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nixpkgs/nixos/modules/services/x11/redshift.nix
8573 34435a9502 redshift: Fix default value of $DISPLAY (#17746)
Before commit 54fa0cfe4e, the `redshift`
service was run with the environment variable `DISPLAY` set to `:0`.

Commit 54fa0cfe4e changed this to
instead use the value of the `services.xserver.display` configuration
option in the value of the `DISPLAY` variable. In so doing, no default
value was provided for the case where `services.xserver.display` is
`null`.

While the default value of `services.xserver.display` is `0`, use of
which by the `redshift` module would result in `DISPLAY` again being
set to `:0`, `services.xserver.display` may also be `null`, to which
value it is set by, e.g., the `lightdm` module.

In the case that `services.xserver.display` is `null`, with the change
made in commit 54fa0cfe4e, the `DISPLAY`
variable in the environment of the `redshift` service would be set to
`:` (a single colon), which, according to my personal experience,
would result in —

  - the `redshift` service failing to start; and

  - systemd repeatedly attempting to restart the `redshift` service,
    looping indefinitely, while the hapless `redshift` spews error
    messages into the journal.

It can be observed that the malformed value of `DISPLAY` is likely at
fault for this issue by executing the following commands in an
ordinary shell, with a suitable `redshift` executable, and the X11
display not already tinted:

  - `redshift -O 2500` — This command should reduce the color
    temperature of the display (making it more reddish).

  - `DISPLAY=':' redshift -O 6500` — This command should raise the
    color temperature back up, were it not for the `DISPLAY`
    environment variable being set to `:` for it, which should cause
    it to, instead, fail with several error messages.

This commit attempts to fix this issue by having the `DISPLAY`
environment variable for the `redshift` service default to its old
value of `:0` in the case that `services.xserver.display` is `null`.

I have tested this solution on NixOS, albeit without the benefit of a
system with multiple displays.
2016-08-17 13:34:26 +02:00

121 lines
3 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
cfg = config.services.redshift;
in {
options.services.redshift = {
enable = mkOption {
type = types.bool;
default = false;
example = true;
description = ''
Enable Redshift to change your screen's colour temperature depending on
the time of day.
'';
};
latitude = mkOption {
type = types.str;
description = ''
Your current latitude, between
<literal>-90.0</literal> and <literal>90.0</literal>.
'';
};
longitude = mkOption {
type = types.str;
description = ''
Your current longitude, between
between <literal>-180.0</literal> and <literal>180.0</literal>.
'';
};
temperature = {
day = mkOption {
type = types.int;
default = 5500;
description = ''
Colour temperature to use during the day, between
<literal>1000</literal> and <literal>25000</literal> K.
'';
};
night = mkOption {
type = types.int;
default = 3700;
description = ''
Colour temperature to use at night, between
<literal>1000</literal> and <literal>25000</literal> K.
'';
};
};
brightness = {
day = mkOption {
type = types.str;
default = "1";
description = ''
Screen brightness to apply during the day,
between <literal>0.1</literal> and <literal>1.0</literal>.
'';
};
night = mkOption {
type = types.str;
default = "1";
description = ''
Screen brightness to apply during the night,
between <literal>0.1</literal> and <literal>1.0</literal>.
'';
};
};
package = mkOption {
type = types.package;
default = pkgs.redshift;
defaultText = "pkgs.redshift";
description = ''
redshift derivation to use.
'';
};
extraOptions = mkOption {
type = types.listOf types.str;
default = [];
example = [ "-v" "-m randr" ];
description = ''
Additional command-line arguments to pass to
<command>redshift</command>.
'';
};
};
config = mkIf cfg.enable {
systemd.user.services.redshift = {
description = "Redshift colour temperature adjuster";
wantedBy = [ "default.target" ];
serviceConfig = {
ExecStart = ''
${cfg.package}/bin/redshift \
-l ${cfg.latitude}:${cfg.longitude} \
-t ${toString cfg.temperature.day}:${toString cfg.temperature.night} \
-b ${toString cfg.brightness.day}:${toString cfg.brightness.night} \
${lib.strings.concatStringsSep " " cfg.extraOptions}
'';
RestartSec = 3;
Restart = "always";
};
environment = {
DISPLAY = ":${toString (
let display = config.services.xserver.display;
in if display != null then display else 0
)}";
};
};
};
}