DEFINITION MODULE ScreenGeometry;

	(********************************************************)
	(*							*)
	(*	    Support module for screen graphics		*)
	(*							*)
	(*  Programmer:		P. Moylan			*)
	(*  Last edited:	6 October 1993			*)
	(*  Status:		OK				*)
	(*							*)
	(********************************************************)

TYPE
    Point = RECORD
		x, y: INTEGER;
	    END (*RECORD*);

    Rectangle =	RECORD
		    top, bottom, left, right: INTEGER;
		END (*RECORD*);

(************************************************************************)

PROCEDURE Inside (x, y: INTEGER;  R: Rectangle): BOOLEAN;

    (* Returns TRUE iff point (x,y) is in (or on the border of) R.	*)

PROCEDURE Adjacent (R1, R2: Rectangle;
				VAR (*OUT*) union: Rectangle): BOOLEAN;

    (* If the union of R1 and R2 is itself a rectangle, returns TRUE	*)
    (* and sets "union" to be the combined rectangle.  Otherwise	*)
    (* returns FALSE, and the "union" result is meaningless.		*)

PROCEDURE TrimLine (VAR (*INOUT*) end1, end2: Point;  R: Rectangle): BOOLEAN;

    (* Modifies end1 and end2, if necessary, to cut off the ends of	*)
    (* the line from end1 to end2 which do not fit in R.		*)
    (* Returns FALSE if none of the line passes through the rectangle.	*)

END ScreenGeometry.