Better support for beat slashes (multi-slash & mixed duration).

Better support for beat slashes (multi-slash & mixed duration).

* lily/context.cc:

  add repeat count visibility proc for use in percent repeat engravers

* lily/double-percent-repeat-engraver.cc (new file):

  create separate engraver for double-measure percent repeats, which listens
  to DoublePercentEvent

* lily/percent-repeat-engraver.cc:

  listen to PercentEvent and create single-measure repeats only

* lily/percent-repeat-item.cc: (brew_slash):

  add count arg to set number of slashes

* lily/percent-repeat-iterator.cc (get_music_list):

  send separate synthetic events for percent, double-percent and beat repeats

  use measure length to choose between full-measure types

  call scheme proc to get slash count for beat repeats

* lily/slash-repeat-engraver.cc:

  listen to RepeatSlashEvent and use slash-count to switch between RepeatSlash
  and DoublePercentRepeat

* ly/engraver-init.ly:

  add Double_percent_repeat_engraver to Voice context

* scm/define-event-classes.scm (event-classes):

  add new classes (double-percent-event/repeat-slash-event)

* scm/define-grob-interface.scm (percent-repeat-interface):

  add slash-count for use by RepeatSlash

* scm/define-grob-properties.scm (all-internal-grob-properties):

  doc slash-count

* scm/define-grobs.scm (all-grob-descriptions):

  set slash-negative-kern in RepeatSlash (required for multi-slash beat repeats)

* scm/define-music-properties.scm (all-music-properties):

  doc slash-count

* scm/define-music-types.scm (music-descriptions):

  add synthetic events DoublePercentEvent and RepeatSlashEvent

* scm/music-functions.scm (calc-repeat-slash-count):

  new function used by Percent_repeat_iterator to check durations; returns
  either number of slashes (if all durations equal) or 0 (if durations vary)

[Neil Puttock, 2010-08-25 21:22:26]

Hi everybody,

You might remember this patch from a while ago. :)

I've dusted it off and made several improvements.

Please review.

Thanks,
Neil

[Graham Percival (old account), 2011-01-22 20:25:03]

Looks excellent, but -- what's a double slash?  :)

http://codereview.appspot.com/212048/diff/64001/lily/percent-repeat-iterator.cc
File lily/percent-repeat-iterator.cc (right):

http://codereview.appspot.com/212048/diff/64001/lily/percent-repeat-iterator....
lily/percent-repeat-iterator.cc:58: event_type = "DoublePercentEvent";
I'm mildly suspicious about this part -- at first glance, it appears that
there's no way for a user to specify "I always want a percent" vs. "I always
want a double percent".

Now, I'm not entirely certain what a percent-vs-double-percent looks like, so if
you're certain that deciding them based on measure length alone is fine, I won't
question you further... but at the moment, this looks slightly dangerous and/or
limiting.

[Graham Percival (old account), 2011-01-22 20:29:17]

On 2011/01/22 20:25:03, Graham Percival wrote:
> Looks excellent, but -- what's a double slash?  :)

Sorry, ignore this; I just checked Notation 1.4.2 Repeats.  Oops.

Patch looks great, passes regtests, and I built the docs from scratch with it. 
I think it's ready to be pushed.

[Neil Puttock, 2011-01-23 23:17:28]

On 2011/01/22 20:29:17, Graham Percival wrote:

> Patch looks great, passes regtests, and I built the docs from scratch with it.

> I think it's ready to be pushed.

Thanks.  I've deliberately left out doc changes (i.e., snippets, removal of
known issue and changes entry), but they'd follow soon after pushing.

Cheers,
Neil

[Carl, 2011-01-24 02:20:06]

LGTM.

Carl

[Graham Percival (old account), 2011-02-10 18:07:15]

No complaints, and I just double-checked that the regtest is ok.  Please push.