Inside Macintosh: More Macintosh Toolbox /

Chapter 9 - Desktop Manager / Desktop Manager Reference

Data Structure

The Desktop Parameter Block

The desktop database functions use the desktop parameter block, a data structure of type DTPBRec:

TYPE  DTPBRec =
      RECORD
         qLink:         QElemPtr;   {next queue entry}
         qType:         Integer;    {queue type}
         ioTrap:        Integer;    {routine trap}
         ioCmdAddr:     Ptr;        {routine address}
         ioCompletion:  ProcPtr;    {completion routine}
         ioResult:      OSErr;      {result code}
         ioNamePtr:     StringPtr;  {file, directory, or }
                                    { volume name}
         ioVRefNum:     Integer;    {volume reference number}
         ioDTRefNum:    Integer;    {desktop database reference }
                                    { number}
         ioIndex:       Integer;    {index into icon list}
         ioTagInfo:     LongInt;    {tag information}
         ioDTBuffer:    Ptr;        {data buffer}
         ioDTReqCount:  LongInt;    {requested length of data}
         ioDTActCount:  LongInt;    {actual length of data}
         filler1:       SignedByte; {unused}
         ioIconType:    SignedByte; {icon type}
         filler2:       Integer;    {unused}
         ioDirID:       LongInt;    {parent directory ID}
         ioFileCreator: OSType;     {file creator}
         ioFileType:    OSType;     {file type}
         ioFiller3:     LongInt;    {unused}
         ioDTLgLen:     LongInt;    {logical length of desktop }
                                    { database}
         ioDTPyLen:     LongInt;    {physical length of desktop }
                                    { database}
         ioFiller4:                 {unused}
                        ARRAY[1..14] OF Integer;
         ioAPPLParID:   LongInt     {parent directory ID of }
                                    { application}
      END;
      DTPBPtr = ^DTPBRec;           {pointer to desktop }
                                    { parameter block}

For a description of the standard fields of a parameter block (qLink, qType, ioTrap, ioCmdAddr, ioCompletion, and ioResult), see the chapter "File Manager" in Inside Macintosh: Files. For other fields of the desktop parameter block, see the relevant routine description provided in the next section.