Re: A barline half length long

[Robin Bannister]

Jiri Zurek wrote: 
> What is wrong with my syntax, please? 

ly:bar-line::calc-bar-size needs a parameter.  

If you get used to writing things like 
>    \override Staff.BarLine #'bar-size = #ly:bar-line::calc-bar-size
you think that is all you ever need to say. 
But the functions for grob properties like #'bar-size all need to be 
told which grob to work with; this is done here implicitly.  

To use this function anywhere else you have to say 
>    (ly:bar-line::calc-bar-size grob)
i.e. you have to explicitly give it a grob as a parameter. 

The function you are making should in turn 
be written to expect a grob as a parameter 
and it is this info that you can relay to the default function. 

>     \override Staff.BarLine #'bar-size = 
>       #(lambda (grob) (* (ly:bar-line::calc-bar-size grob) 0.5))


Cheers,
Robin