Re: Centering a stencil on another stencil

[Thomas Morley]

Hi Paul,

2015-08-11 17:36 GMT+02:00 Paul Morris <address@hidden>:

>
> Nice!  Much simpler.  I’ve updated the LSR snippet with your simpler code.  I 
> also changed it so that the circle is moved so it is centered on the square, 
> which helps show the need for the function (as opposed to centered-stencil).
>
> http://lsr.di.unimi.it/LSR/Item?id=1009
>
> Let me know if there are any further revisions to make.

I'm still not happy with the example, because the second stencil, the
circle, is centered already.
Below, you could replace the line between the ;;;; with 'stil-b' and
would still get the same output.

#(define (center-stencil-on-stencil axis stil-a stil-b)
  "Return a copy of stencil @var{stil-b} that has been
   moved so it is centered on stencil @var{stil-a} on
   @var{axis}. @var{axis} is 0 for X axis, 1 for Y axis."
   (ly:stencil-translate-axis
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
     (ly:stencil-aligned-to stil-b axis CENTER)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
     (interval-center (ly:stencil-extent stil-a axis))
     axis))

The advantage of this coding is that it will work, whether the stencil
is centered or not!!
Therefore I'd extent the example:

square =
#(make-connected-path-stencil
  '((0 0) (4 0) (4 4) (0 4) (0 0))
  0.4 1 1 #f #f)

green-square =
#(stencil-with-color (make-filled-box-stencil '(0 . 2) '(0 . 2)) green)

circle =
#(stencil-with-color (make-circle-stencil 1 0.3 #f) green)

\markup \line {
 \stencil #(ly:stencil-add square circle)
 "   "
 \stencil #(ly:stencil-add square (center-stencil-on-stencil X square circle))
 "   "
 \stencil #(ly:stencil-add square (center-stencil-on-stencil Y square circle))
 "   "
 \stencil #(ly:stencil-add
             square
             (center-stencil-on-stencil Y square
               (center-stencil-on-stencil X square circle)))
}

\markup \line {
 \stencil #(ly:stencil-add square green-square)
 "   "
 \stencil #(ly:stencil-add square (center-stencil-on-stencil X square
green-square))
 "   "
 \stencil #(ly:stencil-add square (center-stencil-on-stencil Y square
green-square))
 "   "
 \stencil #(ly:stencil-add
             square
             (center-stencil-on-stencil Y square
               (center-stencil-on-stencil X square green-square)))
}


As a thought I extended the coding to get the possibility of a
centered stencil in both directions in one go:


#(define (center-stencil-on-stencil axis stil-a stil-b)
  "Return a copy of stencil @var{stil-b} that has been
   moved so it is centered on stencil @var{stil-a} on
   @var{axis}. @var{axis} is 0 for X axis, 1 for Y axis.
   @var{axis} may be set @code{#t}, moving the new stencil
   in directions"
   (if (and (boolean? axis) axis)
       (ly:stencil-translate
         (centered-stencil stil-b)
         (cons
           (interval-center (ly:stencil-extent stil-a X))
           (interval-center (ly:stencil-extent stil-a Y))))
       (ly:stencil-translate-axis
         (ly:stencil-aligned-to stil-b axis CENTER)
         (interval-center (ly:stencil-extent stil-a axis))
         axis)))

test =
#(define-scheme-function (parser location stil-1 stil-2)
  (ly:stencil? ly:stencil?)
  #{
    \markup
      \override #'(word-space . 3)
      \line {
      \stencil #(ly:stencil-add stil-1 stil-2)
      \stencil #(ly:stencil-add stil-1
                                (center-stencil-on-stencil X stil-1 stil-2))
      \stencil #(ly:stencil-add stil-1
                                (center-stencil-on-stencil Y stil-1 stil-2))
      \stencil #(ly:stencil-add stil-1
                                (center-stencil-on-stencil #t stil-1 stil-2))
    }
  #})

square =
#(make-connected-path-stencil
  '((0 0) (4 0) (4 4) (0 4) (0 0))
  0.4 1 1 #f #f)

green-square =
#(stencil-with-color (make-filled-box-stencil '(0 . 2) '(0 . 2)) green)

circle =
#(stencil-with-color (make-circle-stencil 1 0.3 #f) green)

\test #square #circle
\test #square #green-square


Though, it's probably overdone.
What do you think?


Cheers,
  Harm