Re: input code

[Aaron Hill]

On 2019-12-12 5:53 pm, Freeman Gilmore wrote:
> Someday I may write a markup up for some accidentals.   This may help 
> me
> understand what I am doing with markup.   For how I just want to know a
> little about how lexer reads the pitch, the octave. accidental and note
> size; and I may not be able to do that any way.   I know nothing about 
> flex
> and just learned it existed today.    Also, I would like to see how the
> markup works around the accidental to place a string in it space.     I
> read some of *Separating input language and formatter in GNU Lilypond, 
> *and
> found it interesting.   Looking for more details.
>
> I do not need to know all this to learn how to write a markup; just 
> like to
> understand a little about how it works around the accidental.      But 
> I do
> need to learn more about scheme and markups.

While it is well beyond the scope of LilyPond itself, I would recommend 
you look for a copy of Principles of Compiler Design [1], the so-called 
"dragon book".

[1]: https://en.wikipedia.org/wiki/Principles_of_Compiler_Design

This book builds from the ground up a fairly complete picture of how 
compilers work.  It is a very technical book, so do not expect to work 
through it quickly.  However if you are truly interested in the 
underlying details of lexical analyzers ("lexers") and parsers, then 
this will be a great resource.

That said, I am uncertain how a better understanding of LilyPond's 
parser would impact matters of accidentals and markup.  To me, it feels 
like you may be digging too deeply here.  While I always support a 
healthy amount of curiosity, it may prove more practical for you to 
focus your attention on higher-level concerns.

When you talk of markup and accidentals, are you interested in 
redesigning the look of an existing accidental or perhaps inventing a 
new one?  To my knowledge, the only intersection with LilyPond's parser 
would involve the naming of notes.  Take a look at 
scm/define-note-names.scm for an example of how the existing languages 
are defined.  This pattern can easily be extended to support other 
alterations.

Of course, that still may be going further than you need to.  If you 
simply need to replace the normal stencil for a specific Accidental, you 
can do the following:

%%%%
\version "2.18.2"

{ \tweak Accidental.horizontal-skylines
    #ly:grob::horizontal-skylines-from-stencil
  \tweak Accidental.stencil #ly:text-interface::print
  \tweak Accidental.text \markup \vcenter \huge \bold "$"
  fis'1 }
%%%%

If such a replacement needs to happen on a global scale, then something 
like the following may be useful:

%%%%
\version "2.18.2"

dollar = \markup \vcenter \huge \bold "$"

\layout { \context { \Voice
  \override Accidental.before-line-breaking = #(lambda (grob)
    (if (eqv? (ly:grob-property grob 'alteration) SHARP)
      (begin (ly:grob-set-property! grob 'horizontal-skylines
               ly:grob::horizontal-skylines-from-stencil)
             (ly:grob-set-property! grob 'text dollar)
             (ly:grob-set-property! grob 'stencil
               ly:text-interface::print))))
} }

{ e'4 fis' bes' gis' | fis'8 gisis' fis'2 r4 }
%%%%


-- Aaron Hill