Add original-breaks.ly commands

Add original-breaks.ly commands

The commands defined in this patch allow the user to insert breaks
(line and page) from the original manuscript that are conditionally
respected or discarded. This is very useful for entering and
proof-reading music from larger scores.

Actually I would prefer having them enabled automatically (i.e.
parsed on initialisation without requiring to include the file
explicitly. But I think the way it is done in the patch will make
it easier to accept its inclusion.

Two commits:

Add docs for original-breaks.ly

Add original-breaks.ly

Define commands:
- origBreak
- origPageBreak

Depending on the presence and state of variables
- keep-original-breaks
- keep-original-page-breaks

these result in a \break or \pageBreak or nothing.
Default is #t (so when the file is included original
breaks are automatically respected).

Additionally define top-level commands
- \keepOriginalBreaks
- \discardOriginalBreaks
- \keepOriginalPageBreaks
- \discardOriginalPageBreaks

The idea is to let the user enter breaks from the manuscript
she is copying. While working on the content of the score
it is very handy to have LilyPond compile the score with
the breaks of the original manuscript, but of course one
doesn't want to enter hard-coded breaks.

[Dan Eble, 2014-10-07 22:30:53]

On 2014/10/07 08:37:06, uliska wrote:

On 2014/10/07 08:37:06, uliska wrote:

On 2014/10/07 08:37:06, uliska wrote:

On 2014/10/07 08:37:06, uliska wrote:

Important:
* There should be regression tests.

Musing:
* Why not use tags?  (Example below.)
* Does this implementation make it possible to set the option from the lilypond
command line?
* When using original breaks, wouldn't one also want original page size, staff
size, etc.?
* What about hundreds of other features of the original edition?

\version "2.19.0"

originalBreak = { \tag #'originalBreak \break }

music = { c'1 \originalBreak 1 }

\score {
  \new Staff { \music }
}

\score {
  \new Staff { \removeWithTag #'originalBreak \music }
}

[dak, 2014-10-08 03:24:58]

On 2014/10/07 22:30:53, Dan Eble wrote:

> * When using original breaks, wouldn't one also want original page size, staff
> size, etc.?

That would not map well to tags.  Not without additional facilities, I guess. 
Still, I think that tags at least address a large enough problem space that
making them available on the command line makes sense.  And we can still add a
macro like

(define-macro (tagged tags . body)
  `(if (check-against-document-options ,tags) (begin ,@body))

to make the document-level tag specification useful in Scheme-provided content
as well.

[Keith, 2014-10-08 05:01:40]

For this particular task, you should also show the user that he can define at
the top of the input, or in a header file if he uses one,
  originalBreak = \break
and insert before music where we are done with the original breaks,
  originalBreak = {} %\break

That is easy enough to understand, and easy to adapt to other tasks.

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
File Documentation/notation/spacing.itely (right):

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
Documentation/notation/spacing.itely:1857: @end lilypond
Why not store the common music in a variable, and show
 \score {\music}
 \discaredOriginalBreaks
 \score {\music}
?

https://codereview.appspot.com/150670043/diff/1/ly/original-breaks.ly
File ly/original-breaks.ly (right):

https://codereview.appspot.com/150670043/diff/1/ly/original-breaks.ly#newcode36
ly/original-breaks.ly:36: origBreak =
Almost religiously, LilyPond avoids abbreviation.
Maybe  originalBreak ?

[uliska, 2014-10-09 08:11:29]

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
File Documentation/notation/spacing.itely (right):

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
Documentation/notation/spacing.itely:1857: @end lilypond
On 2014/10/08 05:01:40, Keith wrote:
> Why not store the common music in a variable, and show
>  \score {\music}
>  \discaredOriginalBreaks
>  \score {\music}
> ?

Because it wouldn't work that way. \discardOriginalBreaks 
would be interpreted when the command is written. So the
change doesn't have an effect when the variable is called the
second time (but actually it's not the use case to change
the behaviour along the way of a score).

