XDrawArc(3X11) X Version 11(Release 5) XDrawArc(3X11)
NAME
XDrawArc, XDrawArcs, XArc - draw arcs and arc structure
SYNTAX
XDrawArc(display, d, gc, x, y, width, height, angle1, angle2)
Display *display;
Drawable d;
GC gc;
int x, y;
unsigned int width, height;
int angle1, angle2;
XDrawArcs(display, d, gc, arcs, narcs)
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.
x
y Specify the x and y coordinates, which are relative to the
origin of the drawable and specify the upper-left corner of the
bounding rectangle.
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 magnitude of angle2
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XDrawArc(3X11) X Version 11(Release 5) XDrawArc(3X11)
is greater than 360 degrees, XDrawArc or XDrawArcs truncates it to 360
degrees. width, y+height].
These coordinates can be fractionalwa
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circle/ellipse at the endpoint.
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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
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skewed-angle = atan( _width)
(tan(normal-angle)*height)+adjust
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do2not 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.
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-
Page 2 10/89
XDrawArc(3X11) X Version 11(Release 5) XDrawArc(3X11)
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.
SEE ALSO
XDrawLine(3X11), XDrawPoint(3X11), XDrawRectangle(3X11)
Xlib - C Language X Interface
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