Conky is a widget available on Linux, that allows the display of an enormous amount of data about system resources in real-time. Amongst those resources it can display is data available from MPD - Music Player Daemon. However, there are some bits of info that MPD outputs that conky doesn't collect, and some of that is particularly interesting.

It is possible to get that information though, although there are different techniques. For example, this extracts the current queue position and the length of the queue:

${execi 1 (mpc -h romeo status|grep 'playing.'|cut -f2 -d'#'|cut -f1 -d' ')}

As you can see, it requires a bit of shell arcanery, but actually it's pretty straightforward. For the elapsed time, I simply took the values of two conky variables (mpd_length and mpd_elapsed), which appear as 00:00 format time strings, converted them to seconds, subtracted one from the other and turned the result back into a formatted time string. In this case, I wrote a few functions in lua and added the lua script to conky.

For the length of the entire queue, I wrote an application in Rust (which compiles down to optimised machine code). This application fetches the entire playlist from MPD and then iterates through the list extracting the length of the track in seconds, and accumulating the results - then formats the result as a 00:00:00 formatted time string.