Re GIS - Description

Description

ReGIS consisted of five primary drawing commands and a selection of status and device control commands. ReGIS mode was entered by specifying the escape code sequence P0p, and exited with \. The digit in the first sequence was optional and specified a mode, 0 was the default and picked up drawing where it left off, 1 reset the system to a blank slate, and 2 and 3 were the same as 0 and 1, but left a single line of text at the bottom of the screen for entering commands. The sequence P is the generic "Device Control String" (DCS) used in the VT series of terminals, and is also used for a variety of other commands.

All drawing was based on an active pen location. Any command that moved the pen left it there for the next operation, similar to the operation of a mechanical plotter. The coordinate system was 0 to 799 in the X axis, and 0 to 479 in Y, with 0,0 in the upper left. In early implementations such as the VK100 ("GIGI") and VT125, the actual device resolution was only 240 pixels, so the Y coordinates were "folded" so odd and even coordinates were the same location on the screen, but the VT240 and VT241 provided the full 480 pixel vertical resolution. The coordinate system could also be set by the user.

Coordinates could be pushed or pulled from a stack, and every command allowed the stack to be used as a parameter, the "b" parameter pushed the current coordinates on the stack, "e" popped it back off again. Coordinates could be specified in absolute or relative terms;

is an absolute position at x=200, y=100 is a relative position at x=current X+200, y=current Y-100 is absolute x=200, y=unchanged (same as ) is relative, x=unchanged, y=current Y-100

There were four main drawing commands and three control commands;

P "Position", move the pen V "Vector", draw a line C "Curve", draw a circle (C) or arc (A) F "Fill", draws a filled polygon T "Text", output the following string of text S "Screen", a catch-all command for setting a wide variety of modes R "Report", outputs current status W "Write", sets the pen parameters L "Load", loads an alternate character set @ "Macrograph", see below

Each of these commands used the various coordinate modes in different ways, and some had additional parameters that were enclosed in parentheses. Commands could be followed by one or more parameters, allowing continued drawing from a single command. The interpreter was not case sensitive.

Some ReGIS terminals supported color, using a series of registers. These could be set with the s command using a variety of color input styles. s(m3(r100g0b0)) sets color register ("map") 3 to "r"ed using the RGB color system, while s(m3(h120l50s100)) does the same using the HSV system. The W command likewise set a wide variety of different styles, mostly for masking, fills and brushes.

Finally, ReGIS allowed commands to be stored into a "macrograph" and then recalled using the @ operator. Up to 10,000 characters of code could be stored in the macros, each named with a single letter.