get-display-left-top-inset returns non-zero offset for monitor 0 on linux

Following and investigation into tooltips being misplaced in https://github.com/alex-hhh/gui-widget-mixins/issues/3, we determined that the underlying issue is that for some reason on my system I have a non-zero offsets when calling get-display-left-top-inset for monitor zero. This is at variance with the docs.

(require racket/gui)
(get-display-left-top-inset #:monitor 0)
-1200
-370

The full display info is '(linux cs "8.0.0.11" 2 (0 1920 1080 -1200 -370) (1 1200 1920 0 0)) when running

(begin
  (require racket/gui)
  (define (get-display-info)
    (append (list (system-type 'os*) (system-type 'gc) (version) (get-display-count))
            (for/list ([monitor (in-range (get-display-count))])
              (let-values ([(x y) (get-display-size #:monitor monitor)]
                           [(dx dy) (get-display-left-top-inset #:monitor monitor)])
                (list
                 monitor
                 x y dx dy)))))
  (get-display-info))

See also this thread in slack https://racket.slack.com/archives/C06V96CKX/p1618503646014800.

Here is the monitor layout if it helps.

Start with the racket/gui get-display-left-top-inset API and reproduce the supplied monitor-0 output on Linux using the get-display-info snippet. Compare the result with the linked documentation and monitor layout, then confirm that the reported non-zero offset is handled consistently for monitor 0.