1XDrawArc(3)                     XLIB FUNCTIONS                     XDrawArc(3)
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NAME

6       XDrawArc, XDrawArcs, XArc - draw arcs and arc structure
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SYNTAX

9       int  XDrawArc(Display  *display,  Drawable  d, GC gc, int x, int y, un‐
10              signed int width, unsigned int height, int angle1, int angle2);
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12       int XDrawArcs(Display *display, Drawable d,  GC  gc,  XArc  *arcs,  int
13              narcs);
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ARGUMENTS

16       angle1    Specifies  the start of the arc relative to the three-o'clock
17                 position from the center, in units of degrees * 64.
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19       angle2    Specifies the path and extent of  the  arc  relative  to  the
20                 start of the arc, in units of degrees * 64.
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22       arcs      Specifies an array of arcs.
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24       d         Specifies the drawable.
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26       display   Specifies the connection to the X server.
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28       gc        Specifies the GC.
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30       narcs     Specifies the number of arcs in the array.
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32       width
33       height    Specify  the  width and height, which are the major and minor
34                 axes of the arc.
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36       x
37       y         Specify the x and y coordinates, which are  relative  to  the
38                 origin  of  the drawable and specify the upper-left corner of
39                 the bounding rectangle.
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DESCRIPTION

42       XDrawArc draws a single circular or elliptical arc, and XDrawArcs draws
43       multiple  circular or elliptical arcs.  Each arc is specified by a rec‐
44       tangle and two angles.  The center of the circle or ellipse is the cen‐
45       ter of the rectangle, and the major and minor axes are specified by the
46       width and height.  Positive angles  indicate  counterclockwise  motion,
47       and negative angles indicate clockwise motion.  If the magnitude of an‐
48       gle2 is greater than 360 degrees, XDrawArc or XDrawArcs truncates it to
49       360 degrees.
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51       For an arc specified as [x,y,width,height,angle1,angle2], the origin of
52       the major and minor axes is at [x+w_i_d2_t_h_,y+h_e_i_g2_h_t_], and  the  infinitely
53       thin  path describing the entire circle or ellipse intersects the hori‐
54       zontal axis at [x,y+h_e_i_g2_h_t_] and [x+width,y+h_e_i_g2_h_t_] and  intersects  the
55       vertical axis at [x+w_i_d2_t_h_,y] and [x+w_i_d2_t_h_,y+height].  These coordinates
56       can be fractional and so are not  truncated  to  discrete  coordinates.
57       The  path should be defined by the ideal mathematical path.  For a wide
58       line with line-width lw, the bounding outlines for filling are given by
59       the two infinitely thin paths consisting of all points whose perpendic‐
60       ular distance from the path of the  circle/ellipse  is  equal  to  lw/2
61       (which  may  be  a fractional value).  The cap-style and join-style are
62       applied the same as for a line corresponding to the tangent of the cir‐
63       cle/ellipse at the endpoint.
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65       For  an  arc  specified as [x,y,width,height,angle1,angle2], the angles
66       must be specified in the effectively skewed coordinate  system  of  the
67       ellipse  (for  a  circle, the angles and coordinate systems are identi‐
68       cal).  The relationship between these angles and  angles  expressed  in
69       the normal coordinate system of the screen (as measured with a protrac‐
70       tor) is as follows:
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72       skewed-angle=atan⎛⎝tan(normal-angle)*h_we_ii_dg_th_ht_⎞⎠+adjust
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74       The skewed-angle and normal-angle are expressed in radians (rather than
75       in  degrees  scaled by 64) in the range [0,2π] and where atan returns a
76       value in the range [−π2_,π2_] and adjust is:
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78       l l.  0    for normal-angle in the range [0,π2_] π    for normal-angle in
79       the range [π2_,3_π2_] 2π   for normal-angle in the range [3_π2_,2π]
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81       For any given arc, XDrawArc and XDrawArcs do not draw a pixel more than
82       once.  If two arcs join correctly and if the line-width is greater than
83       zero and the arcs intersect, XDrawArc and XDrawArcs do not draw a pixel
84       more than once.  Otherwise, the  intersecting  pixels  of  intersecting
85       arcs are drawn multiple times.  Specifying an arc with one endpoint and
86       a clockwise extent draws the same pixels as specifying the  other  end‐
87       point  and  an equivalent counterclockwise extent, except as it affects
88       joins.
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90       If the last point in one arc coincides with the first point in the fol‐
91       lowing  arc,  the  two arcs will join correctly.  If the first point in
92       the first arc coincides with the last point in the last  arc,  the  two
93       arcs  will  join correctly.  By specifying one axis to be zero, a hori‐
94       zontal or vertical line can be drawn.  Angles are computed based solely
95       on the coordinate system and ignore the aspect ratio.
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97       Both  functions  use  these  GC components: function, plane-mask, line-
98       width, line-style, cap-style, join-style,  fill-style,  subwindow-mode,
99       clip-x-origin,  clip-y-origin,  and  clip-mask.  They also use these GC
100       mode-dependent components: foreground, background, tile, stipple, tile-
101       stipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.
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103       XDrawArc  and  XDrawArcs  can generate BadDrawable, BadGC, and BadMatch
104       errors.
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STRUCTURES

107       The XArc structure contains:
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109       typedef struct {
110            short x, y;
111            unsigned short width, height;
112            short angle1, angle2;             /* Degrees * 64 */
113       } XArc;
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115       All x and y members are signed integers.  The width and height  members
116       are  16-bit  unsigned  integers.  You should be careful not to generate
117       coordinates and sizes out of the 16-bit ranges,  because  the  protocol
118       only has 16-bit fields for these values.
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DIAGNOSTICS

121       BadDrawable
122                 A  value for a Drawable argument does not name a defined Win‐
123                 dow or Pixmap.
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125       BadGC     A value for a GContext argument does not name a defined GCon‐
126                 text.
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128       BadMatch  An InputOnly window is used as a Drawable.
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130       BadMatch  Some  argument  or pair of arguments has the correct type and
131                 range but fails to match in some other way  required  by  the
132                 request.
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SEE ALSO

135       XDrawLine(3), XDrawPoint(3), XDrawRectangle(3)
136       Xlib - C Language X Interface
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140X Version 11                     libX11 1.7.2                      XDrawArc(3)
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