[Usability]multihead screen focus handling

[Havoc Pennington <hp redhat com>]

Hi,

I'm trying to actually use multihead and have noticed that (among
quite a few bugs) we don't seem to have good handling of which screen
is currently focused.

The focused screen matters e.g. when I press a shortcut to change
workspaces, which screen does it affect. Or if I alt+tab, do I get
windows on screen 0 or screen 1 in my list of windows.

Right now the focused screen is the one that contains the focused
window.

 - "the screen containing the mouse cursor" seems a bit more
   convenient to me

 - either way, we don't seem to have any way to change the focused
   screen using only the keyboard (alt+tab lists only windows on the
   focused screen, so there's no way to focus a window on another
   screen)

Havoc