246 lines
8.4 KiB
Groff
246 lines
8.4 KiB
Groff
'\" e
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.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1994, 1996 X Consortium
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.\"
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.\" Permission is hereby granted, free of charge, to any person obtaining
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.\" a copy of this software and associated documentation files (the
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.\" "Software"), to deal in the Software without restriction, including
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.\" without limitation the rights to use, copy, modify, merge, publish,
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.\" distribute, sublicense, and/or sell copies of the Software, and to
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.\" permit persons to whom the Software is furnished to do so, subject to
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.\" the following conditions:
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.\"
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.\" The above copyright notice and this permission notice shall be included
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.\" in all copies or substantial portions of the Software.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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.\" IN NO EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR
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.\" OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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.\" ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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.\" OTHER DEALINGS IN THE SOFTWARE.
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.\"
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.\" Except as contained in this notice, the name of the X Consortium shall
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.\" not be used in advertising or otherwise to promote the sale, use or
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.\" other dealings in this Software without prior written authorization
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.\" from the X Consortium.
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.\"
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.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991 by
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.\" Digital Equipment Corporation
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.\"
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.\" Portions Copyright \(co 1990, 1991 by
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.\" Tektronix, Inc.
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.\"
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.\" Permission to use, copy, modify and distribute this documentation for
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.\" any purpose and without fee is hereby granted, provided that the above
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.\" copyright notice appears in all copies and that both that copyright notice
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.\" and this permission notice appear in all copies, and that the names of
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.\" Digital and Tektronix not be used in in advertising or publicity pertaining
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.\" to this documentation without specific, written prior permission.
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.\" Digital and Tektronix makes no representations about the suitability
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.\" of this documentation for any purpose.
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.\" It is provided "as is" without express or implied warranty.
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.\"
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.\"
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.ds xT X Toolkit Intrinsics \- C Language Interface
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.ds xW Athena X Widgets \- C Language X Toolkit Interface
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.ds xL Xlib \- C Language X Interface
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.ds xC Inter-Client Communication Conventions Manual
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.de EX
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.sp
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.nf
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.ft CW
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..
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.de EE
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.ft R
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.fi
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.sp
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..
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'\" e
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.TH XDrawArc __libmansuffix__ __xorgversion__ "XLIB FUNCTIONS"
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.SH NAME
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XDrawArc, XDrawArcs, XArc \- draw arcs and arc structure
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.SH SYNTAX
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.HP
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int XDrawArc\^(\^Display *\fIdisplay\fP\^, Drawable \fId\fP\^, GC \fIgc\fP\^,
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int \fIx\fP\^, int \fIy\fP\^, unsigned int \fIwidth\fP\^, unsigned int
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\fIheight\fP\^, int \fIangle1\fP\^, int \fIangle2\fP\^);
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.HP
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int XDrawArcs\^(\^Display *\fIdisplay\fP\^, Drawable \fId\fP\^, GC \fIgc\fP\^,
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XArc *\fIarcs\fP\^, int \fInarcs\fP\^);
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.SH ARGUMENTS
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.IP \fIangle1\fP 1i
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Specifies the start of the arc relative to the three-o'clock position
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from the center, in units of degrees * 64.
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.IP \fIangle2\fP 1i
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Specifies the path and extent of the arc relative to the start of the
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arc, in units of degrees * 64.
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.IP \fIarcs\fP 1i
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Specifies an array of arcs.
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.IP \fId\fP 1i
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Specifies the drawable.
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.IP \fIdisplay\fP 1i
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Specifies the connection to the X server.
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.IP \fIgc\fP 1i
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Specifies the GC.
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.IP \fInarcs\fP 1i
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Specifies the number of arcs in the array.
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.IP \fIwidth\fP 1i
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.br
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.ns
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.IP \fIheight\fP 1i
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Specify the width and height, which are the major and minor axes of the arc.
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.IP \fIx\fP 1i
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.br
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.ns
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.IP \fIy\fP 1i
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Specify the x and y coordinates, which are relative to the
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origin of the drawable
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and specify the upper-left corner of the bounding rectangle.
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.SH DESCRIPTION
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.EQ
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delim %%
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.EN
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.B XDrawArc
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draws a single circular or elliptical arc, and
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.B XDrawArcs
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draws multiple circular or elliptical arcs.
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Each arc is specified by a rectangle and two angles.
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The center of the circle or ellipse is the center of the
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rectangle, and the major and minor axes are specified by the width and height.
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Positive angles indicate counterclockwise motion,
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and negative angles indicate clockwise motion.
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If the magnitude of angle2 is greater than 360 degrees,
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.B XDrawArc
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or
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.B XDrawArcs
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truncates it to 360 degrees.
