This topic describes the formats for vector symbol sets (VSS) and image
symbol sets (ISS) held on files (or passed as parameters in symbol-set
manipulation calls).
In either case, definitions start with a two-byte field that gives the
total length of the definitions (including the length field). Then
follows one or more definition components, each of which is in one of the
formats described below (depending upon whether the definitions relate to
an image symbol set (ISS) or to a vector symbol set (VSS)).
|
|
|
| Table 13. Symbol-set definition format |
| Byte |
Field length |
Contents |
| 0 |
2 |
Definition length |
2
2
.
.
. |
L1
2
.
.
. |
Component 1
Component length (L1)
.
.
. |
2 + L1
2+ L1
.
.
. |
L2
2
.
.
. |
Component 2
Component length (L2)
.
.
. |
.
.
. |
.
.
. |
.
.
. |
The following rules must be observed. For the purpose of these rules,
pattern and marker definitions are treated as MODE=2.
- ISS and VSS components must not be mixed within a definition. ISS
definitions cannot be loaded as MODE=3; VSS definitions can be loaded
only as MODE=3.
- For ISS definitions, the following considerations apply to the width
(P) and depth (Q) of the cell matrix in display points:
When either is specified as zero or is not specified, it is assumed to
be equal to the cell width or depth of the actual device (except for
format type '00001'B, where P is assumed to be 9).
When the format type is '00001'B, P (specified or assumed) must be 9.
When P is not a multiple of eight for row-loading format (type
'00011'B), the storage occupied by each row must be padded on the
right with zero bits to the next byte boundary.
Similarly, when Q is not a multiple of eight for column-loading format
(type '00101'B), the storage occupied by each column must be padded at
the bottom with zero bits to the next byte boundary.
- For MODE=1 definitions, the data format must be one that is supported
by the actual device to which the definitions are to be loaded. One
or more components may be specified, either to define different color
planes for a multicolored definition, or to reduce the total length in
cases where only widely-scattered character codes are to be loaded.
Although checks are made, it is possible for a symbol set definition
to pass these checks and still be rejected by the device or controller
when the definitions are actually transmitted.
- For MODE=2 definitions, only one component may be specified for a
monochrome definition, or exactly three components (one for each
color) for a multicolored definition. In the latter case, the
starting character code and the number of codes defined must be the
same for all three color planes.
- For MODE=3 definitions (VSS), only one component may be specified.
- The CLEAR bit is not supported by GDDM, although its setting is not
altered by GDDM before transmitting MODE=1 definitions.
Subtopics:
|
GDDM V3R2 Base Application Programming Reference
Copyright IBM Corporation 1990, 2012