ipywidgets cannot be displayed in the SimplifiedOutputArea widget in the kernel-output example

[yidong72]

I filed the same issue #2926 at the ipywidget repo. No response yet.

I followed the example at
https://github.com/jupyterlab/extension-examples/tree/master/advanced/kernel-output
The ipywidgets can be displayed fine in the notebook cells, but not in the SimpliedOutputArea from @jupyterlab/outputarea created manually. I checked the rendermime, it contains the mimetypes for ipywidgets.
Not sure what I need to do to make it work. Please help. Thanks.

[jtpio]

@yidong72 which version of JupyterLab are you using?

Also are there any errors in the browser dev tools console?

[saswatac]

i am also seeing this in jupyter lab version 4.0.6. to repro, you can put the code to execute as from ipywidgets import IntSlider; IntSlider(value=10) .

In the jupyterlab main panel, the output is IntSlider(value=10) in plain text. On browser console, I see the error "Exception opening new comm"

[saswatac]

Following up on this discussion again. From the debugger on the dev tools, I have identified that the exception opening new comm is -

"Error: Object 'jupyter.widget' not found in registry at .."

The specific message is -

_model_module: "@jupyter-widgets/base"
_model_module_version: "2.0.0"
_model_name: "LayoutModel"
_view_count: null
_view_module: "@jupyter-widgets/base"
_view_module_version: "2.0.0"
_view_name: "LayoutView"

I would expect the basic models to be registered, do I need to somehow register them again in my jupyterlab extension?

@jtpio do you have any suggestions?

[jtpio]

Just to double check it's not related to a recent ipywidgets release: would you be able to try with ipywidgets<8.1.3 and jupyterlab-widgets<3.0.11 (jupyterlab-widgets is the extension providing widget support in JupyterLab).

[saswatac]

i am using ipywidgets==8.1.1 and jupyterlab-widgets==3.0.9

[saswatac]

I was able to make some progress by following the code in https://github.com/jupyter-widgets/ipywidgets/blob/303cae4dc268640a01ce08bf6e22da6c5cd201e4/python/jupyterlab_widgets/src/plugin.ts .

The missing pieces were -

1. The render mime object has a default renderer for "application/vnd.jupyter.widget-view+json." Instead, we need to hook up the rendermime with a kernel widget manager for the specific kernel so that it registers the kernel's comm target.

rendermime.removeMimeType(WIDGET_VIEW_MIMETYPE);
const manager = new KernelWidgetManager(this._sessionContext.session!.kernel!, rendermime);
rendermime.addFactory(
          {
            safe: true,
            mimeTypes: [WIDGET_VIEW_MIMETYPE],
            createRenderer: (options) => new WidgetRenderer(options, manager)
          },
          -10
        );

2. the widget manager needs to be registered with all the available widget models.

WIDGET_REGISTRY.forEach((data) => manager!.register(data));

3. When registering the renderer in 1, option safe should be set to True. otherwise, the text mimetype is always preferred, and widget never gets rendered.

is this the right approach?

I have a follow-up request - for point 2, the WIDGET_REGISTRY list is not exported https://github.com/jupyter-widgets/ipywidgets/blob/303cae4dc268640a01ce08bf6e22da6c5cd201e4/python/jupyterlab_widgets/src/plugin.ts#L62C24-L62C50 . could we export it, or better enhance the IJupyterWidgetRegistry interface to add a method to fetch all the registered widgets?