Merge from vscode merge-base (#22780)

* Revert "Revert "Merge from vscode merge-base (#22769)" (#22779)"

This reverts commit 47a1745180.

* Fix notebook download task

* Remove done call from extensions-ci

extensions/notebook-renderers/src/index.ts

@@ -10,13 +10,21 @@ interface IDisposable {
 	dispose(): void;
 }
 
+interface HtmlRenderingHook {
+	/**
+	 * Invoked after the output item has been rendered but before it has been appended to the document.
+	 *
+	 * @return A new `HTMLElement` or `undefined` to continue using the provided element.
+	 */
+	postRender(outputItem: OutputItem, element: HTMLElement): HTMLElement | undefined;
+}
+
 function clearContainer(container: HTMLElement) {
 	while (container.firstChild) {
 		container.removeChild(container.firstChild);
 	}
 }
 
-
 function renderImage(outputInfo: OutputItem, element: HTMLElement): IDisposable {
 	const blob = new Blob([outputInfo.data()], { type: outputInfo.mime });
 	const src = URL.createObjectURL(blob);
@@ -64,12 +72,17 @@ const domEval = (container: Element) => {
 	}
 };
 
-function renderHTML(outputInfo: OutputItem, container: HTMLElement): void {
+function renderHTML(outputInfo: OutputItem, container: HTMLElement, hooks: Iterable<HtmlRenderingHook>): void {
 	clearContainer(container);
+	let element: HTMLElement = document.createElement('div');
 	const htmlContent = outputInfo.text();
-	const element = document.createElement('div');
 	const trustedHtml = ttPolicy?.createHTML(htmlContent) ?? htmlContent;
 	element.innerHTML = trustedHtml as string;
+
+	for (const hook of hooks) {
+		element = hook.postRender(outputInfo, element) ?? element;
+	}
+
 	container.appendChild(element);
 	domEval(element);
 }
@@ -167,6 +180,8 @@ function renderText(outputInfo: OutputItem, container: HTMLElement, ctx: Rendere
 
 export const activate: ActivationFunction<void> = (ctx) => {
 	const disposables = new Map<string, IDisposable>();
+	const htmlHooks = new Set<HtmlRenderingHook>();
+
 	const latestContext = ctx as (RendererContext<void> & { readonly settings: { readonly lineLimit: number } });
 
 	const style = document.createElement('style');
@@ -210,6 +225,7 @@ export const activate: ActivationFunction<void> = (ctx) => {
 	}
 	`;
 	document.body.appendChild(style);
+
 	return {
 		renderOutputItem: (outputInfo, element) => {
 			switch (outputInfo.mime) {
@@ -220,7 +236,7 @@ export const activate: ActivationFunction<void> = (ctx) => {
 							return;
 						}
 
-						renderHTML(outputInfo, element);
+						renderHTML(outputInfo, element, htmlHooks);
 					}
 					break;
 				case 'application/javascript':
@@ -267,8 +283,6 @@ export const activate: ActivationFunction<void> = (ctx) => {
 				default:
 					break;
 			}
-
-
 		},
 		disposeOutputItem: (id: string | undefined) => {
 			if (id) {
@@ -276,6 +290,14 @@ export const activate: ActivationFunction<void> = (ctx) => {
 			} else {
 				disposables.forEach(d => d.dispose());
 			}
+		},
+		experimental_registerHtmlRenderingHook: (hook: HtmlRenderingHook): IDisposable => {
+			htmlHooks.add(hook);
+			return {
+				dispose: () => {
+					htmlHooks.delete(hook);
+				}
+			};
 		}
 	};
 };