
 	}
 	removeMarkdownPreview(cell: ICellViewModel): Promise<void> {
 		return Promise.resolve();