Add function for overriding broken spanners to LilyPond.

Add function for overriding broken spanners to LilyPond.

The music function \alterBroken is intended to facilitate overrides
applied independently to the pieces of broken spanners--one of the
perennial difficulties faced by users of LilyPond (addressed in
Extending 2.6:"Difficult Tweaks").  The function aims at generalization
by allowing the user to specify the name of the spanner and the property
to be overridden.

The function will override unbroken spanners, but it will ignore
non-spanners with a warning.

The function calls \override and may be prefaced by \once (or followed by
a \revert of the relevant property).

[janek, 2012-07-18 05:22:55]

On Wed, Jul 18, 2012 at 12:43 AM,  <david.nalesnik@gmail.com> wrote:
> The function will override unbroken spanners, but it will ignore
> non-spanners with a warning.

What about things like clef change at a line break - is it possible to
override them using this approach?  It would be nice if i could, for
example, paint a clef before the break in pink :)

cheers,
Janek

[david.nalesnik, 2012-07-18 11:56:05]

Hi Janek,

On Wed, Jul 18, 2012 at 12:22 AM, Janek Warchoł
<janek.lilypond@gmail.com>wrote:

> On Wed, Jul 18, 2012 at 12:43 AM,  <david.nalesnik@gmail.com> wrote:
> > The function will override unbroken spanners, but it will ignore
> > non-spanners with a warning.
>
> What about things like clef change at a line break - is it possible to
> override them using this approach?  It would be nice if i could, for
> example, paint a clef before the break in pink :)
>

Right now the function weeds out non-spanners, so this won't work now.  But
undoubtedly you've tried making the clef before the line break pink :) so
you know it won't work!  The music function could easily be adapted to
check for 'break-aligned-interface too, but beyond that point I'd have to
give this some thought.  Perhaps this is a candidate for a different
function, and possibly the name \alterBroken should be changed to something
more precise?  (I thought \alterBrokenSpanner or \overrideBrokenSpanner
would be an awful lot to type.)

At the moment there's this snippet:
http://lsr.dsi.unimi.it/LSR/Item?id=775

-David

[janek, 2012-07-18 17:50:29]

On Wed, Jul 18, 2012 at 1:56 PM, David Nalesnik
<david.nalesnik@gmail.com> wrote:
> Perhaps this is a candidate for a different function,
> and possibly the name \alterBroken should be changed to something more
> precise?  (I thought \alterBrokenSpanner or \overrideBrokenSpanner would be
> an awful lot to type.)

I prefer short names, too.

> At the moment there's this snippet:
> http://lsr.dsi.unimi.it/LSR/Item?id=775

I haven't seen it before - looks awesome :)
(however, it would be even more awesome if it was one general function
for all purposes ;) )

Janek

[thomasmorley65, 2012-07-18 18:18:34]

2012/7/18 Janek Warchoł <janek.lilypond@gmail.com>:
> On Wed, Jul 18, 2012 at 1:56 PM, David Nalesnik
> <david.nalesnik@gmail.com> wrote:
>> Perhaps this is a candidate for a different function,
>> and possibly the name \alterBroken should be changed to something more
>> precise?  (I thought \alterBrokenSpanner or \overrideBrokenSpanner would be
>> an awful lot to type.)
>
> I prefer short names, too.
>
>> At the moment there's this snippet:
>> http://lsr.dsi.unimi.it/LSR/Item?id=775
>
> I haven't seen it before - looks awesome :)
> (however, it would be even more awesome if it was one general function
> for all purposes ;) )
>
> Janek

Hi Janek,

I wrote this snippet a year ago.
Give me some days and perhaps I come up with sth more elaborated.

-Harm

[janek, 2012-07-18 18:34:38]

On Wed, Jul 18, 2012 at 8:18 PM, Thomas Morley
<thomasmorley65@googlemail.com> wrote:
> 2012/7/18 Janek Warchoł <janek.lilypond@gmail.com>:
>> I haven't seen it before - looks awesome :)
>> (however, it would be even more awesome if it was one general function
>> for all purposes ;) )
>
> I wrote this snippet a year ago.
> Give me some days and perhaps I come up with sth more elaborated.

Wow!
I'm in total awe of your skills and dedication - yours, and both Davids'!
(and, of course, everyone else's - but no one beats you wrt/ scheme
helper functions)

Janek

[david.nalesnik, 2012-07-20 23:37:48]

> > 2012/7/18 Janek Warchoł <janek.lilypond@gmail.com>:
> >> (however, it would be even more awesome if it was one general function
> >> for all purposes ;) )

Considering this some more, I think it's best at the moment to restrict the
function to spanners.  The expanded function encompassing spanners and breakable
items appears to work just fine with the examples I adapted from Harm's snippet.
 However, I'm concerned about other overridable properties, for example those
made available through the 'break-aligned-interface:
http://www.lilypond.org/doc/v2.15/Documentation/internals/break_002daligned_0...

If this patch proves successful, it could later be enhanced to include  
breakable items after more study.

What do you think?

-David