This adds a new `tray-foreground` config option, and uses it instead of
the `tray-background` setting to build up the `_NET_SYSTEM_TRAY_COLORS`
property. I'm pretty sure that the previous behavior was a mistake (this
was introduced in 94298741b6 which is a
pretty large diff). For me and some other people, this results in a
black icon being drawn on top of a black background, which is pretty
useless! I would say that this diff fixes
https://github.com/polybar/polybar/issues/2235. Note: the old code dealt
with `unsigned int` and maxed values out at 0xff. The new code deals
with `uint16_t` and maxes values out at 0xffff. I haven't found the
relevant documentation to justify this change, but from manually
testing, I'm pretty confident this is the right change.
This all matches pretty closely with this code from i3:
[`i3bar/src/xcb.c::init_tray_colors`
code](43e805a00d/i3bar/src/xcb.c (L1490-L1522)),
which you can see also uses the bar's foreground color and maxes values
out at 0xffff, not 0xff.
If you merge this up, I think we should also update
https://github.com/polybar/polybar/wiki/Configuration#bar-settings to
mention the new settings.
Fixes#2235
f488a889bc