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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

Cap Style Omit Byte Masks and Shifts

The gxOmitCapMask enumeration defines which bits in an omit byte correspond to the data compression opcode for the field descriptors in the gxCapRecord structure. The sequence of data is also defined. The omit byte and its related data sequence is given in the section "Caps Data" beginning on page 7-38.

enum gxOmitCapMask {
   gxOmitCapAttributesMask = 0xC0,
   gxOmitCapStartShapeMask = 0x30,
   gxOmitCapEndShapeMask   = 0x0C
};

Constant descriptions

gxOmitCapAttributesMask

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

gxOmitCapStartShapeMask

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

gxOmitCapEndShapeMask

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

Once one of the gxOmitCapMask enumeration masks has been used to select a data compression opcode for a field descriptor in the gxCapRecord structure, the corresponding bit shift from the gxOmitCapShift 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 gxOmitCapShift {
   gxOmitCapAttributesShift= 6,
   gxOmitCapStartShapeShift= 4,
   gxOmitCapEndShapeShift  = 2
};

Constant descriptions

gxOmitCapAttributesShift

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

gxOmitCapStartShapeShift

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

gxOmitCapEndShapeShift

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