Extending a TrillSpanner

For TrillSpanner, the minimum-length property becomes effective only if the set-spacing-rods procedure is called explicitly.

To do this, the springs-and-rods property should be set to ly:spanner::set-spacing-rods.

\version "2.24.0"

\relative c' {
  \key c\minor
  \time 2/4
  c16( as') c,-. des-.
  \once\override TrillSpanner.minimum-length = #15
  \once\override TrillSpanner.springs-and-rods = #ly:spanner::set-spacing-rods
  \afterGrace es4
  \startTrillSpan { d16[( \stopTrillSpan es)] }
  c( c' g es c g' es d
  \hideNotes
  c8)
}