Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /

Chapter 3 - Printer Drivers

Writing Printer Driver Files

After you know which messages you need to override as part of managing certain printing tasks, you need to write your printer driver in three kinds of files:

• You need to write a jump table in an assembly-language file so that QuickDraw GX can invoke the correct code in response to the printing messages that it sends.
• You need to write your message override functions in code files (typically, C language files).
• You need to define in Macintosh resource files the resources that contain the data for your printer driver.

The content of each of these file types is reviewed in this section, with sample code from the ImageWriter II printer driver included. The complete contents of the ImageWriter II driver files are found in the QuickDraw GX sample code.

Each driver must include one or more assembly-language jump tables, one or more files of code (in assembly-language, C, Pascal, or some other language) to write the functions that the driver performs, and one or more resource files. The ImageWriter II printer driver consists of the files shown in Table 3-1.

Table 3-1 Files used to implement the ImageWriter II printer driver

Filename	Contents
CommonDefines.h	The header file containing values and types used in other files
ChooserSupport.a	The assembly-language defines for working with the Chooser-related resources
ChooserSupport.c	The code for the resources used by the Chooser
ChooserSupport.r	The resources needed for the driver to work with the Chooser
newapp.a	The jump table for the overrides provided in the newapp.c module
newapp.c	The implementations of the QuickDraw GX printing messages that this driver overrides
newapp.r	The resources needed for the QuickDraw GX printing messages
oldapp.a	The jump table for the overrides provideded in the oldapp.c module
oldapp.c	The implementations of message overrides for compatibility with the Macintosh Printing Manager
oldapp.r	The resources needed for the Macintosh Printing Manager compatibility messages

This section describes the contents of several of these files. The complete files are found in the QuickDraw GX sample code.

The ImageWriter II printer driver is divided into two portions:

• The portion that provides the overrides of the QuickDraw GX printing messages is found in the files newapp.a, newapp.c, and newapp.r.
• The portion that provides the overrides of the Macintosh Printing Manager compatibility messages is found in the files oldapp.a, oldapp.c, and oldapp.r.

You can develop your printer driver in any number of files. Some developers find it convenient to separate the Macintosh Printing Manager compatibility portion of the code from the QuickDraw GX printing message portion, while others use different criteria to decide which code goes in which file.

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Subtopics

Message Overrides and the Jump Table

The Message Overrides

Using the Printing-Related Collections

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