Re: Redefining stencils in 'tweaks causes grobs to be printed twice

[Neil Puttock]

On 24 November 2010 15:44, Valentin Villenave <address@hidden> wrote:

> % Changing the stencil expression through the
> % 'tweaks alist causes a grob to be printed twice.

It's not really the Tweak_engraver's fault (it's about as rudimentary
it's possible for an engraver to be): it simply acknowledges grobs.

This short scheme engraver will let you know which grobs are being acknowledged:

\layout {
  \context {
    \Voice
    \consists #`((acknowledgers
                  (grob-interface
                   . ,(lambda (trans grob source)
                        (let ((cause (event-cause grob)))
                          (and (ly:stream-event? cause)
                               (pair? (ly:event-property cause 'tweaks))
                               (newline)
                               (display grob)))))))
  }
}

#<Grob DynamicText >
#<Grob DynamicLineSpanner >

When a DynamicLineSpanner is created, it gets its event-cause from the
dynamic grob which triggered its creation:

98 Dynamic_align_engraver::acknowledge_dynamic (Grob_info info)
99 {
100   Stream_event *cause = info.event_cause ();
101   create_line_spanner (cause);

I think the only thing we can do here to prevent the 'tweaks setting
from ending up in the DynamicLineSpanner is to change the event-cause
to the grob instead.

Cheers,
Neil