[xmonad] XMonad.Layout.LayoutScreens in an upside-down T arrangement

[Adam Vogt]

* On Thursday, January 20 2011, Alistair Gee wrote:

>I have 4 monitors, but I am limited two 2 X screens due to my 2 nvidia
>cards. My current screen setup is:
>
>+------------+------------+
>| X screen 0 | X screen 1 |
>| monitor 1  | monitor 3  |
>+------------+------------+
>| X screen 0 | X screen 1 |
>| monitor 2  | monitor 4  |
>+------------+------------+
>
>That is, the nvidia driver combines monitor 1 and monitor 2 into the 1st X
>screen and monitor 3 and monitor 4 into a 2nd X screen.
>
>To recreate the effect of 4 separate X screens, I use
>XMonad.Layout.LayoutScreens to create a 2x2 screen setup. The command I have
>in xmonad.hs is
>
>    layoutScreens 4 Grid
>
>This works well. However, I would like to rearrange my screen setup to be
>instead as follows:
>
>             +------------+
>             |            |
>             |            |
>+------------+------------+------------+
>|            |            |            |
>|            |            |            |
>+------------+------------+------------+
>
>Using the nvidia configuration tool, I can create the above as:
>
>             +------------+
>             | X screen 0 |
>             |            |
>+------------+------------+------------+
>| X screen 1 | X screen 0 | X screen 1 |
>|            |            |            |
>+------------+------------+------------+
>
>or
>             +------------+
>             | X screen 0 |
>             |            |
>+------------+------------+------------+
>| X screen 1 | X screen 1 | X screen 0 |
>|            |            |            |
>+------------+------------+------------+
>
>However, once I do that, how do I use XMonad.Layout.LayoutScreens to create
>a 4 screen setup again, now that the positions of the monitors are different
>(and I can't use Grid to split up the layout)?
>
>TIA

Hi Alistair,

As you suggested, it's a question of writing an alternative layout. I can 
suggest:
http://xmonad.org/xmonad-docs/xmonad-contrib/XMonad-Layout-LayoutBuilder.html

Otherwise it isn't difficult to directly specify the RectangleS more 
directly:

{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
import XMonad
import qualified XMonad.StackSet as W
import XMonad.Util.Font
import XMonad.StackSet

-- use as  layoutScreens (Tee 640 480) 4
data Tee a = Tee { tee_width, tee_height :: Dimension }
    deriving (Read,Show)
instance (Read a, Show a) => LayoutClass Tee a where
    pureLayout (Tee w h) (Rectangle x0 y0 w0 h0) wins = let
            rects = [Rectangle x0 (y0+fi h) w h,
                    Rectangle (x0 + fi w) y0 w h,
                    Rectangle (x0 + fi w) (y0+fi h) w h,
                    Rectangle (x0 + 2 * fi w) (y0+fi h) w h]
        in W.integrate wins `zip` rects

I likely misunderstand whether xmonad sees separate screens (via xinerama):  
Above I assume xmonad gets a single screen, which suports the choice of 
(`layoutScreens` 4). Otherwise you probably have to adjust 

Adam