I did look at DialogBox.pm and a few others. This is why I feld that probably the Show routine was at fault. I did not know where to find Popup till your message, however. In Wm.pm I now see it. Indeed, this part of it would appear to cause the problem. 

    # adjust to not cross screen borders
    if ($X < 0) { $X = 0 }

[download]

Unfortunately, when I change this line my code runs the same. So I'm mystified.

Also in Wm.pm I noted the Post routine. It contains this. 

    $w->geometry("+$X+$Y");
    # $w->MoveToplevelWindow($X,$Y);

[download]

I'm guessing that the commented out MoveToplevelWindow call was replaced by the one to geometry (which works OK on multiple monitors).

Thanks for the leads, however. :)

In reply to Re^4: Tk multiple monitor problem by JohnRS
in thread Tk multiple monitor problem by JohnRS

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