fish-shell/doc_src/cmds/fish_mode_prompt.rst
Johannes Altmanninger c0d1e41313 docs synopsis: add HTML highlighing and automate manpage markup
Recent synopsis changes move from literal code blocks to
[RST line blocks].  This does not translate well to HTML: it's not
rendered in monospace, so aligment is lost.  Additionally, we don't
get syntax highlighting in HTML, which adds differences to our code
samples which are highlighted.

We hard-wrap synopsis lines (like code blocks). To align continuation
lines in manpages we need [backslashes in weird places]. Combined with
the **, *, and `` markup, it's a bit hard to get the alignment right.

Fix these by moving synopsis sources back to code blocks and compute
HTML syntax highlighting and manpage markup with a custom Sphinx
extension.

The new Pygments lexer can tokenize a synopsis and assign the various
highlighting roles, which closely matches fish's syntax highlighing:
- command/keyword (dark blue)
- parameter (light blue)
- operator like and/or/not/&&/|| (cyan)
- grammar metacharacter (black)

For manpage output, we don't project the fish syntax highlighting
but follow the markup convention in GNU's man(1):

	bold text          type exactly as shown.
	italic text        replace with appropriate argument.

To make it easy to separate these two automatically, formalize that
(italic) placeholders must be uppercase; while all lowercase text is
interpreted literally (so rendered bold).
This makes manpages more consistent, see string-join(1) and and(1).

Implementation notes:
Since we want manpage formatting but Sphinx's Pygments highlighing
plugin does not support manpage output, add our custom "synopsis"
directive.  This directive parses differently when manpage output is
specified. This means that the HTML and manpage build processes must
not share a cache, because the parsed doctrees are cached.  Work around
this by using separate cache locations for build targets "sphinx-docs"
(which creates HTML) and "sphinx-manpages".  A better solution would
be to only override Sphinx's ManualPageBuilder but that would take a
bit more code (ideally we could override ManualPageWriter but Sphinx
4.3.2 doesn't really support that).

---

Alternative solution: stick with line blocks but use roles like
:command: or :option: (or custom ones). While this would make it
possible to produce HTML that is consistent with code blocks (by adding
a bit of CSS), the source would look uglier and is harder to maintain.
(Let's say we want to add custom formatting to the [|] metacharacters
in HTML.  This is much easier with the proposed patch.)

---

[RST line blocks]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#line-blocks
[backslashes in weird places]: https://github.com/fish-shell/fish-shell/pull/8626#discussion_r782837750
2022-01-19 22:56:41 +08:00

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1.8 KiB
ReStructuredText

.. _cmd-fish_mode_prompt:
fish_mode_prompt - define the appearance of the mode indicator
==============================================================
Synopsis
--------
.. synopsis::
fish_mode_prompt
::
function fish_mode_prompt
echo -n "$fish_bind_mode "
end
Description
-----------
The ``fish_mode_prompt`` function outputs the mode indicator for use in vi-mode.
The default ``fish_mode_prompt`` function will output indicators about the current Vi editor mode displayed to the left of the regular prompt. Define your own function to customize the appearance of the mode indicator. The ``$fish_bind_mode variable`` can be used to determine the current mode. It will be one of ``default``, ``insert``, ``replace_one``, or ``visual``.
You can also define an empty ``fish_mode_prompt`` function to remove the Vi mode indicators::
function fish_mode_prompt; end
funcsave fish_mode_prompt
``fish_mode_prompt`` will be executed when the vi mode changes. If it produces any output, it is displayed and used. If it does not, the other prompt functions (:ref:`fish_prompt <cmd-fish_prompt>` and :ref:`fish_right_prompt <cmd-fish_right_prompt>`) will be executed as well in case they contain a mode display.
Example
-------
::
function fish_mode_prompt
switch $fish_bind_mode
case default
set_color --bold red
echo 'N'
case insert
set_color --bold green
echo 'I'
case replace_one
set_color --bold green
echo 'R'
case visual
set_color --bold brmagenta
echo 'V'
case '*'
set_color --bold red
echo '?'
end
set_color normal
end
Outputting multiple lines is not supported in ``fish_mode_prompt``.