Re-rastering when copying

GDDM V3R2 Base Application Programming Guide

Re-rastering when copying

GDDM V3R2 Base Application Programming Guide
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For primary devices that use hardware cells to display graphics, such as the IBM 3279 terminal, GDDM creates the picture by rastering the graphics requests in your program. In other words, it converts the graphics primitives into programmed symbols that are subsequently loaded into the PS stores of the primary device.

When the same picture is copied to an alternate device, GDDM cannot simply copy the same programmed symbols to the new device, because the new device may have cells of a different size. For instance, the 3279 display unit has cells of 9 pixels by 12, whereas a typical alternate device, the 3287 printer, has cells of 10 by 8. All the graphics, therefore, have to be re-rastered.

Every call such as GSLINE and GSCHAR must be reprocessed to obtain a copy of the picture on the alternate device. That is why access is required to the symbol sets involved (or their equivalents, if substitution characters were used).

The re-rastering is performed by the GDDM Print Utility. The print file that is passed to the utility contains the various primitives expressed in Graphics Data Format (GDF) (which is introduced in "Modifying graphics pictures that have been loaded into your program" in topic 10.5).

Subtopics:

20.11.1 Mixed graphics and alphanumerics

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