Optional fraction after \afterGrace command

Optional fraction after \afterGrace command

\afterGrace had its fraction determining the position of the aftergrace
notes hardwired to be read from the parser variable afterGraceFraction.
This change here allows for optionally specifying it right as the first
argument of the \afterGrace command.


Also contains commit:

NR: show optional \afterGrace argument

[lemzwerg, 2016-07-22 04:26:01]

LGMT. Thanks a lot!

[mark_opus11.net, 2016-07-22 07:41:00]

On 2016/07/22 04:26:01, lemzwerg wrote:
> LGMT. Thanks a lot!

Might it be a good idea to keep one example using the old define method, which
is still more convenient for setting the value for multiple usages of
\afterGrace (or globally)?

[dak, 2016-07-22 07:55:54]

On 2016/07/22 07:41:00, mark_opus11.net wrote:
> On 2016/07/22 04:26:01, lemzwerg wrote:
> > LGMT. Thanks a lot!
> 
> Might it be a good idea to keep one example using the old define method, which
> is still more convenient for setting the value for multiple usages of
> \afterGrace (or globally)?

Frankly, I decided against doing so since redefining parser behavior by
resetting a global variable controlling its behavior in the middle of a music
expression is a complete abomination.  This is different to how \tupletSpan (or
its equivalent \override) works since \tupletSpan becomes a _part_ of the music
expression.

That's not really something we want to paint as a user interface.  It's also
impossible to reflect with \displayLilyMusic.

I actually asked myself the question "might it be a good idea to keep one
example using the old define method" and my personal answer to that question
ended up being "no".  If anything, i was rather tempted undocumenting it
completely but then the arbitrary default value of 3/4 needed to get mentioned
so that one would be able to understand how custom values were related.  And I
decided that just mentioning where this default was stored would provide a
comparatively small opening in the can of worms.

So this was a conscious decision on my part and I'll require some convincing to
revert.

[mark_opus11.net, 2016-07-22 08:17:46]

On 2016/07/22 07:55:54, dak wrote:
> On 2016/07/22 07:41:00, http://mark_opus11.net wrote:
> > On 2016/07/22 04:26:01, lemzwerg wrote:
> > > LGMT. Thanks a lot!
> > 
> > Might it be a good idea to keep one example using the old define method,
which
> > is still more convenient for setting the value for multiple usages of
> > \afterGrace (or globally)?
> 
> Frankly, I decided against doing so since redefining parser behavior by
> resetting a global variable controlling its behavior in the middle of a music
> expression is a complete abomination.  This is different to how \tupletSpan
(or
> its equivalent \override) works since \tupletSpan becomes a _part_ of the
music
> expression.

I appreciate that reasoning, however the ability to set global behaviour is one 
of lilypond's major strengths - if overriding a default has to be entered at
every
usage of \afterGrace then we are back to making changes with sed scripts.

The default value of 3/4 is almost always not appropriate, and I regularly set
this globally after entering the music to find a suitable value.

Perhaps afterGraceFraction could be somehow included in graceSettings or some
other property of the Voice context?

[dak, 2016-07-23 09:38:57]

Should make Marc happier than me.

[simon.albrecht, 2016-07-24 22:59:35]

LGTM.

https://codereview.appspot.com/304200043/diff/20001/Documentation/notation/rh...
File Documentation/notation/rhythms.itely (right):

https://codereview.appspot.com/304200043/diff/20001/Documentation/notation/rh...
Documentation/notation/rhythms.itely:3436: the length of the main note.  The
default is set as
The wording feels odd to me. Maybe:

This will put the grace notes after some space, equivalent
to a fraction of the duration of the main note.

?

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.ly
File ly/music-functions-init.ly (right):

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.l...
ly/music-functions-init.ly:59: afterGraceFraction = 6/8
What would be the point of 6/8 instead of 3/4?

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.l...
ly/music-functions-init.ly:67: @code{afterGraceFraction} which has a default
value of @code{6/8}.")
(Same fraction as above.)

[dak, 2016-07-28 17:15:20]

https://codereview.appspot.com/304200043/diff/20001/Documentation/notation/rh...
File Documentation/notation/rhythms.itely (right):

https://codereview.appspot.com/304200043/diff/20001/Documentation/notation/rh...
Documentation/notation/rhythms.itely:3436: the length of the main note.  The
default is set as
On 2016/07/24 22:59:35, simon.albrecht wrote:
> The wording feels odd to me. Maybe:
> 
> This will put the grace notes after some space, equivalent
> to a fraction of the duration of the main note.
> 
> ?

Well, I just copied the original text here, just replacing "3/4" with "a
fraction".  I'll see whether I can reword more to your liking.

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.ly
File ly/music-functions-init.ly (right):

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.l...
ly/music-functions-init.ly:59: afterGraceFraction = 6/8
On 2016/07/24 22:59:35, simon.albrecht wrote:
> What would be the point of 6/8 instead of 3/4?

I just retained the original value.  There is no point to it as far as I am
aware.

It's been that way since
commit 5d09e71683990a4615ea4e0c497db31c462e2345
Author: Han-Wen Nienhuys <hanwen@xs4all.nl>
Date:   Sun Nov 28 17:37:42 2004 +0000

    *** empty log message ***

No rationale is found in the ChangeLog entries or similar information and the NR
documentation exclusively talks about 3/4.

I'll change this to 3/4.  I just was too lazy to do all the research for
figuring out whether there was any discernible justification for it, ever.

https://codereview.appspot.com/304200043/diff/20001/ly/music-functions-init.l...
ly/music-functions-init.ly:67: @code{afterGraceFraction} which has a default
value of @code{6/8}.")
On 2016/07/24 22:59:35, simon.albrecht wrote:
> (Same fraction as above.)

Acknowledged.

[dak, 2016-07-28 17:34:20]

Try to address Simon's suggestions

[dak, 2016-07-28 20:39:36]

Reupload after sourceforge downtime