There are four PostScript-related printer escapes: EPSPRINTING, POST-SCRIPT_DATA, POSTSCRIPT_IGNORE, and GETSETSCREENPARAMS.
The EPSPRINTING escape is intended for applications that produce their own PostScript. It suppresses the Windows PostScript header. With this option on, no GDI output functions will work.
The POSTSCRIPT_DATA escape is just like the PASSTHROUGH (also known as DEVICE_DATA) escape except that it is recognized only by PostScript devices. This escape is intended for applications that produce two representations of the output: one intended for PostScript devices and the other for non-PostScript devices. It should be used in conjunction with POSTSCRIPT_IGNORE to make the PostScript driver ignore the GDI representation.
The POSTSCRIPT_IGNORE escape is used to make the PostScript driver ignore or accept all the output. The lpInData parameter points to a Boolean value that indicates whether the GDI functions should be ignored (TRUE) or not (FALSE, the default).
The GETSETSCREENPARAMS escape, new for Windows 3.1, sets and retrieves the current screen parameters, such as angle and frequency, for halftoning. The user can also set these parameters by using the Halftone Frequency and Halftone Angle options in the Advanced Options dialog box.
Detailed descriptions of other escapes are available in the Microsoft Windows Device Driver Adaptation Guide which has driver-oriented descriptions.