bug#25818: 25.2; frame moved off display does not return (OS X)

[martin rudalics]

>> See also https://debbugs.gnu.org/cgi/bugreport.cgi?bug=18801.  It's
>> possible that the problem was introduced from 24.3 to 24.4.
>
> I built 24.3 and 24.4 from source, and it is correct that a regression
> with Emacs' handling of the window system in OS X happened between those
> two releases.
>
> The form I suggested to show the issue,
[...]
> works correctly on 24.3 but not on 24.4 (24.4 has the same behavior as
> 25.1 and 25.2, detailed in my first message).  I guess the regression
> would be in src/nsterm.m, or maybe src/nsfns.m.

So something seems to have happened that Emacs fell into the same trap
as other applications (which, in my understanding, is that the frame
gets displayed on another, probably non-existent, monitor).  I'm afraid
that my only suggestion is to bisect the sources until you've found the
culprit.

(I suppose you verified that the value returned by ‘display-pixel-width’
is the same in 24.3 and 24.4.)

martin