Re: Code folding in Emacs.

[Thibaut Verron <thibaut.verron@gmail.com>]

On 14/10/2021 07:47, David Masterson wrote:
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
>> I just found the following code snippet from here [1] for code folding in Emacs:
>>
>>
>> (global-set-key (kbd "<C-f5>") 'set-selective-display-dlw)
>>
>> (defun set-selective-display-dlw (&optional level)
>>    "Fold text indented same of more than the cursor.
>> If level is set, set the indent level to LEVEL.
>> If 'selective-display' is already set to LEVEL, clicking
>> F5 again will unset 'selective-display' by setting it to 0."
>>    (interactive "P")
>>    (if (eq selective-display (1+ (current-column)))
>>        (set-selective-display 0)
>>      (set-selective-display (or level (1+ (current-column))))))
>>
>> The above code trick seems very simple, but it works for many
>> languages. So I recommend it here.
>>
>> [1] https://discourse.julialang.org/t/code-folding-for-emacs/41421/3
> See Origami.

Which is, sadly, now unmaintained. Most notably, it lacks documentation 
on how to specify a parser, all one can do is guess based on the 
existing ones. There are forks attempting to clear those gaps, but afaik 
it's not there yet -- and they face distribution issues, with package 
repositories refusing to keep several packages with the same name.

It would be great if Emacs had something like origami built-in, aka a 
folding framework with a more flexible way to specify folding points 
than regexps (hideshow) or headers (outline). Essentially something like 
smie, but for folding: define functions to test if we are at an opener, 
at a closer, to find the closer for an opener, to find the subnodes if 
applicable, and let the package merge it all, construct the folding tree 
and take care of the folding.