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Inside Macintosh: QuickDraw GX Environment and Utilities /

Chapter 7 - QuickDraw GX Stream Format / QuickDraw GX Stream Format Reference

Style Object Omit Byte Constants and Data Types

Join Style Omit Byte Masks and Shifts

The gxOmitJoinMask enumeration defines which bits in an omit byte correspond to the data compression opcode for the field descriptors in the gxJoinRecord structure. The sequence of data is also defined. The omit byte and its related data sequence is given in the section "Join Data" beginning on page 7-37.

enum gxOmitJoinMask {
   gxOmitJoinAttributesMask= 0xC0,
   gxOmitJoinShapeMask     = 0x30,
   gxOmitJoinMiterMask     = 0x0C
};

Constant descriptions

gxOmitJoinAttributesMask

The mask used to select the data compression bits for the attributes field descriptor.

gxOmitJoinShapeMask

The mask used to select the data compression bits for the join field descriptor.

gxOmitJoinMiterMask

The mask used to select the data compression bits for the miter field descriptor.

Once one of the gxOmitJoinMask enumeration masks has been used to select a data compression opcode for a field descriptor in the gxJoinRecord structure, the corresponding bit shift from the gxOmitJoinShift enumeration can be applied to the selected bits. The selected bits must be moved to the right by the indicated number of bits to isolate the data compression opcode so that it can be compared to other values.

enum gxOmitJoinShift {
   gxOmitJoinAttributesShift  = 6,
   gxOmitJoinShapeShift       = 4,
   gxOmitJoinMiterShift       = 2
};

Constant descriptions

gxOmitJoinAttributesShift

The bit shift required to isolate the compression bits for the attributes field descriptor.

gxOmitJoinShapeShift

The bit shift required to isolate the compression bits for the join field descriptor.

gxOmitJoinMiterShift

The bit shift required to isolate the compression bits for the miter field descriptor.