Hi Christoph,

On 12/15/17 5:48 PM, Wedler, Christoph wrote:
> Sorry for not having followed this discussion earlier - as the one who
> has somehow introduced `prog-indentation-context', I probably should have...

You checked out early from the previous discussion, so I didn't want to 
drag you in again. Hope that's okay.

> If it works and you tell me how to do it, I have no issues with an
> alternative way to make the indentation function of a "sub mode" work
> for code chunks inside an "outer language" (like ANTLR grammar files).

Is there a reason why you called narrow-to-region in 
antlr-python-indent-action-line anyway, even when using 
prog-indentation-context?

Because you do that, though, the "new way" should work with your code 
automatically. I'm attaching a patch with some minor cleanup, though.

Please try it with a build of Emacs from the 'widen-less' branch. Do you 
know how to build it?

> I you want to try some ANTLR grammar examples yourself, I would
> recommend:
> 
>   - antlr-mode 3.1.4
>     from https://sourceforge.net/projects/antlr-mode/files/
> 
>   - example grammar files, especially lines 46 to 51 in
>     https://github.com/antlr/examples-v3/blob/master/Python/C/C.g
> 
>   - and others in that repo (mentioned in line 100 of antlr-mode.el)

antlr-mode.el says these examples are to see the syntax highlighting. 
Any particular file and place to see how indentation works out? I 
couldn't find one from a cursory search.

> Now to the elements in `prog-indentation-context':
> 
>   - FIRST-COLUMN: I understood that you want to keep (s/th like) that...
> 
>   - (START . END) = the region of the code chunk: well, some indentation
>     engines got confused to see unknown code before code written in the
>     "sub-modes" - for some I could do `narrow-to-region' myself, other
>     engines did widen, like python.  IMHO, modes with widening provide a
>     better indentation experience than those without, see below.
> 
>   - PREVIOUS-CHUNKS: well, I was told to introduce this to be more
>     general... - some modes (like cc-mode) could be told that the code is
>     not some usual "top-level" code, but just some "normal statement".
>     (antlr-mode includes some ugly hack for cc-mode).
> 
> If all this is covered by a better way - fine with me!  Even if does not cover
> PREVIOUS-CHUNKS…

Yup.

> Now to a mode with non-widening indentation function: emacs-lisp mode:
> 
> Consider the following code
>      (defun foo ()
>        (+ 1 3))
> 
> I would assume that the indentation of line 2 does not change
> when I narrow to line 2 - but Emacs-25.1.1 now deletes the first 2
> spaces of line 2...  (yes; I also need to update to a newer Emacs)

Try out the widen-less branch!

And also, can we get your help with the manual? It still says:

Examples include
  @dfn{literate programming} source files that combine documentation and
  snippets of source code, Yacc/Bison programs that include snippets of
  plain C code, etc.  To correctly indent the embedded chunks, the primary
  mode needs to delegate the indentation to another mode's indentation
  engine (e.g., call @code{c-indent-defun} for C code or
  @code{python-indent-line} for Python)

I.e., it still mentions C and c-indent-defun (?). But c-indent-defun 
does not work for embedded chunks (yet)!

Can we replace that mentions with JS and js-indent-line, for instance? 
Would that still make sense?