bug#41897: 28.0.50; JavaScript comment filling with mhtml-mode

[Dmitry Gutov]

Hi Alan,

On 23.06.2020 19:28, Alan Mackenzie wrote:

> > So it's really fine if it's called from HTML/CSS hunks as well?
>
> Not only fine, but necessary.  The literal cache contains entries that
> record things like "C comment between positions 23 and 130".  If somebody
> inserts text before that comment, or inside of it, that cache entry is no
> longer valid, and must be invalidated.  Hence the necessity of the
> before-change function.

But isn't CC Mode confused by chunks of text with a totally different 
syntax?

> > And there's no way to just "reset" it to an appropriate value?
>
> No.  Not without killing its utility as a cache.

What do you mean? Even if the cache is reset at the beginning of a 
function, if the function refers to it multiple times, the first time 
should refill the cache, and the rest of the calls will be able to make 
use of it properly.

> > > > This way, I think it would automatically make it compatible with
> > > > mmm-mode. Or at least more compatible.
>
> > > Maybe putting the two c-foreign-* functions into mmm-mode would work.
>
> > mmm-mode is a minor mode, it doesn't always deal with CC Mode.
>
> The question to consider here is whether any sub-mode of mmm-mode uses CC
> Mode's comment filling without initialising CC Mode.  js-mode and
> mhtml-mode do this.

js-mode can be one of its submodes. c-mode as well, but none of CC Mode 
family of major modes ever worked okay with it, I think.

js-mode mostly works, aside from features like this one.

> > Have you considered adding variables that hold the cache to
> > mhtml--crucial-variable-prefix as well? Would that make it work?
>
> Not without the before-change function, no.  I'm trying to see what the
> point of putting these variables into mhtml's crucial variables would be.

Hopefully, it would make the submode regions inside independent 
"islands", so to speak. Each of them having its own cache structure 
(used or not).

TBH I'm not sure if mhtml-mode does the save-and-restore dance which 
would be necessary for this. mmm-mode does, though.