Re: relative offset of systems [WAS: Center-align a score]

[David Nalesnik]

Hi Harm,

On Thu, Apr 27, 2017 at 3:57 PM, Thomas Morley <address@hidden> wrote:
> Hi David,
>
> nice stuff!
>
> Some comments, though:
>
> 2017-04-27 19:27 GMT+02:00 David Nalesnik <address@hidden>:
>> On Thu, Apr 27, 2017 at 12:22 PM, David Nalesnik
>> <address@hidden> wrote:
>>
>>>
>>> I'll just quote the relevant changes with some context.
>>>
>>> Within the function make-page-stencil:
>>>
>>> [...]
>>>
>
> I see no advantage to add 'extra-y' to the arguments.
> Why not do the calculation in 'add-system' ...

Good point.  Actually, I already incorporated this suggestion in a
patch I'm currently testing.  (Middle of make doc.)  I decided to use
an "extra-offset" property which allows for displacements along both
axes.

>
>>>  (add-to-page (lambda (stencil x y extra-y)
>>
>> Oh, "nota bene" the above line too!
>>
>>>                     (set! page-stencil
>>>                           (ly:stencil-add page-stencil
>>>                             (ly:stencil-translate stencil
>>>                               (cons
>>>                                (+
>>>                                 system-xoffset x)
>>>                                (-
>>>                                 0 y extra-y (prop 'top-margin))) ; NB
>>>
>>>                               )))))
>>>      (add-system
>>>       (lambda (system)
>>>         (let* ((stencil (paper-system-stencil system))
>>>                (y (ly:prob-property system 'Y-offset 0))
>>>                (extra-y (ly:prob-property system 'extra-Y-offset 0)) ; NB
>>>                (is-title (paper-system-title?
>>>                           system)))
>>>           (add-to-page stencil
>>>             (ly:prob-property system 'X-offset 0.0)
>>>             y
>>>             extra-y) ; NB
>
>
> It will fail if system-separator-markup is used.
>
> Here my attempt (for comparison I added greyed stencils)
>
>      (add-system
>       (lambda (system)
>         (let* ((stencil (paper-system-stencil system))
>                (y (ly:prob-property system 'Y-offset 0))
>                (extra-y (ly:prob-property system 'extra-Y-offset 0)) ;; NB
>                (is-title (paper-system-title?
>                           system)))
>
> ;;;; For comparison: print the greyed system-stencil without extra-y
>           (add-to-page (stencil-with-color stencil '(0.8 0.8 0.8))
>             (ly:prob-property system 'X-offset 0.0)
>             y)
> ;;;; The moved system-stencil
>           (add-to-page stencil
>             (ly:prob-property system 'X-offset 0.0)
>             (+ y extra-y)) ;; NB
>
>             (if (and (ly:stencil? system-separator-stencil)
>                      last-system
>                      (not (paper-system-title? system))
>                      (not (paper-system-title? last-system)))
>                 (begin
> ;;;; For comparison: print the greyed system-separator-stencil without 
> 'extra-y
>                   (add-to-page
>                    (stencil-with-color system-separator-stencil '(0.8 0.8 
> 0.8))
>                    0
>
>                    (average (- last-y
>                                (car (paper-system-staff-extents last-system)))
>                             (- y
>                                (cdr (paper-system-staff-extents system)))))
>
> ;;;; The moved system-separator-stencil
>                   (add-to-page
>                    system-separator-stencil
>                    0
>
>                    (+
>                      (average (- last-y
>                                  (car (paper-system-staff-extents 
> last-system)))
>                               (- y
>                                  (cdr (paper-system-staff-extents system))))
>                      (/ extra-y 2)))))  ;; NB
>             (set! last-system system)
> ;;;; set last-y, taking extra-y into account
>             (set! last-y (+ y extra-y)))))  ;; NB
>
> As an example I used:
>
> \paper {
>   system-separator-markup = \slashSeparator
>   ragged-last-bottom = ##t
> }
> top = \repeat unfold 5 { c''4 d'' e'' f'' }
>
> bottom = {
>   \clef bass
>   \repeat unfold 5 { c,1 }
>   \break
> }
>
> \new PianoStaff <<
>   \new Staff {
>     \top
>     \top
>     \top
>   }
>   \new Staff {
>     \bottom
>     \overrideProperty
>     Score.NonMusicalPaperColumn.line-break-system-details
>     #'((extra-Y-offset . 2))
>     \bottom
>     \overrideProperty
>     Score.NonMusicalPaperColumn.line-break-system-details
>     #'((extra-Y-offset . 5))
>     \bottom
>   }
>>>
>
> png attached
>

Thanks so much for pointing this out.  I didn't notice that the
variable "y" was used elsewhere.  As soon as the patch testing has run
its course, I'll add this in.

Wish I could use the greyed background in the regtest, but that's not possible.

Best,
David