> I noticed that I got the vm crashing not 100% when I was trying on 
> DisplayScreen. Now that I retried with Smalltalk fullScreenMode: true,
> it happens to crash it from time to time.

Reminds of a bug I had (years back) in the Windows VM - I assumed that the
size of Display's bits is always up-to-date to the OS window extent (which
isn't always true since it takes a little for Squeak to recognize that the
display extent has changed) which led to crashes very much like you're
seeing.

Interestingly, this behavior would only be exposed if you invoke
#fullscreenMode: manually (the way you did) as the "regular" methods of
going fullscreen (through menu or the navbar) will immediately issue a
Display restore afterwards - bringing the Display's size back to sync with
the os window extent. Might be worthwhile to check out.

Cheers,
  - Andreas