Tk opengl access from multiple threads

[pascucci]

I am trying to draw on the same opengl window (opened through tk/togl)
from a thread that is not the one that opened the window.
On windows it does not draw and on unix I get a coredump.
The reason why I need to do so is that I need to be able to catch the tk

events before the redraw (or any callback) is finished.
So each callback starts a thread that executes the corresponding
function instead of performing direct evaluation of the function.
This woks fine for regular computations but does not work with the
redraw function ......
It looks like the opengl window keeps a record of who opened its window
and denies access to any other thread.
Any idea on how to circumvent this?
Valerio