More comments are warranted: these functions are pretty much full of
potential side effects, and I'd really like to avoid keeping everything
in my head forever.
Along with the comments and the type casting reduction, I sneaked in a
one line change that is clearly correct after reading the flow of the
whole thing: we queue only a relayout after three potential redraws have
been queued. If we manage to miss a redraw and yet still get a relayout
then it means that most of our assumptions are fundamentally wrong, and
that we ought to dump this whole business of computer programming, and
just go back to being a hunter-gatherer species.
c32973158d