bug#26905: 25.2: MacOS: tooltips show in wrong display

[Eli Zaretskii <eliz@gnu.org>]

> From: "Charles A. Roelli" <charles@aurox.ch>
> Date: Sat, 13 May 2017 11:02:04 +0200
> 
> If I remove the marked lines in compute_tip_xy:
> 
>      if (INTEGERP (left) || INTEGERP (right))
>        *root_x = pt.x;
> =>  else if (pt.x + XINT (dx) <= 0)
> =>    *root_x = 0; /* Can happen for negative dx */
>      else if (pt.x + XINT (dx) + width
> 	     <= x_display_pixel_width (FRAME_DISPLAY_INFO (f)))
>        /* It fits to the right of the pointer.  */
>        *root_x = pt.x + XINT (dx);
>      else if (width + XINT (dx) <= pt.x)
>        /* It fits to the left of the pointer.  */
>        *root_x = pt.x - width - XINT (dx);
>      else
>        /* Put it left justified on the screen -- it ought to fit that way.  */
>        *root_x = 0;
> 
> Then the problem is gone.

Those lines were added to fix some problems (whose particulars I
cannot find at the moment), so we shouldn't remove them without
understanding what is going on.