Charts.hs

{-# LANGUAGE CPP #-}

module IHaskell.Display.Charts () where

import           System.Directory
import           Data.Default.Class
import           Graphics.Rendering.Chart.Renderable
import           Graphics.Rendering.Chart.Backend.Cairo
import qualified Data.ByteString.Char8 as Char
import           System.IO.Unsafe

import           IHaskell.Display

width :: Width
width = 450

height :: Height
height = 300

instance IHaskellDisplay (Renderable a) where
  display renderable = do
    pngDisp <- chartData renderable PNG

    -- We can add `svg svgDisplay` to the output of `display`, but SVGs are not resizable in the IPython
    -- notebook.
    svgDisp <- chartData renderable SVG

    return $ Display [pngDisp, svgDisp]

chartData :: Renderable a -> FileFormat -> IO DisplayData
chartData renderable format = do
  switchToTmpDir

  -- Write the PNG image.
  let filename = ".ihaskell-chart.png"
      opts = def { _fo_format = format, _fo_size = (width, height) }
  mkFile opts filename renderable

  -- Convert to base64.
  imgData <- fmap Char.pack $ readFile filename
  return $
    case format of
      PNG -> png width height $ base64 imgData
      SVG -> svg $ Char.unpack imgData
#if MIN_VERSION_Chart_cairo(1,3,0)
mkFile opts filename renderable = renderableToFile opts filename renderable
#else
mkFile opts filename renderable = renderableToFile opts renderable filename
#endif