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

Attachment: scheme-text-spanner-two-staffs.ly
Description: Binary data

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