emit notebook editor selection change.

src/vs/vscode.proposed.d.ts

@@ -1464,6 +1464,11 @@ declare module 'vscode' {
 		readonly cell: NotebookCell;
 	}
 
+	export interface NotebookEditorSelectionChangeEvent {
+		readonly notebookEditor: NotebookEditor;
+		readonly selection?: NotebookCell;
+	}
+
 	export interface NotebookCellData {
 		readonly cellKind: CellKind;
 		readonly source: string;
@@ -1680,11 +1685,12 @@ declare module 'vscode' {
 		 */
 		export const notebookDocuments: ReadonlyArray<NotebookDocument>;
 
-		export let visibleNotebookEditors: NotebookEditor[];
+		export const visibleNotebookEditors: NotebookEditor[];
 		export const onDidChangeVisibleNotebookEditors: Event<NotebookEditor[]>;
 
-		export let activeNotebookEditor: NotebookEditor | undefined;
+		export const activeNotebookEditor: NotebookEditor | undefined;
 		export const onDidChangeActiveNotebookEditor: Event<NotebookEditor | undefined>;
+		export const onDidChangeNotebookEditorSelection: Event<NotebookEditorSelectionChangeEvent>;
 		export const onDidChangeNotebookCells: Event<NotebookCellsChangeEvent>;
 		export const onDidChangeCellOutputs: Event<NotebookCellOutputsChangeEvent>;
 		export const onDidChangeCellLanguage: Event<NotebookCellLanguageChangeEvent>;

src/vs/workbench/api/common/extHost.api.impl.ts

@@ -977,6 +977,10 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 				checkProposedApiEnabled(extension);
 				return extHostNotebook.onDidChangeNotebookCells(listener, thisArgs, disposables);
 			},
+			onDidChangeNotebookEditorSelection(listener, thisArgs?, disposables?) {
+				checkProposedApiEnabled(extension);
+				return extHostNotebook.onDidChangeNotebookEditorSelection(listener, thisArgs, disposables);
+			},
 			onDidChangeCellOutputs(listener, thisArgs?, disposables?) {
 				checkProposedApiEnabled(extension);
 				return extHostNotebook.onDidChangeCellOutputs(listener, thisArgs, disposables);

src/vs/workbench/api/common/extHostNotebook.ts

@@ -870,6 +870,8 @@ export class ExtHostNotebookController implements ExtHostNotebookShape, ExtHostN
 	private readonly _editors = new Map<string, { editor: ExtHostNotebookEditor; }>();
 	private readonly _webviewComm = new Map<string, ExtHostWebviewCommWrapper>();
 	private readonly _commandsConverter: CommandsConverter;
+	private readonly _onDidChangeNotebookEditorSelection = new Emitter<vscode.NotebookEditorSelectionChangeEvent>();
+	readonly onDidChangeNotebookEditorSelection = this._onDidChangeNotebookEditorSelection.event;
 	private readonly _onDidChangeNotebookCells = new Emitter<vscode.NotebookCellsChangeEvent>();
 	readonly onDidChangeNotebookCells = this._onDidChangeNotebookCells.event;
 	private readonly _onDidChangeCellOutputs = new Emitter<vscode.NotebookCellOutputsChangeEvent>();
@@ -1285,6 +1287,11 @@ export class ExtHostNotebookController implements ExtHostNotebookShape, ExtHostN
 			} else {
 				editor.editor.selection = undefined;
 			}
+
+			this._onDidChangeNotebookEditorSelection.fire({
+				notebookEditor: editor.editor,
+				selection: editor.editor.selection
+			});
 		}
 
 		if (data.metadata) {