Graphics Data Descriptor (Gdd) - IBM 6400 Programmer's Reference Manual

Graphics Data Descriptor (GDD)

Length
The Graphics Data Descriptor is the last structured field in the DATA portion of
the Write Graphics Control command. This field specifies the parameters for the
graphics window in the graphics medium presentation space (GPS) and sets the
drawing default conditions. The graphics window limits define the range of
drawing order coordinate values that map to the graphics object area.
Without causing an error, the drawing orders can specify GPS coordinates in the
X ' 8000 ' to X ' 7FFF ' range. The specified GDD graphics window limits select the
part of the drawing order's picture to consider for mapping to the output area.
The format of the GDD field is:
Table 76. Graphics Data Descriptor
Byte Value
0-1 X 001C
'
GDD
2-3 X A6BB
'
4
X ' 00 '
5 X 00
' '
6-7
X 3840
' '
X ' 0960 '
8-9
X 3840
' '
X ' 0960 '
10-13 X 00000000
'
14-15 X 8000
' '
16-17 X 8000
' '
18-19 X 8000
' '
20-21 X 8000
' '
22-27 X ' 000000000000
28-End
Note: See "GDD Initial Graphics Defaults Self-Describing Instructions" on
page 91. Figure 18 shows the Graphics Data Descriptor control parameters
specifying the size of the graphics window.
A6BB Data
Description
-End of Length of Graphics Data Descriptor (GDD)
'
Structured Field ID
'
Unit Base (Measurement Units)
Unit Base is 10 Inches
Reserved
Xg Units per Unit Base
14400 L-units per 10 inches
2400 L-units per 10 inches
Yg Units per Unit Base Yg = Xg
14400 L-units per 10 inches
2400 L-units per 10 inches
Reserved
'
-X 7FFF Xg Left Limit of Graphics Presentation Space
' '
Window See "Notation Conventions" on page 27
-X 7FFF Xg Right Limit of Graphics Presentation Space
' '
Window See "Notation Conventions" on page 27
-X 7FFF Yg Top Limit of Graphics Presentation Space
' '
Window See "Notation Conventions" on page 27
-X 7FFF Yg Bottom Limit of Graphics Presentation Space
' '
Window See "Notation Conventions" on page 27
' Reserved
Initial graphics default. See "GDD Initial Graphics
Defaults Self-Describing Instructions" on page 91
Graphics Command Set
Chapter 3. IPDS Commands Reference
Error Code
X 0202..05
' '
X 020B..05
' '
X ' 0205..05 '
X 0206..05
' '
X 0206..05
' '
87