Brightness adjustment gauge in gnome-control-center screen not responding to brightness hot-keys

Status changed to 'Confirmed' because the bug affects multiple users.

Are those keys detected at all in the system? It could even be a kernel issue. Could you please look at https://wiki.ubuntu.com/Hotkeys/Troubleshooting ; and provide the info pointed there to the report? Thanks.

Brightness keys are working and they can be used to change screen brightness. The problem is the UI in gnome-control-center is not reflecting the change of screen brightness.

Hello -- Please attach logs from the machine that is impacted here, and also the intended release that should be targeted.

Cheers,
Chris

Basically, this issue is about the Brightness bar in the Screen utility (please see the attached image) not reflecting the actual screen brightness in real time.

Change to confirm as Chih has provided the explanation of the bug

Could somebody having the issue open a bug on the GNOME bug tracker?

Filed at https://bugzilla.gnome.org/show_bug.cgi?id=670043

The issue will not block the shipment. But customer would like to see the bug is fixed and user could get the fix via future update.

The attachment "Brightness-fix-for-gnome-settings-daemon-changes.patch" of this bug report has been identified as being a patch. The ubuntu-reviewers team has been subscribed to the bug report so that they can review the patch. In the event that this is in fact not a patch you can resolve this situation by removing the tag 'patch' from the bug report and editing the attachment so that it is not flagged as a patch. Additionally, if you are member of the ubuntu-reviewers team please also unsubscribe the team from this bug report.

[This is an automated message performed by a Launchpad user owned by Brian Murray. Please contact him regarding any issues with the action taken in this bug report.]

The task for Quantal is Fix Committed since g-c-c 3.5 will be uploaded soon to quantal. As for the fix itself, it's a definite SRU candidate so I'll fix the description for SRU paperwork and sponsor the patch ;)

Hello Chih-Hsyuan, or anyone else affected,

Accepted into precise-proposed. The package will build now and then be available in the -proposed repository. Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you please change the bug tag from verification-needed to verification-done. If it does not, change the tag to verification-failed. In either case details of your testing will help us make a better decision. Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Tested gnome-control-center_3.4.2-0ubuntu0.3 in precise-proposed and can fix this bug.

This bug was fixed in the package gnome-control-center - 1:3.4.2-0ubuntu0.3

---------------
gnome-control-center (1:3.4.2-0ubuntu0.3) precise-proposed; urgency=low

  * debian/patches/Brightness-fix-for-gnome-settings-daemon-changes.patch:
    ensure gnome-settings-daemon DBus interface is properly used to be able to
    reflect brightness changes in UI. (LP: #893851)
 -- <email address hidden> (James M. Leddy) Tue, 26 Jun 2012 09:54:49 -0400

Unsubscribing sponsors, I don't see anything to sponsor here.

This issue still occurs in Quantal, it seems like the fix never made it there.

James, from some discussions today it may also be okay to land the fix in Raring and not Quantal. We are likely rolling over to R in the next few weeks.

I really wish there was a way to take back series nominations. I meant for Quantal only, not Raring.

This is still broken in Q as I stated before, although it appears to be fixed in Gnome 3.4 and 3.6 trunks.

Here are all my notes:

1) The signal "Changed" is coming from g-s-d when the brightness hotkeys are pressed:

$ dbus-monitor --session "type='signal',sender='org.gnome.SettingsDaemon'"
In Quantal:
signal sender=:1.6 -> dest=org.gnome.SettingsDaemon serial=397 path=/org/gnome/SettingsDaemon/Power; interface=org.gnome.SettingsDaemon.Power.Screen; member=Changed

On Precise, we see the same signal:
signal sender=:1.17 -> dest=org.gnome.SettingsDaemon serial=8416 path=/org/gnome/SettingsDaemon/Power; interface=org.gnome.SettingsDaemon.Power.Screen; member=Changed

2) I instrumented the on_signal call inside gnome-control-center/panels/sceen/cc-screen-panel.c to emit a g_warning whenever any signal was received, I never saw anything come out in Q. When the same code was used in P, the message was printed. This implies, rather obviously that g-c-c is never getting the signal.

3) I then wrote a simplified test application that attempted to synchronously (for simplicity) connect to the same signal and just print a message if one was received and again, no message was received. I modified this code slightly to listen for signals from Gnome Screensaver and I get signals, so I think my sample code is fine. The sample code is attached later. To run it with the gnome-screensaver and get results, start the code and run "gnome-screensaver-command -a" in another terminal, and you should see:

** (process:17715): WARNING **: we get signal from :1.89: ActiveChanged

If you swap the 3 screensaver related lines with the SettingsDaemon code you will get no output. (replace lines 39-41 with 46-48)

4) I see one more interesting thing that may or may not be a problem:
The signals from SettingsDaemon have a Destination field of the settings daemon itself. Those from Gnome Screensaver have a "null" destination:

signal sender=:1.6 -> dest=org.gnome.SettingsDaemon serial=397 path=/org/gnome/SettingsDaemon/Power; interface=org.gnome.SettingsDaemon.Power.Screen; member=Changed

signal sender=:1.89 -> dest=(null destination) serial=78 path=/org/gnome/ScreenSaver; interface=org.gnome.ScreenSaver; member=ActiveChanged

Perhaps this is a problem? I don't know enough about dbus to be sure.

To compile that test code I posted:

gcc dbus-test.c -o dbus-test `pkg-config --libs --cflags gio-2.0 gtk+-3.0 dbus-glib-1 dbus-1`

Then ./dbus_test to run it.

I don't know if this is directly related to this bug but I can easily crash gnome-settings-daemon by pressing the brightness up/down keys on my keyboard. I'm using gnome-control-center 3.6.3/gnome-settings-daemon 3.6.3 on raring.