Webview API prototype 3 (#44307)

* Webview API prototype 3

Part of #43713

Third try at refining the webview api. This pass reworks  #44165.  Major changes:

- Adds an `id` field to webviews. The id is provided by the extension and identifies the webview. It is used with the new event handling apis.

- Adds a new `onDidChangeActiveEditor` api. This is similar to `onDidChangeActiveTextEditor` but is also fired when you change webviews. It replaces the old `onFocus` and `onBlur` events on the webview itself

- Adds an `onDispose` event ot webviews. This is fired when a webview is closed by the user

- Perist webview state when the editor group changes. This is enabled for all webviews, not just those with keep alive.

* Throw error when trying to access disposed webview

* Improving webview documentation

* Clean up dispose management

* Throw if we receive a bad handle

* Move more event handling to input

* Simplify input updating

* Remove extra container property

* Fixing md security alert button

* Remove extra update container call

* Restore syncing of preview to active editor

* Fixing posting to webview

* Debounce preview updates

* Remove previewUri

* Enable direct window.postMessage instead of window.parent.postMessage

* Fixing scroll position not preserved when updating previews

* Revert parent.postMessage change.

Old behavior was correct

* Properly hide webview container on tab switch

* Make sure we only handle scroll events for the correct document

* Don't try setting negative scroll

* Revert vs code whitespace change

src/vs/workbench/api/node/extHostDocumentsAndEditors.ts

@@ -12,10 +12,16 @@ import { ExtHostTextEditor } from './extHostTextEditor';
 import * as assert from 'assert';
 import * as typeConverters from './extHostTypeConverters';
 import URI from 'vs/base/common/uri';
+import { ExtHostWebview, ExtHostWebviews } from './extHostWebview';
+import { Disposable } from './extHostTypes';
 
 export class ExtHostDocumentsAndEditors implements ExtHostDocumentsAndEditorsShape {
 
+	private _disposables: Disposable[] = [];
+
 	private _activeEditorId: string;
+	private _activeWebview: ExtHostWebview;
+
 	private readonly _editors = new Map<string, ExtHostTextEditor>();
 	private readonly _documents = new Map<string, ExtHostDocumentData>();
 
@@ -23,15 +29,34 @@ export class ExtHostDocumentsAndEditors implements ExtHostDocumentsAndEditorsSha
 	private readonly _onDidRemoveDocuments = new Emitter<ExtHostDocumentData[]>();
 	private readonly _onDidChangeVisibleTextEditors = new Emitter<ExtHostTextEditor[]>();
 	private readonly _onDidChangeActiveTextEditor = new Emitter<ExtHostTextEditor>();
+	private readonly _onDidChangeActiveEditor = new Emitter<ExtHostTextEditor | ExtHostWebview>();
 
 	readonly onDidAddDocuments: Event<ExtHostDocumentData[]> = this._onDidAddDocuments.event;
 	readonly onDidRemoveDocuments: Event<ExtHostDocumentData[]> = this._onDidRemoveDocuments.event;
 	readonly onDidChangeVisibleTextEditors: Event<ExtHostTextEditor[]> = this._onDidChangeVisibleTextEditors.event;
 	readonly onDidChangeActiveTextEditor: Event<ExtHostTextEditor> = this._onDidChangeActiveTextEditor.event;
+	readonly onDidChangeActiveEditor: Event<ExtHostTextEditor | ExtHostWebview> = this._onDidChangeActiveEditor.event;
 
 	constructor(
-		private readonly _mainContext: IMainContext
+		private readonly _mainContext: IMainContext,
+		_extHostWebviews?: ExtHostWebviews
 	) {
+		if (_extHostWebviews) {
+			_extHostWebviews.onDidChangeActiveWebview(webview => {
+				if (webview) {
+					if (webview !== this._activeWebview) {
+						this._onDidChangeActiveEditor.fire(webview);
+						this._activeWebview = webview;
+					}
+				} else {
+					this._activeWebview = webview;
+				}
+			}, this, this._disposables);
+		}
+	}
+
+	dispose() {
+		this._disposables = dispose(this._disposables);
 	}
 
 	$acceptDocumentsAndEditorsDelta(delta: IDocumentsAndEditorsDelta): void {
@@ -117,6 +142,9 @@ export class ExtHostDocumentsAndEditors implements ExtHostDocumentsAndEditorsSha
 		}
 		if (delta.newActiveEditor !== undefined) {
 			this._onDidChangeActiveTextEditor.fire(this.activeEditor());
+
+			const activeEditor = this.activeEditor();
+			this._onDidChangeActiveEditor.fire(activeEditor || this._activeWebview);
 		}
 	}