[IPython-dev] Loading nbextension on widget instantiation

[Thomas Kluyver]

On 17 June 2014 06:37, Nicholas Bollweg <nick.bollweg at gmail.com> wrote:

> We have also encountered this issue: we have, for the moment, dealt with
> it with a mixin for our python-side widget classes that does a require
> against the _view_name:
>

Ah, I was trying to load the JS by displaying HTML with a script tag. I
guess displaying actual javascript directly reduces the async problem. All
the same, I think a cleaner solution would definitely be good.

I was discussing this with Jon yesterday, and we're thinking of changing
around the current scheme a bit, so that rather than registering target
types with the comm manager, and view types with the widget manager,
widgets are define in modules that can be loaded by require.js. Then a
widget that currently specifies a view_name will also specify a
view_module. So in your case, the code would look like this:

class MyWidget(Widget):
    view_name = 'WidgetView'
    view_module = '/nbextensions/ipynbdbtk/js'
    ...

This would result in some incompatibility with existing code, but it should
be possible to update extensions so that they'll work with IPython 2 and 3.
Given that widgets are new, and the APIs somewhat provisional, I think
that's acceptable. We intend to update all of our own widgets to use this,
and get rid of the JS type registries altogether.


> Speaking of documentation: a template for building extensions with widgets
> that that embodied the baseline of knowledge spread all over the community
> would be great. I have used paste before, which seems kind of heavy these
> days. Cookiecutter looks good:
>

I think we're really still working out what best practices are - and
updating IPython's APIs as we work out things like this. By all means
create a template, though - it can evolve as our knowledge and APIs improve.

Andrew:
> I'm not sure, but this *sorta* looks like the same issue I raised in the
thread titled "Javascript ordering semantics". Here's the solution I found
then:...

You're quite right, it is exactly the same issue. I wasn't using widgets
then, so I didn't pay much attention to the thread. I think your solution
is similar to Nicholas', except with the added publication of an HTML
element. In my code, the HTML components are created in JS when the widget
is displayed.

I still think it's worth improving this API in IPython, but I will work in
this solution to support widgets in IPython 2.

Thanks,
Thomas
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