Re: Forced double accidental

[Paul Morris]

On Dec 13, 2012, at 6:50 AM, Thomas Morley <address@hidden> wrote:

> 2012/12/13 Paul Morris <address@hidden>:
> [...]
>> I found a good way to break it.  If you try it with whole notes the stem's 
>> X-extent is (+inf.0 . -inf.0) and you get this error: "programming error: 
>> Infinity or NaN encountered"
> 
> Likely, a check for
> grob::is-live?
> should be helpful.

Thanks, I gave that a try tonight, but 
grob:is-live? 
returned #t for the stem grob for whole notes.  It appears their stem is live 
but with a width of negative infinity.


>> So I tried to work around this with the code below, but when I uploaded it 
>> to the LSR something went wrong, no error messages or anything but the 
>> preview page was just blank.[1]  I put the previous version back but it was 
>> still blank, so I must have broken something.
>> 
>> [1] http://lsr.dsi.unimi.it/LSR/Item?u=1&id=861
> 
> Today I can't see any problems. Sometimes the LSR seems to need a
> little more time.

I came up with the following using "inf?" to check for an infinite value and 
use 0 if so.  It works on my machine.  Blank screen after uploading to the LSR 
again, but maybe it is just taking time to update?  So I left it up this time. 

http://lsr.dsi.unimi.it/LSR/Item?u=1&id=862

Regards,
-Paul


#(define ((shift offsets) grob)
(let* ((note-heads (ly:grob-array->list (ly:grob-object grob 'note-heads)))
       (stem (ly:grob-object grob 'stem))
       (stem-ext (ly:grob-property stem 'X-extent))
       (half-stem-ext (if (inf? (cdr stem-ext)) 0 (cdr stem-ext))))
  (display stem-ext) (newline)
  (for-each
    (lambda (p q)
      (let ((head-ext (interval-length (ly:grob-property p 'X-extent))))
        (ly:grob-translate-axis! p (* q (- head-ext half-stem-ext)) X)))
    note-heads offsets)))


displaceHeads =
#(define-music-function (parser location offsets) (list?)
#{
  \once \override NoteColumn #'before-line-breaking = #(shift offsets)
#}
)

%%%%%%%% EXAMPLE %%%%%%%%

theMusic = \relative c' {
 e4

 \displaceHeads #'(1) 
 \once \override Staff.NoteHead #'stem-attachment = #'(1.09 . -0.34)
 e

 d'

 \displaceHeads #'(-1) 
 \once \override Staff.NoteHead #'stem-attachment = #'(1.11 . -0.34)
 d

 <c, e>

 \displaceHeads #'(0 1) <c e>

 <e'g>

 \displaceHeads #'(-1 0) <e g>

 <f, a c>

 \displaceHeads #'(1 0 0) 
 \once \override Staff.Stem #'stem-begin-position = #-3.3 
 <f a c>

 <c' e g>

 \displaceHeads #'(-1 -1 0) <c e g>

 <ees f a c>

 \displaceHeads #'(0 -1 0 0) <ees f a c>

 <ees, f a c>

 \displaceHeads #'(1 0 0 0) 
 \once \override Staff.Stem #'stem-begin-position = #-4.3 
 <ees f a c>
}

\new Staff {
 \theMusic
}