bug#32307: [feature request] Add standard hooks to toggle common features

[Fu Yuan]

By "standard features" I mean line numbering, format on save, auto-parens, etc.

The current situation have these downsides:

1. complexity in configuration.

Some of the packages that provide these features also provide toggling command,

e.g. toggle-line-number or autoparens-mode.

However, some __are not__, e.g. format on save.

Toggling such feature requires users to implement their own commands.

What's worse, they need to implement a toggling command

for __each and every__ language.

2. problem when other package needs to toggle

For example, I wrote a package that needs to temporarily disable auto-parens.

I have to write code that handles electric-pair-mode, autoparens and paredit.

Further more, byte compiler is not happy

because I was referring functions it doesn't know about.

Here is my thought about it:

Provide toggle commands and corresponding hook for each of these features.

Feature providers add their toggle function to the proper hook.

When user toggles on/off, the toggle command runs each function

in the hook with an aregument indicating that user is turning on or turning off,

maybe t and nil.

How do you think? Have there been similar discussions?

Sincerely, Yuan