From 2fc212c92a6b4d51c12520109d24f7d69a64d2d3 Mon Sep 17 00:00:00 2001
From: Andrea Rossato <andrea.rossato@unibz.it>
Date: Thu, 24 Jan 2008 02:32:07 +0100
Subject: Add emptyLayout to LayoutClass, a method to be called when a
 workspace is empty

darcs-hash:20080124013207-32816-35328360400d6ee06c81586b9e1cc45413df5a61.gz
---
 XMonad/Core.hs   | 7 ++++++-
 XMonad/Layout.hs | 3 +++
 2 files changed, 9 insertions(+), 1 deletion(-)

(limited to 'XMonad')

diff --git a/XMonad/Core.hs b/XMonad/Core.hs
index 877a73a..df9c4b7 100644
--- a/XMonad/Core.hs
+++ b/XMonad/Core.hs
@@ -218,6 +218,10 @@ class Show (layout a) => LayoutClass layout a where
     pureLayout  :: layout a -> Rectangle -> Stack a -> [(a, Rectangle)]
     pureLayout _ r s = [(focus s, r)]
 
+    -- | 'emptyLayout' is called when there is no window.
+    emptyLayout :: layout a -> Rectangle -> X ([(a, Rectangle)], Maybe (layout a))
+    emptyLayout _ _ = return ([], Nothing)
+
     -- | 'handleMessage' performs message handling for that layout.  If
     -- 'handleMessage' returns Nothing, then the layout did not respond to
     -- that message and the screen is not refreshed.  Otherwise, 'handleMessage'
@@ -238,6 +242,7 @@ class Show (layout a) => LayoutClass layout a where
 
 instance LayoutClass Layout Window where
     doLayout (Layout l) r s  = fmap (fmap Layout) `fmap` doLayout l r s
+    emptyLayout (Layout l) r = fmap (fmap Layout) `fmap` emptyLayout l r
     handleMessage (Layout l) = fmap (fmap Layout) . handleMessage l
     description (Layout l)   = description l
 
@@ -245,7 +250,7 @@ instance Show (Layout a) where show (Layout l) = show l
 
 -- | This calls doLayout if there are any windows to be laid out.
 runLayout :: LayoutClass l a => l a -> Rectangle -> Maybe (Stack a) -> X ([(a, Rectangle)], Maybe (l a))
-runLayout l r = maybe (return ([], Nothing)) (doLayout l r)
+runLayout l r = maybe (emptyLayout l r) (doLayout l r)
 
 -- | Based on ideas in /An Extensible Dynamically-Typed Hierarchy of Exceptions/,
 -- Simon Marlow, 2006. Use extensible messages to the handleMessage handler.
diff --git a/XMonad/Layout.hs b/XMonad/Layout.hs
index 01c0428..981541c 100644
--- a/XMonad/Layout.hs
+++ b/XMonad/Layout.hs
@@ -54,6 +54,9 @@ instance (LayoutClass l a, LayoutClass r a) => LayoutClass (Choose l r) a where
     doLayout (SLeft  r l) = (fmap (second . fmap $ SLeft r) .) . doLayout l
     doLayout (SRight l r) = (fmap (second . fmap $ SRight l) .) . doLayout r
 
+    emptyLayout (SLeft  r l) = (fmap (second . fmap $ SLeft r) .) $ emptyLayout l
+    emptyLayout (SRight l r) = (fmap (second . fmap $ SRight l) .) $ emptyLayout r
+
     description (SLeft _ l)  = description l
     description (SRight _ r) = description r
 
-- 
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