Re: slur corehack

[David Wright]

On Tue 24 May 2016 at 17:15:59 (-0700), Flaming Hakama by Elaine wrote:
> > > It seems like the state of the art is to tweak each slur individually
> > > using \shape to specify displacements from current control points.
> >
> > \shape is a very nice tool.
> > This advantage inherits a disadvantage as well: other possibilities to
> > tweak a slur are more and more forgotten.
> >
> 
> I am not suggesting that anything should happen to the \shape command.
> For things like the S-shaped curves, this is necessary.
> 
> I'm just observing that \shape only affects one curve at a time,
> and is not ideal for affecting global curve styles.
> 
> And I suspect that most people would get better mileage out of
> fist setting good default values, then tweaking individual curves.
> 
> In fact, \shape should play nice with setting different defaults, no?
> I would assume that \shape tweaks would be relative any new "house" styles
> applied.
> 
> 
> 
> > > But on the other hand, is there a code-based way to do this?
> > > (If so, this ought to go in the docs tout suite!)
> >
> > The values in define-grobs.scm are the default-values for the
> > properties of the grob.
> > Each one can be changed using tweak or override.
> >
> > /tweak and /override are documented.
> >
> 
> I would say that, on the contrary, \tweak and \override are not documented.
> At least, not well enough to be useful for use with slurs.
> 
> In the case of slurs, searching for "lilypond slurs tweak", the
> documentation that comes up describes how to tweak slurs relative to text,
> not how to tweak the actual curves themselves.
> http://lilypond.org/doc/v2.19/Documentation/learning/outside_002dstaff-objects

I typed that string into google and the top hit was

http://lilypond.org/doc/v2.19/Documentation/notation/modifying-shapes

which is the page you've quoted from in this thread.

The other hits on the first page were
lilypond.org/doc/v2.18/Documentation/snippets/tweaks-and-overrides
lilypondblog.org/2013/11/engraving-challenges-slurs-and-ties/
lsr.di.unimi.it/LSR/Search?q=slur
dvoi.com/files/lilypond/2.16.2/Documentation/notation/modifying-shapes.nl.html
https://github.com/noteflakes/lyp-super-shape-me
etc. (no mention of Learning).

The inefficiency or inconsistency of search engines is hardly a
criticism that can be aimed at LP or its docs.

[...]

> Rather, I am suggesting that the approach of changing all slurs' default
> values should be described in addition to (and probably ahead of) the
> approach of changing a single curve's control points.

I don't understand why you'd describe how to change every foo before
you'd described the effect of making changes to one instance.
And is it sensible to try to teach:

        (spanner-id . "")
        (springs-and-rods . ,ly:spanner::set-spacing-rods)
        (stencil . ,ly:slur::print)
        (thickness . 1.2)
        (vertical-skylines . ,(ly:make-unpure-pure-container
        ly:slur::vertical-skylines
        ly:grob::pure-simple-vertical-skylines-from-extents))
        (Y-extent . ,slur::height)
        (meta . ((class . Spanner)
                 (interfaces . (outside-staff-interface
                                slur-interface))))))

before teaching:

 \shape #'(
             (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
             ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
           ) Slur

?

> For now, here are some proof-of concept intermediate versions from the
> piece that spurred me to try this approach.
> 
> My "default" uses a mix-n-match font set, so this not totally lilypond
> default, but the slur values discussed above are default.
> http://flaminghakama.com/portfolio/piano-trio/pdf/annes-eyes-Lead-default.pdf
> 
> Here is an intermediate version that is too curvy (height-limit too high),
> but was still an improvement over the default (in my opinion):
> http://flaminghakama.com/portfolio/piano-trio/pdf/annes-eyes-Lead-ratio-42-height-limit-7.pdf
> 
> My final version is not ideal to compare since the line breaking is vastly
> different.
> But this uses the values I settled on:
> http://flaminghakama.com/portfolio/piano-trio/pdf/annes-eyes-Lead.pdf

Comparing appearances is pointless unless you either put extra \breaks
into (1) and (2), probably easier, or manually set fewer in (3),
probably harder. Oh, and keep the notes the same.

Cheers,
David.