Fixed gpu upload of PointPrimitive ring buffer.

1 files changed, 6 insertions, 6 deletions

diff --git a/PointPrimitiveRing.hs b/PointPrimitiveRing.hs
index bd9a15b..ff55df5 100644
--- a/PointPrimitiveRing.hs
+++ b/PointPrimitiveRing.hs
@@ -30,9 +30,9 @@ data Ring = Ring
     { rBufferObject :: Word32
     , rStorage      :: GLStorage
     , rObject       :: Object
-    , rSize         :: IORef CPtrdiff
-    , rStart        :: IORef CPtrdiff
-    , ringCapacity  :: CPtrdiff
+    , rSize         :: IORef CPtrdiff -- Current count of Floats in the ring buffer.
+    , rStart        :: IORef CPtrdiff -- Float-index where next vector will be added. TODO: rename this.
+    , ringCapacity  :: CPtrdiff       -- Maximum number of floats in buffer.
     }
 
 addToObjectArray :: GLStorage
@@ -210,9 +210,9 @@ updateRingCommands r = do
     start <- fmap (fromIntegral . (`div` 3)) $ readIORef $ rStart r
     size  <- fmap (fromIntegral . (`div` 3)) $ readIORef $ rSize r
     let mask 0   = []
-        mask cnt = if start + size < cnt
-                    then [(start,size)]
-                    else [(0,start + size - cnt), (start,cnt-start)]
+        mask cnt = case cnt + start - size of
+            st | st > cnt  -> [(st - cnt,size)]
+               | otherwise -> [(0,start), (st,cnt - st)]
     updateCommands (rStorage r) (rObject r) mask
     readIORef (objCommands $ rObject r) >>= mapM_ print
     return ()