Mapping and graphics

GDDM V3R2 Base Application Programming Guide

Mapping and graphics

GDDM V3R2 Base Application Programming Guide
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You can display mapped data and graphics together, and you can use GDDM's interactive graphics facilities on mapped pages. There are two ways of putting graphics onto mapped pages.

One way is simply to define a graphics field on a mapped page using the GSFLD call (see "The graphics field and the image field" in topic 7.5). If you use this method, it is inadvisable to let any graphics overlap a mapped area of the page, because the results are unpredictable.

The other way is to specify to GDDM-IMD an area for graphics within a map, called a graphic area. After an MSDFLD call specifying such a map, the graphic area becomes the graphics field.

You define the graphic area on the Field Definition frame of GDDM-IMD's map editor. You enter an AREA command, specifying the graphic area's size and position in rows and columns. GDDM-IMD shows the graphic area by filling it with % signs, or some other specified symbol.

Whatever the method of creation, GDDM never allows more than one graphics field on a page.

There is always a column of blank spaces one character wide down the left-hand edge of a graphics area. This is because each row of the graphics area starts with an attribute byte, to prevent the attributes of any preceding alphanumeric fields from interfering with the graphics. It has the effect of making the width of the graphics field one character less than that specified to GDDM-IMD.

In a dual-screen configuration of the IBM 3270-PC/GX workstation, the graphics appear on the graphics screen, and the maps appear on the alphanumerics screen. The graphics occupy the same part of the screen as they would in a single-screen configuration. On the IBM 5080 graphics system, the graphics field fills the graphics monitor, and the maps appear on the 3270 screen.

Remember that the depth and width of the graphic area are specified in rows and columns, not physical dimensions. An equal number of rows and columns does not give a square graphic area. This may lead to your graphics having unexpected proportions: circles appearing as ovals and squares as rectangles. One solution is to create a uniform set of world coordinates by issuing a GSUWIN call before opening any graphics segment:


     CALL GSUWIN(-100.0,100.0,-100.0,100.0);

More information is given in "Setting up a coordinate system for drawing graphics" in topic 2.2.1 and "Uniform world coordinates" in topic 7.8.1.

Graphics cannot be used with MSREAD, because this call creates, transmits, and discards a page without providing an opportunity for the program to create graphics on it.

Subtopics:

16.16.1 Example of graphics in a mapped display

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