Re: Descenders affecting line height calculation for lyrics in columns?

[Aaron Hill]

On 2022-01-19 11:41 pm, Bernhard Fisseni wrote:
> [ . . . ] In the
> song, there are some lines with descenders (p, g, q going below the
> baseline).  I show the effect here by inserting "q" in the left
> column. Lilypond seems to calculate the "real" line height of the
> writing, not some kind of nominal text line height, so that a line
> with descenders is higher than a line without. [ . . . ]
> Is this the expected behaviour?

No (but kind of yes).

Firstly, \column and \line work properly, respecting baseline-skip and 
word-space:

%%%%
\markup
  \override #'(baseline-skip . 4)
  \override #'(word-space . 0.5)
  \box \line {
    \box \line \box {
      \column \box { q q q }
      \column \box { x x x }
      \column \box { b b b }
    }
    \box \column \box {
      \line \box { q x b }
      \line \box { q x b }
      \line \box { q x b }
    }
  }
%%%%

In your code, you have nested \columns within \columns, which does not 
work the same as a singular \column would.  \column attempts to align 
the contains markups by their respective baselines.  The baseline of a 
\column ends up being the baseline of its first markup.  See:

%%%%
\markup \concat {
  \column { q x b }
  "q x b"
}
%%%%

Your inner \columns involve two lines of text which makes them much 
taller than the default baseline-skip would permit.  \column avoids 
overlapping ink, so it moves markups further down based on their actual 
extents.  Descenders, then, could definitely result in a taller stencil.

There are likely many ways to tackle this.  (Other folks on the list 
might chime in with their preferred method.)  The simplest option I see 
is manually adjusting the baseline-skip between the inner and outer 
\columns:

%%%%
\markup {
  \fill-line {
    \hspace #1
    \override #'(baseline-skip . 7)
    \column {
      \line { \bold "2."
        \override #'(baseline-skip . 3)
        \column {
          "q This is verse two."
          "q It has two lines."
        }
      }
      \line { \bold "3."
        \override #'(baseline-skip . 3)
        \column {
          "q This is verse three."
          "q It has two lines."
        }
      }
    }
    \hspace #1
    \override #'(baseline-skip . 7)
    \column {
      \line { \bold "4."
        \override #'(baseline-skip . 3)
        \column {
          "This is verse four."
          "It has two lines."
        }
      }
      \line { \bold "5."
        \override #'(baseline-skip . 3)
        \column {
          "This is verse five."
          "It has two lines."
        }
      }
    }
    \hspace #1
  }
}
%%%%

The math above is that two lines at baseline-skip of three plus an extra 
staff space means an effective baseline-skip of seven.


> Secondly, the stanza commands seem to call for defining a two-argument
> macro like \columnstanza, but I got lost in the documentation on the
> different ways and the different types of objects.

Perhaps something like this:

%%%%
#(define-markup-command
  (my-stanza layout props number lines)
  (markup? markup-list?)
  (interpret-markup layout props #{
    \markup \line {
      \bold #number
      \override #'(baseline-skip . 3)
      \column #lines
    }
  #}))

\markup {
  \fill-line {
    \hspace #1
    \override #'(baseline-skip . 7)
    \column {
      \my-stanza "2." {
        "q This is verse two."
        "q It has two lines."
      }
      \my-stanza "3." {
        "q This is verse three."
        "q It has two lines."
      }
    }
    \hspace #1
    \override #'(baseline-skip . 7)
    \column {
      \my-stanza "4." {
        "This is verse four."
        "It has two lines."
      }
      \my-stanza "5." {
        "This is verse five."
        "It has two lines."
      }
    }
    \hspace #1
  }
}
%%%%


-- Aaron Hill