Dan Eble <d...@faithful.be> writes:
> %{
> NullVoice is unlike a Voice in this respect: trying to move it to a
> different Staff with \change fails with this warning:
>
> Change_iterator::process (): NullVoice = `soprano':
> cannot change `Staff' to `S': not changing to same context type: Staff
>
> Apart from the warning, this is inconvenient. The NullVoice remaining
> in the original staff keeps the original staff alive, demanding manual
> work to make it disappear.
>
> The NullVoice context definition contains both of the following:
>
> \alias "Staff"
> \alias "Voice"
>
> My knowledge of contexts is not extensive, but I suggest that the test
> that \change applies is too simple.
The test is
else if (it.get_outlet ()->is_alias (to_type))
{
// No enclosing context was found because the iterator's immediate
// context is the kind that was sought.
/* We could change the current translator's id, but that would make
errors hard to catch.
last->translator_id_string () = get_change
()->change_to_id_string (); */
result = _f ("not changing to same context type: %s", ly_symbol2string
(to_type).c_str ());
}
and that's indeed crapola. What the test should do is check whether the
current context type would be accepted into the hierarchy of the
proposed parent.
A more rigid test would be to check whether the current context type
would be accepted by the parent directly. But I'm not sure we should
rely on such knowledge as a user interface: there might be good reasons
for moving additional (mostly implicit) layers into the context
hierarchy without having to change the bulk of the music.
--
David Kastrup
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