Re: NoteHead X-offset, conflict with ly:grob-relative-coordinate?

[Paul Morris]

Hi David,

On Dec 8, 2012, at 2:03 PM, David Nalesnik <address@hidden> wrote:

> Hi Paul,
> 
> On Sat, Dec 8, 2012 at 12:00 PM, Paul Morris <address@hidden> wrote:
> 
> [snip]
> 
>>> 
>>> In this case you can make use of the 'stem-attachment property:
>>> 
>>> \override NoteHead #'stem-attachment = #'(-0.8 . 0)
>> 
>> Thanks David,  I hadn't thought of using stem-attachment.  It works for 
>> single notes, but unfortunately does not seem to work for repositioning 
>> individual noteheads within chords, which is what I want to do.
>> 
>> For example, the snippet below changes stem-attachment to try to reposition 
>> every other note (colored green as well just for purposes of illustration).  
>> But the notes in a given chord all end up on the same side of the stem 
>> rather than some on one side and some on the other.
>> 
>> (I tried using the extra-offset property, and it worked, but it is applied 
>> after the spacing has been set, and so could lead to collisions or bad 
>> horizontal spacing.  The X-offset property, on the other hand, is applied 
>> before spacing is determined.)
>> 
>> -Paul
>> 
>> \version "2.16.1"
>> 
>> note-counter = 1
>> 
>> CustomNoteHeads =
>> #(lambda (grob)
>>  (let*
>>    (
>>      (notecol (ly:grob-parent grob 0))
>>      (rel-coord (ly:grob-relative-coordinate grob notecol 0))
>>    )
>>    (cond ((=  0 (modulo note-counter 2))
>>      (set! (ly:grob-property grob 'stem-attachment) '(-0.8 . 0))
>>      (set! (ly:grob-property grob 'color) green)
>>    ))
>>    (set! note-counter (+ 1 note-counter))
>> ))
>> 
>> \score {
>>  \new Staff
>>    \with {
>>      \override NoteHead #'before-line-breaking = \CustomNoteHeads
>>    }
>>    {
>>        <c'' e''> <d'' f''> <e'' g'' b''> <f'' a'' c'''>
>>        <c' e'> <d' f'> <e' g' b'> <f' a' c''>
>>        }
>>  \layout { }
>> }
> 
> You posted this question awhile back
> (http://www.mail-archive.com/address@hidden/msg70733.html).  Is
> the solution I provided there no longer working for you?

Yes, your solution still works well (thanks again!).  

I think by using tiny examples that focus on how X-offset is not working, it 
hasn't been clear that I'm working on a more automated approach.  I have 
written some code to automatically apply certain offsets in certain cases[1], 
so I do not have to manually apply them.

I use ly:grob-relative-coordinate to find out which side of the stem a note 
head is on (in order to know which side I need to place the next note head), 
but then for some reason that prevents changing the X-offset of the NoteHead 
from having any effect.

My current approach is to override the NoteHead rather than the NoteColumn as 
in your solution.  I could override the NoteColumn instead (and this might even 
be a better way to go...), but I will still need to determine which side of the 
stem a note is on, so might still need to use ly:grob-relative-coordinate to do 
that and would run into the same problem.

But maybe there is another way to tell which side of the stem a note head is 
on, without using ly:grob-relative-coordinate?

Anyway, thanks again for your help.  

-Paul

[1] Notes that are 3 semitones apart are placed on opposite sides of the stem.  
This is for use with an alternative notation system (http://twinnote.org)


> I needed to change some values to deal with normal note-shapes, but
> this seems to work just fine:
> 
> #(define ((shift offsets) grob)
>  (let ((note-heads (ly:grob-array->list (ly:grob-object grob 'note-heads))))
>    (for-each
>      (lambda (p q) (set! (ly:grob-property p 'X-offset) q))
>      note-heads offsets)))
> 
> displaceHeads =
> #(define-music-function (parser location offsets) (list?)
>  #{
>    \once \override NoteColumn #'before-line-breaking = #(shift offsets)
>  #}
> )
> 
> theMusic = {
>  \displaceHeads #'(0 0 1.3)
>  <c' e' g' >4
> 
>  \displaceHeads #'(0 1.3 1.3)
>  <d' f' a'>
> 
>  \displaceHeads #'(0 1.3 1.3)
>  <d' f' a'>
> 
>  \displaceHeads #'(0 0 1.3)
>  < c' e' g'>
> 
>  \displaceHeads #'(-1.3 -1.3 0)
>  < c'' e'' g''>
> 
>  \displaceHeads #'(-1.3 -1.3 0)
>  < c''' e''' g'''>
> 
>  \displaceHeads #'(0 0 1.3)
>  < c e g>
> 
>  \displaceHeads #'(0 -1.3 0)
>  < c'' e'' g''>
> 
>  \displaceHeads #'(0 0 -1.3)
>  < c'' e'' g''>
> }
> 
> \new Staff {
>  \theMusic
> }
> 
> -David