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Graphics Input for Local Application Programs
For PC DOS application programs, the GPI makes the connection between
the real device such as the mouse and the application program, and
controls the way movement is sampled. However, echoing of the movement
on the screen is a function of the local application program.
The Relationship Between Alphanumerics and Graphics
The IBM 5279 and 5379 work stations can handle both alphanumeric (or
character) data and all-points-addressable data. These two types of data
can both be displayed at the same time, the alphanumeric data effectively
lying on top of the graphics data. Any alphanumeric data is always visible,
and it is possible to control for each alphanumeric character whether its
background is opaque or transparent, so that any graphics data beneath
can be seen.
This function allows host application programs to combine the performance
and convenience of 3270 data stream alphanumerics with the flexibility of
graphics within the same picture.
A host application program can write character strings in either the
alphanumeric layer or the graphics layer. In alphanumeric mode, the
characters appear in fixed cell positions, with all the field formatting
capabilities of the IBM 3270 system. In graphics mode, the characters can
be positioned on any pel, using either image or vector character sets (as
described earlier, in the section "Vector Graphics" on page 41). Users can
also define their own characters in both layers.
Printing Support
The IBM 5279 and 5379 work stations offer a variety of ways to print
display data from application programs.
Using a Printer Attached to the 3274 Control Unit
The 3270 system facility for sending the contents of a host application
program's presentation space to a printer attached to the 3274 Control Unit
continues to be available, so users who currently operate in this way can
continue to do so if they wish. Printing can be initiated by the operator or
by the application program. Only alphanumeric data can be printed in this
way.
Direct Printing of PC DOS Application Programs
PC DOS application programs in the work station can use a directly
attached PC printer in the same way as previously, except that the DOS
Spool facility is not supported. The Print key causes the presentation space
of an application program that is using the emulated Color Graphics
Adapter to be printed immediately.
Chapter 4. The Graphics Control Program
45
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