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Inside Macintosh: QuickDraw GX Environment and Utilities /

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

Opcode Constants and Data Types

Operation Opcode Byte

Bits 6 and 7 of the operation opcode byte are the operation opcode. This opcode provides a description of the data record that follows. Each operation opcode is defined in the gxGraphicsOperationOpcode enumeration.

enum gxGraphicsOperationOpcode {
   gxNewObjectOpcode = 0x00,
   gxSetDataOpcode   = 0x40,
   gxSetDefaultOpcode= 0x80,
   gxReservedOpcode  = 0xC0,
   gxNextOpcode      = 0xFF,
};

Constant descriptions

gxNewObjectOpcode

Data for a new object follows.

gxSetDataOpcode

Attributes for the current object follow.

gxSetDefaultOpcode

Replace current default with the object that follows.

gxReservedOpcode

This opcode is reserved for future expansion.

gxNextOpcode

This constant is used by the current operand field to indicate that an opcode is coming.

Bits 0 through 5 of the operation opcode byte are the record size in bytes (1 to 63 bytes). The gxObjectSizeMask constant, binary 111111, masks bits 0 through 5 to select the record size. For additional information about the stream format for the record size, see the section "Record Size" beginning on page 7-11.

#define gxObjectSizeMask   0x3F

The gxOpcodeShift constant allows you to compare gxGraphicsOperationOpcode constants with other values.

#define gxOpcodeShift   6