A few days ago I started reading up on how animations work, in
preparation for starting to use them in a more complex way than
I'd done before. I found it a bit difficult to get my head around;
in particular the many different classes involved, how they relate
to each other, and how to fit them together.
So once I had worked that out, I sat down to express it in the form
of documentation.
The largest change here is an expansion of the docs on [Animation]
itself, including a new section "Using animations" with several
paragraphs laying out how one typically fits together
AnimationController, TickerProvider, CurvedAnimation and/or Tween,
and AnimatedWidget subclasses. [Animation] also gets an expanded
"See also" list, a revised conceptual intro, and a new summary line.
There are also revisions on [TickerProvider], [AnimatedController],
and elsewhere; some new exposition, some revisions for clarity, and
various small fixes.