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Technote 1133The New |
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CONTENTS
The New PrGeneral Opcode |
For the past 12 years, printer driver developers have used the print record's |
kPrVersionOpLaserWriter driver version 8.4 introduced several new PrGeneral opcodes, including a new opcode for driver version information: kPrVersionOp. Using kPrVersionOp is now the recommended way for applications to find out the printer driver currently in use. Remember that for printer drivers that haven't been updated to use this new PrGeneral opcode, your application needs to keep its wDev-checking code as well. |
For more information on the extended print record opcodes introduced with LaserWriter version 8.4,
read the Print Hints column The All-New LaserWriter
Driver Version 8.4 in develop Issue 27. There you'll find a table that lists all the other PrGeneral opcodes
supported in Apple printer drivers. See the article Meet
PrGeneral, the Trap That Makes the Most of the Printing Manager in develop Issue 3 for more information on PrGeneral. |
From now on, Apple's Developer Support Center will assign all printer drivers a wDev ID of 255. If you have an old wDev ID number (which is less than 255), you should still use the number you were assigned so that you don't break any applications that vary their behavior based on your driver's wDev. In addition, you should implement the new kPrVersionOp opcode as described here so that new applications can take advantage of it with your driver. |
Listing 1 shows the new opcode and structures that you'll need to implement in your PDEF 7 resource. You need to place your creator type in the driver.creator field of the TPrVersion structure. You should also place your version number in driver.release so that application developers know what version of the driver is available. |
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Listing 1. The new version opcode and structures
enum {
...
kPrVersionOp = 22 // LaserWriter version 8.4 and later only
};
typedef struct {
OSType architecture; // Architecture (for example, 'pwpc', 'm68k')
OSType creator; // Driver's creator type (for example, 'AAPL')
unsigned long release; // Release number (for example, 0x8480)
unsigned long interfaces; // Interfaces version (for example, 0x8480)
} TVersion;
typedef struct {
short iOpCode; // Must be kPrVersionOp
short iError; // For returning errors
long lReserved; // Reserved, set to 0
TVersion driver; // Driver information
TVersion reserved; // Reserved, set to 0
} TPrVersion;
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That's all you'll need to do to support the new PrGeneral opcode in your driver--hard to believe, but true!
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Although Apple doesn't recommend that application developers check the wDev field of the print record, many do. They assume that the wDev value means they can count on certain features being present in the printer. For instance, many developers assume that a wDev of 3 means the printer driver supports PostScript™. In fact, it indicates only that the current printer uses the Apple LaserWriter driver. This leaves out the possibility that a user has a non-Apple PostScript printer driver with an ID of, say, 243. |
Even though Apple doesn't recommend that application developers rely on the wDev field (or the new PrGeneral opcode, for that matter), if you're going to change application behavior based on the number or creator returned, at least do so properly so that your applications don't break with future releases of printer drivers. We recommend that you use the PrGeneral kPrVersionOp opcode, if available, to get the structure and then check the driver.creator and driver.release fields to determine the current printer driver and
version (see Listing 1). You should also continue to support the old wDev method for printer drivers that have not yet updated to the new PrGeneral opcode. For your reference, the PrGeneral Version sample that accompanies this column shows how to retrieve the version and wDev information properly.
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As you can see, the changes that printer driver and application developers need to make to support the new PrGeneral opcode are minimal. We've already adopted this new method with the LaserWriter version 8.4.x drivers. We hope you will, too! |
wDev RegistrationAlthough from all printer drivers will now be assigned a wDev ID of 255,
we still request that you register your printer driver with Apple's Developer Support Center
to avoid creator type conflicts. To do so, register at our wDev registration page. You need to provide the following information: |
You'll receive confirmation of your registration within five to ten working days.
If you have questions about wDev registration, write to devprograms@apple.com. |
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