Technical Q&A QD15

Incorrect Inside Macintosh Volume V documentation

Q: Inside Macintosh Volume V, page 103, says that when a PICT pattern opcode (for instance, 0x0012) comes along, and the pattern isn't a dither pattern, the full pixMap data follows the old-style 8-byte pattern. The pixMap data structure shown on page 104 starts with an unused long (baseAddr placeholder), followed by the rowBytes, bounds, and so on. However, looking at the Pict.r file on the October 1992 Developer CD, at the same opcode (BkPixPat == 0x0012), the first data field after the old-style pattern (hex string[8]) is the rowBytes field (broken down into three bitstrings). The baseAddr placeholder field isn't there. Which is correct?

A: The Inside Macintosh Volume V documentation on pages 103-104 is wrong. The Pict.r file correctly describes the format of the PnPixPat and BkPixPat opcodes. So there shouldn't be a baseAddr field in the pixMap record of a pattern as stored in the PnPixPat of a PICT. However, the baseAddr does occur in a 'ppat' resource as described on page 79. Thanks for pointing out this discrepancy.