[luatex] adjusting `hyphenate` callback for single function

[Werner LEMBERG]

Folks,


being a complete newbie who wants to experiment a little with LuaTeX,
I ask for some help to improve `texinfo.tex` for generating the
documentation of LilyPond.

Within the `@code` macro, I want to do two things.

(a) Hook into the `hyphenate` callback to insert hyphenation
    discretionaries based on some constraints.

(b) Hook into `pre_linebreak_filter` (or rather `contribute_filter`?)
    to inhibit line breaks before/after a single character if
    preceded/followed by a (single) space.  In other words, this space
    should be replaced with `@tie{}`.

How can I do that?  I guess I have to do the following.

(1) Write hooks `code_hyphenate` and `code_pre_linebreak_filter`.

(2) At the beginning of `@code`, append the `code_hyphenate` hook.

(3) At the end of `@code`, remove the `code_hyphenate` hook.

Assuming this is the correct approach I have some questions.

* It's not written explicitly in the LuaTeX manual but I guess that
  the argument to the `hyphenate` hook is a single word.

* I couldn't find information in the manual about the order of hooks.
  It seems that I have to save the original hook by myself and call it
  before/after, right?

* Is there already some code available that I could use as a starting
  point?


    Werner