> > If it's generally true that the parent window can in fact draw in
> > the child area you could very simply make 
> > glIsOverlayRenderer() return false
> > - the entire purpose of this method is to figure out if 
> > Squeak can or can
> > not draw on top of that context.
> 
> But how comes this call isn't used at all? The only sender of
> #isOverlayRenderer is in drawSimulatedOn:! And I don't see 
> any difference in speed whether glIsOverlayRenderer() returns
> 0 or 1 ...

There's no difference in speed. The primitive is used (as you're saying for
yourself) and the reason it's used in #drawSimulatedOn: is simple enough to
understand. When we have an overlay window that Squeak cannot draw into then
we have to dump it at certain points, such as when we drag the wonderland
around. Because otherwise the region that is occupied by the overlay window
will not be drawn correctly (mind you, at this point is the actual 3D area
somewhere else on the screen and not at the point where you've remembered
the coordinates and where your overlay window still resides).

  - Andreas