XDrawArc(3X11) AIX (XLIB FUNCTIONS) XDrawArc(3X11)
NAME
XDrawArc, XDrawArcs, XArc - draw arcs and arc structure
SYNTAX
XDrawArc(_d_i_s_p_l_a_y, _d, _g_c, _x, _y, _w_i_d_t_h, _h_e_i_g_h_t, _a_n_g_l_e_1,
_a_n_g_l_e_2)
Display *_d_i_s_p_l_a_y;
Drawable _d;
GC _g_c;
int _x, _y;
unsigned int _w_i_d_t_h, _h_e_i_g_h_t;
int _a_n_g_l_e_1, _a_n_g_l_e_2;
XDrawArcs(_d_i_s_p_l_a_y, _d, _g_c, _a_r_c_s, _n_a_r_c_s)
Display *_d_i_s_p_l_a_y;
Drawable _d;
GC _g_c;
XArc *_a_r_c_s;
int _n_a_r_c_s;
ARGUMENTS
_a_n_g_l_e_1 Specifies the start of the arc relative to the
three-o'clock position from the center, in units
of degrees * 64.
_a_n_g_l_e_2 Specifies the path and extent of the arc relative
to the start of the arc, in units of degrees * 64.
_a_r_c_s Specifies an array of arcs.
_d Specifies the drawable.
_d_i_s_p_l_a_y Specifies the connection to the X server.
_g_c Specifies the GC.
_n_a_r_c_s Specifies the number of arcs in the array.
_w_i_d_t_h
_h_e_i_g_h_t 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 rela-
tive to the origin of the drawable and specify the
upper-left corner of the bounding rectangle.
DESCRIPTION
delim %% _X_D_r_a_w_A_r_c draws a single circular or elliptical arc,
and _X_D_r_a_w_A_r_c_s 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 rectan-
gle, and the major and minor axes are specified by the width
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XDrawArc(3X11) AIX (XLIB FUNCTIONS) XDrawArc(3X11)
and height. Positive angles indicate counterclockwise
motion, and negative angles indicate clockwise motion. If
the magnitude of angle2 is greater than 360 degrees,
_X_D_r_a_w_A_r_c or _X_D_r_a_w_A_r_c_s 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 over 2} , ~y +^ {height over 2} ]%,
and the infinitely thin path describing the entire circle or
ellipse intersects the horizontal axis at % [ x, ~y +^
{height over 2} ]% and % [ x +^ width , ~y +^ { height over
2 }] % and intersects the vertical axis at % [ x +^ { width
over 2 } , ~y ]% and % [ x +^ { width over 2 }, ~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 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:
% roman "skewed-angle" ~ = ~ atan left ( tan ( roman "normal-angle" )
* width over height right ) +^ adjust%
The skewed-angle and normal-angle are expressed in radians
(rather than in degrees scaled by 64) in the range % [ 0 ,
~2 pi ]% and where atan returns a value in the range % [ -
pi over 2 , ~pi over 2 ] % and adjust is:
%0% for normal-angle in the range % [ 0 , ~pi over 2 ]%
%pi% for normal-angle in the range % [ pi over 2 , ~{3 pi} over 2 ]%
%2 pi% for normal-angle in the range % [ {3 pi} over 2 , ~2 pi ]%
For any given arc, _X_D_r_a_w_A_r_c and _X_D_r_a_w_A_r_c_s 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,
_X_D_r_a_w_A_r_c and _X_D_r_a_w_A_r_c_s 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.
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XDrawArc(3X11) AIX (XLIB FUNCTIONS) XDrawArc(3X11)
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 com-
ponents: foreground, background, tile, stipple, tile-
stipple-x-origin, tile-stipple-y-origin, dash-offset, and
dash-list.
_X_D_r_a_w_A_r_c and _X_D_r_a_w_A_r_c_s can generate _B_a_d_D_r_a_w_a_b_l_e, _B_a_d_G_C, and
_B_a_d_M_a_t_c_h errors.
STRUCTURES
The _X_A_r_c 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
_B_a_d_D_r_a_w_a_b_l_e
A value for a Drawable argument does not name a
defined Window or Pixmap.
_B_a_d_G_C A value for a GContext argument does not name a
defined GContext.
_B_a_d_M_a_t_c_h An _I_n_p_u_t_O_n_l_y window is used as a Drawable.
_B_a_d_M_a_t_c_h 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)
_X_l_i_b - _C _L_a_n_g_u_a_g_e _X _I_n_t_e_r_f_a_c_e
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