'\"!  eqn | eqn | mmdoc
'\"macro stdmacro
.if n .pH g3x11.XDrArc @(#)XDrArc	40.3 of 1/19/90
.ds tk X Toolkit
.br
.ds xT X Toolkit Intrinsics \- C Language Interface
.ds xI Intrinsics
.ds xW Athena X Widgets \- C Language X Toolkit Interface
.ds xL Xlib \- C Language X Interface
.ds xC Inter-Client Communication Conventions Manual
.ds Rn 3
.ds Vn 2.2
.hw XtMake-Geometry-Request XtQuery-Geometry wid-get
.na
.de Ds
.nf
.\\$1D \\$2 \\$1
.ft 1
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.LP
.KS
.TA .5i 3i
.ta .5i 3i
.nf
..
.de FN
.fi
.KE
.LP
..
.de IN		\" send an index entry to the stderr
.tm \\n%:\\$1:\\$2:\\$3
..
.de C{
.KS
.nf
.D
.\"
.\"	choose appropriate monospace font
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.\"
.ie "\\*(.T"480" .ft L
.el .ie "\\*(.T"300" .ft L
.el .ie "\\*(.T"202" .ft PO
.el .ie "\\*(.T"aps" .ft CW
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.DE
.R
..
.de Pn
.ie t \\$1\fB\^\\$2\^\fR\\$3
.el \\$1\fI\^\\$2\^\fP\\$3
..
.de PN
.ie t \fB\^\\$1\^\fR\\$2
.el \fI\^\\$1\^\fP\\$2
..
.de NT
.ne 7
.ds NO Note
.if \\n(.$>$1 .if !'\\$2'C' .ds NO \\$2
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.de NE
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.ie n .sp
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.ny0
.nr X
.if \nX=0 .ds x} XDrawArc 3X11 "9/1/88" "XWIN 3.0" "\&"
.if \nX=1 .ds x} XDrawArc 3X11 "9/1/88" "XWIN 3.0"
.if \nX=2 .ds x} XDrawArc 3X11 "" "\&"
.if \nX=3 .ds x} XDrawArc "" "" "\&"
.TH \*(x}
.SH NAME
XDrawArc, XDrawArcs \- draw arcs
.SH SYNTAX
.\" $Header: XArc.f,v 1.1 88/02/26 09:58:12 mento Exp $
XDrawArc\^(\^\fIdisplay\fP, \fId\fP\^, \fIgc\fP\^, \fIx\fP\^, \fIy\fP\^, \fIwidth\fP\^, \fIheight\fP\^, \fIangle1\fP\^, \fIangle2\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Drawable \fId\fP\^;
.br
      GC \fIgc\fP\^;
.br
      int \fIx\fP\^, \fIy\fP\^;
.br
      unsigned int \fIwidth\fP\^, \fIheight\fP\^;
.br
      int \fIangle1\fP\^, \fIangle2\fP\^;
.LP
.\" $Header: XArcs.f,v 1.1 88/02/26 09:58:12 mento Exp $
XDrawArcs\^(\^\fIdisplay\fP, \fId\fP\^, \fIgc\fP\^, \fIarcs\fP\^, \fInarcs\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Drawable \fId\fP\^;
.br
      GC \fIgc\fP\^;
.br
      XArc *\fIarcs\fP\^;
.br
      int \fInarcs\fP\^;
.SH ARGUMENTS
.\" $Header: angle1.a,v 1.2 88/05/13 09:05:46 mento Exp $
.IP \fIangle1\fP 1i
Specifies the start of the arc relative to the three-o'clock position
from the center, in units of degrees * 64.
.\" $Header: angle2.a,v 1.1 88/02/26 10:04:51 mento Exp $
.IP \fIangle2\fP 1i
Specifies the path and extent of the arc relative to the start of the
arc, in units of degrees * 64.
.\" $Header: arcs.a,v 1.1 88/02/26 10:04:53 mento Exp $
.IP \fIarcs\fP 1i
Specifies a pointer to an array of arcs.
.\" $Header: d.a,v 1.1 88/02/26 10:04:25 mento Exp $
.IP \fId\fP 1i
Specifies the drawable. 
.\" $Header: display.a,v 1.1 88/02/26 10:26:29 mento Exp $
.IP \fIdisplay\fP 1i
Specifies the connection to the X\s-2WIN\s+2 server.
.\" $Header: gc.a,v 1.2 88/05/09 11:20:34 mento Exp $
.IP \fIgc\fP 1i
Specifies the GC.
.\" $Header: narcs.a,v 1.1 88/02/26 10:29:11 mento Exp $
.IP \fInarcs\fP 1i
Specifies the number of arcs in the array.
.ds Wh , which are the major and minor axes of the arc
.\" $Header: w+h_gen.a,v 1.2 88/08/04 11:21:28 mento Exp $
.IP \fIwidth\fP 1i
.br
.ns
.IP \fIheight\fP 1i
Specify the width and height\*(Wh.
.ds Xy , which are relative to the origin of the drawable \
and specify the upper-left corner of the bounding rectangle
.\" $Header: xy_gen.a,v 1.2 88/08/04 11:22:37 mento Exp $
.IP \fIx\fP 1i
.br
.ns
.IP \fIy\fP 1i
Specify the x and y coordinates\*(Xy.
.SH DESCRIPTION
.\" $Header: XArc.d,v 1.5 88/10/23 21:15:52 rws Exp $
.EQ
delim %%
.EN
.PN XDrawArc
draws a single circular or elliptical arc, and 
.PN 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 is greater than 360 degrees, 
.PN XDrawArc
or 
.PN XDrawArcs
truncates it to 360 degrees.
.LP
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.
.LP
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:
.Ds
% roman "skewed-angle" ~ = ~ atan left ( tan ( roman "normal-angle" )
 * width over height right ) +^ adjust%
.De
.LP
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:
.LP
.Ds
.TA 1i 2i
.ta 1i 2i
%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  ]%
.De
.LP
For any given arc, 
.PN XDrawArc
and
.PN XDrawArcs
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, 
.PN XDrawArc
and
.PN 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.
.LP
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.
.LP
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.
.EQ
delim off
.EN
.LP
.ds fd .PN XDrawArc
.ds fe .PN XDrawArcs
\*(fd
and
\*(fe
can generate
.PN BadDrawable ,
.PN BadGC ,
and
.PN BadMatch 
errors.
.SH DIAGNOSTICS
.\" $Header: baddrawable.e,v 1.1 87/09/04 08:22:59 mento Exp $
.TP 1i
.PN BadDrawable
A value for a Drawable argument does not name a defined Window or Pixmap.
.\" $Header: badgc.e,v 1.1 87/09/04 08:23:02 mento Locked $
.TP 1i
.PN BadGC
A value for a GContext argument does not name a defined GContext.
.\" $Header: badmatch1.e,v 1.3 87/09/09 18:18:54 mento Exp $
.TP 1i
.PN BadMatch
An
.PN InputOnly
window is used as a Drawable.
.\" $Header: badmatch2.e,v 1.3 87/09/11 11:53:42 mento Exp $
.TP 1i
.PN 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.
.SH "SEE ALSO"
XDrawLine(3X11),
.br
XDrawPoint(3X11),
.br
XDrawRectangle(3X11)
.br
\fI\*(xL\fP
