Bert Freudenberg wrote:
> In normal drawing it is not necessary to redraw portions of of the  
> display because the whole screen bitmap is cached. When the Squeak  
> window needs to be redrawn, just the right bits from that bitmap  (which 
> is called Display) are copied to the screen. Morphic just  draws into 
> the bitmap and tells the system to update the changed  portions.
> 
> If you draw yourself via FFI, you also need to get hold of the redraw  
> events yourself. There is no support for this in regular Squeak.

IIRC, then Tim's unspeakable host window stuff supports it.

Cheers,
   - Andreas