Electric indentation (Was: Re: js.el changes)

Electric indentation (Was: Re: js.el changes)

[Daniel Colascione]

On Friday 14 August 2009, you wrote:
> 4. I removed the "electric indentation" feature implemented by
> js-auto-indent-flag and js-insert-and-indent.  I appreciate the intent,
> but it's not consistent with the way the other programming modes work,
> and this behavior should be implemented separately---as a minor mode
> that can be used generally.  Feel free to suggest this on emacs-devel.

I agree that a generic toggle switch for electric indentation would be nice. However, there's quite a bit of precedent for modes implementing their own electric indentation, often using complex logic (see c-electric-brace).

To me, the simplest option would be to create a new trivial minor mode, electric-indentation-mode, and modify all current mode-specific indentation code to check that mode's flag instead of relying on something mode-specific like js-auto-indent-flag or c-electric-flag. The actual mode-specific indentation can survive otherwise unchanged.

Re: Electric indentation (Was: Re: js.el changes)

[Lennart Borgman]

On Fri, Aug 21, 2009 at 6:18 PM, Daniel Colascione<danc@merrillprint.com> wrote:
> On Friday 14 August 2009, you wrote:
>> 4. I removed the "electric indentation" feature implemented by
>> js-auto-indent-flag and js-insert-and-indent.  I appreciate the intent,
>> but it's not consistent with the way the other programming modes work,
>> and this behavior should be implemented separately---as a minor mode
>> that can be used generally.  Feel free to suggest this on emacs-devel.
>
> I agree that a generic toggle switch for electric indentation would be nice. However, there's quite a bit of precedent for modes implementing their own electric indentation, often using complex logic (see c-electric-brace).
>
> To me, the simplest option would be to create a new trivial minor mode, electric-indentation-mode, and modify all current mode-specific indentation code to check that mode's flag instead of relying on something mode-specific like js-auto-indent-flag or c-electric-flag. The actual mode-specific indentation can survive otherwise unchanged.


Maybe it could be done similar to indent-line-function etc?

Re: Electric indentation (Was: Re: js.el changes)

[Daniel Colascione]

On Friday 21 August 2009, you wrote:
> On Fri, Aug 21, 2009 at 6:28 PM, Daniel Colascione<danc@merrillprint.com> wrote:
> > On Friday 21 August 2009, you wrote:
> >> Maybe it could be done similar to indent-line-function etc?
> >
> > Err, how do you mean? Different electric keys require different behavior in different modes. One variable can't be used to dispatch to all these various pieces of code. You could have electric-indentation-mode call a mode-specific function that decides what to do with a given electric key, but isn't that just reimplementating the keymap mechanism?
> 
> 
> It allows you to have a minor mode to toggle the behaviour.

I feel like we're talking past each other. Right now, a mode like js-mode or cc-mode binds keys that are supposed to be electric to a mode-specific function. Let's use cc-mode as an example: it binds { to c-electric-brace. c-electric-brace runs self-insert-command and checks whether the variable c-electric-flag is true. If it is, it performs some specific indentation operations.

My proposal is to create a new globalized minor mode called electric-indentation-mode. An electric insert function like c-electric-brace, instead of checking a mode-specific flag, would instead check the value of the variable electric-indentation-mode. That way, the user can use one interface to enable or disable electric indentation for all supported modes at once.

Re: Electric indentation (Was: Re: js.el changes)

[Lennart Borgman]

On Fri, Aug 21, 2009 at 6:35 PM, Daniel Colascione<danc@merrillprint.com> wrote:
> On Friday 21 August 2009, you wrote:
>> On Fri, Aug 21, 2009 at 6:28 PM, Daniel Colascione<danc@merrillprint.com> wrote:
>> > On Friday 21 August 2009, you wrote:
>> >> Maybe it could be done similar to indent-line-function etc?
>> >
>> > Err, how do you mean? Different electric keys require different behavior in different modes. One variable can't be used to dispatch to all these various pieces of code. You could have electric-indentation-mode call a mode-specific function that decides what to do with a given electric key, but isn't that just reimplementating the keymap mechanism?
>>
>>
>> It allows you to have a minor mode to toggle the behaviour.
>
> I feel like we're talking past each other. Right now, a mode like js-mode or cc-mode binds keys that are supposed to be electric to a mode-specific function. Let's use cc-mode as an example: it binds { to c-electric-brace. c-electric-brace runs self-insert-command and checks whether the variable c-electric-flag is true. If it is, it performs some specific indentation operations.
>
> My proposal is to create a new globalized minor mode called electric-indentation-mode. An electric insert function like c-electric-brace, instead of checking a mode-specific flag, would instead check the value of the variable electric-indentation-mode. That way, the user can use one interface to enable or disable electric indentation for all supported modes at once.


Yes, you are right, we were talking past each other. I see now how you
mean. (But maybe a globalized minor mode would be better?)

I do not know which way is the best. Using a function instead would
make it possible to define common default behaviour, but I do not know
if it is useful.