$home/manuals/unix_v8/9/circle

CIRCLE(9.3)                                                        CIRCLE(9.3)



NAME
       circle,  disc,  arc,  ellipse, eldisc, elarc - circle drawing functions
       for jerq

SYNOPSIS
       #include <jerq.h>

       void circle(bp, p, r, f) Bitmap *bp; Point p; int r; Code f;

       void disc(bp, p, r, f) Bitmap *bp; Point p; int r; Code f;

       void arc(bp, p0, p1, p2, f) Bitmap *bp; Point p0, p1, p2; Code f;

       void ellipse(bp, p, a, b, f) Bitmap *bp; Point p; int a, b; Code f;

       void eldisc(bp, p, a, b, f) Bitmap *bp; Point p; int a, b; Code f;

       void elarc(bp, p0, a, b, p1, p2, f) Bitmap *bp; Point p0, p1,  p2;  int
       a, b; Code f;

DESCRIPTION
       Circle  draws the best approximate circle of radius r centered at point
       p in the Bitmap bp with Code f.  The circle is guaranteed to be symmet‐
       rical about the horizontal, vertical and diagonal axes.  Disc draws the
       corresponding disc.

       Arc draws a circular arc centered on p0,  travelling  counter-clockwise
       from p1 to the point on the circle closest to p2.

       Ellipse  draws an ellipse centered at p with horizontal semi-axis a and
       vertical semi-axis b in Bitmap bp with Code f.  Eldisc draws the corre‐
       sponding elliptical disc.  Elarc draws the correspoding elliptical arc,
       travelling counter-clockwise from the ellipse point closest  to  p1  to
       the  point  closest  to p2.  (Beware the regrettable difference between
       the calling conventions for arc and elarc.)

BUGS
       When an endpoint of an arc lies on a tail of an ellipse  so  thin  that
       its  ends degenerate into straight lines, elarc does not try to distin‐
       guish which `side' of the tail the point belongs on.



                                                                   CIRCLE(9.3)