Choosing a suitable mode of graphics text

GDDM V3R2 Base Application Programming Guide

Choosing a suitable mode of graphics text

GDDM V3R2 Base Application Programming Guide
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Before issuing any GSCHAR or GSCHAP calls to create graphics text, you can use the GSCM call to specify a value of 1, 2, or 3 for the mode of the text.


     CALL GSCM(3);          /* Set character mode to 3 - vector text.*/

The mode applies to all subsequent GSCHAP and GSCHAR calls until the character mode is changed again. If the program uses segments, opening a new segment resets the mode to the default. If the character-mode attribute is not specified, the default is mode-1.

The character mode determines which type of symbol set is used to draw the characters. A symbol set is a collection of characters and other symbols; usually they are all a particular style, or font, such as Times Roman or Gothic.

For a fuller description of symbol sets, see "Using symbol sets" in topic 12.0. Briefly, there are two sorts:

Image symbols

These are defined in terms of pixels. They can be either built into the terminal, in which case they are called hardware symbols, or loaded into it from the host computer.

Vector symbols

These are defined in terms of straight and curved lines. They are loaded into the terminal from the host, except in the cases described in "On the IBM 3270-PC/G and /GX workstations" in topic 4.6.2.

GDDM supplies a number of image and vector symbol sets. In addition, users can create their own.

Graphics text Modes-1 and -2 are highly device-dependent. This topic describes their use primarily on terminals that use the 3270 data stream such as the IBM 3472-G. Differences on other types of device are described in "Device variations with graphics text" in topic 4.6.

The relative advantages and disadvantages of the three modes on all types of terminal are discussed later, in "Advantages and disadvantages of each character mode" in topic 4.2.2.

A display that shows the letter E written twice in mode-1 graphics text and once in mode-2 graphics text. Whereas the mode-1 letters are confined within the character cells of the device, the mode-2 character is written across cells.

Figure 14. Mode-1 and mode-2 graphics text

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