Re: \override multiple properties?

[Aaron Hill]

On 2020-02-02 2:26 am, David Kastrup wrote:
> Aaron Hill <address@hidden> writes:
>
> > Music functions certainly give you the most flexibility, although
> > there are simple cases where you can use 2.19's \etc keyword as a
> > shorthand to defining the function yourself:
> >
> > %%%%
> > \version "2.19"
> >
> > stemColor = \override Stem.color = \etc
> >
> > { d'8 \stemColor #red e' f' \undo \stemColor ##f g' }
> > %%%%
> >
> > Note the \undo command above is less ideal as one needs to provide a
> > dummy argument to the function.
>
> Why not \undo \stemColor #red here ?  ##f makes no sense.

I did not want to give the impression that the arguments *had* to match. 
 One could just as easily say \undo \stemColor #blue and get the same 
outcome.  \undo only seems to care about which properties are 
\overridden, not the specific values.  So the argument to the music 
function in this case does not matter.  My choice of "false" was purely 
arbitrary, but I guess it was too confusing.

A scenario where the mismatch would make sense is using the function 
several times in a row:

%%%%
{ d \stemColor #red e f \stemColor #blue g a
  \stemColor #green f c \undo \stemColor #'() d }
%%%%

This pattern reinforces that it is not required to \undo each 
application of the function.

If \undo \stemColor #'() proves to be undesirable, nothing stops a user 
just doing the \undo by hand with a manual \revert Stem.color or a 
suitably-defined \noStemColor.


-- Aaron Hill