Re: Scheme predicative types

[Aaron Hill]

On 2020-09-18 2:01 am, Martín Rincón Botero wrote:
> [ . . . ] The thing I couldn't adapt from your script
> is the Text part, when the user writes a new tempo with a construction 
> like
> \tempo "Allegro". I suppose I have to somehow put my \once \override
> TextSpanner #'(bound-details right text) in some sort of conditional so
> that when the user puts a text, it displays a text, when it's a 
> metronome,
> a metronome :-), but I couldn't figure out how to adapt what you 
> already
> had.

You could do things with conditionals, but it might make better sense to 
simply use a null markup when an element is not present.  Consider:

%%%%
\version "2.20.0"

#(define (tempo? arg)
   (and (ly:music? arg)
        (not (null? (extract-typed-music arg 'tempo-change-event)))))

tempoTextSpan =
#(define-scheme-function
   (leftmarkup tempo lefthalign righthalign)
   (markup? tempo? number? number?)
   (set! tempo (first (extract-typed-music tempo 'tempo-change-event)))
   (let ((tempo-unit (ly:prob-property tempo 'tempo-unit #f))
         (metronome-count (ly:prob-property tempo 'metronome-count #f))
         (text (ly:prob-property tempo 'text #f))
         )
     (set! tempo-unit
       (if (ly:duration? tempo-unit)
           #{ \markup {
             \note #(ly:duration->string tempo-unit) #UP
               } #}
           #{ \markup \null #} ))
     (set! metronome-count
       (cond ((number-pair? metronome-count)
              #{ \markup { = \concat {
                 #(format #f "~d" (car metronome-count)) -
                 #(format #f "~d" (cdr metronome-count)) } } #})
             ((number? metronome-count)
              #{ \markup { =
                 #(format #f "~d" metronome-count) } #})
             (else #{ \markup \null #})))
     (set! text
       (if (markup? text)
           #{ \markup \abs-fontsize #11 \upright #text #}
           #{ \markup \null #}))
     #{
\once \override TextSpanner.bound-details.left-broken.text = ##f
\once \override TextSpanner.bound-details.right-broken.text = ##f
\once \override TextSpanner #'(bound-details left text) =  \markup 
\halign
#lefthalign \abs-fontsize #11 #leftmarkup
\once \override TextSpanner #'(bound-details right text) = \markup 
\halign
#righthalign \line { #text \abs-fontsize #10 \general-align #Y #DOWN 
#tempo-unit
\abs-fontsize #11 \upright #metronome-count }
     #}))

{
  \tempoTextSpan "accel." \tempo 4 = 80 #LEFT #RIGHT
  c'4\startTextSpan 4 4 4 2 2 d'1\stopTextSpan R1
  \tempoTextSpan "rall." \tempo "Adagio" 4 = 65-70 #LEFT #CENTER
  d'4\startTextSpan 4 4 4 2 2 e'1\stopTextSpan R1
  \tempoTextSpan "rit." \tempo \markup \box "Grave" #LEFT #LEFT
  e'4\startTextSpan 4 4 4 2 2 f'1\stopTextSpan R1 \bar "|."
}
%%%%

The advantage of the above approach is that the final markup is really 
nothing more than a concatenation of the elements.


> I also wasn't successful in adding \once \omit Score.MetronomeMark
> \tempo #tempo-unit = #metronome-count, so that the MIDI can pick up the 
> new
> tempo mark, if a metronome is given (probably because the new tempo is
> converted to a markup and can't be used as a "real" tempo definition
> anymore?).

This is not going to be easy to solve.  You need to know when then 
\stopTextSpan occurs so that the \tempo command applies at that moment.  
However that information is entirely unknown at the time of 
\tempoTextSpan.

I would suggest handling MIDI tempo manually, that way you can issue as 
many \tempo commands as needed to properly simulate the accel, rall, and 
rit instructions.

Otherwise, this whole thing really looks like a job for a custom 
engraver/performer.


-- Aaron Hill

tempo-text-span.cropped.png
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