* afterResume had *two* different implementations, so the historical one
that handled frontlight fixups no longer ran
(regression since #10426)
* isFrontlightOn was completely broken, for a couple of reasons:
* There was no is isFrontlightOnHW implementation, so when it ran, it
mostly always thought the frontlight was on, because
self.fl_intensity doesn't change on toggle off.
* _decideFrontlightState was never called on Kindle,
so isFrontlightOnHW was never really called, making isFrontlightOn
completely useless. Call it in setIntensityHW's coda, as it ought to
be. And properly document that.
Generic *was* calling _decideFrontlightState is setIntensity, but
*before* actually setting the frontlight, which makes no goddamn sense,
so get rid of that, too.
* Also fix frontlight toggle notifications (regression since #10305)
TL;DR: The PowerD API being a mess strikes again.
Companion PR to https://github.com/koreader/koreader-base/pull/884
* Basically flags devices known to be stable when using PxP inversion.
* Plus, random fix for #4870 ;).
* A few FrontLight tweaks & cleanups on Kobo:
* Moved the Kobo-specific startup status insanity to Kobo-specific init
* Made turnOff/turnOn frontlight do a smooth ramp down/up
* On Kobo, use turnOff/turnOn for suspend/resume, to get that smooth toggle
* On Kobo, for NaturalLight w/ a mixer, only set warmth for setWarmth, and only set Brightness for setBrightness, otherwise, it tried to set both with not in-sync values, which made the FL widget jittery.
I believe this should be `if isKobo()`, or better yet that the entire
block should be moved to `KoboPowerD:init()` because afaik that is the
only platform where the system doesn't provide trustworthy frontlight
information. But to be absolutely sure that I don't break anything (and I
don't want to spend any time on this atm) I'm temporarily excluding only
Android where this behavior is known to be problematic.
See discussion in https://github.com/koreader/koreader/issues/3118#issuecomment-334995879
References #3118 (using keyword "references" because phrases like "possibly fixes"
result in GH autoclose).
