MirBSD manpage: XArc(3), XDrawArc(3), XDrawArcs(3)


XDrawArc(3X11)           XLIB FUNCTIONS            XDrawArc(3X11)

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. and specify the upper-
               left corner of the bounding rectangle

     x
     y         Specify the x and y coordinates, which are rela-
               tive to the origin of the drawable.

DESCRIPTION

XDrawArc draws a single circular or elliptical arc, and
XDrawArcs 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 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 magni-
tude of angle2 is greater than 360 degrees, XDrawArc or
XDrawArcs truncates it to 360 degrees.

For an arc specified as _e__g__t_], and the
[ x, y, width, height, angle1,_a_d_t_h_,2y+ t2e origin of the
major and minor axes is at [x+ 2

XFree86 Version 4.5.0 1

XDrawArc(3X11) XLIB FUNCTIONS XDrawArc(3X11)

_i__t__, y+height]. These coordinates can
befwfirdatcht,ion]ahleaina_nhdt[]s+oanadreinntoetrsterutnscatheedtvtheoer_dgiihcstac]reatxediscoaotrdi-se
[nxa+tweisd.thT,hey+pathhshouldtbe defined by,the ideal mathematical
path. For a wide line with line-width lw, the bounding out-
lines 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:

skewed-angle = atan| __i__t__|
|tan(normal-angle)*height|+adjust

The skewed-angle and normal-angle are expressed in_̅ia̅]dands
adjustris:an in degrees scaled by 64) in 3_ie̅i,̅3_i̅i̅2i̅i̅i̅,i̅]2[0, 2i̅i̅]
2i̅i̅ where fornnormal-angleainethe rangea[ie̅i̅2,i-̅i2̅2
iFo̅r any gifvoern naorrcm,alX-DarnagwlAercinantdheXDrraanwgAerc[s2do2not 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 endpoint and an equivalent counterclockwise
extent, except as it affects joins.

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.

XFree86 Version 4.5.0 2

XDrawArc(3X11) XLIB FUNCTIONS XDrawArc(3X11)

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 Window or Pixmap.

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

     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.