Patch for issue #1116 (one stencil in fill-line)

Patch for issue #1116 (one stencil in fill-line)

Avoid translation of stencils if only one markup is given as argument for fill-line.
Regressions not checked yet.

[joeneeman, 2010-06-30 18:34:35]

Are you still waiting for someone to review this? If so, here are a couple minor
things:

http://codereview.appspot.com/1689041/diff/2001/3001
File scm/define-markup-commands.scm (right):

http://codereview.appspot.com/1689041/diff/2001/3001#newcode848
scm/define-markup-commands.scm:848: X RIGHT fill-space line-stencils)))
These two set!s could be written more concisely as
(set! line-stencils
  (stack-stencils-padding-list
   X RIGHT fill-space empty-stencil)))

http://codereview.appspot.com/1689041/diff/2001/3001#newcode850
scm/define-markup-commands.scm:850: (if (> word-count 1)
I know there aren't many comments in the code, but that doesn't mean you can't
add one...

[Neil Puttock, 2010-07-01 22:27:42]

Hi Alexander,

LGTM.

It just needs some regression tests; the examples from #1116 and #382 should
suffice.

Cheers,
Neil

http://codereview.appspot.com/1689041/diff/2001/3001
File scm/define-markup-commands.scm (right):

http://codereview.appspot.com/1689041/diff/2001/3001#newcode845
scm/define-markup-commands.scm:845: (set! line-stencils empty-stencil)
Hmm, line-stencils isn't appropriate from this point, since it's no longer a
list of stencils; perhaps it would be clearer to bind to another variable?

http://codereview.appspot.com/1689041/diff/2001/3001#newcode847
scm/define-markup-commands.scm:847: (stack-stencils-padding-list
indent

http://codereview.appspot.com/1689041/diff/2001/3001#newcode848
scm/define-markup-commands.scm:848: X RIGHT fill-space line-stencils)))
On 2010/06/30 18:34:35, joeneeman wrote:
> These two set!s could be written more concisely as
> (set! line-stencils
>   (stack-stencils-padding-list
>    X RIGHT fill-space empty-stenc

No, they're part of the `if' form above.

[perpeduumimmobile, 2010-07-12 16:14:01]

On 2010/06/30 18:34:35, joeneeman wrote:
> Are you still waiting for someone to review this?

Sorry, missed the notifications - I don't usually check my gmail account.

> http://codereview.appspot.com/1689041/diff/2001/3001#newcode848
> scm/define-markup-commands.scm:848: X RIGHT fill-space line-stencils)))
> These two set!s could be written more concisely as [..]
As Neil noted, it's for the if.

> http://codereview.appspot.com/1689041/diff/2001/3001#newcode850
> scm/define-markup-commands.scm:850: (if (> word-count 1)
> I know there aren't many comments in the code, but that doesn't mean you can't
> add one...
Okay. :-) Better?

[perpeduumimmobile, 2010-07-12 16:18:35]

On 2010/07/01 22:27:42, Neil Puttock wrote:
> Hi Alexander,
> 
> LGTM.
Thanks.

> It just needs some regression tests; the examples from #1116 and #382 should
> suffice.

I did not write those - I'm not yet perfectly convinced that the handling of
word-space is the right thing to do (see below).

> http://codereview.appspot.com/1689041/diff/2001/3001#newcode845
> scm/define-markup-commands.scm:845: (set! line-stencils empty-stencil)
> Hmm, line-stencils isn't appropriate from this point, since it's no longer a
> list of stencils; perhaps it would be clearer to bind to another variable?

Not sure how to name it, then. I used the large if clause, but I'm not sure if
this is good coding style in scheme? Looks more like an early return from
imperative languages...

> http://codereview.appspot.com/1689041/diff/2001/3001#newcode847
> scm/define-markup-commands.scm:847: (stack-stencils-padding-list
> indent
Done.


Regarding word-space:

I reintroduced word-space property to ensure that texts don't collide. This
seems not the best way, though. Consider

\markup \column {
  \fill-line { "|" "|" "|" "|" }
  \fill-line { "|" "veeeeeeeeeeeeeeeeeeeeeeeeeeery long text"
               "veeeeeeeeeeeeeeeeeeeery long text" "|" }
}

(Without word-space in the last version of my patch, this let's the texts
collide.)
Expected output should be this text fitted into one line, not exceeding the
linewidth unless absolutely necessary (i.e., text-width + (n-1)*word-space >
linewidth).
I think the best way would be to solve some minimization problem in the
springs-and-rods style:
- fix the leftmost and rightmost markup to hit the boundaries of the line
- minimize sum over all squared distances of center of texts and optimal
  center points, which are at (2*i / (2*n+1) * line-width) for n stencils,
  subject to non-overlapping texts.
  Perhaps, a weight should be added depending on the lengths of the texts:
  The narrower the text, the more visible is the deviation from the optimal
  position, IMHO.
IIUC, the necessary code for the optimization is already there, but I don't
know where to look. I certainly could reinvent the wheel and implement the
Simplex algorithm in Scheme, but I'm sure someone already did better.