Mutability?

[jackfirth]

Can a pict snip redraw itself when the pict field changes? I tried this, but it didn't work:

(define example-snip (new pict-snip% [pict first-pict]))

example-snip

(thread
 (λ ()
   (sleep 3)
   (set-field! pict example-snip second-pict)))

The first pict shows up in the DrRacket REPL as a snip, but it never changes to the second pict. My guess is that pict-snip% has no way to respond to a field mutation by telling its administrator that it's been resized. Maybe a set-pict method would work?