Re: alternatives not taken into account in automatic accidentals

[Dan Eble]

On 9 Aug 2009, at 15:46, Trevor Daniels wrote:

> Mark Polesky wrote Sunday, August 09, 2009 7:31 PM
> > Well, that's not a functional barline, it's just printed.

Mark,

I appreciate your reply.  Applying this statement to certain other  
figures (e.g. key signature or clef) would indicate a bug.  Does a non- 
functional bar line differ from those?

> > Note that manual bar lines are purely visual. They do not affect
> > any of the properties that a normal bar line would affect, such as
> > measure numbers, accidentals, line breaks, etc.

I thought that all bar lines affect line breaking, even invisible ones.

> > They do not affect
> > the calculation and placement of subsequent automatic bar lines.
> > When a manual bar line is placed where a normal bar line already
> > exists, the effects of the original bar line are not altered.
> >
> > If anyone likes this change, feel free to make it;
>
> Thanks Mark - pushed.

Should the manual explain that a feature doesn't work as expected, but  
stop short of citing a work around?

I am aware of "!" which could be used in this situation, but is there  
anything better?  Is there something I could wrap in a variable to  
insert a bar line and reset the accidental state as if it were a new  
measure?

stanzaBar = { \bar "||" ... }

Even that would not necessarily satisfy me, because I routinely use  
the following function for line breaking in hymn tunes, and I would  
want the accidental behavior to depend on the visibility of the bar  
line (or presence of a line break, even if the bar line is invisible).

% At a place where there would normally be a bar line, print "|".
% At a mid-measure line break, print "||".
% Otherwise, do not print a bar.
meterBar =
{
  \bar "meter"
  \applyOutput #'Timing #handle-meter-bar-line
}

In case it is relevant, here is the applied function. (I know it's not  
perfect. For one thing, the double bar lines still consume space when  
they are invisible.)

#(define (handle-meter-bar-line grob orig-ctx context)
   (let ((grob-name (cdr (assoc 'name (ly:grob-property grob 'meta)))))
     (if (and (equal? grob-name 'BarLine)
              (equal? (ly:grob-property grob 'glyph) "meter"))
         (let* ((measurePos (ly:context-property context 'measurePosition))
                (measureLen (ly:context-property context 'measureLength))
                (mid-measure (and (ly:moment<? ZERO-MOMENT measurePos)
                                  (ly:moment<? measurePos measureLen))))
           (if mid-measure
               (begin
                 (set! (ly:grob-property grob 'break-visibility) #(#t #f #f))
                 (set! (ly:grob-property grob 'glyph) "||"))
               (set! (ly:grob-property grob 'glyph) "|"))))))

Thanks,
--
Dan