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Inside Macintosh: QuickDraw GX Environment and Utilities /

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

Ink Object Omit Byte Constants and Data Types

Transfer Omit Byte Masks and Shifts

The gxOmitTransferMask1 enumeration defines which bits in an omit byte correspond to the data compression opcode for the field descriptors in the gxTransferMode structure. The sequence of data is also defined. The omit byte and its related data sequence is given in the section "Transfer Mode Data" beginning on page 7-44.

enum gxOmitTransferMask1 {
   gxOmitTransferSpaceMask    = 0xC0,
   gxOmitTransferSetMask      = 0x30,
   gxOmitTransferProfileMask  = 0x0C
};

Constant descriptions

gxOmitTransferSpaceMask

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

gxOmitTransferSetMask

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

gxOmitTransferProfileMask

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

Once one of the gxOmitTransferMask1 enumeration masks has been used to select a data compression opcode for a field descriptor in the gxTransferMode structure, the corresponding bit shift from the gxOmitTransferShift1 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 gxOmitTransferShift1 {
   gxOmitTransferSpaceShift   = 6,
   gxOmitTransferSetShift     = 4,
   gxOmitTransferProfileShift = 2
};

Constant descriptions

gxOmitTransferSpaceShift

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

gxOmitTransferSetShift

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

gxOmitTransferProfileShift

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

The gxOmitTransferMask2 enumeration defines which bits in a second omit byte correspond to the data compression opcode for additional field descriptors in the gxTransferMode structure. The sequence of data is also defined. The omit byte and its related data sequence is given in the section "Transfer Mode Data" beginning on page 7-44.

enum gxOmitTransferMask2 {
   gxOmitTransferSourceMatrixMask= 0xC0,
   gxOmitTransferDeviceMatrixMask= 0x30,
   gxOmitTransferResultMatrixMask= 0x0C,
   gxOmitTransferFlagsMask       = 0x03
};

Constant descriptions

gxOmitTransferSourceMatrixMask

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

gxOmitTransferDeviceMatrixMask

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

gxOmitTransferResultMatrixMask

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

gxOmitTransferFlagsMask

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

Once one of the gxOmitTransferMask2 enumeration masks has been used to select a data compression opcode for a field descriptor in the gxTransferMode structure, the corresponding bit shift from the gxOmitTransferShift2 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 gxOmitTransferShift2 {
   gxOmitTransferSourceMatrixShift  = 6,
   gxOmitTransferDeviceMatrixShift  = 4,
   gxOmitTransferResultMatrixShift  = 2,
   gxOmitTransferFlagsShift         = 0
};

Constant descriptions

gxOmitTransferSourceMatrixShift

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

gxOmitTransferDeviceMatrixShift

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

gxOmitTransferResultMatrixShift

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

gxOmitTransferFlagsShift

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