broken TextSpanner

[address@hidden]

Somewhere in the docs I ran across this structure (v2.20 or v2.22).  I have not 
been able to find it again:


  \override TextSpanner.bound-details.left.text = \markup{\dynamic "mf" "dim."}
  \override TextSpanner.bound-details.right.text = \markup{ \dynamic "pp" }
  \override TextSpanner.breakable = ##t

An example showed how this produced a mezzo-forte with 'dim.' at \startTextSpan 
and after the line break the end note with 'pp' at \stopTextSpan.

What I get is "mf dim."......'pp'

line break

'mfdimpp' all jammed together and overlapping under the note after the break.


Is such a thing possible as in the above code or do I need to work around this 
some other way?

-David