Bug#858793: gnome-settings-daemon: setting backlight not working on OLED displays: use randr --brightness instead

[Claudio Sacerdoti Coen]

Package: gnome-settings-daemon
Version: 3.22.2-1
Severity: normal
Tags: upstream

Dear Maintainer,

laptops with OLED display do not have a backlight. To increase/decrease
the brightness of the display the only way is to call

     xrandr --brightness percentage

and there are scripts out there to compute the next percentage from the
kind of request (up/down) and the brightness level (read from
/sys/devices/...)

* What led up to the situation?
The current version of GNOME, however, simply does nothing when the user
requires to increase/decrease brightness. The icons showing the
increase/decrease are presented to the user, but nothing happens.
GNOME writes into /sys/devices/..., but that operations has no effect on
the hardware (of course!)

* What exactly did you do (or not do) that was effective (or ineffective)?

Call xrandr by hand. I could use ACPI to do that automatically when the
Fn button is pressed, but it does not play nicely with GNOME. Moreover
the GNOME slider for the setting still does nothing.

* What outcome did you expect instead?
GNOME should detect that the screen is an OLED one and use xrandr to set
the brightness.

-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.8.0-0.bpo.2-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gnome-settings-daemon depends on:
ii  dconf-gsettings-backend [gsettings-backend]  0.26.0-2+b1
ii  gsettings-desktop-schemas                    3.22.0-1
ii  libasound2                                   1.1.3-5
ii  libc6                                        2.24-9
ii  libcairo2                                    1.14.8-1
ii  libcanberra-gtk3-0                           0.30-3
ii  libcanberra0                                 0.30-3
ii  libcolord2                                   1.3.3-2
ii  libcups2                                     2.2.1-8
ii  libfontconfig1                               2.11.0-6.7+b1
ii  libgdk-pixbuf2.0-0                           2.36.5-2
ii  libgeoclue-2-0                               2.4.5-1
ii  libgeocode-glib0                             3.20.1-2
ii  libglib2.0-0                                 2.50.3-1
ii  libgnome-desktop-3-12                        3.22.2-1
ii  libgtk-3-0                                   3.22.9-4
ii  libgudev-1.0-0                               230-3
ii  libgweather-3-6                              3.20.4-1
ii  liblcms2-2                                   2.8-4
ii  libnm0                                       1.6.2-2
ii  libnotify4                                   0.7.7-1+b1
ii  libnspr4                                     2:4.12-6
ii  libnss3                                      2:3.26.2-1
ii  libpam-systemd                               232-19
ii  libpango-1.0-0                               1.40.4-1
ii  libpangocairo-1.0-0                          1.40.4-1
ii  libpolkit-gobject-1-0                        0.105-17
ii  libpulse-mainloop-glib0                      10.0-1
ii  libpulse0                                    10.0-1
ii  librsvg2-2                                   2.40.16-1+b1
ii  libupower-glib3                              0.99.4-4+b1
ii  libwacom2                                    0.22-1+b1
ii  libwayland-client0                           1.12.0-1
ii  libx11-6                                     2:1.6.4-3
ii  libxext6                                     2:1.3.3-1+b2
ii  libxi6                                       2:1.7.9-1
ii  libxtst6                                     2:1.2.3-1
ii  nautilus-data                                3.22.3-1

Versions of packages gnome-settings-daemon recommends:
ii  iio-sensor-proxy  2.0-4
ii  pulseaudio        10.0-1

gnome-settings-daemon suggests no packages.

-- no debconf information