Will WinIO will remove the need for emulation with getReportedCursorPosition?

[mpilgrem]

WinIO has seen https://gitlab.haskell.org/ghc/ghc/-/issues/806 closed, the issue referred to in the documentation for reportCursorPositionCode.

However, to date, I have not been able to get getChar on Windows with WinIO to behave as I would expect; see https://gitlab.haskell.org/ghc/ghc/-/issues/21488.

[mpilgrem]

GHC issue #21488 is fixed in GHC 9.2.5, but not in GHC 9.4.3 or GHC 9.4.4. So, on Windows, with GHC 9.2.5 and:

ghc-options:
- -with-rtsopts=--io-manager=native

module Main (main) where

import Control.Exception
import qualified Data.List as L
import Data.Maybe
import System.Console.ANSI hiding (getReportedCursorPosition)
import System.IO
import System.Timeout

main :: IO ()
main = do
  -- set no buffering (if 'no buffering' is not already set, the contents of
  -- the buffer will be discarded, so this needs to be done before the cursor
  -- positon is emitted)
  hSetBuffering stdin NoBuffering
  -- ensure that echoing is off
  input <- bracket (hGetEcho stdin) (hSetEcho stdin) $ \_ -> do
    hSetEcho stdin False
    reportCursorPosition
    hFlush stdout -- ensure the report cursor position code is sent to the
                  -- operating system
    getReportedCursorPosition
  print input

getReportedCursorPosition :: IO String
getReportedCursorPosition = getReport "\ESC[" ["R"]

getReport :: String -> [String] -> IO String
getReport _ [] = error "getReport requires a list of terminating sequences."
getReport startChars endChars = do
  fromMaybe "" <$> timeout 500000 (getStart startChars "")
 where
  endChars' = mapMaybe L.uncons endChars

  getStart :: String -> String -> IO String
  getStart "" r = getRest r
  getStart (h:hs) r = do
    c <- getChar
    if c == h
      then getStart hs (c:r)
      else return $ reverse (c:r)

  getRest :: String -> IO String
  getRest r = do
    c <- getChar
    case lookup c endChars' of
      Nothing -> getRest (c:r)
      Just es -> getEnd es (c:r)

  getEnd :: String -> String -> IO String
  getEnd "" r = return $ reverse r
  getEnd (e:es) r = do
    c <- getChar
    if c /= e
      then getRest (c:r)
      else getEnd es (c:r)

works as it currently does on Unix-like operating systems.

[mpilgrem]

GHC issue #21488 is fixed in GHC 9.2.5 to 9.2.8, GHC 9.4.5 to 9.4.8, GHC 9.6.1 to 9.6.6, GHC 9.8.4, GHC 9.10.1 and GHC 9.12.1.