Allow left-handed fret-markups

Allow left-handed fret-markups

By adding a new boolean subproperty: left-handed.
- Extends Documentation/notation/fretted-strings.itely
- Extends Documentation/changes.tely
- Extenss scm/define-grob-properties.scm
- Adds regtest input/regression/fret-diagrams-left-handed.ly
- Disables the possibility to use negative string-distance

[thomasmorley651, 2018-01-22 22:12:48]

please review

[Carl, 2018-01-22 23:52:29]

Looks good to me, but I have one suggestion.

Thanks,

Carl

https://codereview.appspot.com/339270043/diff/1/scm/fret-diagrams.scm
File scm/fret-diagrams.scm (right):

https://codereview.appspot.com/339270043/diff/1/scm/fret-diagrams.scm#newcode365
scm/fret-diagrams.scm:365: ((and (eq? orientation 'landscape) left-handed)
I would tend to write this as 
 ((eq? orientation 'landscape)
    (cons fret-coordinate (if left-handed (- (1- string-count)
string-coordinate)
                                                                  (-
string-coordinate (1- string-count)))
  (eq? orientation 'opposing-landscape)
     (cons (- fret-coordinate) (if left-handed (- string-coordinate  (1-
string-count))
                                                                         (- (1-
string-count) string-coordinate)))
  (else (cons (if left-handed (- string-coordinate) string-coordinate) (-
fret-coordinate)))))

I think it shows the structure better (i.e. it shows three different
orientations, and it explicitly shows where the left-handed changes things (y
coordinate for landscape, x coordinate for regular).  But I don't insist on this
by any means.

[thomasmorley651, 2018-01-23 09:30:15]

On 2018/01/22 23:52:29, Carl wrote:
> Looks good to me, but I have one suggestion.
> 
> Thanks,
> 
> Carl
> 
> https://codereview.appspot.com/339270043/diff/1/scm/fret-diagrams.scm
> File scm/fret-diagrams.scm (right):
> 
>
https://codereview.appspot.com/339270043/diff/1/scm/fret-diagrams.scm#newcode365
> scm/fret-diagrams.scm:365: ((and (eq? orientation 'landscape) left-handed)
> I would tend to write this as 
>  ((eq? orientation 'landscape)
>     (cons fret-coordinate (if left-handed (- (1- string-count)
> string-coordinate)
>                                                                   (-
> string-coordinate (1- string-count)))
>   (eq? orientation 'opposing-landscape)
>      (cons (- fret-coordinate) (if left-handed (- string-coordinate  (1-
> string-count))
>                                                                          (-
(1-
> string-count) string-coordinate)))
>   (else (cons (if left-handed (- string-coordinate) string-coordinate) (-
> fret-coordinate)))))
> 
> I think it shows the structure better (i.e. it shows three different
> orientations, and it explicitly shows where the left-handed changes things (y
> coordinate for landscape, x coordinate for regular).  But I don't insist on
this
> by any means.

Yep, the difference between left- and right-handed are certain negative instead
of a positive values.
I'd love to use a multiplier retrieved from left-handed.
Though, how to code properly and user-friendly.
One could do
(1) separate conditions (that's what I've done). Disadvantage: code is more
complex. No multiplier.
(2) Let 'left-handed accept RIGHT/LEFT. Disadvantage is the need to input it via
an quasiquoted list
(3) Let 'left-handed accept -1/1. Disadvantage: it may be not that obvious to
the user what -1/1 actually means
(4) Let 'left-handed accept symbols left/right. Disadvantage: need to transform
these symbols into -1/1. 
Something like (if (eq? left-handed 'left) -1 1) needs to be added.
(4) Drop 'left-handed and get the -1/1 from (sign string-distance)

Opinions?

[dak, 2018-01-23 09:55:04]

thomasmorley65@gmail.com writes:

> Yep, the difference between left- and right-handed are certain negative
> instead of a positive values.
> I'd love to use a multiplier retrieved from left-handed.
> Though, how to code properly and user-friendly.
> One could do
> (1) separate conditions (that's what I've done). Disadvantage: code is
> more complex. No multiplier.
> (2) Let 'left-handed accept RIGHT/LEFT. Disadvantage is the need to
> input it via an quasiquoted list
> (3) Let 'left-handed accept -1/1. Disadvantage: it may be not that
> obvious to the user what -1/1 actually means
> (4) Let 'left-handed accept symbols left/right. Disadvantage: need to
> transform these symbols into -1/1.
> Something like (if (eq? left-handed 'left) -1 1) needs to be added.
> (4) Drop 'left-handed and get the -1/1 from (sign string-distance)
>
> Opinions?

We use enough properties of the LEFT/RIGHT kind ((2) and (3) are really
the same option apart from examples/docs) that I don't see a reason to
diverge here.  A property 'handedness set to LEFT or RIGHT would be in
that ballpark.

It's similar to text-direction.

> https://codereview.appspot.com/339270043/

-- 
David Kastrup

[thomasmorley651, 2018-01-23 10:42:26]

On 2018/01/23 09:55:04, dak wrote:
> mailto:thomasmorley65@gmail.com writes:
> 
> > Yep, the difference between left- and right-handed are certain negative
> > instead of a positive values.
> > I'd love to use a multiplier retrieved from left-handed.
> > Though, how to code properly and user-friendly.
> > One could do
> > (1) separate conditions (that's what I've done). Disadvantage: code is
> > more complex. No multiplier.
> > (2) Let 'left-handed accept RIGHT/LEFT. Disadvantage is the need to
> > input it via an quasiquoted list
> > (3) Let 'left-handed accept -1/1. Disadvantage: it may be not that
> > obvious to the user what -1/1 actually means
> > (4) Let 'left-handed accept symbols left/right. Disadvantage: need to
> > transform these symbols into -1/1.
> > Something like (if (eq? left-handed 'left) -1 1) needs to be added.
> > (4) Drop 'left-handed and get the -1/1 from (sign string-distance)
> >
> > Opinions?
> 
> We use enough properties of the LEFT/RIGHT kind ((2) and (3) are really
> the same option apart from examples/docs) that I don't see a reason to
> diverge here.  A property 'handedness set to LEFT or RIGHT would be in
> that ballpark.

Well, we would need to teach the user why
\markup
  \override #'(fret-diagram-details . ((handedness . LEFT))) 
  \fret-diagram #"6-x;5-3-3;4-2-2;3-o;2-1;1-o;"
not works, without using proper quasiquote/unquote.

That's why I listed (2) _and_ (3)

Btw, I found only a single place where we use `(...  ,RIGHT ) etc in the docs:
http://lilypond.org/doc/v2.19/Documentation/notation/displaying-pitches#ottav...
Without explaining what ` and , actually means, though.

[thomasmorley651, 2018-01-24 21:29:09]

David's suggestion

[thomasmorley651, 2018-01-24 21:46:13]

oversight

[thomasmorley651, 2018-01-25 21:13:43]

fix glitch exposed by fret-diagram-origin.ly