Fix for spaceleak in layouts.

It's not the best solution because it requires an extra pass over the state that should not be needed.
It is better than an ever growing state though.

Libraries/iTasks/UI/Layout.icl

@@ -934,12 +934,13 @@ extractDownstreamChange (lui,moves)
 	# mbChildChange = extractDownstreamChildChange lui moves
 	# (mbLui,moves)  = confirmChangesAndEffects_ (lui, moves)
 	= case (mbChildChange,mbLui) of
-		(Just (InsertChild ui), Just lui)     = (ReplaceUI ui,(lui,moves))
-		(Just RemoveChild, Just lui)          = (ReplaceUI (UI UIEmpty 'DM'.newMap []),(lui,moves))
-		(Just (ChangeChild change), Just lui) = (change,(lui,moves))
-		(Nothing, Just lui)                   = (NoChange,(lui,moves))
+		(Just (InsertChild ui), Just lui)     = (ReplaceUI ui, cleanupState_ (lui,moves))
+		(Just RemoveChild, Just lui)          = (ReplaceUI (UI UIEmpty 'DM'.newMap []), cleanupState_ (lui,moves))
+		(Just (ChangeChild change), Just lui) = (change, cleanupState_ (lui,moves))
+		(Nothing, Just lui)                   = (NoChange, cleanupState_ (lui,moves))
 		_ = abort "extractDownstreamChange: at the top-level, an lui should always be returned"
 
+
 //For each node we need to extract one of the following changes:
 // 1. Just (InsertChild x)        - The node did not exist client-side, but does now
 // 2. Just (RemoveChild)          - The node existed previously but should not
@@ -1321,3 +1322,17 @@ confirmEffect_ (ESToBeApplied x) = ESApplied x
 confirmEffect_ (ESToBeUpdated _ x) = ESApplied x
 confirmEffect_ (ESToBeRemoved x) = ESNotApplied
 confirmEffect_ es = es
+
+//This extra pass should not be necessary, but without it the moves table is
+//leaking memory
+//TODO: Figure out why some moved items are still in the table
+cleanupState_ :: (LUI,LUIMoves) -> (LUI,LUIMoves) 
+cleanupState_ (lui,moves) = (lui, onlyKeep usedMoveIds moves)
+where
+	onlyKeep keep moves = ('DM'.fromList o (filter (\(k,_) -> isMember k keep)) o 'DM'.toList) moves
+
+	usedMoveIds = collect lui
+
+	collect (LUINode _ _ items _ _) = flatten (map collect items)
+	collect (LUIMoveSource moveId) = [moveId:maybe [] (collect o snd) ('DM'.get moveId moves)]
+	collect _ = []