# Class: `SingleWidgetShell` [@jupyterlite/application](../modules/jupyterlite_application.md).SingleWidgetShell The application shell. ## Hierarchy - `Widget` ↳ **``SingleWidgetShell``** ↳↳ [`ISingleWidgetShell`](../interfaces/jupyterlite_application.ISingleWidgetShell.md) ## Implements - `IShell` ## Constructors ### `constructor` > > **`new SingleWidgetShell`**() #### Overrides Widget.constructor #### Defined in [packages/application/src/singleWidgetShell.ts:32](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L32) ## Properties ### `_currentChanged` > > `Private` **`_currentChanged`**: `Signal`<[`SingleWidgetShell`](jupyterlite_application.SingleWidgetShell.md), `void`\> #### Defined in [packages/application/src/singleWidgetShell.ts:110](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L110) ### `_main` > > `Private` **`_main`**: `Panel` #### Defined in [packages/application/src/singleWidgetShell.ts:109](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L109) ### `node` > > `Readonly` **`node`**: `HTMLElement` Get the DOM node owned by the widget. #### Implementation of JupyterFrontEnd.IShell.node #### Inherited from Widget.node #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:37 ## Accessors ### `currentChanged` > > `get` **`currentChanged`**(): `ISignal`<[`ISingleWidgetShell`](../modules/jupyterlite_application.md#isinglewidgetshell), `void`\> A signal emitted when the current widget changes. #### Returns `ISignal`<[`ISingleWidgetShell`](../modules/jupyterlite_application.md#isinglewidgetshell), `void`\> #### Defined in [packages/application/src/singleWidgetShell.ts:46](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L46) ### `currentWidget` > > `get` **`currentWidget`**(): ``null`` \| `Widget` The current widget in the shell's main area. #### Returns ``null`` \| `Widget` #### Implementation of JupyterFrontEnd.IShell.currentWidget #### Defined in [packages/application/src/singleWidgetShell.ts:53](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L53) ### `dataset` > > `get` **`dataset`**(): `DOMStringMap` The dataset for the widget's DOM node. #### Returns `DOMStringMap` #### Implementation of JupyterFrontEnd.IShell.dataset #### Inherited from Widget.dataset #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:81 ### `disposed` > > `get` **`disposed`**(): `ISignal`<`this`, `void`\> A signal emitted when the widget is disposed. #### Returns `ISignal`<`this`, `void`\> #### Implementation of JupyterFrontEnd.IShell.disposed #### Inherited from Widget.disposed #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:33 ### `hiddenMode` > > `get` **`hiddenMode`**(): `HiddenMode` Get the method for hiding the widget. #### Returns `HiddenMode` #### Implementation of JupyterFrontEnd.IShell.hiddenMode #### Inherited from Widget.hiddenMode #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:85 > > `set` **`hiddenMode`**(`value`): `void` Set the method for hiding the widget. #### Parameters | Name | Type | | :------ | :------ | | `value` | `HiddenMode` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.hiddenMode #### Inherited from Widget.hiddenMode #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:89 ### `id` > > `get` **`id`**(): `string` Get the id of the widget's DOM node. #### Returns `string` #### Implementation of JupyterFrontEnd.IShell.id #### Inherited from Widget.id #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:73 > > `set` **`id`**(`value`): `void` Set the id of the widget's DOM node. #### Parameters | Name | Type | | :------ | :------ | | `value` | `string` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.id #### Inherited from Widget.id #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:77 ### `isAttached` > > `get` **`isAttached`**(): `boolean` Test whether the widget's node is attached to the DOM. #### Returns `boolean` #### Implementation of JupyterFrontEnd.IShell.isAttached #### Inherited from Widget.isAttached #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:45 ### `isDisposed` > > `get` **`isDisposed`**(): `boolean` Test whether the widget has been disposed. #### Returns `boolean` #### Implementation of JupyterFrontEnd.IShell.isDisposed #### Inherited from Widget.isDisposed #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:41 ### `isHidden` > > `get` **`isHidden`**(): `boolean` Test whether the widget is explicitly hidden. #### Returns `boolean` #### Implementation of JupyterFrontEnd.IShell.isHidden #### Inherited from Widget.isHidden #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:49 ### `isVisible` > > `get` **`isVisible`**(): `boolean` Test whether the widget is visible. #### Notes A widget is visible when it is attached to the DOM, is not explicitly hidden, and has no explicitly hidden ancestors. #### Returns `boolean` #### Implementation of JupyterFrontEnd.IShell.isVisible #### Inherited from Widget.isVisible #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:57 ### `layout` > > `get` **`layout`**(): ``null`` \| `Layout` Get the layout for the widget. #### Returns ``null`` \| `Layout` #### Implementation of JupyterFrontEnd.IShell.layout #### Inherited from Widget.layout #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:109 > > `set` **`layout`**(`value`): `void` Set the layout for the widget. #### Notes The layout is single-use only. It cannot be changed after the first assignment. The layout is disposed automatically when the widget is disposed. #### Parameters | Name | Type | | :------ | :------ | | `value` | ``null`` \| `Layout` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.layout #### Inherited from Widget.layout #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:119 ### `parent` > > `get` **`parent`**(): ``null`` \| `Widget` Get the parent of the widget. #### Returns ``null`` \| `Widget` #### Implementation of JupyterFrontEnd.IShell.parent #### Inherited from Widget.parent #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:93 > > `set` **`parent`**(`value`): `void` Set the parent of the widget. #### Notes Children are typically added to a widget by using a layout, which means user code will not normally set the parent widget directly. The widget will be automatically removed from its old parent. This is a no-op if there is no effective parent change. #### Parameters | Name | Type | | :------ | :------ | | `value` | ``null`` \| `Widget` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.parent #### Inherited from Widget.parent #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:105 ### `title` > > `get` **`title`**(): `Title`<`Widget`\> The title object for the widget. #### Notes The title object is used by some container widgets when displaying the widget alongside some title, such as a tab panel or side bar. Since not all widgets will use the title, it is created on demand. The `owner` property of the title is set to this widget. #### Returns `Title`<`Widget`\> #### Implementation of JupyterFrontEnd.IShell.title #### Inherited from Widget.title #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:69 ## Methods ### `activate` > > **`activate`**(): `void` Post an `'activate-request'` message to the widget. #### Notes This is a simple convenience method for posting the message. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.activate #### Inherited from Widget.activate #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:204 ### `activateById` > > **`activateById`**(`id`): `void` Activate a widget in its area. #### Parameters | Name | Type | | :------ | :------ | | `id` | `string` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.activateById #### Defined in [packages/application/src/singleWidgetShell.ts:60](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L60) ### `add` > > **`add`**(`widget`, `area?`, `options?`): `void` Add a widget to the application shell. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `widget` | `Widget` | The widget being added. | | `area?` | ``"main"`` | Optional region in the shell into which the widget should be added. | | `options?` | `IOpenOptions` | Optional open options. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.add #### Defined in [packages/application/src/singleWidgetShell.ts:78](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L78) ### `addClass` > > **`addClass`**(`name`): `void` Add a class name to the widget's DOM node. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `name` | `string` | The class name to add to the node. #### Notes If the class name is already added to the node, this is a no-op. The class name must not contain whitespace. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.addClass #### Inherited from Widget.addClass #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:157 ### `children` > > **`children`**(): `IterableIterator`<`Widget`\> Create an iterator over the widget's children. #### Returns `IterableIterator`<`Widget`\> A new iterator over the children of the widget. #### Notes The widget must have a populated layout in order to have children. If a layout is not installed, the returned iterator will be empty. #### Implementation of JupyterFrontEnd.IShell.children #### Inherited from Widget.children #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:130 ### `clearFlag` > > **`clearFlag`**(`flag`): `void` Clear the given widget flag. #### Notes This will not typically be called directly by user code. #### Parameters | Name | Type | | :------ | :------ | | `flag` | `Flag` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.clearFlag #### Inherited from Widget.clearFlag #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:259 ### `close` > > **`close`**(): `void` Send a `'close-request'` message to the widget. #### Notes This is a simple convenience method for sending the message. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.close #### Inherited from Widget.close #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:211 ### `contains` > > **`contains`**(`widget`): `boolean` Test whether a widget is a descendant of this widget. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `widget` | `Widget` | The descendant widget of interest. | #### Returns `boolean` `true` if the widget is a descendant, `false` otherwise. #### Implementation of JupyterFrontEnd.IShell.contains #### Inherited from Widget.contains #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:138 ### `dispose` > > **`dispose`**(): `void` Dispose of the widget and its descendant widgets. #### Notes It is unsafe to use the widget after it has been disposed. All calls made to this method after the first are a no-op. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.dispose #### Inherited from Widget.dispose #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:29 ### `fit` > > **`fit`**(): `void` Post a `'fit-request'` message to the widget. #### Notes This is a simple convenience method for posting the message. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.fit #### Inherited from Widget.fit #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:197 ### `hasClass` > > **`hasClass`**(`name`): `boolean` Test whether the widget's DOM node has the given class name. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `name` | `string` | The class name of interest. | #### Returns `boolean` `true` if the node has the class, `false` otherwise. #### Implementation of JupyterFrontEnd.IShell.hasClass #### Inherited from Widget.hasClass #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:146 ### `hide` > > **`hide`**(): `void` Hide the widget and make it hidden to its parent widget. #### Notes This causes the [isHidden](jupyterlite_application.SingleWidgetShell.md#ishidden) property to be `true`. If the widget is explicitly hidden, this is a no-op. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.hide #### Inherited from Widget.hide #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:229 ### `notifyLayout` > > `Protected` **`notifyLayout`**(`msg`): `void` Invoke the message processing routine of the widget's layout. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `msg` | `Message` | The message to dispatch to the layout. #### Notes This is a no-op if the widget does not have a layout. This will not typically be called directly by user code. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.notifyLayout #### Inherited from Widget.notifyLayout #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:279 ### `onActivateRequest` > > `Protected` **`onActivateRequest`**(`msg`): `void` A message handler invoked on an `'activate-request'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onActivateRequest #### Inherited from Widget.onActivateRequest #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:314 ### `onAfterAttach` > > `Protected` **`onAfterAttach`**(`msg`): `void` A message handler invoked on an `'after-attach'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onAfterAttach #### Inherited from Widget.onAfterAttach #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:356 ### `onAfterDetach` > > `Protected` **`onAfterDetach`**(`msg`): `void` A message handler invoked on an `'after-detach'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onAfterDetach #### Inherited from Widget.onAfterDetach #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:370 ### `onAfterHide` > > `Protected` **`onAfterHide`**(`msg`): `void` A message handler invoked on an `'after-hide'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onAfterHide #### Inherited from Widget.onAfterHide #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:342 ### `onAfterShow` > > `Protected` **`onAfterShow`**(`msg`): `void` A message handler invoked on an `'after-show'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onAfterShow #### Inherited from Widget.onAfterShow #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:328 ### `onBeforeAttach` > > `Protected` **`onBeforeAttach`**(`msg`): `void` A message handler invoked on a `'before-attach'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onBeforeAttach #### Inherited from Widget.onBeforeAttach #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:349 ### `onBeforeDetach` > > `Protected` **`onBeforeDetach`**(`msg`): `void` A message handler invoked on a `'before-detach'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onBeforeDetach #### Inherited from Widget.onBeforeDetach #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:363 ### `onBeforeHide` > > `Protected` **`onBeforeHide`**(`msg`): `void` A message handler invoked on a `'before-hide'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onBeforeHide #### Inherited from Widget.onBeforeHide #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:335 ### `onBeforeShow` > > `Protected` **`onBeforeShow`**(`msg`): `void` A message handler invoked on a `'before-show'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onBeforeShow #### Inherited from Widget.onBeforeShow #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:321 ### `onChildAdded` > > `Protected` **`onChildAdded`**(`msg`): `void` A message handler invoked on a `'child-added'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `ChildMessage` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onChildAdded #### Inherited from Widget.onChildAdded #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:377 ### `onChildRemoved` > > `Protected` **`onChildRemoved`**(`msg`): `void` A message handler invoked on a `'child-removed'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `ChildMessage` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onChildRemoved #### Inherited from Widget.onChildRemoved #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:384 ### `onCloseRequest` > > `Protected` **`onCloseRequest`**(`msg`): `void` A message handler invoked on a `'close-request'` message. #### Notes The default implementation unparents or detaches the widget. