======Synopsis:======
[[on]] [<modes>]switch_windows [<serial#>] [-|^]<match> { <action> }

======Description:======
This hook is triggered whenever the client changes what it thinks
your "current" window is in any given context.

======Parameters:======
|$0 |the old screen number|
|$1 |the old window number|
|$2 |the new screen number|
|$3 |the new window number|

======Other Notes:======
Note that the window might change through forces other than the
window keybindings.  You can get a pretty good idea when this
happens, though, because $0 and $2 will be different.