Re: \unset in paper block

[Simon Albrecht]

Hi Werner,

IIRC these assignments in \paper and \layout and \header blocks are 
functionally equivalent to defining a variable in Scheme like

#(define left-margin 100)

(omitting the unit here for simplicity).

The kind of \unset you’re asking for requires the previous value to have 
been saved onto some stack, which I doubt exists/is accessible here.

Maybe you could work around by calculating left-margin and right-margin:

\paper {
  left-margin = #(/ (- paper-width line-width) 2)
  right-margin = #left-margin
}

Best, Simon

On 02.08.19 10:45, Werner LEMBERG wrote:
> I wonder whether it is possible to use \unset in the paper block.  The
> use-case is lyluatex, which sets `left-margin'; I want to unset this
> value so that lilypond only takes the line width into account to
> automatically center it.
>
> In other words, I would like to have
>
>     % from lyluatex
>     \paper {
>       left-margin = 100\pt
>       line-width = 200\pt
>     }
>
>     ...
>
>     % user code
>     \paper {
>       \unset left-margin
>     }
>
>
>      Werner
>
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