structure TextBuilder :> TEXT_BUILDER =
struct
  val xSpace = 13
  val xSpace3 = xSpace * 3
  val ySpace = 25
  val fontSize = 30.0

  fun accToDrawMsg (textAcc, cursorAcc) =
    let
      open MailboxType
      open DrawMsg

      val textAcc = Vector.concat textAcc
      val cursorAcc = Vector.concat cursorAcc

      val textMsg = REDRAW_TEXT textAcc
      val cursorMsg = REDRAW_CURSOR cursorAcc
    in
      [DRAW textMsg, DRAW cursorMsg]
    end

  fun buildCursor (posX, posY, fWindowWidth, fWindowHeight, r, g, b) =
    let
      val left = posX + 9
      val left = Real32.fromInt left
      val right = left + 12.0

      val top = Real32.fromInt posY
      val bottom = top + fontSize + 2.0

      val halfHeight = fWindowHeight / 2.0
      val top = (~(top - halfHeight)) / halfHeight
      val bottom = (~(bottom - halfHeight)) / halfHeight

      val halfWidth = fWindowWidth / 2.0
      val left = (left - halfWidth) / halfWidth
      val right = (right - halfWidth) / halfWidth

      val vec =
       #[ left, top, r, g, b
        , right, top, r, g, b