I have to apology to
Igor Eisberg again.
He was right pretending the effects of the setting "MIUI optimisations" are much wider and deeper than only the power saving feature of the apps.
I found out that disabling it causes the main dysfunction of the automatic brightness.
Enabling back this settings was not enough to restore the normal behavior of the auto brightness. Even wiping the caches then installing the rom again had not effect.
I have to restore a backup that includes the system partition to get the auto brightness working fine again.
In other words, now, I understand perfectly why this settings has been removed and its value forces to enabled.
Disabling it can give unexpected trouble almost everywhere.
BTW, the auto brightness of my Whyred remains affected by a flaw that isn't related to the "MIUI optimisations".
The screen lights on normally when the power button is pressed, but it goes on very slowly through the opening a magnetic holster (that use the magnetic sensor of the phone).
It's brightness starts very low, it stays like this more than one second before it ramps up to the normal brightness.
But I know this flaw comes from Xiaomi and not from Xiaomi.eu.
Anyway, I still struggle to distinguish what is under the control of xiaomi.eu and what's is not but I don't expect any answer to this question as it must be too long and complicated to be written here.
