Re: Autobeaming

[Joe Neeman]

On Tue, 2009-12-29 at 15:48 -0700, Carl Sorensen wrote:
> On 12/29/09 2:14 PM, "Joe Neeman" <address@hidden> wrote:
> > I much prefer leaving it as a context property. Grob properties of the
> > TimeSignature grob should be things that affect the appearance of the
> > TimeSignature grob, not the creation of beams.
> > 
> > If you were to use a context property, why would you need the special
> > command \overrideTimeSignatureSettings to change it? That is, why
> > couldn't people just use \set? If it helps, we could extend \set to
> > allow nested properties (the same thing that
> > http://codereview.appspot.com/182042/show does for paper-block
> > variables).
> 
> Because I want to be able to \revert, not just \unset.  I want to be able to
> change to some custom behavior, then go back to the default behavior without
> having to know what the default behavior is in detail.
> 
> IIUC, \override is roughly equivalent to \set value (cons new-value
> old-value).  I want to have that functionality, so that old-value is still
> available for a \revert.
> 
>  But certainly nested properties would help in making this change.
> 
> Why have we decided that context properties can only be \set, and grob
> properties can only be \overridden?  In version 2.0 we had two kinds of
> properties, layout properties and translation properties.  I think that
> translation properties in those days are what we now call context
> properties, and that what were then called layout properties are now called
> grob properties.  Also, in version 2.0 we could either \set (destructively
> assign a value) or \override (push a value on the stack).  In fact,
> according to the documentation, \override and \revert were the equivalent of
> push and pop.

I don't know the reason; I don't think I was even using LilyPond back in
the 2.0 days.  But it does sound perfectly reasonable to have context
(or translation, if you prefer) properties that can be overridden and
reverted.  I can have a look at adding this (if you wouldn't rather have
a go yourself).

> If we could allow nested context properties, and get \set to do the
> equivalent of \override, and \unset do the equivalent of \revert, then I'd
> be all set to do TimeSignatureDefinitions as a context property.

\unset is actually important for internally-used context properties.  So
we would have to _add_ a revert function instead of just changing the
behaviour of \unset.

Cheers,
Joe