bug#21348: 25.0.50; Screen scaling factor >=2 causes menus, tooltips to display in the wrong place

[martin rudalics]

> I'm on Ubuntu 14.04.3 using a Dell XPS 13, which has screen resolution
> 3200x1800. In order to make the menus large enough to read, the screen
> is scaled at x2.
>
> However, at that scale setting, Emacs shows tooltips and menus at an
> offset a few inches down and to the right of the mouse pointer.
>
> Using the settings panel I can change the scaling factor. If I reduce it
> below 2, for example to 1.88, then Emacs displays menus and tooltips
> where I would expect. At a scale setting equal to or higher than 2x, the
> menus and tooltips are shifted down and to the right.

What does evaluating for a maximized frame

(frame-geometry)

and

(display-monitor-attributes-list)

return for you?  And please tell me whether mouse warping is also
affected by this: Put

(let ((position (window-absolute-pixel-position)))
  (set-mouse-absolute-pixel-position
   (car position) (cdr position)))

into *scratch*, move point after it and type C-x C-e.  Is the mouse
pointer shifted from the upper left corner of the cursor glyph by the
same amount as the menus and tooltips?

martin