Modifying the Device Communications Process(IM:XP)

Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /: Chapter 2 - Printing Extensions / Printing Extension Tasks

Modifying the Device Communications Process
You can develop a printing extension to modify the manner in which each printed page is sent to the printer. For example, you can develop an extension that creates a PostScript file copy of each document that is printed. This extension overrides the printing message that sends data to the printer (the GXDumpBuffer message, which is described on page 4-142 in the chapter "Printing Messages") and copies the buffer to a file.