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.LP
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For an arc specified as %[ ~x, ~y, ~width , ~height, ~angle1, ~angle2 ]%,
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the origin of the major and minor axes is at
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% [ x +^ {width over 2} , ~y +^ {height over 2} ]%,
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and the infinitely thin path describing the entire circle or ellipse
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intersects the horizontal axis at % [ x, ~y +^ {height over 2} ]% and
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% [ x +^ width , ~y +^ { height over 2 }] %
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and intersects the vertical axis at % [ x +^ { width over 2 } , ~y ]% and
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% [ x +^ { width over 2 }, ~y +^ height ]%.
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These coordinates can be fractional
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and so are not truncated to discrete coordinates.
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The path should be defined by the ideal mathematical path.
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For a wide line with line-width lw,
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the bounding outlines for filling are given
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by the two infinitely thin paths consisting of all points whose perpendicular
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distance from the path of the circle/ellipse is equal to lw/2
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(which may be a fractional value).
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The cap-style and join-style are applied the same as for a line
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corresponding to the tangent of the circle/ellipse at the endpoint.
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.LP
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For an arc specified as % [ ~x, ~y, ~width, ~height, ~angle1, ~angle2 ]%,
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the angles must be specified
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in the effectively skewed coordinate system of the ellipse (for a
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circle, the angles and coordinate systems are identical).
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The
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relationship between these angles and angles expressed in the normal
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coordinate system of the screen (as measured with a protractor) is as
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follows:
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.LP
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.EX
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% roman "skewed-angle" ~ = ~ atan left ( tan ( roman "normal-angle" )
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* width over height right ) +^ adjust%
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.EE
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.LP
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The skewed-angle and normal-angle are expressed in radians (rather
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than in degrees scaled by 64) in the range % [ 0 , ~2 pi ]% and where atan
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returns a value in the range % [ - pi over 2 , ~pi over 2 ] %
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and adjust is:
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.LP
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.TS
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l l.
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%0% for normal-angle in the range % [ 0 , ~pi over 2 ]%
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%pi% for normal-angle in the range % [ pi over 2 , ~{3 pi} over 2 ]%
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%2 pi% for normal-angle in the range % [ {3 pi} over 2 , ~2 pi ]%
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.TE
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.LP
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For any given arc,
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.B XDrawArc
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and
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.B XDrawArcs
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do not draw a pixel more than once.
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If two arcs join correctly and if the line-width is greater than zero
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and the arcs intersect,
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.B XDrawArc
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and
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.B XDrawArcs
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do not draw a pixel more than once.
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Otherwise,
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the intersecting pixels of intersecting arcs are drawn multiple times.
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Specifying an arc with one endpoint and a clockwise extent draws the same pixels
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as specifying the other endpoint and an equivalent counterclockwise extent,
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except as it affects joins.
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.LP
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If the last point in one arc coincides with the first point in the following
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arc, the two arcs will join correctly.
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If the first point in the first arc coincides with the last point in the last
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arc, the two arcs will join correctly.
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By specifying one axis to be zero, a horizontal or vertical line can be
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drawn.
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Angles are computed based solely on the coordinate system and ignore the
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aspect ratio.
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.LP
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Both functions use these GC components:
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function, plane-mask, line-width, line-style, cap-style, join-style,
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fill-style, subwindow-mode, clip-x-origin, clip-y-origin, and clip-mask.
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They also use these GC mode-dependent components:
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foreground, background, tile, stipple, tile-stipple-x-origin,
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tile-stipple-y-origin, dash-offset, and dash-list.
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.LP
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.B XDrawArc
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and
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.B XDrawArcs
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can generate
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.BR BadDrawable ,
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.BR BadGC ,
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and
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.B BadMatch
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errors.
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.SH STRUCTURES
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The
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.B XArc
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structure contains:
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.LP
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.EX
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typedef struct {
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short x, y;
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unsigned short width, height;
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short angle1, angle2; /\&* Degrees * 64 */
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} XArc;
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.EE
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.LP
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All x and y members are signed integers.
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The width and height members are 16-bit unsigned integers.
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You should be careful not to generate coordinates and sizes
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out of the 16-bit ranges, because the protocol only has 16-bit fields
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for these values.
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.SH DIAGNOSTICS
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.TP 1i
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.B BadDrawable
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A value for a Drawable argument does not name a defined Window or Pixmap.
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.TP 1i
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.B BadGC
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A value for a GContext argument does not name a defined GContext.
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.TP 1i
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.B BadMatch
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An
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.B InputOnly
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window is used as a Drawable.
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.TP 1i
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.B BadMatch
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Some argument or pair of arguments has the correct type and range but fails
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to match in some other way required by the request.
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.SH "SEE ALSO"
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XDrawLine(__libmansuffix__),
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XDrawPoint(__libmansuffix__),
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XDrawRectangle(__libmansuffix__)
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.br
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\fI\*(xL\fP
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