Re: web-mode.el

[Dmitry Gutov]

On 14.06.2012 5:49, Lennart Borgman wrote:
> On Thu, Jun 14, 2012 at 2:33 AM, Dmitry Gutov<address@hidden>  wrote:
> > Lennart Borgman<address@hidden>  writes:
> >
> >
> > > However it might not be worth the trouble. The real problem lies in
> > > the Emacs C core. Parsing functions can currently not be stopped from
> > > parsing things outside of the major mode chunk they belong too.
> > > (mumamo.el goes a long way to try to address this problems as far as
> > > possible. That makes the code quite complicated. A rewrite of the C
> > > core makes things very simple. In addition to this rewrite of the
> > > scheduling functions to add suitable tools for handling chunk finding
> > > might be necessary, but that is much simpler.)=C2=A7
> >
> >  From what I know, mmm-mode counteracts this problem effectively enough,
> > narrowing buffer to chunks during fontification, binding
> > font-lock-dont-widen to t, etc.
>
> I am afraid that is a total misunderstanding. Narrowing etc does not
> help because it does not affect all the functions involved.

I must've mixed it up with multi-mode. mmm-mode does not indeed call 
narrow-to-region there, and instead calls respective 
font-lock-fontify-region-function's with chunk start and end positions.

https://github.com/purcell/mmm-mode/blob/master/mmm-region.el#L793

> > Anyway, you've seen the list of my immediate gripes about how MuMaMo
> > works for ERB, and I'm inclined to fault chunk detection
>
> Chunk detection must logically be done from the start of the file. In
> the first version of MuMaMo I tried to do chunk detection from
> anywhere in the file. That worked for simple cases but not for more
> complicated cases so I rewrote this several years ago.
>
> I have no idea about what trouble you have had. Perhaps you could
> describe them? (Maybe there are still pieces of code I have forgotten
> to rewrite?)

https://bugs.launchpad.net/nxhtml/+bug/946464

> > and indentation logic in your code
>
> Indentation is surpricingly hard actually. One problem is that you
> have to do some language specific parsing (which the major mode
> normally does). Another problem is getting this to work with chunks
> and across chunks. There are several alternatives for this in
> mumamo.el - and unfortunately I think there might some trouble there.

One important thing that I'm almost certain your code doesn't do is set 
indent-line-function in all chunks to the same value.
This function, when called, should save (- (current-column) 
(current-indentation)) value, to restore it after indentation if it's 
positive.
Then it should go (back-to-indentation), look in what chunk the point is 
now, and act accordingly.

> I suspect you have been looking at some of the easier cases. Please
> take a look at the test cases. There should be more, but I think I
> have written test cases for some of the troublesome cases.

I posit that I've managed to make the examples from the bug above work 
better then they do with eruby-html-mumamo-mode, using lesser (I think?) 
amount of code.
Nothing is perfect, of course, but all templates in my current projects 
I've tried yet have shown no problems.