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).