1XDrawArc(3)                     XLIB FUNCTIONS                     XDrawArc(3)
2
3
4

NAME

6       XDrawArc, XDrawArcs, XArc - draw arcs and arc structure
7

SYNTAX

9       int  XDrawArc(Display  *display,  Drawable  d,  GC  gc,  int  x, int y,
10              unsigned  int  width,  unsigned  int  height,  int  angle1,  int
11              angle2);
12
13       int  XDrawArcs(Display  *display,  Drawable  d,  GC gc, XArc *arcs, int
14              narcs);
15

ARGUMENTS

17       angle1    Specifies the start of the arc relative to the  three-o'clock
18                 position from the center, in units of degrees * 64.
19
20       angle2    Specifies  the  path  and  extent  of the arc relative to the
21                 start of the arc, in units of degrees * 64.
22
23       arcs      Specifies an array of arcs.
24
25       d         Specifies the drawable.
26
27       display   Specifies the connection to the X server.
28
29       gc        Specifies the GC.
30
31       narcs     Specifies the number of arcs in the array.
32
33       width
34       height    Specify the width and height, which are the major  and  minor
35                 axes of the arc.
36
37       x
38       y         Specify  the  x  and y coordinates, which are relative to the
39                 origin of the drawable and specify the upper-left  corner  of
40                 the bounding rectangle.
41

DESCRIPTION

43       XDrawArc draws a single circular or elliptical arc, and XDrawArcs draws
44       multiple circular or elliptical arcs.  Each arc is specified by a  rec‐
45       tangle and two angles.  The center of the circle or ellipse is the cen‐
46       ter of the rectangle, and the major and minor axes are specified by the
47       width  and  height.   Positive angles indicate counterclockwise motion,
48       and negative angles indicate clockwise motion.   If  the  magnitude  of
49       angle2  is greater than 360 degrees, XDrawArc or XDrawArcs truncates it
50       to 360 degrees.
51
52       For an arc specified as [x,y,width,height,angle1,angle2], the origin of
53       the  major  and minor axes is at [x+w_i_d2_t_h_,y+h_e_i_g2_h_t_], and the infinitely
54       thin path describing the entire circle or ellipse intersects the  hori‐
55       zontal  axis  at [x,y+h_e_i_g2_h_t_] and [x+width,y+h_e_i_g2_h_t_] and intersects the
56       vertical axis at [x+w_i_d2_t_h_,y] and [x+w_i_d2_t_h_,y+height].  These coordinates
57       can  be  fractional  and  so are not truncated to discrete coordinates.
58       The path should be defined by the ideal mathematical path.  For a  wide
59       line with line-width lw, the bounding outlines for filling are given by
60       the two infinitely thin paths consisting of all points whose perpendic‐
61       ular  distance  from  the  path  of the circle/ellipse is equal to lw/2
62       (which may be a fractional value).  The cap-style  and  join-style  are
63       applied the same as for a line corresponding to the tangent of the cir‐
64       cle/ellipse at the endpoint.
65
66       For an arc specified as  [x,y,width,height,angle1,angle2],  the  angles
67       must  be  specified  in the effectively skewed coordinate system of the
68       ellipse (for a circle, the angles and coordinate  systems  are  identi‐
69       cal).   The  relationship  between these angles and angles expressed in
70       the normal coordinate system of the screen (as measured with a protrac‐
71       tor) is as follows:
72
73       skewed-angle=atan⎛⎝tan(normal-angle)*h_we_ii_dg_th_ht_⎞⎠+adjust
74
75       The skewed-angle and normal-angle are expressed in radians (rather than
76       in degrees scaled by 64) in the range [0,2π] and where atan  returns  a
77       value in the range [−π2_,π2_] and adjust is:
78
79       l l.  0    for normal-angle in the range [0,π2_] π    for normal-angle in
80       the range [π2_,3_π2_] 2π   for normal-angle in the range [3_π2_,2π]
81
82       For any given arc, XDrawArc and XDrawArcs do not draw a pixel more than
83       once.  If two arcs join correctly and if the line-width is greater than
84       zero and the arcs intersect, XDrawArc and XDrawArcs do not draw a pixel
85       more  than  once.   Otherwise,  the intersecting pixels of intersecting
86       arcs are drawn multiple times.  Specifying an arc with one endpoint and
87       a  clockwise  extent draws the same pixels as specifying the other end‐
88       point and an equivalent counterclockwise extent, except as  it  affects
89       joins.
90
91       If the last point in one arc coincides with the first point in the fol‐
92       lowing arc, the two arcs will join correctly.  If the  first  point  in
93       the  first  arc  coincides with the last point in the last arc, the two
94       arcs will join correctly.  By specifying one axis to be zero,  a  hori‐
95       zontal or vertical line can be drawn.  Angles are computed based solely
96       on the coordinate system and ignore the aspect ratio.
97
98       Both functions use these GC  components:  function,  plane-mask,  line-
99       width,  line-style,  cap-style, join-style, fill-style, subwindow-mode,
100       clip-x-origin, clip-y-origin, and clip-mask.  They also  use  these  GC
101       mode-dependent components: foreground, background, tile, stipple, tile-
102       stipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.
103
104       XDrawArc and XDrawArcs can generate BadDrawable,  BadGC,  and  BadMatch
105       errors.
106

STRUCTURES

108       The XArc structure contains:
109
110       typedef struct {
111            short x, y;
112            unsigned short width, height;
113            short angle1, angle2;             /* Degrees * 64 */
114       } XArc;
115
116       All  x and y members are signed integers.  The width and height members
117       are 16-bit unsigned integers.  You should be careful  not  to  generate
118       coordinates  and  sizes  out of the 16-bit ranges, because the protocol
119       only has 16-bit fields for these values.
120

DIAGNOSTICS

122       BadDrawable
123                 A value for a Drawable argument does not name a defined  Win‐
124                 dow or Pixmap.
125
126       BadGC     A value for a GContext argument does not name a defined GCon‐
127                 text.
128
129       BadMatch  An InputOnly window is used as a Drawable.
130
131       BadMatch  Some argument or pair of arguments has the correct  type  and
132                 range  but  fails  to match in some other way required by the
133                 request.
134

SEE ALSO

136       XDrawLine(3), XDrawPoint(3), XDrawRectangle(3)
137       Xlib - C Language X Interface
138
139
140
141X Version 11                     libX11 1.6.9                      XDrawArc(3)
Impressum