[Trevor Daniels, 2014-10-09 10:21:45]

I've not followed the corresponding email discussion closely, and maybe I've
missed something, but how is this better than simply using \obreak for an
original break, and \nbreak for a new, required, break, having defined 

obreak = \break
nbreak = <>

in order to obtain the original breaks.  And then simply redefining

obreak = <>
nbreak = \break

to remove the original breaks and activate the new ones?  And equivalently for
page breaks.

This has the advantage that newly inserted breaks don't interfere with the
original ones.

It would also be trivial to remove all these editing aids finally with a simple
global edits.

That seems so simple anyone can do it without adding anything to the base code
and almost a page to the documentation.

Trevor

[Graham Percival, 2014-10-09 10:41:36]

On Thu, Oct 09, 2014 at 10:21:45AM +0000, tdanielsmusic@googlemail.com wrote:
> I've not followed the corresponding email discussion closely, and maybe
> I've missed something, but how is this better than simply using \obreak
> for an original break, and \nbreak for a new, required, break, having
> defined
> 
> obreak = \break
> nbreak = <>
...
> That seems so simple anyone can do it without adding anything to the
> base code and almost a page to the documentation.

This method is already in the documentation!  At least, it used to
be... Learning Manual, "tips for typesetting" or something like
that?  it's just possible it was moved to Notation or Usage at
some point.  But it was definitely in the docs ten years ago.
(yes, literally 10 years ago.  Mao, where did the time go?)

Cheers,
- Graham

[dak, 2014-10-09 10:44:07]

On 2014/10/09 10:21:45, Trevor Daniels wrote:

> It would also be trivial to remove all these editing aids finally with a
simple
> global edits.

I think the basic point was to get different aspects of the same document
_without_ doing any edits on it.

[fedelogy, 2014-10-09 21:44:32]

2014-10-09 12:41 GMT+02:00 Graham Percival <graham@percival-music.ca>:

> On Thu, Oct 09, 2014 at 10:21:45AM +0000, tdanielsmusic@googlemail.com
> wrote:
> > I've not followed the corresponding email discussion closely, and maybe
> > I've missed something, but how is this better than simply using \obreak
> > for an original break, and \nbreak for a new, required, break, having
> > defined
> >
> > obreak = \break
> > nbreak = <>
> ...
> > That seems so simple anyone can do it without adding anything to the
> > base code and almost a page to the documentation.
>
> This method is already in the documentation!  At least, it used to
> be... Learning Manual, "tips for typesetting" or something like
> that?  it's just possible it was moved to Notation or Usage at
> some point.  But it was definitely in the docs ten years ago.
> (yes, literally 10 years ago.  Mao, where did the time go?)
>

It's actually in Usage:
http://lilypond.org/doc/v2.19/Documentation/usage/typesetting-existing-music

But it's not enough, you should also use the information provided here:
http://lilypond.org/doc/v2.19/Documentation/notation/explicit-breaks

```
There are cases when manual \break or \pageBreak commands are ignored by
LilyPond. There are two commands to override this behavior:

\override NonMusicalPaperColumn.line-break-permission = ##f
\override NonMusicalPaperColumn.page-break-permission = ##f
```

[Keith, 2014-10-10 04:36:14]

On 2014/10/09 08:11:29, uliska wrote:
> On 2014/10/08 05:01:40, Keith wrote:
> > Why not store the common music in a variable, and show
> >  \score {\music}
> >  \discaredOriginalBreaks
> >  \score {\music}
> > ?
> 
> Because it wouldn't work that way. \discardOriginalBreaks 
> would be interpreted when the command is written. 

Oh.  I see how it works now.

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
File Documentation/notation/spacing.itely (right):

https://codereview.appspot.com/150670043/diff/1/Documentation/notation/spacin...
Documentation/notation/spacing.itely:1842: \discardOriginalBreaks
In that case you could do everything you describe in this documentation by
typing
  origBreak = {} %\break
here instead of \discardOriginalBreaks, and then we don't need the include file.

Do you plan to add a command-line option like -doriginal-breaks so you can
switch behaviors from the command line?