[notacoward]

My two favorites were xev, for finding out which key/event codes I needed to put in config files, and xnest, for trying out new window managers or containing window-happy applications in a single top-level window before workspaces became a common thing.

[ajross]

Also xmag, for those "what is going on at the pixel level" questions that screenshots are poor at answering. Alas, this doesn't work on wayland for obvious (yet... deeply regrettable) security reasons.

[natmaka]

For Wayland there is now "wev"

https://lists.freedesktop.org/archives/wayland-devel/2019-Au...