Every widget tap runs as its own headless task in the same JS runtime,
and the tasks interleave at every await. Each one loaded the stored
snapshot, edited it and saved it back, then refreshed from the server.
That went wrong in three ways:
- two taps loaded the same snapshot and the second save dropped the
first change;
- the refresh of the first tap read the server before the second tap's
archive landed and was stored anyway, so the message came back (seen
on the emulator with a slow `Email/set`);
- a redraw of an older snapshot could land after a newer one, leaving
buttons that act on a message the widget no longer shows.
The snapshot now only holds what the server last said. A button's
change is kept as a pending op next to it and laid over it when a
widget draws; it stays until a refresh that started after the server
took it has been stored (calendar and task changes only count as caught
up by a refresh that loaded calendar and tasks). A call that fails
drops its op, which also undoes an archive made offline: before, the
failed refresh kept the edited snapshot and the message stayed hidden
although it was never archived. Reads, writes and redraws of the
widget data run one at a time, and every redraw draws the latest view.
Linus Rath