3 files changed, 38 insertions(+), 2 deletions(-)

M src/Data/CSS/Style.hs
A src/Data/CSS/Style/Selector/LowerWhere.hs
M stylist.cabal

@@ 12,6 12,7 @@ module Data.CSS.Style(
 import Data.CSS.Style.Selector.Index
 import Data.CSS.Style.Selector.Interpret
 import Data.CSS.Style.Selector.Specificity
+import Data.CSS.Style.Selector.LowerWhere
 import Data.CSS.Style.Importance
 import Data.CSS.Style.Common
 import qualified Data.CSS.Style.Cascade as Cascade


@@ 25,7 26,9 @@ import Data.List (elemIndex)
 
 -- | A parsed CSS stylesheet from which you can query styles to match an element.
 type QueryableStyleSheet parser = QueryableStyleSheet' (ImportanceSplitter (
-        PropertyExpander parser (OrderedRuleStore (InterpretedRuleStore StyleIndex))
+        PropertyExpander parser (
+            OrderedRuleStore (WhereLowerer (InterpretedRuleStore StyleIndex))
+        )
     )) parser
 
 -- | More generic version of `QueryableStyleSheet`.

@@ 0,0 1,32 @@
+{-# LANGUAGE OverloadedStrings #-}
+module Data.CSS.Style.Selector.LowerWhere(
+        WhereLowerer(..)
+    ) where
+
+import Data.CSS.Syntax.Selector
+import Data.CSS.Style.Common
+
+lowerSelector :: Selector -> Selector
+lowerSelector (Element sel) = Element $ lowerSelector' sel
+lowerSelector (Child sel x) = Child (lowerSelector sel) x
+lowerSelector (Descendant sel x) = Descendant (lowerSelector sel) x
+lowerSelector (Adjacent sel x) = Adjacent (lowerSelector sel) x
+lowerSelector (Sibling sel x) = Sibling (lowerSelector sel) x
+
+lowerSelector' :: [SimpleSelector] -> [SimpleSelector]
+lowerSelector' (Psuedoclass c args:sel)
+    | c `elem` ["is", "where"], ([Element arg'], []) <- parseSelectors args =
+        arg' ++ lowerSelector' sel
+lowerSelector' (test:tests) = test : lowerSelector' tests
+lowerSelector' [] = []
+
+data WhereLowerer s = WhereLowerer s
+
+instance RuleStore s => RuleStore (WhereLowerer s) where
+    new = WhereLowerer new
+    addStyleRule (WhereLowerer self) priority rule =
+        WhereLowerer $ addStyleRule self priority $ rule {
+            inner = StyleRule (lowerSelector sel) props psuedo
+        }
+      where StyleRule sel props psuedo = inner rule
+    lookupRules (WhereLowerer self) el = lookupRules self el

@@ 61,7 61,8 @@ library
   -- Modules included in this library but not exported.
   other-modules:       Data.CSS.Syntax.StylishUtil,
                        Data.CSS.Style.Importance, Data.CSS.Style.Common, Data.CSS.Style.Cascade,
-                       Data.CSS.Style.Selector.Index, Data.CSS.Style.Selector.Interpret, Data.CSS.Style.Selector.Specificity
+                       Data.CSS.Style.Selector.Index, Data.CSS.Style.Selector.Interpret,
+                           Data.CSS.Style.Selector.Specificity, Data.CSS.Style.Selector.LowerWhere
   
   -- LANGUAGE extensions used by modules in this package.
   -- other-extensions: