F18, Gnome: displays failing to span

[Dave Mitchell]

I have a new laptop that I've just installed F18 on. I've plugged an
external VGA monitor in, and used System Settings / Displays to 
position the external screen above the laptop screen. This works as far as
the mouse is concerned: I can move the cursor above the top of the laptop
LCD and it appears near the bottom of the external LCD. However, I can't
open any windows in, or move any windows to the top external LCD.

When dragging a window using the title bar, the window stops moving as
soon as the window's title bar hits the black gnome top bar at the top of
the laptop screen, even though the mouse continues into the external
screen above.

When dragging a window using Super + left mouse, I can drag a window about
80% into the top screen, but it bounces back as soon as the mouse is
released.

Within gnome shell, I can drag windows to the top screen, but again they
bounce back when the mouse is released.

Here's a bit of ASCII art of my layout:

  +----------------------------+
  |                            |
  |       1920 x 1080          |
  |       external LCD         |
  |                            |
  |        (empty)             |
  +--------------------------- +
  
  +----------------------------+
  | Activities   date    icons |
  +----------------------------+
  |                            |
  |       1920 x 1080          |
  |       laptop LCD           |
  |                            |
  |    (lots of windows)       |
  +----------------------------+


-- 
"I do not resent criticism, even when, for the sake of emphasis,
it parts for the time with reality".
    -- Winston Churchill, House of Commons, 22nd Jan 1941.