Fix wall zoning

src/Geometry/Zone.hs

@@ -3,7 +3,7 @@ module Geometry.Zone
     ( ddaExt
     , ddaExt'
     , ddaSq
---    , ddaSqStream
+    , ddaSqStream
     , ddaStream
     , ddaStreamX
     , ddaStreamY
@@ -144,6 +144,17 @@ ddaExt' s sp@(V2 sx sy) ep@(V2 ex ey)
                          [y1 .. y2] 
         | otherwise = zip (map (divTo s) [y2x,y2x+xdy..])
                          [y2-1 .. y1-1] 
+ddaSqStream :: Float -> Point2 -> Point2 -> Stream (Of (V2 Int)) Identity ()
+ddaSqStream s sp ep = S.each [V2 x y | x <- makeInterval sx ex, y <- makeInterval sy ey]
+  where
+    V2 sx sy = sizeZoneOfPoint' s sp
+    V2 ex ey = sizeZoneOfPoint' s ep
+
+makeInterval :: Int -> Int -> [Int]
+makeInterval x y
+    | x < y = [x-1..y+1]
+    | otherwise = [y-1..x+1]
+
 ddaStream :: Float -> Point2 -> Point2 -> Stream (Of (V2 Int)) Identity ()
 ddaStream s sp ep = S.map (sizeZoneOfPoint' s)
     $  S.yield sp
@@ -160,11 +171,11 @@ xIntercepts :: Float -> Point2 -> Point2 -> Stream (Of Point2) Identity ()
 {-# INLINE xIntercepts #-}
 xIntercepts s (V2 sx sy) (V2 ex ey) 
     | xdx == 0  = mempty
-    | xdx > 0   = S.each $ zipWith V2 [sx',sx'+xdx*50..ex] [sy',sy'+ydx*50..ey]
-    | otherwise = S.each $ zipWith V2 [sx'-50,sx'+xdx*50-50..ex-50] [sy',sy'+ydx*50..ey]
+    | xdx > 0   = S.each $ zipWith V2 [sx',sx'+xdx*50..ex] ([sy',sy'+ydx*50..ey] ++ repeat ey)
+    | otherwise = S.each $ zipWith V2 [sx'-50,sx'+xdx*50-50..ex-50] ([sy',sy'+ydx*50..ey] ++ repeat ey)
   where
     xdx = signum (ex - sx)
-    ydx = (ey - sy) / abs (ex - sx)
+    ydx = (ey - sy) / abs (ex - sx) -- carefull: if this is zero
 
     sy' = sy + ydx * abs (sx - sx')
     sx' | xdx < 0 = sx - modTo s sx