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onCloseRequest #### Inherited from Widget.onCloseRequest #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:286 ### `onFitRequest` > > `Protected` **`onFitRequest`**(`msg`): `void` A message handler invoked on a `'fit-request'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onFitRequest #### Inherited from Widget.onFitRequest #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:307 ### `onResize` > > `Protected` **`onResize`**(`msg`): `void` A message handler invoked on a `'resize'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `ResizeMessage` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onResize #### Inherited from Widget.onResize #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:293 ### `onUpdateRequest` > > `Protected` **`onUpdateRequest`**(`msg`): `void` A message handler invoked on an `'update-request'` message. #### Notes The default implementation of this handler is a no-op. #### Parameters | Name | Type | | :------ | :------ | | `msg` | `Message` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.onUpdateRequest #### Inherited from Widget.onUpdateRequest #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:300 ### `processMessage` > > **`processMessage`**(`msg`): `void` Process a message sent to the widget. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `msg` | `Message` | The message sent to the widget. #### Notes Subclasses may reimplement this method as needed. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.processMessage #### Inherited from Widget.processMessage #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:268 ### `removeClass` > > **`removeClass`**(`name`): `void` Remove a class name from the widget's DOM node. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `name` | `string` | The class name to remove from the node. #### Notes If the class name is not yet added to the node, this is a no-op. The class name must not contain whitespace. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.removeClass #### Inherited from Widget.removeClass #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:168 ### `setFlag` > > **`setFlag`**(`flag`): `void` Set the given widget flag. #### Notes This will not typically be called directly by user code. #### Parameters | Name | Type | | :------ | :------ | | `flag` | `Flag` | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.setFlag #### Inherited from Widget.setFlag #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:252 ### `setHidden` > > **`setHidden`**(`hidden`): `void` Show or hide the widget according to a boolean value. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `hidden` | `boolean` | `true` to hide the widget, or `false` to show it. #### Notes This is a convenience method for `hide()` and `show()`. | #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.setHidden #### Inherited from Widget.setHidden #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:238 ### `show` > > **`show`**(): `void` Show the widget and make it visible to its parent widget. #### Notes This causes the [isHidden](jupyterlite_application.SingleWidgetShell.md#ishidden) property to be `false`. If the widget is not explicitly hidden, this is a no-op. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.show #### Inherited from Widget.show #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:220 ### `testFlag` > > **`testFlag`**(`flag`): `boolean` Test whether the given widget flag is set. #### Notes This will not typically be called directly by user code. #### Parameters | Name | Type | | :------ | :------ | | `flag` | `Flag` | #### Returns `boolean` #### Implementation of JupyterFrontEnd.IShell.testFlag #### Inherited from Widget.testFlag #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:245 ### `toggleClass` > > **`toggleClass`**(`name`, `force?`): `boolean` Toggle a class name on the widget's DOM node. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `name` | `string` | The class name to toggle on the node. | | `force?` | `boolean` | Whether to force add the class (`true`) or force remove the class (`false`). If not provided, the presence of the class will be toggled from its current state. | #### Returns `boolean` `true` if the class is now present, `false` otherwise. #### Notes The class name must not contain whitespace. #### Implementation of JupyterFrontEnd.IShell.toggleClass #### Inherited from Widget.toggleClass #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:183 ### `update` > > **`update`**(): `void` Post an `'update-request'` message to the widget. #### Notes This is a simple convenience method for posting the message. #### Returns `void` #### Implementation of JupyterFrontEnd.IShell.update #### Inherited from Widget.update #### Defined in node_modules/@lumino/widgets/types/widget.d.ts:190 ### `widgets` > > **`widgets`**(`area`): `IterableIterator`<`Widget`\> Return the list of widgets for the given area. #### Parameters | Name | Type | Description | | :------ | :------ | :------ | | `area` | ``"main"`` | The area | #### Returns `IterableIterator`<`Widget`\> #### Implementation of JupyterFrontEnd.IShell.widgets #### Defined in [packages/application/src/singleWidgetShell.ts:99](https://github.com/jupyterlite/jupyterlite/blob/55b565b/packages/application/src/singleWidgetShell.ts#L99)