Direction operators in event-function

[Urs Liska]

I'm scratching my head  thanks to some weird behaviour (at least it 
looks like that for me). In a simple event-function any explicit 
direction operator used when calling the event will be propagated to the 
created objects:

\version "2.19.82"

propagate-direction =
#(define-event-function (text)(markup?)
   #{
     -\markup #text
   #})

{
  g'1 ^\propagate-direction "Up"
}

When I use explicit tweaks I can specify directions for multiple 
elements as well (but independently from any direction operators):

propagate-direction =
#(define-event-function (text)(markup?)
   #{
     -\tweak direction #UP
     -(
     -\tweak direction #UP
     -\markup #text
   #})

{
  g'1 \propagate-direction "Up" g' )
}

But if I simply create two elements in the event-function the explicit 
direction operator takes no effect:

propagate-direction =
#(define-event-function (text)(markup?)
   #{
     -(
     -\markup #text
   #})

{
  g'1 ^\propagate-direction "Up" g' )
}

(here both the slur and the text are printed below the staff.

Why is that?
And more importantly: how can I achieve the goal of creating more than 
one element in an event-function and still have the explicit directions 
from the calling code be applied?

And why can't I access the explicit direction operator from within the 
event-function? I understand that the *generated* direction isn't 
accessible at that moment, but an explicit setting should be known at 
that point, isn't it?

Thanks
Urs