Here is the final picture:

I invistigated the following modifications:

A) let preempt = () instead of Thread.yield () in thread_posix.ml (modif
de OCaml)

B) adding proper enter/leaving_blocking_section in glut (file wrap_glut.c)

C) using a timer instead of an idle function for the interactive thread
(I need to redraw the surface when it is moving and I do it event when
it is not moving ;-).

Here are the time mesurments (+X means with modif X, -X means without
modif X):

+A+B+C : ~43s
+A-B+C : loop (never a chance to change thread)

-A+B+C : ~43s
-A-B+C : ~89s

-A+B-C : ~85s

So the real problem were
- a bug in glut (enter_blocking_section was really usefull before
entering the mainLoop !!)
- it is a bad idea to use an Idlefunc with lablGlut if another thread
needs some CPU. Better say I want 20 frames per seconds => I use a times
every 50ms.

- The periodic calls to yield from OCaml are not bad they allow a little
scheduling and did a partial fix of the lablGlut bug, but still this was
not enough to really "fix the bug" (see -A-B+C). But, may be I would
have prefer to discover the bug sooner ...

See my next post ...
-- 
Christophe Raffalli
Université de Savoie
Batiment Le Chablais, bureau 21
73376 Le Bourget-du-Lac Cedex

tél: (33) 4 79 75 81 03
fax: (33) 4 79 75 87 42
mail: Christophe.Raffalli@univ-savoie.fr
www: http://www.lama.univ-savoie.fr/~RAFFALLI
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