From 1c21d0580c70b1351ee8c58ba853ddb032635f34 Mon Sep 17 00:00:00 2001
From: Dmitri Iouchtchenko <johnnyspoon@gmail.com>
Date: Wed, 23 Jan 2013 05:38:50 +0100
Subject: Avoid repainting elements in X.A.GridSelect

Ignore-this: 8e926cebc8d458a06a05f7457ae40b68

darcs-hash:20130123043850-7d114-908a346dd3d8a84cd896fcde1505d41284f01795.gz
---
 XMonad/Actions/GridSelect.hs | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/XMonad/Actions/GridSelect.hs b/XMonad/Actions/GridSelect.hs
index bb392d9..513d4ac 100644
--- a/XMonad/Actions/GridSelect.hs
+++ b/XMonad/Actions/GridSelect.hs
@@ -238,10 +238,11 @@ data TwoDState a = TwoDState { td_curpos :: TwoDPosition
                              , td_paneY :: Integer
                              , td_drawingWin :: Window
                              , td_searchString :: String
+                             , td_elementmap :: TwoDElementMap a
                              }
 
-td_elementmap :: TwoDState a -> [(TwoDPosition,(String,a))]
-td_elementmap s = zipWith (,) positions sortedElements
+generateElementmap :: TwoDState a -> TwoDElementMap a
+generateElementmap s = zip positions sortedElements
   where
     TwoDState {td_availSlots = positions,
                td_searchString = searchString} = s
@@ -337,11 +338,11 @@ updateAllElements =
       s <- get
       updateElements (td_elementmap s)
 
-grayoutAllElements :: TwoD a ()
-grayoutAllElements =
+grayoutElements :: Int -> TwoD a ()
+grayoutElements skip =
     do
       s <- get
-      updateElementsWithColorizer grayOnly (td_elementmap s)
+      updateElementsWithColorizer grayOnly $ drop skip (td_elementmap s)
     where grayOnly _ _ = return ("#808080", "#808080")
 
 updateElements :: TwoDElementMap a -> TwoD a ()
@@ -473,11 +474,17 @@ transformSearchString f = do
           let oldSearchString = td_searchString s
               newSearchString = f oldSearchString
           when (newSearchString /= oldSearchString) $ do
-            -- FIXME: grayoutAllElements + updateAllElements paint some fields twice causing flickering
-            --        we would need a much smarter update strategy to fix that
-            when (length newSearchString > length oldSearchString) grayoutAllElements
             -- FIXME curpos might end up outside new bounds
-            put s { td_searchString = newSearchString }
+            let s' = s { td_searchString = newSearchString }
+                m = generateElementmap s'
+                s'' = s' { td_elementmap = m }
+                oldLen = length $ td_elementmap s
+                newLen = length $ td_elementmap s''
+            -- All the elements in the previous element map should be
+            -- grayed out, except for those which will be covered by
+            -- elements in the new element map.
+            when (newLen < oldLen) $ grayoutElements newLen
+            put s''
             updateAllElements
 
 -- | By default gridselect used the defaultNavigation action, which
@@ -653,8 +660,11 @@ gridselect gsconfig elements =
                                                 td_paneX = screenWidth,
                                                 td_paneY = screenHeight,
                                                 td_drawingWin = win,
-                                                td_searchString = "" }
-                            evalTwoD (updateAllElements >> (gs_navigate gsconfig)) s
+                                                td_searchString = "",
+                                                td_elementmap = [] }
+                                m = generateElementmap s
+                            evalTwoD (updateAllElements >> (gs_navigate gsconfig))
+                                     (s { td_elementmap = m })
                       else
                           return Nothing
     liftIO $ do
-- 
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