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In the Settings app on the Librem 5, after selecting "Power" there is a slider for "Screen Brightness". It kind of works, but it is very jumpy and often jumps back to its previous position. I'm pretty sure it is not a general problem with that kind of sliders because a similar slider control for "System Volume" works perfectly.

Here is a video clip showing the problem:

brightness2

How to reproduce:

• Open Settings app
• Select "Power"
• Move "Screen Brightness" slider to somewhere in the middle
• Drag slider to the right quickly, and quickly lift the finger. Then the slider first follows your finger but then as the finger is lifted the slider jumps back to its original position

To make the slider stay where you want it, the best way seems to be to keep holding the finger in place for a while in the new slider position, then lifting the finger after a second or so. Then the slider usually ends up where you wanted it, sometimes after flickering back and forth between the old and new positions.

This is on a Librem 5 Birch, recently reflashed and with the latest updates installed, in case that matters (phosh 0.7.0 and gnome-control-center 1:3.34.0.1+20042+git6fca0505-1pureos0). But I think this issue has been around for some time, it's not something that appeared in recent changes.

Since the "System Volume" slider in the Sound settings seems to work perfectly, it never seems to have problems like this, one idea would be to check if that slider is setup differently in some way, and see if the "Screen Brightness" slider could be setup in the same way. It looks like exactly the same kind of control, so it's a little funny that one of the sliders works fine and the other doesn't.