Re: [Lilypond-auto] Issue 3363 in lilypond: Scripts misplaced with cross-staff slurs

[lilypond]

Comment #13 on issue 3363 by address@hidden: Scripts misplaced with  
cross-staff slurs
http://code.google.com/p/lilypond/issues/detail?id=3363

"A big problem we've been having is in defining terms.  The staccato is  
surely not cross-staff, but it depends on cross-staff grobs."

The staccato has been marked 'cross-staff' for a long time by  
ly:script-interface::calc-cross-staff, and the patch Mike wrote for the  
related issue 3327 would mark the staccato 'cross-staff' for other reasons  
that seemed logical at the time.
We were building consensus for a definition "cross-staff: true for objects  
whose placement relative to their parent Staff (or Lyrics, etc.) depends on  
the spacing of staves on the page."

The problem here seems to be that the pure-height of the stem with the  
staccato is miscalculated in stem.cc.  It seems that the second stem's  
height should be calculated relative to the upper staff, but instead the  
third stem's height is calculated as if its note was on the upper staff.   
This problem does not seem to be due to the timing of iterators, but rather  
due to the order and way in which pure-height functions call each other  
during layout.

The various internal flags 'calc_beam' 'pure' 'cross_staff' are trying to  
organize the order of layout decisions, but it is not clear how.  It seems  
to me that this staccato should recuse itself from influencing  
staff-spacing ("sorry, I'm cross-staff, I don't know what space I need just  
yet, I can give you my 'pure-height' as an estimate") but then when  
cross-staff items are being placed, fell free to trigger the final decision  
of the Stem and Beam.

Currently, the staccato asks for only the pure-height of the Stem, and that  
pure-height happens to be a spectacularly bad estimate.

Attachments:
        3363.png  7.5 KB

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