Re: visualize-padding

[Aaron Hill]

On 2020-01-22 7:26 am, Paolo Prete wrote:
> The problem is associated with:
>
> https://lists.gnu.org/archive/html/lilypond-user/2020-01/msg00467.html
>
> Sorry if I insist again with this: is there a fix (or work-around) for 
> it?
> The function is ***very*** useful, You can really see what happens with 
> the
> discussed property, and you can really use therefore a ruler for fine
> tuning .

I started to take a look at this, but got side-tracked.  My work 
schedule is erratic at the best of days, plus I have been trying to get 
over a cold; so I am uncertain I will be able to dig in more deeply.

My initial impression is that accessing certain properties out of 
sequence can cause problems.  The NR includes a brief section on 
unpure-pure-containers mentioning how one must be careful when accessing 
properties relating to Y-axis concerns.  Beam in particular is called 
out as something to avoid touching, and I imagine that TupletBracket 
cares about Beam.  I also know there is internal caching of computed 
results at various stages of processing, so perhaps an unintended 
side-effect of these things is that it all goes awry when the normal 
pattern of access is interrupted.  And since much of this work is done 
at the C++ level, it becomes difficult for Scheme code to influence 
effectively.

All of my helper functions for overlaying stencils are really just 
hacks; they might work for some grobs and fail for others.  And when 
things stop working, you just have to look for another hack.  For 
instance, if messing with the stencil for TupletBracket is not working, 
perhaps you could use another grob to host the debug annotation.  
TupletNumber might be more accepting of modification, which you should 
be able to get via (ly:grob-object bracket-grob 'number).  But be aware 
that you might have to do things the other way around, working from 
TupletNumber.after-line-breaking which would mean getting the bracket 
from the number: (ly:grob-object number-grob 'bracket).


-- Aaron Hill