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Ulm's Oberon Library:
TermLineGraphics

NAME

TermLineGraphics - support of line graphics on ASCII terminals

SYNOPSIS

(* graphics characters *)
CONST verticalLine = 0;
CONST horizontalLine = 1;
CONST lowerRightCorner = 2;
CONST upperRightCorner = 3;
CONST upperLeftCorner = 4;
CONST lowerLeftCorner = 5;
CONST cross = 6;
CONST leftTee = 7;
CONST rightTee = 8;
CONST bottomTee = 9;
CONST topTee = 10;
CONST chars = 11;
(* character sets *)
CONST standard = 0; graphics = 1;



TYPE GraphicsChar =                    
   RECORD
      set: SHORTINT;
      char: CHAR;
   END;
TYPE CharSet = ARRAY chars OF GraphicsChar; (* graphics charset *)



TYPE SetProc = PROCEDURE (s: Streams.Stream; charset: SHORTINT);



PROCEDURE Init(s: Streams.Stream; charset: CharSet; setCharset: SetProc);
PROCEDURE Draw(s: Streams.Stream; char: SHORTINT);
PROCEDURE HLine(s: Streams.Stream; line, column, length: INTEGER);
PROCEDURE VLine(s: Streams.Stream; line, column, length: INTEGER);
PROCEDURE Box(s: Streams.Stream; line, column, lines, columns: INTEGER);

DESCRIPTION

TermLineGraphics adds basic line drawing capabilities to ASCII terminals. Terminals that support line graphics usually provide an alternate character set for graphics characters. TermLineGraphics uses only a subset of all the graphics characters that may be supported by a particular terminal. The information for a specific character, i.e. the character set it belongs to and it's ASCII-code, is stored in a record of type GraphicsChar.

Init has to be called by the underlying terminal implementation with the set of graphics characters in charset and a procedure for changing character sets in setCharset. If Init was not called, TermLineGraphics uses a default set of non-graphics characters for drawing.

Draw draws a single graphics character.

HLine draws a horizontal line.

VLine draws a vertical line.

Box draws a rectangle.

The drawing procedures do not test for valid screen coordinates.

AUTHOR

Ralf Beck