Re: Make Grob::name accessible to Scheme (issue 203090043 by address@hidden)

[Paul Morris]

David Nalesnik-2 wrote
> On 2015/02/16 07:56:10, dak wrote:
>> "Needing to determine the name of a grob" should actually rarely be
>> necessary:
>> the pervasive information connected to the functionality of a grob is
>> rather its
>> interfaces.  That's the usual criterion for deciding whether to deal with
>> a
>> particular grob.  Relaying on the name makes it harder to create variants
>> of
>> existing grobs.
> 
> I see what you are saying.  I'm aware that grob recognition takes place
> through interfaces, and that the user could use grob::has-interface.

Hmmm... would it be a good idea to also have a ly:grob-has-interface scheme
function?  That would make it just as easy to use interfaces for identifying
grobs as it would be to use grob names (with ly:grob-name).  And that would
help encourage the use of the "interfaces" approach.

Looks like currently one would have to use the following and then check the
list for a particular interface:

Function: ly:grob-interfaces grob
    Return the interfaces list of grob grob. 

Cheers,
-Paul

P.S. FWIW, here's one marginal use case.  I've been using grob names to
differentiate key signature grobs from key cancellation grobs, within a
custom engraver that acknowledges the key-signature-interface.  I could add
a second engraver for the key-cancellation-interface to deal with key
cancellation grobs, but since both key signatures and key cancellations have
the key-signature-interface, I would still need a way to differentiate
between them in the engraver that acknowledges the key-signature-interface. 
Either ly:grob-name or (better yet) ly:grob-has-interface would be helpful
to have for this kind of thing.



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