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XDrawArc(3)                     XLIB FUNCTIONS                     XDrawArc(3)




NAME

       XDrawArc, XDrawArcs, XArc - draw arcs and arc structure


SYNTAX

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

       int  XDrawArcs(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 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  rec-
       tangle and two angles.  The center of the circle or ellipse is the cen-
       ter 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+_____,y+______], and the infinitely
       thin path describing the entire circle or ellipse intersects the  hori-
       zontal  axis  at [x,y+______] and [x+width,y+______] and intersects the
       vertical axis at [x+_____,y] and [x+_____,y+height].  These coordinates
       can  be  fractional  and  so are not truncated 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 perpendic-
       ular  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 cir-
       cle/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  identi-
       cal).   The  relationship  between these angles and angles expressed in
       the normal coordinate system of the screen (as measured with a protrac-
       tor) is as follows:


       skewed-angle=atan(tan(normal-angle)*_<i>e_<i>i_<i>g_<i>h_<i>t_)+adjust


       The skewed-angle and normal-angle are expressed in radians (rather than
       in degrees scaled by 64) in the range [0,2n] and where atan  returns  a
       value in the range [-_,_] and adjust is:


       l l.  0    for normal-angle in the range [0,_] n    for normal-angle in
       the range [_,__] 2n   for normal-angle in the range [__,2n]

       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 end-
       point and an equivalent counterclockwise extent, except as  it  affects
       joins.

       If the last point in one arc coincides with the first point in the fol-
       lowing 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  hori-
       zontal 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.


STRUCTURES

       The XArc structure contains:


       typedef struct {
            short x, y;
            unsigned short width, height;
            short angle1, angle2;             /* Degrees * 64 */
       } XArc;


       All  x and y members are signed integers.  The width and height members
       are 16-bit unsigned integers.  You should be careful  not  to  generate
       coordinates  and  sizes  out of the 16-bit ranges, because the protocol
       only has 16-bit fields for these values.


DIAGNOSTICS

       BadDrawable
                 A value for a Drawable argument does not name a defined  Win-
                 dow or Pixmap.

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

       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(3), XDrawPoint(3), XDrawRectangle(3)
       Xlib - C Language X Interface



X Version 11                     libX11 1.6.9                      XDrawArc(3)

xorg-libX11 1.6.9 - Generated Mon Oct 21 19:05:35 CDT 2019
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