Re: Better parse-partial-sexp; multiple major modes

[Lennart Borgman (gmail)]

Daniel Colascione wrote:
>> Also, Lennart is asking for it to work nicely with multiple major modes.
>> Surely this would be a Good Thing.  Files containing several major modes
>> are commonplace (awk or sed embedded within a shell script, html
>> embedded within php, ....).
> 
> After several attempts at using and understanding multiple major mode
> facilities, I'm convinced the only way forward is core support for the
> concept. Lennart's done a fine job with what's in Emacs currently. But
> anything involving multiple major modes today is a quivering mound of
> hacks. All the work Lennart's had to do to get modes playing nice with
> each other is a testament to that.

Are you suggesting that you have problems using MuMaMo today? If so then
please report it as a bug.

> Maybe a core solution could be something like this: in a given buffer,
> each character has a chunk-name character property. You'd buffer-locally
> map chunk names to major modes. For each chunk name, create a buffer
> containing just the text assigned to that chunk. Make the major-mode the
> major mode for the chunk buffer, and let that major-mode handle
> fontification, keybindings, and so on. In the main buffer, assemble the
> various bits from the chunk-buffers and allow the user to navigate the
> combined buffer normally.

This was an idea I played with at the beginning when I wrote mumamo.el.

I am afraid I think the concepts involved (like buffer local etc) must
be considered quite a bit more first before going in this direction. It
is unclear to me now whether chunk-buffers really would be of any help.
They might be, but I am not sure.

> Keybindings with point at a particular character would just be the
> keybindings present in that character's chunk-buffer. If you need
> special keybindings common across all chunk buffers, just bind the key
> in all the chunk buffers. If a given chunk needs placeholder text to
> represent text of some other chunk, it should be possible add it to that
> chunk buffer without affecting any of the others.
> 
> Anyway, this scheme is:
> 
> 1) Robust - no messing around with variables, no tweaking fontification

Unfortunately I do not think that will hold.

I think the way to go is "interface style". font-lock has some good
support for making multiple major modes possible.

> 2) Backwards compatible - a major-mode doesn't need to know it's being
> used this way

Are you aware of that a major mode does not need to know anything when
used in MuMaMo?

> 3) Versatile - you can compose arbitrary modes this way, even recursively

The main difficulty with sub-modes in sub-modes is stability. How do you
find the sub-modes in sub-modes after buffer changes?

I think I know how to implement this in MuMaMo, but I do not have time
right now. (And it is not very much needed.)

> 4) Conceptually simple (I hope)
> 
> Any thoughts?
> 
> 
>