Nushell script demonstrating mouse handler.

mouse-test.nu

# Mouse event handler with escape option
while true {
    let event = input listen
    
    # Check for keyboard input to exit
    if $event.type == "key" {
        if $event.code == "Esc" {
            print "Exiting on Escape key..."
            break
        } else {
            print $"Exiting on key press: ($event.code)"
            break
        }
    }
    
    # Handle mouse events
    if $event.type == "mouse" {
        match $event.kind {
            "Left_down" => { print $"Left click at ($event.col), ($event.row)" }
            "Right_down" => { print $"Right click at ($event.col), ($event.row)" }
            "moved" => { print $"Mouse moved to ($event.col), ($event.row)" }
        }
    }
}

It seems that moved events are throttled to only one somehow. And the coordinates are those of the window itself, not the per-program space. So would likely need to take over the screen contents to make use of this, maybe with alt-screen. Columnar/x coords work fine though, it's only vertically that things change as you print.