xob - X Overlay Bar

A lightweight configurable overlay volume/backlight/progress/anything
bar for the X Window System (and Wayland compositors with XWayland).
Each time a new value is read on the standard input, it is displayed as
a tv-like bar over other windows. It then vanishes after a configurable
amount of time. A value followed by a bang '!' is displayed using an
alternate color to account for special states (e.g. muted audio). There
is also support for overflows (when the value exceeds the maximum).