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

[martin rudalics]

> 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.
> Evaluating the following form positions the frame to its expected location
> (abutting the right edge of the right monitor):

I'm not familiar with multiple monitors.  But according to the Elisp
manual ...

`left'
     The position, in pixels, of the left (or right) edge of the frame
     with respect to the left (or right) edge of the screen.  The value
     may be:

    an integer
          A positive integer relates the left edge of the frame to the
          left edge of the screen.  A negative integer relates the
                                      ^^^^^^^^^^^^^^^^
          right frame edge to the right screen edge.

    `(+ POS)'
          This specifies the position of the left frame edge relative
          to the left screen edge.  The integer POS may be positive or
          negative; a negative value specifies a position outside the
          screen or on a monitor other than the primary one (for
          multi-monitor displays).

    `(- POS)'
          This specifies the position of the right frame edge relative
          to the right screen edge.  The integer POS may be positive or
          negative; a negative value specifies a position outside the
          screen or on a monitor other than the primary one (for
          multi-monitor displays).

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

Simply disregard this message if you were aware of what you were doing.

martin