'\" e

.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1994, 1996 X Consortium

.\"

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.\" a copy of this software and associated documentation files (the

.\" "Software"), to deal in the Software without restriction, including

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.\" ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

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.\" Except as contained in this notice, the name of the X Consortium shall

.\" not be used in advertising or otherwise to promote the sale, use or

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.\" from the X Consortium.

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.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991 by

.\" Digital Equipment Corporation

.\"

.\" Portions Copyright \(co 1990, 1991 by

.\" Tektronix, Inc.

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.\" Permission to use, copy, modify and distribute this documentation for

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.\"

.ds xT X Toolkit Intrinsics \- C Language Interface

.ds xW Athena X Widgets \- C Language X Toolkit Interface

.ds xL Xlib \- C Language X Interface

.ds xC Inter-Client Communication Conventions Manual

.na

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'\" e

.TH XDrawArc __libmansuffix__ __xorgversion__ "XLIB FUNCTIONS"

.SH NAME

XDrawArc, XDrawArcs, XArc \- draw arcs and arc structure

.SH SYNTAX

.HP

int XDrawArc\^(\^Display *\fIdisplay\fP\^, Drawable \fId\fP\^, GC \fIgc\fP\^,

int \fIx\fP\^, int \fIy\fP\^, unsigned int \fIwidth\fP\^, unsigned int

\fIheight\fP\^, int \fIangle1\fP\^, int \fIangle2\fP\^); 

.HP

int XDrawArcs\^(\^Display *\fIdisplay\fP\^, Drawable \fId\fP\^, GC \fIgc\fP\^,

XArc *\fIarcs\fP\^, int \fInarcs\fP\^); 

.SH ARGUMENTS

.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.

.IP \fIangle2\fP 1i

Specifies the path and extent of the arc relative to the start of the

arc, in units of degrees * 64.

.IP \fIarcs\fP 1i

Specifies an array of arcs.

.IP \fId\fP 1i

Specifies the drawable. 

.IP \fIdisplay\fP 1i

Specifies the connection to the X server.

.IP \fIgc\fP 1i

Specifies the GC.

.IP \fInarcs\fP 1i

Specifies the number of arcs in the array.

.ds Wh , which are the major and minor axes of the arc

.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

.IP \fIx\fP 1i

.br

.ns

.IP \fIy\fP 1i

Specify the x and y coordinates\*(Xy.

.SH DESCRIPTION

.EQ

delim %%

.EN

.ZN XDrawArc

draws a single circular or elliptical arc, and 

.ZN 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, 

.ZN XDrawArc

or 

.ZN 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:

.LP

.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

.TS

l l.

%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  ]%

.TE

.LP

For any given arc, 

.ZN XDrawArc

and

.ZN 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, 

.ZN XDrawArc

and

.ZN 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.

.LP

.ZN XDrawArc

and

.ZN XDrawArcs

can generate

.ZN BadDrawable ,

.ZN BadGC ,

and

.ZN BadMatch 

errors.

.SH STRUCTURES

The

.ZN XArc

structure contains:

.LP

.EX

typedef struct {

	short x, y;

	unsigned short width, height;

	short angle1, angle2;             /\&* Degrees * 64 */

} XArc;

.EE

.LP

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.

.SH DIAGNOSTICS

.TP 1i

.ZN BadDrawable

A value for a Drawable argument does not name a defined Window or Pixmap.

.TP 1i

.ZN BadGC

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

.TP 1i

.ZN BadMatch

An

.ZN InputOnly

window is used as a Drawable.

.TP 1i

.ZN 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(__libmansuffix__),

XDrawPoint(__libmansuffix__),

XDrawRectangle(__libmansuffix__)

.br

\fI\*(xL\fP