Folding by levels (like a vim)

Question

How can I implement folding behaviour like a vim? In vim I has this code:

set foldenable          " enable folding
set foldmethod=indent   " fold sections by indentation
set foldcolumn=1        " display folding column
set foldlevel=0         " first folding level is open

I need close all fold levels 'level by level'. When I unfold some 'folding level', included fold levels must be closed.

Maybe I can implement this with HideShow plugin or another variant?

Answer 1

There are a lot of different implementations of folding for emacs. Some are specific to a particular programming language or syntax, others are more generic. Of the generic ones, it sounds like yafolding is exactly what you're asking for. I tried it out, and while it feels somewhat slow, it does work.

Another I tried is called origami, and I liked the results a lot better. It goes by indentation if that's all it knows about your file, but if it's one of a dozen or so supported languages then it uses syntax markers like curly braces to do the folding. It was also much quicker to fold an entire file. On the other hand, it apparently comes with no pre-configured keybindings, so to use it you'll have to set those up yourself (it does provide a keymap to add them to).

There are a number of others you might check out; run M-x list-packages and then search for "fold".

Many people also use outline-minor-mode to do folding and organization of code. It works off of embedded headline markers in comments rather than the structure of the code, but that's handy for many things as well. It also has the advantage of being built-in.

Answer 2

I recommend trying outline-indent.el, an Emacs package that offers a minor mode for code folding and outlining based on indentation levels. The outline-indent.el package leverages the built-in outline-minor-mode, which is maintained by the Emacs developers and has less chance of being abandoned like origami.el.

The built-in outline-minor-mode, which outline-indent.el is based on, enables utilizing functions such as folding and moving indented blocks up or down, significantly enhancing the editing experience for indented text.

(The origami.el package is no longer actively maintained and has known bugs that can affect its reliability and performance.)