I'm running Ubuntu Linux with two displays. The one on the left is a laptop which I use for terminals and whatnot. Directly in front of me is a larger monitor I use for editing.

I noticed that every time I started DrRacket it would show up on the primary (left) screen. After some digging it appeared that the problem was in frame:size-pref-mixin. My test program is at the end of this description.

I believe that the issue is due to get-display-left-top-inset returning negative numbers in some cases. In this instance the left number is -1920 per the following trace statement I inserted into get-sizes/maximzed when I was figuring this out:

mon 1 delta 769 x 307 left -1920 top 0 mon size 1920 x 1080

This fails the first <= test I that I have changed resulting in the window position always being recalculated. I changed the second one to account for vertical placement of multiple monitors.

With these changes I can turn off the secondary monitor, resulting in the window going to the primary monitor. Turning the secondary monitor back on puts the window back on the secondary monitor. I changed the display configuration to have the primary on the right and it worked there as well. I haven't done really extensive testing but the basic mechanism seems to work right except for the two items I have changed so maybe this is sufficient.

This is pretty thorny code and I don't have any Mac or Windows platforms. The two simple changes in this PR make it work for me but it may break code on other platforms.

Demo program is below (github apparently won't allow me to attach an .rkt file). Run the program then move the window to another monitor and close it. Run the program again. Not sure how to unit test this so I didn't bother.

#lang racket

(require racket/gui framework)

(define window-title "Demo Issue")
(define size-prefs 'demo-size-prefs)
(define posn-prefs 'demo-posn-prefs)

(frame:setup-size-pref
 size-prefs 300 100
 #:position-preferences posn-prefs)

(define where-window%
  (class (frame:size-pref-mixin
          (frame:basic-mixin
           frame%))
    (super-new
     [label window-title]
     [size-preferences-key size-prefs]
     [position-preferences-key posn-prefs])

    (define/override (on-size width height)
      (super on-size width height))

    (define/override (on-move x y)
      (super on-move x y))))

(let ([new-es 
       (make-eventspace)])
  (parameterize ([current-eventspace new-es])
    (let ([f (new where-window%)])
      (send f show #t))))

I also noticed a very minor documentation error that should be self-explanatory.