arc(3G)

NAME
     arc, arci, arcs - draw a circular arc

FORTRAN 77 SPECIFICATION
     subroutine arc(x, y, radius, stang, endang)
     real x, y, radius
     integer*4 stang, endang

     subroutine arci(x, y, radius, stang, endang)
     integer*4 x, y, radius, stang, endang

     subroutine arcs(x, y, radius, stang, endang)
     integer*2 x, y, radius
     integer*4 stang, endang

     All of the routines named above are functionally the same.  They differ
     only in the type assignments of their parameters.

PARAMETERS
     x          expects the x coordinate of the center of the arc. The center
                of the arc is the center of the circle that would contain the
                arc.

     y          expects the y coordinate of the center of the arc.  The center
                of the arc is the center of the circle that would contain the
                arc.

     radius     expects the length of the radius of the arc.  The radius of
                the arc is the radius of the circle that would contain the
                arc.

     stang      expects the measure of the start angle of the arc. The start
                angle of the arc is measured from the positive x-axis.

     endang     expects the measure of the end angle of the arc. The end angle
                of the arc is measured from the positive x-axis.

DESCRIPTION
     arc draws an unfilled circular arc in the x-y plane (z = 0). To draw an
     arc in a plane other than the x-y plane, define the arc in the x-y plane
     and then rotate or translate the arc.

     An arc is drawn as a sequence of line segments, and therefore inherits
     all properties that affect the drawing of lines.  These include the
     current color, writemask, line width, stipple pattern, shade model, line
     antialiasing mode, and subpixel mode.  The stipple pattern is initialized
     to bit zero of the current linestyle before the arc is drawn, then
     shifted continuously through the segments of the arc.

     An arc is defined in terms of the circle that contains it.  All
     references to the radius and center of the arc refer to the radius and
     center of the circle that contains the arc. The angle swept out by the
     arc is the angle from the start angle counter-clockwise to the end angle.

     The start and end angles are defined relative to the positive x-axis. (To
     speak more precisely, because the arc might not be centered on the
     origin, the start and end angles are defined relative to the right
     horizontal radius of the circle containing the arc).  Positive values for
     an angle indicate a counter-clockwise rotation from the horizontal.
     Negative values indicate a clockwise rotation from the horizontal.

     The basic unit of angle measure is a tenth of a degree. The value 900
     indicates an angle of 90 degrees in a counter-clockwise direction from
     the horizontal. Thus, an arc that spans from a start angle of 10 degrees
     (stang = 100) to an end angle of 5 degrees (endang = 50) is almost a
     complete circle.

     After arc executes, the graphics position is undefined.

SEE ALSO
     arcf, bgnclo, circ, crvn, linewi, linesm, lsrepe, scrsub, setlin, shadem,
     subpix

BUGS
     When the line width is greater than 1, small notches will appear in arcs,
     because of the way wide lines are implemented.