Re: 'avoid-slur proposals

[Neil Puttock]

2009/4/11 Mark Polesky <address@hidden>:
> 'avoid-slur proposals:
>
> 1. remove 'avoid-slur from Slur properties
>
>   Why does Slur have an 'avoid-slur property?

So they avoid phrasing slurs.

>   Can anyone give an example where the command
>   \override Slur #'avoid-slur = #<something>
>   has an effect?

\relative c' {
  \override Slur #'avoid-slur = #'outside
  c\( d( e) f\)
}

> 2. add a choice: 'ignore
>
>   \override Fingering #'avoid-slur = ##f triggers the
>   message: "warning: Ignoring grob for slur: Fingering.
>   avoid-slur not set?"
>
>   Staff.Accidental also triggers the warning (and I don't
>   know how many others). Perhaps the warning could be
>   removed if the user demonstrates intent like this:
>   \override Fingering #'avoid-slur = #'ignore

>   By the way, is there a way to suppress this warning? I'm
>   working on a macro that could potentially trigger this
>   warning dozens of times in a single compile. Something
>   akin to \override NoteColumn #'ignore-collision = ##t
>   but for Slur instead?

Sounds like a good idea, and only requires one extra line of code for
#'avoid-slur = #'ignore.

> 3. rewrite the docstring.

>   So here's my new docstring. Notice that I'm so adamant
>   about the 'ignore choice that I've incorporated it
>   already. Perhaps it's a little too long, but I prefer
>   it this way. The super-concise version that's there
>  nowhas confused me for long enough.
>
> __________________________________
>
>
> Method of handling slur collisions.
> Choices are 'inside, 'outside, 'around,and 'ignore.
>
> 'inside adjusts the slur if needed to keep the grob inside
> the slur. 'outside moves the grob vertically to the outside
> of the slur. 'around moves the grob vertically to the
> outside of the slur only if there is a collision. 'ignore
> does not move either. In grobs whose notational significance
> depends on vertical position (such as accidentals, clefs,
> etc.), 'outside and 'around behave like 'ignore.
>
> __________________________________
>

That's much clearer.

For 'around, though it's implied in your description, it's probably
better to say that it behaves like 'inside unless there's a collision.

> 4. implement 'avoid-ties and 'avoid-phrasing-slurs?
>
>   just an idea.

An unnecessary complication for phrasing slurs, since they're nearly
identical to slurs (and duplicate most of the code).

Judging by the number of `ugh' comments related to avoid-slur in the
source, extending the same behaviour to ties is probably undesirable
(though it would be good if they avoided clefs and time signatures).

> 5. answer 2 more of my questions
>
>   Why is it that\override Script #'avoid-slur = ##f
>   looks like 'inside for staccato dots, but looks like
>   'around for accents? And why do neither of them actually
>   ignore the slurs, as the current docstring suggests they
>   might?

You can't override 'avoid-slur for scripts unless you use \tweak or
override scriptDefinitions; the engraver gets the default properties
from default-script-alist *after* you've used \override:

\relative c' {
  c4-\tweak #'avoid-slur ##f ->( d)
  \set scriptDefinitions =
    #(cons '("staccato" .
             ((script-stencil . (feta . ("staccato" . "staccato")))
              (side-relative-direction .  -1)
              (quantize-position . #t)
              (avoid-slur . #f)
              (toward-stem-shift . 0.5)
              (padding . 0.20)
              (script-priority . -100)))
           default-script-alist)
  c4-.( d)
}

>   And finally, why trigger a warning for Fingering and
>   Staff.Accidental (and, as previously stated, I don't know
>   how many others) but not for Staff.TimeSignature and
>   Staff.Clef?

You'll get a warning for any graphical grob that the Slur_engraver
acknowledges.  If you take a look at slur-engraver.cc you'll see that
it acknowledges the following:

Accidental
Fingering
Script
TextScript
Tie
TupletNumber

The warning is inside the auxiliary method which does the acknowledging.

Regards,
Neil