The set of commits to support !361 has grown long enough that perhaps a separate "kwinbrightness tweaks only" MR is warranted. Here's what's cooking:
daemon/controllers/kwinbrightness: Sort displays in order of priority
(This was originally only meant as a quality-of-life improvement, but now also benefits the next commit below by starting out with the "main" display in the set of legacy displays.)
daemon: Don't mix internal and external displays in legacy brightness controls
Before the introduction of kwinbrightness, the legacy set of displaysincluded either the internal laptop screen, or all external monitors.This was done by adding only displays from the same detector tothe legacy set.
KWinDisplayDetector includes all kinds of displays, which means thebehavior under Wayland was now different than under X11 where KWinis not used. Using kwinbrightness, internal and external displayswould all be part of the same legacy set. Scrolling the brightnessapplet icon would adjust all displays whereas on X11 it would onlyadjust the laptop display.
To prevent this inconsistency, add an extra condition for displaysin the legacy set to also match each other's isInternal() boolean.This restores the original behavior for the time being.
In the long run, we'll remove the legacy brightness API andassociated display set, replacing it with a new per-display API.
daemon/controllers/kwinbrightness: Set label manually for internal outputs
Internal outputs will now show up as "Built-in Screen".
Once KScreen (via KWin) provides a nicer string than it currentlydoes, we can remove the part again that sets the current string.The i18nc() expression is reused from BacklightBrightness, so noextra work for translators.