From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jesse Gibbons <jgibbons2357@gmail.com>
Subject: Re: How to set default screen brightness?
Date: Sat, 15 Jun 2019 13:22:23 -0600
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To: Tobias Geerinckx-Rice <me@tobias.gr>
Cc: help-guix@gnu.org

On Sat, 15 Jun 2019 19:41:13 +0200
Tobias Geerinckx-Rice <me@tobias.gr> wrote:

> Jesse,
>=20
> Jesse Gibbons wrote:
> > My Librem 13 laptop battery lasts much longer with a lower=20
> > screen
> > brightness. When it runs gnome on guix (and I haven't tried any=20
> > other
> > de) I have to turn down the brightness every time. This is not=20
> > so with
> > my other partition running PureOS. Is there a way to configure a
> > default screen brightness in guix/gnome? =20
>=20
> Guix doesn't have a notion of =E2=80=98default=E2=80=99 screen brightness=
 because=20
> it doesn't know anything about brightness.
>=20
> My guess is that PureOS uses systemd; systemd provides a=20
> backlight.service that reads the backlight brightness at shutdown,=20
> stores it to disc, and writes that value back to the device at=20
> next start-up.
>=20
> It would be a relatively trivial service to add, but that hasn't=20
> been done yet :-)
>=20
> We do already provide a simple, script-friendly abstraction tool=C2=B9:
>=20
>   $ guix install light
>   $ sudo light -S 50 # percentage
>=20
> It can even run setuid.
>=20
> Kind regards,
>=20
> T G-R
>=20
> [1]: As opposed to manually reading and writing `find /sys -path=20
> *backlight*brightness*`.

Thanks. I think I can add a service using the `light` tool.
Administrators will likely prefer to install it on anything with a
display that runs on battery power, so I might contribute it in
gnu/services/pm.scm if nobody beats me to it.
-Jesse