Graphics.Win32.GDI.Clip.enumClipboardFormats fails on success.

[fryguybob]

According to the documentation for the Win32 EnumClipboardFormats function:

 http://msdn.microsoft.com/en-us/library/ms649038(VS.85).aspx

A return value of zero is only an error if a subsequent call to GetLastError does not return ERROR_SUCCESS. The following code is what I would expect:

errorWinNotErrorSuccess :: (Num a) => String -> IO a
errorWinNotErrorSuccess fn_name = do
  err_code <- getLastError
  if err_code == 0 then return 0 else failWith fn_name err_code

failIfZeroAndNotErrorSuccess :: Num a => String -> IO a -> IO a
failIfZeroAndNotErrorSuccess wh act = do
  v <- act
  if v == 0 then errorWinNotErrorSuccess wh else return v

enumClipboardFormats :: ClipboardFormat -> IO ClipboardFormat
enumClipboardFormats format =
  failIfZeroAndNotErrorSuccess "EnumClipboardFormats" $ c_EnumClipboardFormats format

Instead of the current:

enumClipboardFormats :: ClipboardFormat -> IO ClipboardFormat
enumClipboardFormats format =
  failIfZero "EnumClipboardFormats" $ c_EnumClipboardFormats format

[igloo]

Thanks for the report and suggestion!

[pcapriotti]

Pushed as  6c035c1fb7cb0bba64cdea3a3e1a84c19ef4cd18