Tests for `arcDCCW` and `arcDCW`

arcTest.hs

import Control.Monad
import Diagrams.Coordinates
import Diagrams.BoundingBox
-- import Diagrams.Backend.Postscript.CmdLine
-- import Diagrams.Backend.SVG.CmdLine
import Diagrams.Backend.Rasterific.CmdLine

import Diagrams.Backend.CmdLine

import Data.Default.Class

import Data.List
import Data.List.Split

-- > [1,2,3,4,5,6,...]
--
-- Wrap after 'n' elements into a new row.
--
-- > [ [1,2,3]
-- > , [4,5,6]
-- > , ...
-- > ]

type DB b = D (V b) (N b)

tableOf :: Int -> [Diagram B] -> Diagram B
tableOf = tableOf' def

tableOf' :: CatOpts (N B) -> Int -> [Diagram B] -> Diagram B
tableOf' opts n ds = vcat' opts
               (map (hcat' opts) [[sized w h d | (w,d) <- zip widths row] | (h,row) <- zip heights rows])
  where
    rows = chunksOf n ds
    cols = transpose rows

    heights = map (abs . (^._y) . boxExtents . boundingBox) rows
    widths  = map (abs . (^._x) . boxExtents . boundingBox) cols

    sized ((/2)->w) ((/2)->h) = centerXY . withEnvelope (fromPoints [(-w) ^& (-h), (w ^& h)]) . centerXY

    half = (/2)

tests :: V2 (N B) -> [(String,Diagram B)]
tests start
    = [ (name, pad 1.1 . centerXY $ tableOf' (with & sep.~0.1) 4 (generate test))
      | (test,name) <- [ (diaCCW, "DCCW")
                       , (diaCW,  "DCW")
                       ]
      ]
  where
    vectors u v = arrowBetween 0 (0 .+^ u) # lc red
               <> arrowBetween 0 (0 .+^ v) # lc green

    diaCCW u v = arcDCCW (direction u) (direction v) # strokeLocTrail <> vectors u v
    diaCW  u v = arcDCW  (direction u) (direction v) # strokeLocTrail <> vectors u v

    generate test =
        [ withEnvelope (circle 1 :: DB B) $ test start (f start)
        | f <- map (rotate . (@@ turn) . (/16) . fromIntegral) [0..15]
        ]

-- main = mainWith (tests unitX)

-- Rasterific
main = gifMain [(bg white . snd . last $ tests (f unitX), 4)
               | f <- map (rotate . (@@ turn) . (/32) . fromIntegral) [0..31]
               ]