Legacy Document

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

Dash Style Omit Byte Masks and Shifts

The gxOmitDashMask1 enumeration defines which bits in an omit byte correspond to the a data compression opcode for the field descriptors in the gxDashRecord structure. The sequence of data is also defined. The omit byte and its related data sequence are given in the section "Dash Data" beginning on page 7-37.

enum gxOmitDashMask1 {
   gxOmitDashAttributesMask   = 0xC0,
   gxOmitDashShapeMask        = 0x30,
   gxOmitDashAdvanceMask      = 0x0C,
   gxOmitDashPhaseMask        = 0x03
};

Constant descriptions

gxOmitDashAttributesMask

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

gxOmitDashShapeMask

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

gxOmitDashAdvanceMask

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

gxOmitDashPhaseMask

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

Once one of the gxOmitDashMask1 enumeration masks has been used to select data compression bits for a field descriptor in the gxDashRecord structure, the corresponding bit shift from the gxOmitDashShift1 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 bits so that they can be compared to other values.

enum gxOmitDashShift1 {
   gxOmitDashAttributesShift  = 6,
   gxOmitDashShapeShift       = 4,
   gxOmitDashAdvanceShift     = 2,
   gxOmitDashPhaseShift       = 0
};

Constant descriptions

gxOmitDashAttributesShift

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

gxOmitDashShapehift

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

gxOmitDashAdvanceShift

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

gxOmitDashPhaseShift

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

The gxOmitDashMask2 enumeration defines which bits in a second omit byte correspond to the data compression bits for additional field descriptors in the gxDashRecord structure. The sequence of data is also continued. The use of this mask and shift are described in the section "Dash Data" beginning on page 7-37.

enum gxOmitDashMask2 {
   gxOmitDashScaleMask = 0xC0
};

Constant descriptions

gxOmitDashScaleMask

The mask for the data compression bits for the scale field descriptor.

Once one of the gxOmitDashMask2 enumeration masks has been used to select data compression bits for a field descriptor in the gxDashRecord structure, the corresponding bit shift from the gxOmitDashShift2 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 bits so that they can be compared to other values.

enum gxOmitDashShift2{
      gxOmitDashScaleShift = 6
};

Constant descriptions

gxOmitDashScaleShift

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