Re: stretchable systems

[Han-Wen Nienhuys]

[to l-devel]

Nicolas Sceaux wrote:
> Hi,
>
> Considering a piece with N-staff systems, with no room on a page for 3
> systems, only for two, but with lot of space left, I can't find if it is
> possible to automatically enlarge (I hope that this word won't make this
> message marked as spam) the space between staves in a system, up to a
> certain distance, so that there should be less space between the two
> systems.

(snip picture)

> If this does not exist yet, but is sponsorable, I'm interested.

I'll think about it. Unfortunately, I don't see how we can add this in a 
"simple" way. Right now, systems are simply formatted, and then output 
as a stencil. The finished systems are then spread across the pages.

For such a thing to be possible, we have to add another formatting pass, 
and a mechanism to get the range for vertical extents, instead of the 
stencils. Then the page breaking is done, and only then, the final shape 
of a system is determined.  Another option is to make stencils 
stretchable, iow. remember the complete composition of a Stencil, and 
then have

  Stencil::get_extent (Real stretch_factor, Axis a)

Then, in the end you could do

  interpret_stencil (y_stretch_factor, system)

and the system would be spaced wider in vertical sense. It would be very 
neat, but it would also make Stencil much more complex (each stencil 
would carry a spring-and-rod problem inside). Also, I'm not sure yet 
that this would be good enough to do what you want.  It would be neat, 
because we'd have a way to do more advanced horizontal spacing too: we 
could space prefatory matter (key/time sig), accidentals, etc. tighter 
in cramped lines.

Both options would be A LOT of work: between 2 to 6 months full-time 
work.  I guess it will be necessary for good typesetting, but IMO there 
are currently more pressing problems in the typesetting engine.

Isn't it easier to cook up a hack? We can already stretch systems, with 
some  hairy code. You could do it in a 2 pass process: first determine 
page breaks and space available, then setup a

  adjustVerticalSpace #FACTOR #SYSTEM-NUMBER

function and  dump

   { \adjustVerticalSpacing #0.5  #1
     \skip 1 * 4 \lineBreak
     \adjustVerticalSpacing #0.5  #2
     \skip 1 * 4 \lineBreak
     \adjustVerticalSpacing #0.5  #3
     \pageBreak
     \skip 1 * 4 \lineBreak
     \adjustVerticalSpacing #0.75  #4
        ..
   }

Voice which you include in the score.

--
 Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen