This is a non standard write command that writes the driver preferences.
- io_Message
-
mn_ReplyPort set if quick I/O is not possible
- io_Command
-
PRD_WRITEPREFS
- io_Flags
-
IOB_QUICK set if quick I/O is possible
- io_Length
-
the length of the buffer
- io_Data
-
a buffer
- io_Actual
-
the number of bytes copied to the driver prefs.
The printer driver checks the buffer before copying it to its preferences. So you don't have to worry about changing the printer driver between PRD_READPREFS and PRD_WRITEPREFS.