SUMMARY If System Settings> Power Management > Dim screen is checked and a time is set, after the specified time, only the laptop screen dims, not external monitors. "Screen Energy Saving" has effect on all the monitors. My monitors certainly support different brightness. They are connected through USB-C and DP. They are recent Dells. It does not have to do anything with Primary monitor - I tried to set it to external monitors but it had no affect. I am on X, Kubuntu 21.10.
*** Bug 469272 has been marked as a duplicate of this bug. ***
469272 reports the problem only in wayland, but not in X11 > Screen dimming is only applied to laptop display, not connected external displays in Wayland, works in X11
Reproduced on Wayland. But from a battery conservation point of view, there is no need to dim external displays, right? The external displays don't draw power from the laptop. So I am tempted to close this as INTENTIONAL or NOT A BUG...
Well, it is just not about battery but also about electricity cost and by extension climate, so I think it is a bug.
On the other hand I do know that controlling the backlight of external displays can be complicated, and sometimes is impossible. Let's see what the developers think about this.
Plasma versions prior to 6.2 had technical limitations that prevented setting the brightness of both internal and external displays together. This issue has not been addressed so far, but with the recent introduction of per-display brightness controls, we need to rethink dimming in a multi-monitor environment. I'm leaning towards dimming all the screens. The energy angle certainly speaks for it, and it also looks more consistent to the user. Unlike the "Change screen brightness" setting, which uses a percentage of the maximum brightness, dimming uses a percentage of the current brightness of each monitor - so that's less awkward if applied across multiple screens with different brightness ranges. The current infrastructure is still limited in some ways that will omit the correct brightness being restored after wake-up, reboots and reconnecting. This would still speak for limiting the impact to just the single internal screen, which at least can't be unplugged. Hopefully we can resolve these limitations before too long, and focus entirely on the desired user experience.
(In reply to Jakob Petsovits from comment #6) > I'm leaning towards dimming all the screens. Was this implemented? If yes, it may be the cause of a regression: I have an external monitor connected, that uses a different brightness than my laptop screen. With the recent upgrade, all screens now get dimmed. However, when returning from idle, **ALL SCREENS GET SET TO THE SAME BRIGHTNESS**. This really breaks things for my work flow, because I set the laptop screen and external monitor to have different brightnesses. Is it possible to restore the screen brightnesses individually?
(In reply to gi1242 from comment #7) > Was this implemented? Actually yes, dimming for all screens is now a feature in Plasma 6.2. So I figure we can mark this bug as resolved. > (...) However, when returning from idle, **ALL SCREENS GET SET TO THE SAME BRIGHTNESS**. (...) > > Is it possible to restore the screen brightnesses individually? I've already put a fix into the 6.2 branch to restore brightness to each monitor's original value, but it didn't make it for 6.2.0. Please upgrade to 6.2.1 when it gets released next week (sorry I couldn't make it happen on time for the initial release).
(In reply to Jakob Petsovits from comment #8) > > Is it possible to restore the screen brightnesses individually? > > I've already put a fix into the 6.2 branch to restore brightness to each > monitor's original value, but it didn't make it for 6.2.0. Please upgrade to > 6.2.1 when it gets released next week (sorry I couldn't make it happen on > time for the initial release). Thanks so much. I'll post back if I have issues after I upgrade to 6.2.1