Start documenting how to write frontend extensions

[Carreau]

This if course require more work, but the request for custom key binding
is too high, and the process of writing extensions too widespread on the
internet.

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This is the base to write an extension, @michaelpacer requested on a private communication how to also bind ^[ to go-to-command-mode / Esc, I''m writing that to see if it's sufficient information.

@michaelpacer I'll give you push access to my fork, so that you can update the PR if there are issues, and fix english mistakes that will make you eyes bleed. If it's unclear I can also update the relevant part. We can hopefully reach quickly an acceptable state.

@JanSchulz , @damianavila and @juhasch also write a lot of extensions and might want to give their input on that.

[juhasch]

This is a good idea, IMO. Currently I cannot be much of help, hopefully in a few weeks.

@jcb91 is also very active, maybe he has some comments/additions ?

[jcb91]

@juhasch thanks for ping-ing me in on this (not really sure what the appropriate word for the action is, or even if one exists, so ping will have to do!).

@Carreau good plan, I recall frequently coming to
your docs on extensions after trying to google how to alter some notebook behaviour.
I'd be happy to contribute some time to improve/extend/update docs.
Would you prefer comments on here, or PRs to your fork?

[jcb91]

As a side note, I've been contemplating for a little while trying to write a hotkey-rebinder extension, which could be used to neatly rebind any named actions (calling javascript extensions without named actions is obviously a bit more difficult). I'll post back here if/when I get round to it.

[takluyver]

I have opened Carreau#6 with some improvements to this.

[Carreau]

I have opened Carreau#6 with some improvements to this.

Merged.

[minrk]

extensions

[Carreau]

Done.

[damianavila]

A little bit late, but LGTM, please also check this which is closely related: jupyter/enhancement-proposals#7

[jcb91]

So, as far as altering keyboard shortcuts goes, I made this nbextension. It doesn't do CodeMirror shortcuts yet, as they seem more complicated, but I expect it could.