On Thursday 11 July 2019 11:40:33 pm David C. Rankin wrote:
> 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.

I've used GUI tools that will show you key identifiers.  Alas, I didn't take 
notes of what it was.  It was related to:

xbindkeys
xbindkeys-config
xdotool

Found it!  xev (from a command line)

See the thread "How to use mouse click as part of a keyboard shortcut?" 
(Jun/July 2018) for more info on how to map the keypress to an action.

Best,
Michael