New module ColorCache

1 files changed, 66 insertions, 0 deletions

diff --git a/src/ColorCache.hs b/src/ColorCache.hs
new file mode 100644
index 0000000..9a76a90
--- /dev/null
+++ b/src/ColorCache.hs
@@ -0,0 +1,66 @@
+{-# LANGUAGE CPP #-}
+------------------------------------------------------------------------------
+-- |
+-- Module: ColorCache
+-- Copyright: (c) 2012 Jose Antonio Ortega Ruiz
+-- License: BSD3-style (see LICENSE)
+--
+-- Maintainer: jao@gnu.org
+-- Stability: unstable
+-- Portability: portable
+-- Created: Mon Sep 10, 2012 00:27
+--
+--
+-- Caching X colors
+--
+------------------------------------------------------------------------------
+
+module ColorCache(withColors) where
+
+#if defined XFT
+-- import Graphics.X11.Xft
+#endif
+import Data.IORef
+import Graphics.X11.Xlib
+import System.IO.Unsafe (unsafePerformIO)
+import Control.Monad.Trans (MonadIO, liftIO)
+import Control.Exception (SomeException, handle)
+
+data DynPixel = DynPixel { allocated :: Bool
+                         , pixel     :: Pixel
+                         }
+
+-- | Get the Pixel value for a named color: if an invalid name is
+-- given the black pixel will be returned.
+initColor :: Display -> String -> IO DynPixel
+initColor dpy c = handle black $ (initColor' dpy c)
+  where
+    black :: SomeException -> IO DynPixel
+    black = (const . return $ DynPixel False (blackPixel dpy $ defaultScreen dpy))
+
+type ColorCache = [(String, Color)]
+{-# NOINLINE colorCache #-}
+colorCache :: IORef ColorCache
+colorCache = unsafePerformIO $ newIORef []
+
+getCachedColor :: String -> IO (Maybe Color)
+getCachedColor color_name = lookup color_name `fmap` readIORef colorCache
+
+putCachedColor :: String -> Color -> IO ()
+putCachedColor name c_id = modifyIORef colorCache $ \c -> (name, c_id) : c
+
+initColor' :: Display -> String -> IO DynPixel
+initColor' dpy c = do
+  let colormap = defaultColormap dpy (defaultScreen dpy)
+  cached_color <- getCachedColor c
+  c' <- case cached_color of
+          Just col -> return col
+          _        -> do (c'', _) <- allocNamedColor dpy colormap c
+                         putCachedColor c c''
+                         return c''
+  return $ DynPixel True (color_pixel c')
+
+withColors :: MonadIO m => Display -> [String] -> ([Pixel] -> m a) -> m a
+withColors d cs f = do
+  ps <- mapM (liftIO . initColor d) cs
+  f $ map pixel ps