Move towards resolving picture rendering bug

The bug concerns a mutable vector storing the amount of data that has
been poked.

src/Dodge/Debug/Picture.hs

@@ -72,7 +72,7 @@ lineOnScreenCone cfig w p1 p2 =
 
 drawWallFace :: Config -> World -> Wall -> Picture
 drawWallFace cfig w wall
-    | isRHS sightFrom x y || not (wlIsOpaque wall) = blank
+    | isRHS sightFrom x y || not (wlIsOpaque wall) = mempty
     | otherwise = setDepth (-1) . color (withAlpha 0 black) . polygon $ points
   where
     (x, y) = _wlLine wall
@@ -226,6 +226,7 @@ drawWallsNearYou w = concat $ do
     return $ setLayer DebugLayer $ foldMap f $ wlsNearPoint p w
   where
     f wl = color violet $ thickLine 3 [a, b]
+        <> uncurryV translate (0.5 *^ (a + b)) (scale 0.05 0.05 . text $ show (_wlID wl))
       where
         (a, b) = _wlLine wl