On 07/11/2019 04:35 PM, Mike Bird wrote:
> On Thu July 11 2019 14:28:29 andre_debian@... wrote:
>> On my laptop computer , the keys F11 and F12,
>> adjusts the brightness of the screen.
>> But on Debian-Stretch with trinity, these two keys do nothing.
> I can't help you with F11 and F12 but if it's a 70% brightness
> you want you can put "xbacklight -set 70" in a file called
> ".xsessionrc" in your home directory.

You can also check for an interface through, e.g.

  /sys/class/backlight/acpi_video0/

or e.g.

  /sys/class/backlight/intel/

within each directory you should have a sysfs structure for 'brightness' and
'max_brightness'

For example, you can check the current and max brightness with:

  cat /sys/class/backlight/acpi_video0/brightness

  cat /sys/class/backlight/acpi_video0/max_brightness

To set, you must be root (or EUID 0 with sudo, etc..) and

  echo 5 > /sys/class/backlight/acpi_video0/brightness

I just use a script that reads the last set value from
/usr/local/share/brightness on startup (set in ~/.kde/Autostart) and use an
alias to the script `bl` that then allows adjustment with `bl +` or `bl -` or
`bl value`.

You can also end up in the circumstance where your F11/F12 are actually
setting the values in:

  /sys/class/backlight/acpi_video0/brightness

but your video driver (e.g. Nvidia, etc..) is using

  /sys/class/backlight/nvidiabl/brightness

In that case you can use a similar script at startup to background a watch
with inotifywait that watches .../acpi_video0/brightness and then sets
.../nvidiabl/brightness whenever it changes.

Bottom line, few desktops actually have interfaces to manufacturer keyboard
mappings for specific hardware hotkeys. (plasma -- hiss, seems to do better
than others) Some distros used to provide specific packages, and KDE used to
have for example Sony hotkeys package and a few others. But that is they type
of package that must be maintained with every new crop of laptops. (e.g. Sony
hotkeys doesn't mean a whole lot anymore...) So mapping your own key to the
feature you use to control brightness is probably the only reliable way to
make sure they work.

-- 
David C. Rankin, J.D.,P.E.