Hi,
Attached is a version of the regression test
scheme-text-spanner.ly which shows that problems arise when the engraver is used simultaneously in different contexts. I've smply created a StaffGroup in which both Staff contexts contain the same material as in the original reg test.
You can see that the first text spanner does not appear in the lower Staff.
The problem appears to be the use of constants in the engraver definition. All spanners appear when I replace the variable definition
(event-drul '(() . ()))
with
(cons (list) (list))
and later (line 157):
(set! event-drul '(() . ()))
with
(set! event-drul (cons (list) (list)))
I'd like to fix the problem, but I have several questions:
(1) Would (cons '() '()) be acceptable? The problem is fixed, but I wonder about the
usage of the literal _expression_ '() since there are multiple usages of set-car! and set-cdr! applied to the variable.
(2) Should '() in all variable definitions, set! expressions be changed to (list) ?
Thanks,
David
scheme-text-spanner-two-staffs.ly