"Trevor Daniels" <t.dani...@treda.co.uk> writes:
> David Kastrup wrote Saturday, October 13, 2012 1:01 AM
>>
>> In ly/music-functions-init.ly I see code like the following:
>>
>> crossStaff =
>> #(define-music-function (parser location notes) (ly:music?)
>> (_i "Create cross-staff stems")
>> #{
>> \override Stem #'cross-staff = #cross-staff-connect
>> \override Flag #'style = #'no-flag
>> $notes
>> \revert Stem #'cross-staff
>> \revert Flag #'style
>> #})
>>
>> There is a problem with that: in terms of stack operations, \override
>> and \revert are not opposing pairs: \override is pop+push (so that
>> multiple overrides in a row don't accrue cruft), \revert is pop. So the
>> net effect of this sequence is "pop", while it should be neutral.
>
> What would be the effect of this? The implication is that something
> goes wrong, but bugs in this area have never been reported, AFAIK.
>
> I understand stacks, pop and push, but I'm clearly missing something
> here. Perhaps it's due to my unfamiliarity with the structure of the
> stack(s).
Each context has its own stack, so popping too much only makes a
difference if the stack actually was non-empty to start with.
Check out
\new Staff \with { autoBeaming = ##f }
{ \override Flag #'style = #'mensural c8 c \crossStaff c c c c c c }
After the crossStaff, the flag style has reverted to normal again rather
than mensural.
--
David Kastrup
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