I think they mean FSpOpenDF (https://dev.os9.ca/techpubs/mac/Files/Files-53.html#HEADING5...), a (relatively) late addition to the Mac API.
I think they mean FSpOpenDF (https://dev.os9.ca/techpubs/mac/Files/Files-53.html#HEADING5...), a (relatively) late addition to the Mac API.
The FSSpec calls added in System 7 are mostly new interfaces to existing File Manager functionality. There's an actual high-level `OpenDF()` call, which is like `FSOpen()` except that it won't try to open a driver when the name begins with `.`.
Some applications call `OpenDF()` without checking its availability, but fall back to `FSOpen()` or equivalent if `OpenDF()` returns `paramErr`, which is what the parent is witnessing. See `68k/modules/ams-fs/Files.cc` in the `metamage_1` repo.
If the error message is confusing people, maybe it's time to implement `OpenDF()` for real.
That, or add this information to the error message: OpenDF not implemented, falling back to FSOpen