Trigger mimerender extension from another extension

[aliasmrchips]

I made a mimerender extension and I am able to trigger the extension by opening a file from the file browser. I can also trigger the extension in the output cell of a notebook by using IPython.display({my_mimetype: data}, raw=True). I would like to do "the same thing" but using javascript (i.e., from within another extension). So, I would make the data object locally and then call something, trigger an event, generate a message or send a signal that would do the equivalent of IPython.display.

In other words, let's say I have two extensions; foo and bar. The "foo" extension will render objects of type "foo" and the "bar" extension will render objects of type "bar".

example.foo.json

{
    "key": "value",
    "index": 0
}

example.bar.json

{
    "index": 0
}

Note that the "bar" mimetype is actually a subset of the "foo" mimetype. So, I can open .foo.json and .bar.json files and they will be rendered (in separate tabs) by their respective extensions. So far, so good.

However, since all the data required to render a "bar" type document is included in a "foo" type document, I would like to include that capability in the "foo" extension. So, the sequence of events would be: 1) Open the "foo" document with the "foo" extension. 2) Do something within the "foo" extension (click on a link or a button or something) that will result in 3) the "bar" extension rendering the "bar" portion of the original "foo" document (again in a separate jlab tab).

I am not sure what the correct mechanism to do this is. My inclination is to have the "foo" extension generate a message or emit a signal (similar to what the filebrowser must be doing), but have been so far unsuccessful.

[jasongrout]

For reference: this question started in a conversation on Gitter [1, 2].

[jasongrout]

1) Open the "foo" document with the "foo" extension. 2) Do something within the "foo" extension (click on a link or a button or something) that will result in 3) the "bar" extension rendering the "bar" portion of the original "foo" document (again in a separate jlab tab).

So in the end, you want two tabs, one with the foo rendering, and one with the bar rendering? Or do you want the bar rendering inside the foo tab?

[aliasmrchips]

Separate tabs. As if, I had opened two files with the file browser.

[jasongrout]

So it sounds like the suggestions on gitter are appropriate:

Look at how the rendermime registry is used in JupyterLab: https://github.com/jupyterlab/jupyterlab/blob/8dc587729e5f2b2fa6087e854f0f988c0232802e/packages/tooltip/src/widget.ts#L71-L80 https://github.com/jupyterlab/jupyterlab/blob/7fb018558f9c812e3e2a3355fb6ab7c1a30486d8/packages/inspector/src/handler.ts#L152-L160 https://github.com/jupyterlab/jupyterlab/blob/d322d6b1f2d7abb32a2ab1c1a457beaa006ec8c1/packages/outputarea/src/widget.ts#L391 Take one of those as an example for:

1. Create a bundle of data
2. Ask the registry for a renderer for that mimetype
3. Create a new MainAreaWidget with that renderer as the content
4. Add that MainAreaWidget to the dock panel.

[aliasmrchips]

Ok, I think I get it now. For steps 3) and 4), I assume I would do something like in the tutorial?https://github.com/jupyterlab/jupyterlab/blob/master/docs/source/developer/extension_tutorial.rst

Is there an "app" instance I can access from within a mimerender extension?

[jasongrout]

You are going to have to make a normal extension for this.

[aliasmrchips]

What handles this (creating a new MainAreaWidget) normally? For example, when you open a file in the file browser? The FileBrowser extension or something else?

[jasongrout]

Whoever wants to create a widget. See the astronomy picture of the day tutorial in the docs, for example.

[aliasmrchips]

Ok, two more questions:

1. Is there an example of making a mimerender extension from a normal extension?
2. Is there an example of lumino signals/messaging?

[saulshanabrook]

@aliasmrchips

Is there an example of making a mimerender extension from a normal extension?

Here is an example of adding a rendermime widget but that won't add the file handling part.

Is there an example of lumino signals/messaging?

Tons!

Here is one I just made up

import { Signal, ISignal } from '@lumino/signaling';

type SENDER = string;
type VALUE = number;
const s = new Signal<SENDER, VALUE>("sender");

const si: ISignal<SENDER, VALUE> = s;
// I can't emit on the ISignal only on the concrete
// this lets us protect emission and only provide the ability to connect

function slot(sender: SENDER, args: VALUE) {
  console.assert(sender === "sender")
  console.assert(args === 123)
}
// Connect a function to be called on each emmission
si.connect(slot);

// Emit some value. all connected "slots" (callbacks) will be called
s.emit(123)

// disconnect your slot when you are done.
si.disconnect(slot)

[aliasmrchips]

Trying the signaling example, I get this error:

I have split the code between two extensions with the "emit" in one and the "slot" connect in the other. Any ideas?