XDrawArc(3X11)                       SysV                       XDrawArc(3X11)



NAME
     XDrawArc, XDrawArcs - draw arcs

SYNTAX
     XDrawArc(display, d, gc, x, y, width, height, angle1, angle2)
           Display *display;
           Drawable d;
           GC gc;
           int x, y;
           unsigned int width, height;
           int angle1, angle2;

     XDrawArcs(display, d, gc, arcs, narcs)
           Display *display;
           Drawable d;
           GC gc;
           XArc *arcs;
           int narcs;

ARGUMENTS
     angle1    Specifies the start of the arc relative to the three-o'clock
               position from the center, in units of degrees * 64.

     angle2    Specifies the path and extent of the arc relative to the start
               of the arc, in units of degrees * 64.

     arcs      Specifies a pointer to an array of arcs.

     d         Specifies the drawable.

     display   Specifies the connection to the X server.

     gc        Specifies the GC.

     narcs     Specifies the number of arcs in the array.

     width
     height    Specify the width and height, which are the major and minor
               axes of the arc.

     x
     y         Specify the x and y coordinates, which are relative to the
               origin of the drawable and specify the upper-left corner of the
               bounding rectangle.

DESCRIPTION
     XDrawArc draws a single circular or elliptical arc, and XDrawArcs draws
     multiple circular or elliptical arcs.  Each arc is specified by a
     rectangle and two angles. The center of the circle or ellipse is the
     center of the rectangle, and the major and minor axes are specified by
     the width and height.  Positive angles indicate counterclockwise motion,
     and negative angles indicate clockwise motion. If the magnitude of angle2
     is greater than 360 degrees, XDrawArc or XDrawArcs truncates it to 360
     degrees.

     For an arc specified as [ x, y, width, height, angle1, angle2], the
     origin of the major and minor axes is at [x+width, y+height], and the
     infinitely thin path describing the entire cir2
cle or el2
lipse intersects
     the horizontal axis at [x, y+height] and [x+width, y+height] and
     intersects the vertical axis at2[x+width, y] and [x+wid2
th, y+height].
     These coordinates can be fractional a2
nd so are not tru2
ncated to discrete

     coordinates.  The path should be defined by the ideal mathematical path.
     For a wide line with line-width lw, the bounding outlines for filling are
     given by the two infinitely thin paths consisting of all points whose
     perpendicular distance from the path of the circle/ellipse is equal to
     lw/2 (which may be a fractional value).  The cap-style and join-style are
     applied the same as for a line corresponding to the tangent of the
     circle/ellipse at the endpoint.

     For an arc specified as [ x, y, width, height, angle1, angle2], the
     angles must be specified in the effectively skewed coordinate system of
     the ellipse (for a circle, the angles and coordinate systems are
     identical).  The relationship between these angles and angles expressed
     in the normal coordinate system of the screen (as measured with a
     protractor) is as follows:

     skewed-angle = atan|tan(normal-angle)*_width|+adjust
The skewed-angle and norm
|al-angle are expreh
se
se
id
ghi
tn
| radians (rather than in
degrees scaled by 64) in the range [0, 2π] and where atan returns a value in
the range [-π, π] and adjust is:
            2  2
     0         for normal-angle in the range [0, π]
     π         for normal-angle in the range [π, 2
3π]
     2π        for normal-angle in the range [2
3π,22π]
                                              2
     For any given arc, XDrawArc and XDrawArcs do not draw a pixel more than
     once. If two arcs join correctly and if the line-width is greater than
     zero and the arcs intersect, XDrawArc and XDrawArcs do not draw a pixel
     more than once.  Otherwise, the intersecting pixels of intersecting arcs
     are drawn multiple times.  Specifying an arc with one endpoint and a
     clockwise extent draws the same pixels as specifying the other endpoint
     and an equivalent counterclockwise extent, except as it affects joins.

     If the last point in one arc coincides with the first point in the
     following arc, the two arcs will join correctly. If the first point in
     the first arc coincides with the last point in the last arc, the two arcs
     will join correctly.  By specifying one axis to be zero, a horizontal or
     vertical line can be drawn.  Angles are computed based solely on the
     coordinate system and ignore the aspect ratio.

     Both functions use these GC components: function, plane-mask, line-width,
     line-style, cap-style, join-style, fill-style, subwindow-mode, clip-x-
     origin, clip-y-origin, and clip-mask.  They also use these GC mode-
     dependent components: foreground, background, tile, stipple, tile-
     stipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

     XDrawArc and XDrawArcs can generate BadDrawable, BadGC, and BadMatch
     errors.

DIAGNOSTICS
     BadDrawable
               A value for a Drawable argument does not name a defined Window
               or Pixmap.

     BadGC     A value for a GContext argument does not name a defined
               GContext.

     BadMatch  An InputOnly window is used as a Drawable.

     BadMatch  Some argument or pair of arguments has the correct type and
               range but fails to match in some other way required by the
               request.

SEE ALSO
     XDrawLine(3X11), XDrawPoint(3X11), XDrawRectangle(3X11)
     Xlib - C Language X Interface