[NTG-context] TeX trigger in MP macro

[Peter Rolf]

Hi all,

Currently I am using

\startuniqueMPgraphic{foo}
  ...
  if (\DbgFill=0) :
    fill whatever
  fi
  ...
\stopuniqueMPgraphic

in my MP graphics. \DbgFill (0|1) is just a trigger, which prevents
filling in case of visual debugging. Instead of always writing this
'long' form, it should be possible to use a self written mp-macro
instead. But my naive approach

def dbg_fill (expr p) =
  if (\DbgFill=0) :
    fill p ;
  fi
enddef ;

doesn't work. I get

>> DbgFill
! Unknown relation will be considered false.


How do I realize this trigger inside pure MP code and set it outside in
TeX? The trigger should be global and can change during runtime. Any
help is welcome.

Greetings, Peter