Drawing circles around various objects

The \circle command draws circles around \markup objects. For other objects, specific tweaks may be required, as demonstrated for rehearsal marks and measure numbers.

\version "2.24"

\relative c' {
  c1
  \set Score.rehearsalMarkFormatter =
    #(lambda (mark context)
             (make-circle-markup (format-mark-numbers mark context)))
  \mark \default

  c2 d^\markup {
    \override #'(thickness . 3) {
      \circle foo
    }
  }
  \override Score.BarNumber.break-visibility = #all-visible
  \override Score.BarNumber.stencil =
    #(make-stencil-circler 0.1 0.25 ly:text-interface::print)
}