change Dmenu functions to return IO/X (Maybe String)

dmenu exits with code 1 when you hit Escape, and I wanna create a contrib that
takes advantage of that.

This required changes in four contribs (Commands, DirectoryPrompt, ShellPrompt,
and WorkspaceDir), and might require changes in users' Configs. Also, I'm not
sure some of the changes I made to the client code are very Haskelly. Would
appreciate input there.

darcs-hash:20071006070959-78224-eeefb4300d6d3de7b199f2b1ad37ba43384e03f1.gz

1 files changed, 11 insertions, 7 deletions

diff --git a/Dmenu.hs b/Dmenu.hs
index 222d668..e5542c9 100644
--- a/Dmenu.hs
+++ b/Dmenu.hs
@@ -21,6 +21,7 @@ module XMonadContrib.Dmenu (
 
 import XMonad
 import qualified StackSet as W
+import System.Exit
 import System.Process
 import System.IO
 import Control.Monad.State
@@ -32,7 +33,9 @@ import Control.Monad.State
 
 -- %import XMonadContrib.Dmenu
 
-runProcessWithInput :: FilePath -> [String] -> String -> IO String
+-- | Returns Just output if the command succeeded, and Nothing if it didn't.
+-- This corresponds to dmenu's notion of exit code 1 for a cancelled invocation.
+runProcessWithInput :: FilePath -> [String] -> String -> IO (Maybe String)
 runProcessWithInput cmd args input = do
     (pin, pout, perr, ph) <- runInteractiveProcess cmd args Nothing Nothing
     hPutStr pin input
@@ -41,16 +44,17 @@ runProcessWithInput cmd args input = do
     when (output==output) $ return ()
     hClose pout
     hClose perr
-    waitForProcess ph
-    return output
-    
+    exitCode <- waitForProcess ph
+    case exitCode of
+      ExitSuccess   -> return (Just output)
+      ExitFailure _ -> return Nothing
+
 -- | Starts dmenu on the current screen. Requires this patch to dmenu:
 -- <http://www.jcreigh.com/dmenu/dmenu-3.2-xinerama.patch>
-dmenuXinerama :: [String] -> X String
+dmenuXinerama :: [String] -> X (Maybe String)
 dmenuXinerama opts = do
     curscreen <- (fromIntegral . W.screen . W.current) `liftM` gets windowset :: X Int
     io $ runProcessWithInput "dmenu" ["-xs", show (curscreen+1)] (unlines opts)
 
-dmenu :: [String] -> X String
+dmenu :: [String] -> X (Maybe String)
 dmenu opts = io $ runProcessWithInput "dmenu" [] (unlines opts)
-