Re: Issue 3918: Add \alternatingTimeSignatures (issue 97110045)

[David Kastrup]

Paul Morris <address@hidden> writes:

> David Kastrup wrote
>> There is not one "code that handles overriding stencils".  Overrides are
>> a general mechanism.  So we are talking about the code _interpreting_
>> stencils.  This code will tend to be some get_property ("stencil") call.
>> There are a lot of those from a lot of different engravers.
>> 
>> Making this consistently workable would require tampering with a lot of
>> call sites.
>
> Ah, ok, I get it now. Thanks for the explanation.  (So if someone tries to
> override a stencil with a markup, the markup is actually set as the grob's
> stencil property at that point, and it's not until an engraver tries to
> interpret it that an error is given, because a stencil is expected and not a
> markup.)

Overrides are type-checked early, so you'd get the error early.
Callbacks are considered valid when type-checking however, so a callback
returning something unfitting will lead to a late error message
(hopefully).

-- 
David Kastrup