#(define ((make-custom-dot-bar-line dot-positions) grob extent)

   "Draw dots (repeat sign dots) at @var{dot-positions}. The
coordinates of @var{dot-positions} are equivalent to the
coordinates of @code{StaffSymbol.line-positions}, a dot-position
of X and a line-position of X indicate the same vertical position."

   (let* ((staff-space (ly:staff-symbol-staff-space grob))
          (dot (ly:font-get-glyph (ly:grob-default-font grob) "dots.dot"))
          (stencil empty-stencil))
     (for-each
      (lambda (dp)
        (set! stencil (ly:stencil-add stencil
                        (ly:stencil-translate-axis dot (* dp (/ staff-space 2)) Y))))
      dot-positions)
     stencil))

% With the procedure above we can define custom bar-lines, for example,
% one that resembles standard repeat sign bar lines except it has
% three dots at staff positions -3, 0, and 3.

#(add-bar-glyph-print-procedure "*" (make-custom-dot-bar-line '(-3 0 3)))
\defineBarLine ".|*" #'("" "*" "")
\defineBarLine "*|." #'("" "*" "")

% We can also customize the dot positions used in all default repeat signs
% by redefining the print procedure of the colon bar glyph (":"). On a staff
% with line-positions of '(-4 -2 2 4) the default repeat sign dots appear
% at '(-3 3), but we can put them at '(-1 1) instead.

#(add-bar-glyph-print-procedure ":" (make-custom-dot-bar-line '(-1 1)))


\new Staff \with {
  \override StaffSymbol.line-positions = #'(-4 -2 2 4)
  \override StaffSymbol.staff-space = #1.3
} {
  \relative f' {
    g1
    \bar ".|*"
    g
    \bar "*|."
    g
    \bar ".|:-|"
    g
    \bar ":|."
    g
    \repeat volta 2 {
      g
    }
  }
}