Add a LayoutClass to allow different layouts for portrait and landscape monitors.

[gcoakes]

Problem Description

I wrote a simple instance of LayoutClass which will allow you to specify two different layouts, one for portrait and one for landscape. I wanted to scope out whether this would be accepted as a PR before I took the effort of integrating it with xmonad-contrib directly rather than just in my config.

Configuration File

Please include the smallest configuration file that reproduces the
problem you are experiencing:

data EitherRatio p l a = EitherRatio (p a) (l a)
  deriving (Show, Read)

instance (LayoutClass p a, LayoutClass l a) => LayoutClass (EitherRatio p l) a where
  runLayout (W.Workspace i (EitherRatio p l) ms) r@(Rectangle rx ry rw rh)
    | rw < rh = do
        (lrs, newP) <- runLayout (W.Workspace i p ms) r
        return $ (lrs, fmap (`EitherRatio` l) newP)
    | rw >= rh = do
        (lrs, newL) <- runLayout (W.Workspace i l ms) r
        return $ (lrs, fmap (EitherRatio p) newL)

  handleMessage (EitherRatio p l) msg = do
    mp <- handleMessage p msg
    ml <- handleMessage l msg
    return $ case (mp, ml) of
      (Just np, Just nl) -> Just $ EitherRatio np nl
      (Just np, Nothing) -> Just $ EitherRatio np l
      (Nothing, Just nl) -> Just $ EitherRatio p nl
      _                  -> Nothing

  description (EitherRatio p l) =
    "[ " ++ description p ++ " | " ++ description l ++ " ]"

Checklist

• I've read CONTRIBUTING.md

• I tested my configuration with xmonad-testing

[geekosaur]

There's already a layout modifier that does this by comparing to a fixed horizontal size, which is less than ideal, so I don't see a reason it would be rejected.

[liskin]

Might be a good idea to have them both in one module, but the XMonad.Layout.PerScreen name seems non-intuitive to me (I wouldn't look there if I was trying to find it), so maybe it's not as good an idea after all. :-)

[byorgey]

Looks great to me! And generally speaking, the bar for including new modules in xmonad-contrib is not that high---as long as it won't make xmonad crash and would be useful to someone, there's no good reason to exclude it. So your contribution would be most welcome.

[gcoakes]

I'm not going to be pursuing this PR anymore. There were some issues associated with stale window decorations, and I've since stopped using it. If anyone wants to pick this up, I still think it would be useful to the project, but I won't personally be using it.