For automatic display turn-off, we now allow setting an idle timeoutwhen the screen is locked, down to 0 seconds. This makes sense whenthe session transitions from unlocked to locked, allowing the user toturn off the display at the same time as the lockscreen would appear.
Unfortunately, it didn't work for a 0 second timeout. The issue isthat low timeout values also affect user interaction on wakeup,i.e. when trying to enter the password the user now has 0 secondsavailable to type their password. This prevents us from simplyremoving the check for >0 seconds when registering DPMS timeouts.
Instead, this commit splits the timeout when locked into two internalmember variables.
For the traditional "timeout when locked" value, we now apply a(hardcoded) minimum duration to allow uninterrupted authenticationwhen the lock screen is already active.
In addition, we introduce a new "timeout when activating lock" valuethat uses the configured value as is (more or less - applying anextremely short minimum may help prevent unintended behavior).This new timeout only gets used when switching from unlockedto locked, and is replaced by the regular "timeout when locked"thereafter until the session gets unlocked again.
Suspend/resume handling receives some extra care to behave well.Unlocked timeouts also apply a minimum duration for extra safety.
Extra commit to fix a pre-existing (but related) issue:
actions/bundled/dpms: Less fragile code for pre-turn-off fading
Simplifies the code for better readability.
Also solves an issue on X11 when an activating screen lockerreduces the idle timeout, or for idle timeouts shorter than thehardcoded 5 second fade-out grace period. In either of these cases,both the fade and action timeouts would be signaled immediatelyafter one another, but in the wrong order. The observed effect wasthat the screen turned off first, the user moves their mouse toavoid locking, and the screen comes back on but fades out anyway.
The refactored version avoids these kinds of race conditions bysimply connecting the turn-off action to the screen helper's fadedOutsignal, or in case of Wayland, directly to the timeout like before.No hardcoded fade-out times are necessary anymore.