GXPD 36 - Locating the Selected Printer (15-Sept-95)

With GX installed, the 'STR ' -8192 resource is supported for backward compatibility in applications that are not GX-printing savvy. In this case the 'STR ' -8192 resource gives the name of the default DTP file on the desktop. For applications that are GX-printing savvy, the concept of a default printer is not important because the user can pick any printer from the GX Print dialog.

Once you've located the 'STR ' -8192, and you have the name of the current printer, you can then determine the printer's zone and type using the 'PAPA' resource id -8192 in the driver (if the traditional printing architecture is in use) or by accessing the printer's 'comm' resource (if the GX printing architecture is in use).

Here is some sample code which demonstrates how to do this.

// Current Printer info sample code
//
// Dave Polaschek and David Hayward
// Developer Technical Support
// AppleLink: DEVSUPPORT
//
// Copyright 1995, Apple Computer,Inc
//
// Check the default printer under GX or old printing architecture.
// Print out the name, entityType, and zone.
//
// davep	8/16/95	initial cut


#include <stdio.h>
#define gestaltGXVersion            'qdgx'   // in PrintingManager.h (old) or GXPrinting.h (new)
#define gestaltGXPrintingMgrVersion 'pmgr'   // in PrintingManager.h (old) or GXPrinting.h (new)
#define gestaltAliasMgrAttr         'alis'   // in Aliases.h

#define printingResourceID			0xE000			// 0xE000 = -8192


OSErr		GetCurrentPrinter(Str255 printer);
OSErr		test(void);
Boolean		gxInstalled(void);
Boolean		validPrinter(void);


/*---------------------------------------------------------------------------*\
		This function returns true if QuickDraw GX printing is available
\*---------------------------------------------------------------------------*/
Boolean gxInstalled(void)
{
	long version;

	if (Gestalt(gestaltGXVersion, &version) == noErr)
		if (Gestalt(gestaltGXPrintingMgrVersion, &version) == noErr)
			return(true);
	return(false);
}


/*---------------------------------------------------------------------------*\
		This function returns the network entity of the currently 
		selected printer, and as an added bonus, you get an error code, too!
\*---------------------------------------------------------------------------*/
OSErr GetCurrentPrinter(Str255 printer)
{
	StringHandle	theDriver;
	Handle			thePrinter;
	OSErr			theErr;
	short			resFileRefnum;

	theDriver = GetString(printingResourceID);
	if (!theDriver) goto BADDriver;

	if (gxInstalled()) {
		short	vRefNum;
		long	dirID;
		FSSpec	theFile;
		long	resSize;

		theErr=FindFolder(kOnSystemDisk,kDesktopFolderType,kDontCreateFolder,&vRefNum,&dirID);
		if (theErr != noErr) goto BADDriver;

		theErr=FSMakeFSSpec(vRefNum,dirID,*theDriver,&theFile);
		if (theErr != noErr) goto BADDriver;

		resFileRefnum = FSpOpenResFile(&theFile,fsRdPerm);
		if (resFileRefnum == -1) goto BADResFile;

		thePrinter = Get1Resource('comm', 0);
		if (!thePrinter) goto BADPrinter;

		if (*((long *)*thePrinter) != 'PPTL') goto BADPrinter;

		resSize = GetHandleSize(thePrinter)-6;
		BlockMoveData((*thePrinter)+6,printer,resSize);
	} else {
		Boolean 	aliasCallsPresent;
		Boolean 	aliasResourcePresent;
		long		resSize,response;
		AliasHandle	theAlias;
		
		aliasCallsPresent = ((Gestalt(gestaltAliasMgrAttr,&response) == noErr) &&			(response & 1));

		theAlias = (AliasHandle) GetResource('alis',printingResourceID);
		aliasResourcePresent = !!(theAlias);
		
		if (aliasCallsPresent && aliasResourcePresent) {
			FSSpec	fileSpec;
			Boolean	wasChanged;

			theErr = ResolveAlias(NULL, theAlias,&fileSpec,&wasChanged);
			if (theErr != noErr) goto BADDriver;

			resFileRefnum = FSpOpenResFile(&fileSpec,fsRdPerm);
			if (resFileRefnum == -1) goto BADResFile;
		} else {
			resFileRefnum = OpenResFile(*theDriver);
			if (resFileRefnum == -1) goto BADResFile;
		}
		thePrinter = Get1Resource('PAPA', printingResourceID);
		if (!thePrinter) goto BADPrinter;
		resSize = GetHandleSize(thePrinter);
		BlockMoveData(*thePrinter,printer,resSize);
	}
	ReleaseResource(thePrinter);
	CloseResFile(resFileRefnum);

	return(noErr);

// Error returns
BADPrinter:
	CloseResFile(resFileRefnum);
BADResFile:
	theErr = ResError();
BADDriver:
	return(theErr);
}


/*---------------------------------------------------------------------------*\
		This function is called by the test harness. Doesn't do much 
		except prove that things work without crashing.
\*---------------------------------------------------------------------------*/
OSErr test(void)
{
	OSErr	testValue;
	Str255	printerEntity;

	testValue = GetCurrentPrinter(printerEntity);
	if (testValue)
		return testValue;
	else {
		Str31			printer,type,zone;
		unsigned char	*currentString;

		currentString = printerEntity;
		BlockMove(currentString,printer,Length(currentString)+1);
		p2cstr(printer);
		
		currentString += Length(currentString) + 1;
		BlockMove(currentString,type,Length(currentString) + 1);
		p2cstr(type);
		
		currentString += Length(currentString) + 1;
		BlockMove(currentString,zone,Length(currentString) + 1);
		p2cstr(zone);

		printf("Current Printer name = %s\n"
				"EntityType = %s\n"
				"Zone = %s\n",printer,type,zone);
		return noErr;
	}
}


/*---------------------------------------------------------------------------*\
		This function tells if there's a valid printer selected (i.e. not
		aimed at a driver that's since been deleted or no printer selected
		since last System sw install) in the chooser
\*---------------------------------------------------------------------------*/
Boolean validPrinter(void)
{
	Str255	printerEntity;
	
	if (GetCurrentPrinter(printerEntity) != noErr)
		return false;
	else if (Length(printerEntity) == 0)
		return false;
	else
		return true;
}


// Simple testbed for Macintosh sample code
//
// Dave Polaschek
// Developer Technical Support
// AppleLink: DEVSUPPORT
//
// Copyright 1995, Apple Computer,Inc
//
// This file contains main, and nothing else.
// dave	8/15/95	initial cut

#include <stdio.h>
extern OSErr test(void);		// in CurrentPrinter.c


void main(void)
{
	OSErr	testResult;
	
	testResult = test();

	printf("Return value from test() = %d\n",testResult);
}

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