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researchv10 Dan Cross

.ds ZZ DEVELOPMENT PACKAGE
.TH ELLIPSE 3L "630 MTG"
.XE "ellipse()"
.XE "eldisc()"
.XE "eldiscture()"
.XE "elarc()"
.SH NAME
ellipse, eldisc, eldiscture, elarc \- draw an ellipse
.SH SYNOPSIS
.B "#include <dmd.h>"
.sp
.B "void ellipse (bp, p, a, b, f)"
.PP
.B "void eldisc (bp, p, a, b, f)"
.PP
.B "void eldiscture (bp, p, a, b, t, f)"
.PP
.B "void elarc (bp, p, a, b, p1, p2, f)"
.PP
.B Bitmap \(**bp;   
.br
.B Point p, p1, p2;
.br
.B int a, b;
.br
.B Texture16 \(**t;
.br
.B Code f;
.SH DESCRIPTION
The
.I ellipse
function
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 .
.PP
The
.I eldisc
function
draws an elliptical disc centered at
.I p
with horizontal semi-axis
.I a
and vertical semi-axis
.I b
in Bitmap
.I bp
with Code
.IR f .
.PP
The
.I eldiscture
function
draws an elliptical disc centered at
.I p
with horizontal semi-axis
.I a
and vertical semi-axis
.I b
in Bitmap
.I bp
using Texture16
.I t
with Code
.IR f .
.PP
The
.I elarc
function
draws the corresponding elliptical arc, traveling
counterclockwise from the ellipse point closest to
.I p1
to the point closest to
.IR p2 .
Note: Differences exist between the calling conventions for
.I arc
and
.IR elarc .
.SH EXAMPLE
The following routine can be used to allow a user to sweep out an
ellipse by holding button 1 down.
When button 1 is released,
the ellipse is filled using the elliptical disc routine.
.PP
.RS 3
.nf
.ft CM
#include <dmd.h>

main()
{
	sweep_eldisc();
	request(KBD);
	wait(KBD);
}
  
sweep_eldisc()
{
   Point p, c;
   int a, b;

   request(MOUSE);

   while (!button1() )
      wait (MOUSE);       
   c = p = mouse.xy;
   while (button1())
      if (!eqpt(p, mouse.xy)){
         if( !eqpt( p, c))  /* undraw old ellipse */
            ellipse (&display, c, a, b, F_XOR);
         p = mouse.xy;
         a = abs (p.x - c.x);
         b = abs (p.y - c.y);
         ellipse (&display, c, a, b, F_XOR);
      }
   ellipse (&display, c, a, b, F_XOR);
   eldisc  (&display, c, a, b, F_XOR);
}
.fi
.RE
.SH SEE ALSO
circle(3L), jcircle(3L), jellipse(3L).

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