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 Rev. Release 5 Page 1 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. Rev. Release 5 Page 2 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 Rev. Release 5 Page 3