Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /

Chapter 6 - Printing Resources / Printing Resources Reference

Resources Used for Printing Extensions and Printer Drivers

The Override ('over') Resource

You must provide at least one override resource, of type gxOverrideType, for any printing extension or printer driver that you develop. This resource provides QuickDraw GX with a list of the messages that you are overriding in your extension or driver, along with the ID of the resource in which to find the code for your override's implementation. Figure 6-1 shows the structure of an override resource.

Figure 6-1 The override resource

The override resource consists of a variable number of records, each of which specifies a message, a resource type, a resource ID, and an offset value. Each entry tells QuickDraw GX the name of a printing message that you are overriding and where to find the code for your override.

• Count. The number of message entries in the resource.
• Message ID. The ID of the message that you are overriding. QuickDraw GX defines an integer constant that you use here for each message. These constants are shown in Table 6-2 on page 6-15.
• Resource ID. The ID of the resource in which the code for your override can be found.
• Jump table offset. The offset into the jump table . This is the number of bytes from the beginning of the jump table to the jump instruction for your override code. The first 4 bytes in the jump table must be reserved for use by QuickDraw GX, so your first offset must be 4. You can read about the jump table in the chapter "Printing Extensions" in this book.

You need to provide separate override resources for different kinds of printing messages. There are three kinds of messages:

• Universal messages, used for all imaging systems.
• Imaging system messages, used for specific imaging systems. Some messages are raster imaging messages, some messages are PostScript imaging messages, and some are vector imaging messages.
• Macintosh Printing Manager messages, used to provide compatibility with the Macintosh Printing Manager interface for printing. Printing extensions cannot override Macintosh Printing Manager messages; if an extension does specify that it is overriding a Macintosh Printing Manager call, that message override is ignored.

The ID of each override resource indicates which kind of messages are specified in the resource. Different values are used in override resources for printing extensions than are used for printer drivers, as shown in Table 6-1.

Table 6-1 Override resource IDs

Message type	Extension resource ID	Driver resource ID
Universal	gxExtensionUniversalOverrideID	gxDriverUniversalOverrideID
Imaging system	0	gxDriverImagingOverrideID
MacintoshPrinting Manager	Not allowed	gxDriverCompatibilityOverrideID

Imaging system messages are actually separated into categories: messages for the raster imaging system, PostScript imaging system, and vector imaging system. The identifier used for each message type is shown in Table 6-2.

Table 6-2 Printing message constants

Message type	Constant	Value
Universal	gxInitialize gxShutDown	0 1
	gxJobIdle gxJobStatus gxPrintingEvent	2 3 4
	gxJobFormatDialog gxFormatDialog gxJobPrintDialog gxFilterPanelEvent gxHandlePanelEvent gxParsePageRange	5 6 7 8 9 10
	gxDefaultJob gxDefaultFormat gxDefaultPaperType gxDefaultPrinter	11 12 13 14
	gxCreateSpoolFile gxSpoolPage gxSpoolData gxSpoolResource gxCompleteSpoolFile	15 16 17 18 19
	gxCountPages gxDespoolPage gxDespoolData gxDespoolResource gxCloseSpoolFile	20 21 22 23 24
	gxStartJob gxFinishJob gxStartPage gxFinishPage gxPrintPage	25 26 27 28 29
	gxSetupImageData gxImageJob gxImageDocument gxImagePage gxRenderPage gxCreateImageFile	30 31 32 33 34 35
	gxOpenConnection gxCloseConnection gxStartSendPage gxFinishSendPage	36 37 38 39
	gxWriteData gxBufferData gxDumpBuffer gxFreeBuffer	40 41 42 43
	gxCheckStatus gxGetDeviceStatus gxFetchTaggedData	44 45 46
	gxGetDTPMenuList gxDTPMenuSelect gxHandleAlertFilter	47 48 49
	gxJobFormatModeQuery	50
	gxWriteStatusToDTPWindow gxInitializeStatusAlert gxHandleAlertStatus gxHandleAlertEvent	51 52 53 54
	gxCleanupStartJob gxCleanupStartPage gxCleanupOpenConnection gxCleanupStartSendPage	55 56 57 58
	gxDefaultDesktopPrinter gxCaptureOutputDevice	59 60
	gxOpenConnectionRetry gxExamineSpoolFile	61 62
	gxFinishSendPlane gxDoesPaperFit gxChooserMessage	63 64 65
	gxFindPrinterProfile gxFindFormatProfile gxSetPrinterProfile gxSetFormatProfile	66 67 68 69
Macintosh Printing Manager	gxPrOpenDoc gxPrCloseDoc gxPrOpenPage gxPrClosePage gxPrintDefault gxPrStlDialog gxPrJobDialog gxPrStlInit gxPrJobInit gxPrDlgMain gxPrValidate gxPrJobMerge gxPrGeneral gxConvertPrintRecordTo gxConvertPrintRecordFrom gxPrintRecordToJob	0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Raster imaging system	gxRasterDataIn gxRasterLineFeed gxRasterPackageBitmap	0 1 2
PostScript imaging system	gxPostscriptQueryPrinter gxPostscriptInitializePrinter gxPostscriptResetPrinter gxPostscriptExitServer gxPostscriptGetStatusText gxPostscriptGetPrinterText gxPostscriptScanStatusText gxPostscriptScanPrinterText gxPostscriptGetDocumentProcSetList gxPostscriptDownloadProcSetList gxPostscriptGetPrinterGlyphsInformation gxPostscriptStreamFont gxPostscriptDoDocumentHeader gxPostscriptDoDocumentSetUp gxPostscriptDoDocumentTrailer gxPostscriptDoPageSetUp gxPostscriptSelectPaperType gxPostscriptDoPageTrailer gxPostscriptEjectPage gxPostscriptProcessShape	0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Vector imaging system	gxVectorPackageShape gxVectorLoadPens gxVectorVectorizeShape	0 1 2

Listing 6-1 shows a typical override resource definition. You can also find examples of override resource definitions in Listing 2-24 on page 2-38 in the chapter "Printing Extensions" and in Listing 3-20 on page 3-56 in the chapter "Printer Drivers."

Listing 6-1 An example of an override resource

#define mySegment 0
#define firstOffset 4

resource gxOverrideType (gxExtensionUniversalOverrideID, sysHeap,
                                                      purgeable)
{
   {
   /* message to override     segmentID    jump table offset */

      gxInitialize,           mySegment,     firstOffset+0,
      gxShutDown,             mySegment,     firstOffset+4,
      gxJobPrintDialog,       mySegment,     firstOffset+8,
      gxHandlePanelEvent,     mySegment,     firstOffset+12,
      gxDespoolPage,          mySegment,     firstOffset+16
   };
};

This resource specifies the universal messages that an extension is overriding. In this case, five messages are being overridden. Each of these messages is found in a code segment with a resource ID of mySegment. The jump ('JMP') statement for the gxInitialize message is found at the first offset (4 bytes) from the start of the jump table, and the jump statements for the subsequent messages are each located 4 bytes apart.

IMPORTANT

Each jump table entry is 4 bytes long, and QuickDraw GX reserves the first 4 bytes in the table for its own use. This means that your first jump table entry must be located at an offset of 4 bytes from the beginning of the table. For this reason, the firstOffset constant in Listing 6-1 is defined with a value of 4.

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