Re: Wrong glissando for notes with duration longa

[Thomas Morley]

2017-10-03 17:04 GMT+02:00 Thomas Morley <address@hidden>:
> 2017-10-03 13:14 GMT+02:00 David Kastrup <address@hidden>:
>> Thomas Morley <address@hidden> writes:
>>
>>> Hi all,
>>>
>>> in Staff-context glissando is wrongly positioned if between notes with
>>> duration \longa
>>>
>>> \version "2.19.65"
>>> \new Staff { c''\longa \glissando c'' }
>>>
>>> Bug is present for 2.18.2 up to current master.
>>> Worked in 2.16.2
>>
>> Stem for a longa is treated differently I think.  It's part of the
>> notehead or something?
>
> Yep, the longa-"Stem" is part of the note-head.
>
> But why did it work back in 2.16.2?
> I compared glissando-engraver.cc of current master and 2.16.2 and
> found nothing suspicious.
> Ofcourse, I don't really know C++, so I may overlook relevant stuff pretty 
> fast.
>
>> There is the problem of longa stems getting cut
>> off for preview images as well if I remember correctly.  Maybe it's
>> related?
>
> Well, no clue.
>
> Cheers,
>   Harm

Ok, the following code returns different values for 2.16.2 and 2.18.2 ff

{
  \override NoteHead #'after-line-breaking =
    #(lambda (grob)
      (format
        #t
        "\nVersion: ~a: longa-note-head-stencil Y-extent: ~a"
        (lilypond-version)
        (ly:stencil-extent (ly:grob-property grob 'stencil) Y)))
  c'\longa
}

->
Version: 2.16.2: longa-note-head-stencil Y-extent: (-0.550006 . 0.550006)
Version: 2.19.65: longa-note-head-stencil Y-extent: (-0.72 . 3.519982)

It's caused by:

commit f494ef0afc8aed378bd778cd51a294804a8ee5d4
Author: Phil Holmes <address@hidden>
Date:   Mon Jul 29 16:09:29 2013 +0100

    Corrects bounding box for longa (Issue 826)

related is:

commit b27354f5fd0df898310a354c4031c2c701ecebaa
Author: Phil Holmes <address@hidden>
Date:   Mon Jul 29 15:21:46 2013 +0100

    Fixes bounding boxes for breves, improves longas (Issue 3480)

Those patches tackle the skyline-problem, which causes the cut off previews.
So it's no good option to revert them.

Maybe glissando should look at staff-position?


Cheers,
  Harm