Re: A vision for multiple major modes: some design notes

[Dmitry Gutov]

On 04/21/2016 05:24 PM, Stefan Monnier wrote:
> I haven't kept up with this discussion, but I think it'd worthwhile
> taking a look at what things like SublimeText do for syntax
> highlighting, because it's a lot more powerful than what font-lock does
> (IOW it lets you define contexts and is hence closer to a parser whereas
> font-lock is closer to a lexer), and it might be an interesting starting
> point for multiple major modes.

Indeed. If anyone's interested, here's some documentation: 
https://www.sublimetext.com/docs/3/syntax.html

Apparently, Sublime, TextMate, Atom and even Vim all use this or similar 
approaches. If it were somehow adopted for Emacs (plenty of details 
would need to be worked out), it would allow describing more complex 
grammars, and e.g. support a related Ruby feature that I'm having 
difficulty implementing right now.

Further, if it provides a different mechanism of syntactic parsing, it 
could be an alternative to using islands to make parse-partial-sexp skip 
over "foreign" regions. Although, unless we're going to change how we 
write indentation code, we'd still need to be able to compute the 
current paren nesting. Ultimately, the new way of defining a grammar 
could also be a way to define and apply "island" boundaries 
automatically, without the need for third-party code.

Where it's less likely to help, though, is with being able to combine 
and reuse settings and code from multiple major modes in one file. For 
anything like that to happen, the syntax definitions would have to be 
using a format that's highly composable, at least. I'm not sure I'm 
seeing that in any of the current grammars in the aforementioned 
editors. And the current way to combine the functionality from different 
languages is to call different major mode functions and switch between 
sets of buffer-local variables. Not sure what's the alternative for that.