er ()
renderSlideFilter w h s = do
  clearCanvas w h
  let cw = toDouble $ canvasW gCfg
      ch = toDouble $ canvasH gCfg
      tcy = textContextY gCfg
  C.scale (toDouble w / cw) (toDouble h / ch)
  void $ yposSequence tcy s
  renderWave

renderSlide :: [[Double -> C.Render Double]] -> Int -> Int -> Int -> C
renderSlideFilter :: Int -> Int -> [Double -> C.Render Double] -> C.Render ()
renderSlideFilter w h s = do
  clearCanvas w h
  let cw = toDouble $ canvasW gCfg
      ch = toDouble $ canvasH gCfg
      tcy = textContextY gCfg
  C.scale (toDouble w / cw) (toDouble h / ch)
  void $ yposSequence tcy s
  renderWave
renderSlideFilter w h s = do
  clearCanvas w h
  let cw = toDouble $ canvasW gCfg
      ch = toDouble $ canvasH gCfg
      tcy = textContextY gCfg
  C.scale (toDouble w / cw) (toDouble h / ch)
  void $ yposSequence tcy s
  renderWave