Reporting of layer colours: underlining is not supported

ansi-terminal/src/System/Console/ANSI.hs

@@ -783,6 +783,8 @@ hGetCursorPosition h = fmap to0base <$> getCursorPosition'
 -- emulated, but the emulation does not work on Windows Terminal and (2) of
 -- difficulties in obtaining the data emitted into the console input stream.
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 reportLayerColor :: ConsoleLayer -> IO ()
 reportLayerColor = hReportLayerColor stdout
@@ -814,6 +816,8 @@ hReportLayerColor h layer = hPutStr h $ reportLayerColorCode layer
 -- as mintty, that are not based on the Windows' Console API. (Command Prompt
 -- and PowerShell are based on the Console API.)
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 getReportedLayerColor :: ConsoleLayer -> IO String
 getReportedLayerColor = Internal.getReportedLayerColor
@@ -831,6 +835,8 @@ getReportedLayerColor = Internal.getReportedLayerColor
 -- and PowerShell are based on the Console API.) This function also relies on
 -- emulation that does not work on Windows Terminal.
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 getLayerColor :: ConsoleLayer -> IO (Maybe(RGB Word16))
 getLayerColor = hGetLayerColor stdout
@@ -847,6 +853,8 @@ getLayerColor = hGetLayerColor stdout
 -- and PowerShell are based on the Console API.) This function also relies on
 -- emulation that does not work on Windows Terminal.
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 hGetLayerColor :: Handle -> ConsoleLayer -> IO (Maybe (RGB Word16))
 hGetLayerColor h layer = do
@@ -886,6 +894,8 @@ hGetLayerColor h layer = do
 -- >     [(col, _)] -> putStrLn $ "The color was " ++ show col ++ "."
 -- >     (_:_) -> putStrLn $ "Error: parse not unique"
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 layerColor :: ConsoleLayer -> ReadP (RGB Word16)
 layerColor layer = do

ansi-terminal/src/System/Console/ANSI/Codes.hs

@@ -289,6 +289,8 @@ reportCursorPositionCode = csi [] "6n"
 -- terminals (2) of difficulties in obtaining the data emitted into the
 -- console input stream. See 'System.Console.ANSI.getReportedLayerColor'.
 --
+-- Underlining is not supported.
+--
 -- @since 0.11.4
 reportLayerColorCode :: ConsoleLayer -> String
 reportLayerColorCode Foreground = osc "10" "?"

ansi-terminal/unix/System/Console/ANSI/Internal.hs

@@ -21,6 +21,8 @@ getReportedCursorPosition :: IO String
 getReportedCursorPosition = getReport "\ESC[" ["R"]
 
 getReportedLayerColor :: ConsoleLayer -> IO String
+getReportedLayerColor Underlining =
+  error "getReportedLayerColor does not support underlining."
 getReportedLayerColor layer =
   getReport ("\ESC]" ++ pS ++ ";rgb:") ["\BEL", "\ESC\\"]
  where