Gromit-MPX is an on-screen annotation tool that works with any Unix desktop environment under X11 as well as Wayland.
None of the existing display configuration tools does what I think is "the right thing".
xrandr
to read the systems' current statexrandr
invocation to reflect the desired configurationxclip is a command line utility that is designed to run on any system with an X11 implementation.
xclip provides an interface to X selections ("the clipboard") from the command line. It can read data from standard in or a file and place it in an X selection for pasting into other X applications. xclip can also print an X selection to standard out, which can then be redirected to a file or another program.