Re: Default values for grob properties not listed on IR page

[Aaron Hill]

On 2020-02-03 1:50 pm, Daniel Rosen wrote:
> How do I find the default value for a grob property if that property
> isn't listed on the grob's IR page-for instance, the default value for
> Glissando.thickness?

The documentation is in part generated from the define-grobs.scm file, 
where each grob and its default property values are listed.  If no value 
is mentioned, then the grob does not have a default value within its 
definition.

Since the thickness property is not an absolute measure but a relative 
one based on the line thickness of the associated StaffSymbol, it might 
be safe to infer an unset thickness property is the same as a setting of 
1 (as in 100%).  Simple experimentation will prove this theory is 
correct.

However, if you want to dig deeper... Glissando uses the 
ly:line-spanner::print stencil procedure, and a search in the source 
tree will find line-spanner.cc housing its implementation.  
Line_spanner::print delegates the creation of the line stencil to 
Line_interface::line.  The very first thing this function does is 
compute the line thickness.  And as predicted, it obtains the line 
thickness of the staff lines via 
Staff_symbol_referencer::line_thickness, scaling it according to the 
thickness property of the grob with unity as the fallback value.


-- Aaron Hill