bug#21173: 25.0.50; New frames positioned off screen with multiple monitors

[Francis Litterio <flitterio@gmail.com>]

martin rudalics <rudalics <at> gmx.at> writes:

>  > In buffer *scratch*:
>  >
>  >    (setq f (make-frame '((left . -1))))
>  >    #<frame emacs <at> IZSYSTEM023 015257f0>
>  >
>  >    (frame-parameter f 'left)
>  >    3155
>  >
>  > The left offset of the new frame appears to be 1920 pixels too
>  > far to the right.

> ... you try to the position the right edge of the frame by 1 pixel 
left
> of the right edge of the "screen".  Didn't you get exactly that?

No. The new frame is completely off-screen, almost a full monitor's
width right of the right edge of the the right monitor.  It's left
frame parameter has been computed incorrectly by function
x_calc_absolute_position.

> That
> is, talking about a "left offset" in this case is misleading.
> What was your "right offset?

An Emacs frame does not have a "right offset".  The (left . -1)
above means to set the left frame parameter to whatever value
is needed to position the right edge of the frame at the right
edge of the display.  That does not happen in my case,
because my display's left offsets start at -1980 (at the
left edge of the left monitor) and proceed to 0 (the left
edge of the right monitor) and then to +1979 (right edge of
the right monitor).

Function x_calc_absolute_position does not account for the fact
that my left monitor's left offsets are negative.  I believe that
is the root of the bug.
--
Fran
flitterio <at> gmail.com