Bug 496870

Summary:	Feature Request - Add a global slider, for controlling all connected screens' brightness at once, to the Brightness and Color widget
Product:	[Plasma] plasmashell	Reporter:	Markus Hartung <mail>
Component:	Brightness and Color widget	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	CONFIRMED ---
Severity:	wishlist	CC:	john.kizer, natalie_clarius, postix
Priority:	NOR
Version First Reported In:	master
Target Milestone:	1.0
Platform:	Other
OS:	Other
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Markus Hartung 2024-11-30 16:29:21 UTC

I love the new per monitor brightness slider.

I would like to have a merged slider that controls the brightness globally.

From my understanding of human light perception is that the brightness sensitivity is non-linear, similar to out hearing. So monitors map this non-linear curve to a linear curve with a value between 0 and 100, where the perceived brightness difference would be the same if changing from 10 to 12 than 90 to 92.

I think the are three types of scenarios here. 

1. The monitors are of same brand or have 1to1 mapping of the brightness level so 42 on monitor is perceived as same brightness as 42 on the same monitor.

In this scenario it makes sense to just link the level of brightness together so increasing by one increases by one on both and vice versa on decreased brightness.

2. The monitors have different brightness levels, either that the monitor are less bright due to hardware limitations or that the manufacturer has a different curve. So for example 42 is 60 on the other monitor.

Here's it's more tricky to implement a global adjustment. One naive implementation would be to just change value proportionally using a factor. And if one monitor reaches 0 or 100 no further adjustment is possible. 

3. This is for me a scenario that is unlikely, the user want for some reason have different perceived brightness of their monitor.

I vote for this scenario to be unsupported unless someone have a good reason for it.

Comment 1 John Kizer 2024-12-10 00:32:47 UTC

Hi - have you seen that using global keyboard shortcuts, or scrolling over the brightness widget, adjusts all supported monitors simultaneously? (As announced in https://pointieststick.com/2024/08/23/this-week-in-kde-per-monitor-brightness-control-and-update-then-shut-down/)

Is that the feature that you're requesting?

Comment 2 postix 2024-12-13 10:37:11 UTC

Please see https://invent.kde.org/plasma/powerdevil/-/issues/38#note_1081433 for more context.

Comment 3 Markus Hartung 2024-12-13 11:21:38 UTC

(In reply to John Kizer from comment #1)
> Hi - have you seen that using global keyboard shortcuts, or scrolling over
> the brightness widget, adjusts all supported monitors simultaneously? (As
> announced in
> https://pointieststick.com/2024/08/23/this-week-in-kde-per-monitor-
> brightness-control-and-update-then-shut-down/)
> 
> Is that the feature that you're requesting?

Yeah, that's the feature I'm referring to.

With that I get two sliders, one per monitor. I want a third slider for the global brightness.

Comment 4 John Kizer 2024-12-14 00:34:38 UTC

Thanks for explaining!