Re: Access the first/last line of a markup

[Aaron Hill]

On 2019-03-11 2:49 am, Urs Liska wrote:
> Hi,
>
> returning to my notorious "center-markup-over-measure" issue I was
> pointed to yet another issue: vertical alignment when the last line
> contains descenders or the first line does not contain ascenders.
>
> Since I am manually placing the markups (given as arguments) using
> ly:stencil-combine-at-edge above and below the staff I can't use
> staff-padding for padding against the baseline. So what I *think* I
> need is retrieving the first and last lines of the markup (which would
> be the same if it's a single line markup) and analyze that. However,
> that seems difficult. I checked with \displayMusic -\markup ... to see
> if I could retrieve stuff from that expression, and although it seems
> complicated-but-feasible for most cases it would fail with e.g.
> \wordwrap because there's no notion of the resutling lines yet.
>
> I can also access the resulting stencils after using
> grob-interpret-markup. However, I have no idea if/how it is possible
> to get to the information I need (either a "sub-stencil" for the
> first/last line or some information through the stencil-extent).
>
> Do you think there's any automatic solution I can pursue - or will I
> be left manually adjusting the padding on a case-by-case basis?
>
> Thanks for any suggestions

A *hack* using transparent glyphs to force alignment:

%%%%
\version "2.19.82"

#(define-markup-command (ascender-descender-placeholder layout props) ()
  (let* ((sten (interpret-markup layout props #{
            \markup \transparent \overlay { d p } #} ))
         (yex (ly:stencil-extent sten Y)))
    (ly:make-stencil (ly:stencil-expr sten) empty-interval yex)))

#(define-markup-command (apply-hack layout props arg) (markup?)
  (interpret-markup layout props #{ \markup \concat {
    \ascender-descender-placeholder $arg } #} ))

bad = -\tweak color #(rgb-color 0.9 0 0) \etc
good = -\tweak color #(rgb-color 0 0.8 0) \etc

{ \time 3/4
  f'4\bad^"d" _"d" f'4\bad^"x" \bad_"x" f'4^"p" \bad_"p"
  f'4\good^\markup \apply-hack "d" _\markup \apply-hack "d"
  f'4\good^\markup \apply-hack "x" \good_\markup \apply-hack "x"
  f'4^\markup \apply-hack "p" \good_\markup \apply-hack "p"
  f'2.^\markup \override #'(line-width . 35) \wordwrap \apply-hack
    { raucous racoon commune consume cocoa-cream macaroons }
  _\markup \override #'(line-width . 35) \wordwrap \apply-hack
    { museum owner unaware wax moose wears mauve mascara }
}
%%%%

This presumes that "d" and "p" are suitable exemplars of ascenders and 
descenders in the font being used.

If you want to visualize what is happening, replace "\transparent" in 
the markup command definition with something like "\with-color #blue".


-- Aaron Hill

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