Basically, I needed Night Light Filter.
Searched on Qubes places, and found only Redshift.
Installing anything in dom0 is not recommended.
Thus, I posted two posts:
Understanding security implications of running Redshift -or similar software- in dom0
Is there a way to Night Light Filter or Grayscale without installing anything in dom0
(The forum doesn’t allow me to put more than two links, so I can’t put links of posts.)
In the second post, a software called sct was mentioned by solene. Thanks to her.
I am no cybersecurity expert when it comes to code, thus I’m asking for studying this very small code.
I think it’ll be amazing if it was studied and vulnerabilities were cleaned, as I see that Redshift (used by many Qubes users) is much code, that may be not as safe to run in dom0. Isn’t that right? Please let me know! Because I think if Redshift is safe to run in dom0, then there’s no reason to study this.
There is the code. Source: https://www.umaxx.net/dl/sct-0.5.tar.gz. The archive contains:
MakefileREADMEsct.1(a man page)sctd.1(a man page)sctd.shsct.c.
I think only sctd.sh and sct.c are needed.
schd.sh:
#!/bin/sh
readonly S_V="0.5" S_YR="2017-2020"
s_err() {
logger -i -p daemon.err -s -t "sctd" "error: ${1}"; exit 1
}
s_hm() {
local h m
h=$(date +"%H" | sed -e 's/^0//') || s_err "hours failed"
m=$(date +"%M" | sed -e 's/^0//') || s_err "minutes failed"
printf "$((h*60 + m))\n"
}
s_run() {
local r hm=$(s_hm) inc=2 t=${1:-4500} sct=$(which sct) || s_err "sct not found"
[ $hm -gt 720 ] && { t=$((t + inc * (1440 - hm))); } ||
{ t=$((t + inc * hm)); }
while :; do
hm=$(s_hm)
[ $hm -gt 720 ] && { t=$((t - inc)); } || { t=$((t + inc)); }
r=$(${sct} ${t})
[ $? -eq 0 ] && { logger -i -p daemon.info -s -t "sctd" "${r}"; } ||
{ s_err "${r}"; }
sleep 60
done
}
s_main() {
[ $# -eq 1 ] && [ "${1}" = "version" ] &&
{ printf "sctd %s (c) %s Aaron Bieber, Joerg Jung\n" ${S_V} ${S_YR};
exit 0; }
[ $# -gt 1 ] &&
{ printf "usage: sctd [<temp>]\n%7ssctd version\n" " ";
exit 1; }
[ $# -eq 1 ] &&
{ [ -z "${1##*[!0-9]*}" -o "${1}" -lt 2000 -o "${1}" -gt 9000 ] &&
s_err "temp failed"; }
trap "s_err \"signal received\"" 1 2 3 13 15
s_run "$@"
}
s_main "$@"
sct.c:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xproto.h>
#include <X11/Xatom.h>
#include <X11/extensions/Xrandr.h>
#define S_V "0.5"
#define S_YR "2015-2020"
enum { S_RED, S_GREEN, S_BLUE, S_MAX };
static const float s_wp[][S_MAX] = { /* whitepoint values from redshift */
{ 1.00000000, 0.18172716, 0.00000000 }, /* 1000K */
{ 1.00000000, 0.42322816, 0.00000000 },
{ 1.00000000, 0.54360078, 0.08679949 },
{ 1.00000000, 0.64373109, 0.28819679 },
{ 1.00000000, 0.71976951, 0.42860152 },
{ 1.00000000, 0.77987699, 0.54642268 },
{ 1.00000000, 0.82854786, 0.64816570 },
{ 1.00000000, 0.86860704, 0.73688797 },
{ 1.00000000, 0.90198230, 0.81465502 },
{ 1.00000000, 0.93853986, 0.88130458 },
{ 1.00000000, 0.97107439, 0.94305985 },
{ 1.00000000, 1.00000000, 1.00000000 }, /* 6500K */
{ 0.95160805, 0.96983355, 1.00000000 },
{ 0.91194747, 0.94470005, 1.00000000 },
{ 0.87906581, 0.92357340, 1.00000000 },
{ 0.85139976, 0.90559011, 1.00000000 },
{ 0.82782969, 0.89011714, 1.00000000 },
{ 0.80753191, 0.87667891, 1.00000000 },
{ 0.78988728, 0.86491137, 1.00000000 }, /* 10000K */
{ 0.77442176, 0.85453121, 1.00000000 } };
static double s_avg(int t, double r, int c) {
return s_wp[t / 500][c] * (1 - r) + s_wp[t / 500 + 1][c] * r;
}
#define S_YELLOW "\x1b[93m"
#define S_RST "\x1b[0m"
static void s_run(const char *s) {
Display *d;
XRRScreenResources *sr = NULL;
XRRCrtcGamma *cg;
unsigned long t;
double r, g;
int i, j, sz;
char *e;
errno = 0, t = strtoul(s, &e, 10);
if (s[0] == '\0' || *e != '\0' || (errno == ERANGE && t == ULONG_MAX))
errx(1, "temp failed");
if (t < 1000 || t > 10000)
t = 6500, warnx("temp range");
t -= 1000, r = t % 500 / 500.0;
if (!(d = XOpenDisplay(NULL)) || !(sr = XRRGetScreenResourcesCurrent(d,
RootWindow(d, DefaultScreen(d)))))
err(1, "XOpenDisplay or XRRGetScreenResourcesCurrent failed");
for (i = 0; i < sr->ncrtc; i++) {
sz = XRRGetCrtcGammaSize(d, sr->crtcs[i]);
if (!(cg = XRRAllocGamma(sz)))
err(1, "XRRAllocGamma failed");
for (j = 0; j < sz; j++) {
g = 65535.0 * j / sz;
cg->red[j] = g * s_avg(t, r, S_RED);
cg->green[j] = g * s_avg(t, r, S_GREEN);
cg->blue[j] = g * s_avg(t, r, S_BLUE);
}
XRRSetCrtcGamma(d, sr->crtcs[i], cg);
XFree(cg);
}
printf(isatty(fileno(stdout)) ? S_YELLOW "Temperature: %luK" S_RST "\n" :
"Temperature: %luK\n", t + 1000);
XFree(sr), XCloseDisplay(d);
}
int main(int argc, char *argv[]) {
if (argc == 2 && !strcmp(argv[1], "version")) {
puts("sct "S_V" (c) "S_YR" Ted Unangst, Joerg Jung");
return 0;
}
if (argc > 2)
errx(1, "usage: sct [<temp>]\n%12ssct version", "");
s_run((argc == 2) ? argv[1] : "6500");
return 0;
}
Ideally, you can compile it in an offline qube and move the produced binary into dom0. Or you can install the compiler in dom0 (maybe gcc is already there?), but it is not really seen as best practice.