drained: handle missed "changing" events

[bobrippling]

Sometimes my watch will change (with drained active) past the threshold and not deactivate drained. On debugging, the interval isn't set, so we set it unconditionally to ensure we have a charge "watcher".

[thyttan]

Does this mean something is broken in the event handling somewhere?

I mean, why would we be missing to set the interval in the 'charging'-listener?

[thyttan]

We also discussed some weird event listener behavior on #4141.

Could this be something similar?

[bobrippling]

Good memory! I would initially say no, and that drained just starts too late but that can't be the case - drained is running when I plug my watch in to charge 🤔

It could well be something with the firmware, like #4141. I'll see if I can get more details

[thyttan]

@bobrippling I'm thinking of opening an issue re event handling on espruino/Espruino. Have you managed to understand the problem any more?

[bobrippling]

I'm afraid not - still at square one!

[stweedo]

There is one specific case i found with version 0.08 of drained where if it's started while the watch is charging, it will not deactivate when crossing the threshold until a new charging event happens by reconnecting the charger.

[gfwilliams]

Just mentioned in espruino/Espruino#2702 (comment) but:

I don't think drained uses notify? But there was an issue with notify calling stopEventPropagation on hide, so if any other app did show a notification with notify (eg 'low battery') and then hide it on a charging event then any other 'charging' event handlers would not be called and it'd cause this exact issue

[bobrippling]

Yeah, no use of notify - I haven't gotten to the bottom of this so maybe we merge this PR to handle the problem until I do suss it out?

[thyttan]

It feels a bit antithetical to start running an interval while we try to preserve battery as much as possible. But maybe it's negligible.

[bobrippling]

What about this change I've just pushed?

[thyttan]

Looks good to me!

[gfwilliams]

Looks great to me!