From 3185922bb3460eae40aa08084682db608cfa69c4 Mon Sep 17 00:00:00 2001
From: Jeremy Tuloup <jeremy.tuloup@gmail.com>
Date: Fri, 4 Dec 2020 21:33:56 +0100
Subject: [PATCH] Toggle header visibility

---
 packages/application-extension/package.json |  2 ++
 packages/application-extension/src/index.ts | 39 +++++++++++++++++++--
 packages/application/src/shell.ts           |  7 ++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/packages/application-extension/package.json b/packages/application-extension/package.json
index 43131b5ef..c33d3d32c 100644
--- a/packages/application-extension/package.json
+++ b/packages/application-extension/package.json
@@ -44,7 +44,9 @@
     "@jupyterlab/codemirror": "^3.0.0-rc.12",
     "@jupyterlab/docregistry": "^3.0.0-rc.12",
     "@jupyterlab/docmanager": "^3.0.0-rc.12",
+    "@jupyterlab/mainmenu": "^3.0.0-rc.12",
     "@jupyterlab/notebook": "^3.0.0-rc.12",
+    "@jupyterlab/settingregistry": "^3.0.0-rc.12",
     "@jupyterlab/translation": "^3.0.0-rc.12",
     "@lumino/widgets": "^1.14.0"
   },
diff --git a/packages/application-extension/src/index.ts b/packages/application-extension/src/index.ts
index ad1c8ffea..aaffc3231 100644
--- a/packages/application-extension/src/index.ts
+++ b/packages/application-extension/src/index.ts
@@ -19,6 +19,8 @@ import { PageConfig, Text, Time } from '@jupyterlab/coreutils';
 
 import { IDocumentManager, renameDialog } from '@jupyterlab/docmanager';
 
+import { IMainMenu } from '@jupyterlab/mainmenu';
+
 import { NotebookPanel } from '@jupyterlab/notebook';
 
 import { ITranslator, TranslationManager } from '@jupyterlab/translation';
@@ -62,7 +64,10 @@ const KERNEL_STATUS_FADE_OUT_CLASS = 'jp-ClassicKernelStatus-fade';
  * The command IDs used by the application plugin.
  */
 namespace CommandIDs {
-  export const open = 'docmanager:open';
+  /**
+   * Toggle Top Bar visibility
+   */
+  export const toggleTop = 'application:toggle-top';
 }
 
 /**
@@ -391,6 +396,35 @@ const title: JupyterFrontEndPlugin<void> = {
   }
 };
 
+/**
+ * Plugin to toggle the top header visibility.
+ */
+const topVisibility: JupyterFrontEndPlugin<void> = {
+  id: '@jupyterlab-classic/application-extension:top',
+  requires: [IClassicShell],
+  optional: [IMainMenu],
+  activate: (
+    app: JupyterFrontEnd<JupyterFrontEnd.IShell>,
+    classicShell: IClassicShell,
+    menu: IMainMenu | null
+  ) => {
+    const top = classicShell.top;
+
+    app.commands.addCommand(CommandIDs.toggleTop, {
+      label: 'Show Header',
+      execute: (args: any) => {
+        top.setHidden(top.isVisible);
+      },
+      isToggled: () => top.isVisible
+    });
+
+    if (menu) {
+      menu.viewMenu.addGroup([{ command: CommandIDs.toggleTop }], 2);
+    }
+  },
+  autoStart: true
+};
+
 /**
  * A simplified Translator
  */
@@ -426,7 +460,7 @@ const tree: JupyterFrontEndPlugin<void> = {
         const [, path] = matches;
 
         app.restored.then(() => {
-          commands.execute(CommandIDs.open, {
+          commands.execute('docmanager:open', {
             path,
             factory: NOTEBOOK_FACTORY
           });
@@ -453,6 +487,7 @@ const plugins: JupyterFrontEndPlugin<any>[] = [
   shell,
   spacer,
   title,
+  topVisibility,
   translator,
   tree
 ];
diff --git a/packages/application/src/shell.ts b/packages/application/src/shell.ts
index 32211bc8c..737c1beb1 100644
--- a/packages/application/src/shell.ts
+++ b/packages/application/src/shell.ts
@@ -114,6 +114,13 @@ export class ClassicShell extends Widget implements JupyterFrontEnd.IShell {
     return this._main.widgets[0];
   }
 
+  /**
+   * Get the top area panel
+   */
+  get top(): Widget {
+    return this._topHandler.panel;
+  }
+
   /**
    * Return the list of widgets for the given area.
    *