Re: Why does -dbackend=svg -dcrop remove system-system-spacing?

[David Wright]

On Wed 06 Jan 2021 at 11:34:24 (-0500), Trevor Bača wrote:
> On Tue, Jan 5, 2021 at 11:31 PM David Wright wrote:
> > On Tue 05 Jan 2021 at 19:05:30 (-0500), Trevor Bača wrote:
> > > I love the functionality for cropped SVGs! (Added back in 2019, or around
> > > then?)
> > >
> > > Question: it appears that cropped multisystem SVGs remove all whitespace
> > > between systems. Is this supposed to happen?
> >
> > I think that removing all the margins is the functionality "crop" is
> > supposed to add to LP. To generate the equivalent cropped and packed
> > image without this facility would be quite tedious to do (unless
> > someone has a trick for doing it?).
> >
> > > %%% BEGIN %%%
> > > […]
> > > %%% END %%%
> > >
> > > Called with ...
> > >    lilypond -dbackend=svg -dcrop test.ly
> > > ... produces test.cropped.svg as attached here.
> > >
> > > Screenshot:
> > > […]
> > >
> > > Seems like cropping should be around the edges of the image (rather than
> > > between systems)?
> >
> > If you just want to crop the whole page image, you can do that easily
> > at the end of a normal run with the usual utilities. If you require
> > LP to set the entire score on a single page, just use a very long
> > custom page (as in NR §4.1.2: width, then length).
> 
> I'm sorry; I don't understand.
> 
> What I want Lily to do: remove whitespace from the *edges* of an SVG.

As I said, you run LP as normal, and then trim to taste. So, taking
your example, I ran it with
$ lilypond-2.21.80-1.linux-64/bin/lilypond --svg -dno-point-and-click Bača.ly
and then edited the first line of Bača.svg, resulting in Bača-trimmed.svg.
The end of the first line is modified from
 width="210.00mm" height="297.00mm" viewBox="0 0 119.5016 169.0094">
to
 width="192.00mm" height="297.00mm" viewBox="4.5 0 109.5016 169.0094">
which I did by inspection. As you use SVG files in your workflow,
I assume you can carry this out more easily and precisely¹ with some
particular tool. (I'm PDF-centric myself.) I only considered X because
I was inspecting the file on a landscape screen (and you didn't remove
the tagline anyway).

> What Lily actually does when -dcrop is set: removes whitespace from the
> edges *and from between all systems* of an SVG.

That's right, so that your file contains all the information,
unencumbered by margins, ready for some sort of further processing.
Obviously, I don't know what that will be in your case.

It reminds me of those PNG files that you find in browsers' cache,
which have a strip or grid of little images that are used internally,
either as a toolbar, or displayed sequentially like a movie.

> So my question is: is Lily supposed to remove whitespace from *between*
> systems when -d[c]rop is set?

AIUI yes. But this is policy: I await pronouncements from higher-ups.

¹ I believe the modifications need to be kept proportional, in order
  to preserve the aspect ratio.

Cheers,
David.

txtI_Z5r68B60.txt
Description: Text document

binzDjbNHeztJ.bin
Description: image/svg

binUtjPtWMfni.bin
Description: image/svg