Hi David,
as promised I tried out your updated function(s).
Well, you can't call this a complete test suite, but it seems to
work perfectly. Many thanks.
Attached is a version showing that it also/still works with
phrasingSlurs.
I find the warnings very useful. I assume it isn't possible to find
out and display the 'real' place in the source where the problem
comes from? As it is, I only know that there is a changed curve that
doesn't work anymore, but don't know where it is (which can of
course be difficult to pin down in larger pieces.
If it isn't possible to identify the calling line in the source
code, would it be possible to mark the respective curve red? This
way one could easily spot the problematic grob.