Re: Tweaking glissando timing stems

[Thomas Morley]

Am Do., 10. Okt. 2019 um 14:51 Uhr schrieb Leo Correia de Verdier
<address@hidden>:
>
> Dear list!
>
> I'm soon going to start engraving a piece that contains very many glissandi 
> with timing marks (or actually, glissandi with broken bowing and 
> articulations during the way). The snippet in 
> http://lilypond.org/doc/v2.19/Documentation/notation/expressive-marks-as-lines#glissando
>  mentions the stems might need to be repositioned slightly, and I was 
> wondering if this would be possible to automate.
>
> I realize this will be complicated, since it (as I understand it at least) 
> will require changing stem lengths and notehead attachments after the 
> horizontal spacing is calculated (possibly changing pitches too, but the 
> solution I’m imagining would not do that). So I would need to access the 
> calculated positions of the stems and of the endpoints of the glissando. Is 
> that possible? Where and what do I need to read up to accomplish it? Or has 
> someone already done something similar?
>
> I have seen Piaras Hobans code in this thread: 
> https://lists.gnu.org/archive/html/lilypond-user/2014-03/msg00717.html , and 
> it’s interesting for me, but it relies on the stems being equally spaced, 
> which they shouldn’t be in my case.
>
> In the following example I’m looking for a way to calculate up and y-diff in 
> the glissNote function, instead of having to type them in by hand after 
> looking at the resulting score. (The gap between the stems and glissando-line 
> is intentional, the articulation positioning is just not done yet). I have 
> not done it minimal because I wanted to give a glimpse of the point of the 
> notation also.
>
> %%%%%%%%%
>
> \version "2.19.82"
>
> glissNote = #(define-music-function (up y-diff note) (boolean? number? 
> ly:music?)
>                #{ \tweak transparent ##t
>                   \tweak no-ledgers ##t
>                   \tweak stem-attachment #(cons (if up -1 1) y-diff)
>                   #note #} )
>
> glissRest = #(define-music-function (staff-position rest) (number? ly:music?)
>                #{ \tweak Y-offset #staff-position
>                  \tweak layer #-1
>                  \tweak whiteout #10
>                  \parenthesize
>                  #rest #} )
>
> glissSkip = #(define-music-function (music) (ly:music?)
>                #{ \override NoteColumn.glissando-skip = ##t
>                   #music
>                   \revert NoteColumn.glissando-skip #} )
>
> \relative c'' {
>   \time 6/8
>   \set glissandoMap = #'((1 . 1))
>   <a f'>16-> -\tweak layer #-2 \glissando
>   \glissSkip {
>     <a \glissNote ##f #.5 f'>8-. <a \glissNote ##f #0.3 f'>16-. <a \glissNote 
> ##f #.1 f'>8->
>     << {\glissRest #2.5 r8 s4} \\
>        {d,8_-_> <a' \glissNote ##f #-0.4 f'>^.  <a \glissNote ##f #-.6 f'>^.} 
> >>
>   }
>   \time 2/4 <a a'>2--
> }
>
>   %%%%%%%%%%
>
> Thanks a lot!
> /Leo

Hi Leo,

the topic of glissando-stems pops up from time to time.
See older discussions, p.e. here:
https://codereview.appspot.com/4661061/#ps1

Some time ago I started to code something in this regard and took your
request to polish it a bit.
Though, there are still some TODOs:
- Scripts are not always positioned nicely.
- "Inner" beams 'positions can't be affected from Glissando.after-line-breaking.
etc

Furthermore I'm not sure the whole approach fits your needs.
Nevertheless the code is attached, probably you'll find the
calculation for "gliss-stem-intersections" helpful.

Cheers,
  Harm

glissando-stems-03.ly
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glissando-stems-03.png
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