[Xmonad] moving layouts to Workspace

[David Roundy]

Hi all,

I've been thinking that we'd be better off if the contents of layouts were
moved to Workspace, something like

data Workspace i l a = Workspace  { tag :: !i, layouts :: (l a,[l a]), stack :: StackOrNot a }
    deriving (Show, Read, Eq)

Thus the layout for each workspace would be stored with that workspace.
This seems cleaner than the current approach of using a Data.Map.Map to
figure out what the layout is for each workspace, since the data type would
enforce that a layout exists for each workspace, rather than relying on an
invarient that each workspace must have an entry in the map (an invarient I
broke while writing DynamicWorkspaces, embarassingly crashing xmonad).

This change would be pretty pervasive, and a fair amount of work, so I'm
not keen on making it unless there's some sort of consensus that it looks
like a good idea.  Personally, I think it'll be far more beautiful.  There
*are* bits of code that'll get trickier (e.g. Operations.broadcastMessage).
But in my mind any such complexities are outweighed by the greater
modularity, that one can modify a Workspace in isolation--and in a way that
doesn't cause xmonad to crash when the workspace ids get out of sync with
the contents of the Data.Map layouts.
-- 
David Roundy
http://www.darcs.net