in some cases, sliding the brightness slider to the right (brighter) actually dims the screen more

[Matt Fischer]

In some cases if you slide the brightness slider to the right (brighter) you actually get a screen that first dims before becoming brighter as you keep sliding.

To repro this you need to start with the brightness at a medium level, not too high or too low. Then close the Control Center. Re-open the control center, click Brightness, and then move the slider right.

You can also repro this by holding your finger on the slider and moving it around, without closing the window. I've only seen it on raising the brightness, usually around the 20 mark.

[Chris Wayne (cwayne)]

I've seen the same going the other way as well (with the patch to fix 0 brightness). Marking as confirmed.

[Matt Fischer (mfisch)]

I've run a test where I play with the slider while running the following in a terminal:

while true; do /usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness; done

This dumps the brightness levels out fairly often.

[Matt Fischer (mfisch)]

I've also noticed that if you have "Dim screen to save power" enabled it can be confusing in the following way:

Slider is 2/3 the way up, brightness is 175. The screen goes idle, brightness drops to 70. You grab the slider to lower the brightness. Concurrently with you sliding the slider lower, the Idle dim disables, so the first thing you see as you lower the slider is brightness going from 70 to 175, then slowly down as you slide, 170, 165, 160, etc. This looks strange.

The issue still occurs for me in the following way, even with "Dim screen to save power" disabled:

Start with the brightness fairly high, slide the bar to the right, lowering the brightness. When it gets to about 25, start sliding back up. The brightness will momentarily go to 20 before increasing.

Here's an example
22
22
22
22
22
22 <- start sliding up
20
20
20
20
28
28
28
35
35
35

I can still repro the issue using a mouse, so it's not just a touch issue.

[Matt Fischer (mfisch)]

I will also note that max brightness on the device is 255, min is 0, leaving a lot of steps in between for the slider. On my laptop the max is 20. I queried my team and the max values were: 7, 8, 7, 7, and 20 for me. *I cannot repro it on systems who have such a small step amount.*

[Matt Fischer (mfisch)]

Possibly related to:
https://bugs.launchpad.net/gnome-control-center/+bug/893851

jmleddy is going to get that patch into Q and then we'll retry these. Meanwhile I will assign to myself.

[Matt Fischer (mfisch)]

Porting the fix from https://bugs.launchpad.net/gnome-control-center/+bug/893851 forward did NOT solve this bug.

[Sean Feole (sfeole)]

Matt, after a weekend of use on Raring I did not see issues with the brightness slider. I didn't see this issue at all. The brightness slider is working as expected (so far).

Can you confirm on your end?

[Matt Fischer (mfisch)]

I can still easily repro this.

[David Francis (dave-francis-uk)]

In past couple of days I have loaded both OpenSUSE and Fedora with Gnome 3.16.2 desktops onto a Zoostorm Plex tablet (Celeron N2807 CPU and Intel Bay Trail graphics) and both exhibit the same fault that moving slider to the right decreases brightness and to the left increases it. Fedora is fully updated and working well, whereas OpenSUSE worked until updates were installed whereupon it crashed beyond recovery so had to be abandoned.
The fault is permanently there, irrespective of whether it is accessed via the drop-down top right or via the Tools icon/All Settings/Power.