%%% DEFINITIONS FOR IMPROVED BOXING (NOT NESCESSARY BUT SPECIFYING THICKNESS AND PADDING WILL NOT WORK WITHOUT THIS!)
#(define*-public ((box-grob-stencil-with-thickness #:optional (thick 0.1) (pad 0)) grob)
  (let* ((xext (ly:grob-extent grob grob 0))
         (yext (ly:grob-extent grob grob 1))
         (xext (interval-widen xext pad))
         (yext (interval-widen yext pad)))
    (ly:stencil-add
      (make-filled-box-stencil (interval-widen xext thick) (cons (- (car yext) thick) (car yext)))
      (make-filled-box-stencil (interval-widen xext thick) (cons (cdr yext) (+ (cdr yext) thick)))
      (make-filled-box-stencil (cons (cdr xext) (+ (cdr xext) thick)) yext)
      (make-filled-box-stencil (cons (- (car xext) thick) (car xext)) yext))))

#(define-public (box-grob-stencil grob)
   (let* ((det (ly:grob-property grob 'details))
          (thick (assoc-get 'box-thickness det 0.1))
          (pad (assoc-get 'box-padding det 0)))
     ((box-grob-stencil-with-thickness thick pad) grob)))


%%% DEFINITION FOR BOXING SYSTEMS
#(define (find-parent-system grob)
   (if (null? grob)
       grob
       (if (grob::has-interface grob 'system-interface)
           grob
           (let ((X-dir (find-parent-system (ly:grob-parent grob X))))
             (if (null? X-dir)
                 (find-parent-system (ly:grob-parent grob Y))
                 X-dir)))))

boxCurrentSystem = <>
  -\tweak
  after-line-breaking
  #(lambda (grob)
     (let ((sys (find-parent-system grob)))
       (ly:grob-set-property! sys 'stencil box-grob-stencil)))
  -\tweak
  stencil
  ##f
  -\markup""

boxCurrentSystemWith =
#(define-music-function (thick pad) (number? number?)
   #{
     <>
     -\tweak
     after-line-breaking
     #(lambda (grob)
        (let* ((sys (find-parent-system grob))
               (det (ly:grob-property sys 'details))
               (det (cons* (cons 'box-thickness thick)
                           (cons 'box-padding pad)
                           det)))
          (ly:grob-set-property! sys 'stencil box-grob-stencil)
          (ly:grob-set-property! sys 'details det)))
     -\tweak
     stencil
     ##f
     -\markup""
   #})


%%% EXAMPLE
{
  c1 \break
  \boxCurrentSystem
  c \break
  c \break
  \boxCurrentSystemWith #0.4 #1
  c
}