RE: Feedback about Battery Status Events

> On Tue, Oct 18, 2011 at 1:57 AM, Mounir Lamouri <mounir@lamouri.fr>
> wrote:
> > On 10/18/2011 01:15 AM, Jonas Sicking wrote:
> >>
> >> I think the idea was to return null on devices which don't use
> >> battery at all. On my desktop machine there is no way I'm going to
> >> hot plug a battery and start carrying it away (I probably wouldn't
> >> get past the downstairs security guards anyway, despite 5 years of ice
> hockey).
> >
> > And how can you know that? Do we have a sure way to know if a system
> > is a laptop or a desktop? Off hand, I would say a desktop doesn't have
> > a battery and a laptop has one... I don't see how to differentiate a
> > desktop with a battery-less laptop. In addition, it might increase the
> > risk of fingerprinting with a desktop returning null and a laptop
> > returning a BatteryManager with level=1.0 and state="charging".
> 
> It's possible that we can't tell the difference yeah. In which case we
should
> return a object with level=1.0 and .charging=true (or .state="charging" or
> whatever we agree on is the method for indicating being plugged in).
> 
> What I was thinking was that if we *know* that it's a device that can't
have
> battery, we should return null for .battery.
> 
> However, the more I think about it, it's bad if the edge case is that
.battery
> doesn't exist, since that means that script will come to depend on it
existing
> and throw when it doesn't.
> 
> So I'm sold on the idea of .battery existing and returning "full charge
and
> charging" state when we can't find battery information.
> 
> >> On a device which has battery, but where one isn't currently plugged
> >> in it seems appropriate to return 0 for level of charge and true for
> >> charging. If a battery which is charged to 50% is plugged in simply
> >> change the charge level to 50% and fire the appropriate events.
> >
> > It would be probably be better to have level=1.0 and state="charging"
> > when the battery is removed. That way, script will not disable stuff
> > thinking the device power is low.
> 
> I don't really have strong feelings either way. In a sense the battery is
> completely empty since if you unplugged the cable the device would
> immediately shut down.
> 
> On the other hand the user is unlikely to do so, and instead more likely
to
> plug in a battery before unplugging the cable. So we don't really know
what
> the battery level is going to be once it actually matters.
> 
> So I'm fine with going level=1.0 and charging=true here too.
> 

In that case, when the user plugs in a battery (with whatever amount of
juice remaining), he would see a drop in battery level from 1 to some
value <1, which seems counter-intuitive.

IMO if the device does not have a battery, level should be 0 (device will be
dead if you pull the plug), chargingState should be charging (the web app
can feel free to use full functionality without worrying about power),
remaining should be 0 (in sync with the level).

These values together, and the fact that they remain unchanged over time,
can be used as an (almost consistent?) indication that the device does not
have a battery, if that information is of interest to the web app. 

- Cathy.