V9/jtools/man/man3/circle.3

.TH CIRCLE 3
.CT 2 graphics
.SH NAME
circle, disc, arc, ellipse, eldisc, elarc \- circle-drawing functions
.SH SYNOPSIS
.B #include <jerq.h>
.PP
.B void circle(bp, p, r, f)
.B "Bitmap *bp; Point p; int r; Code f;
.PP
.B void disc(bp, p, r, f)
.B "Bitmap *bp; Point p; int r; Code f;
.PP
.B void arc(bp, p0, p1, p2, f)
.B "Bitmap *bp; Point p0, p1, p2; Code f;
.PP
.B void ellipse(bp, p, a, b, f)
.B "Bitmap *bp; Point p; int a, b; Code f;
.PP
.B void eldisc(bp, p, a, b, f)
.B "Bitmap *bp; Point p; int a, b; Code f;
.PP
.B "void elarc(bp, p0, a, b, p1, p2, f)
.B "Bitmap *bp; Point p0, p1, p2; int a, b; Code f;
.SH DESCRIPTION
.I Circle
draws the best approximate circle of radius
.I r
centered at Point
.I p
in the Bitmap
.I bp
with Code
.IR f .
The circle is guaranteed to be symmetrical about the horizontal,
vertical and diagonal axes.
.I Disc
draws the corresponding disc.
.PP
.I Arc
draws a circular arc centered on
.IR p0 ,
traveling counter-clockwise
from
.I p1
to the point on the circle closest to
.IR p2 .
.PP
.I Ellipse
draws an ellipse centered at
.I p
with horizontal semi-axis
.I a
and vertical semi-axis
.I b
in Bitmap
.I bp
with Code
.IR f .
.IR Eldisc
draws the corresponding elliptical disc.
.I Elarc
draws the corresponding elliptical arc, traveling
counter-clockwise from the ellipse point closest to
.I p1
to the point closest to
.IR p2 .
(Beware the regrettable difference between the calling conventions for
.I arc
and
.IR elarc .)
.SH BUGS
When an endpoint of an arc lies near a tail of
an ellipse so thin that its ends degenerate into
straight lines,
.I elarc
does not try to distinguish which side of the tail the
point belongs on.