Ui.State, Ui.Diff, Ui.Sync

diff :: State.State → State.State → Either DiffError [Update.Update]

data Update
    = ViewUpdate ViewId ViewUpdate
    | BlockUpdate BlockId BlockUpdate
...

data ViewUpdate =
    CreateView
    | DestroyView
    | ViewSize Types.Rect
...

sort :: [Update] → [Update]

sync :: State.State → [Update.Update] → BlockSamples →
    IO (Maybe State.StateError)

do_updates :: BlockSamples → [Update.Update] → State.StateT IO ()
do_updates block_samples updates = do
    actions <- mapM (run_update block_samples) updates
    -- Trans.liftIO $ putStrLn ("run updates: " ++ show updates)
    Trans.liftIO (Ui.send_action (sequence_ actions))

run_update :: BlockSamples → Update.Update → State.StateT IO (IO ())

• Diff is nasty icky code.
• Update track region hack.
• But printing Updates is useful for debugging.
• Since I hardly ever change the GUI now, I can live with this.