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<HTML><HEAD><TITLE>Xlib Programming Manual: XDrawArcs</TITLE></HEAD><BODY><H1 ALIGN=center>XDrawArcs</H1><H2>Syntax</H2><!.IN "XDrawArcs" "" "@DEF@"><CODE><PRE>XDrawArcs(<B>display</B>, <B>d</B>, <B>gc</B>, <B>arcs</B>, <B>narcs</B>) <A HREF="../../display/opening.html#Display">Display</A> *<B>display</B>; Drawable <B>d</B>; <A HREF="../../GC/manipulating.html">GC</A> <B>gc</B>; <A HREF="./#XArc">XArc</A> *<B>arcs</B>; int <B>narcs</B>;</PRE></CODE><H2>Arguments</H2><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>d</B><TD> Specifies the drawable. <TR><TD> <B>gc</B><TD> Specifies the GC.<TR><TD> <B>arcs</B><TD> Specifies an array of arcs.<TR><TD> <B>narcs</B><TD> Specifies the number of arcs in the array.</TABLE><H2>Description</H2><B>XDrawArcs()</B>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 therectangle, 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, <B>XDrawArcs()</B>truncates it to 360 degrees.<P>For an arc specified as<I>[ x, y, width, height, angle1, angle2 ]</I>,the origin of the major and minor axes is at <I>[ x + width / 2 , y + height / 2 ]</I>, and the infinitely thin path describing the entire circle or ellipse intersects the horizontal axis at <I>[ x, y + height / 2 ]</I> and <I> [ x + width , y + height / 2 ]</I>and intersects the vertical axis at <I>[ x + width / 2, y ]</I> and <I>[ x + width / 2, y + height ]</I>.These coordinates can be fractionaland 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 perpendiculardistance 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 linecorresponding to the tangent of the circle/ellipse at the endpoint.<P>For an arc specified as <I>[ x, y, width, height, angle1, angle2 ]</I>,the angles must be specifiedin the effectively skewed coordinate system of the ellipse (for acircle, the angles and coordinate systems are identical). Therelationship between these angles and angles expressed in the normalcoordinate system of the screen (as measured with a protractor) is asfollows:<P>skewed-angle <I>= atan ( tan ( </I>normal-angle<I> ) * width / height ) + adjust</I><P>The skewed-angle and normal-angle are expressed in radians (ratherthan in degrees scaled by 64) in the range <I>[ 0, 2 pi ]</I> and where atanreturns a value in the range <I>[ -pi / 2 , pi / 2 ]</I>and adjust is:<P><TABLE><TR><TD><I>0 <TD>for normal-angle in the range <I>[ 0, pi / 2 ]<TR><TD>pi <TD>for normal-angle in the range <I>[ pi / 2 , 3 pi / 2 ]<TR><TD>2 pi <TD>for normal-angle in the range <I>[ 3 pi / 2 , 2 pi ]</TABLE><P>For any given arc, <B>XDrawArcs()</B>does 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, <B>XDrawArc()</B>does 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 pixelsas specifying the other endpoint and an equivalent counterclockwise extent,except as it affects joins.<P>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 bedrawn.Angles are computed based solely on the coordinate system and ignore theaspect ratio.<P>This function uses these GC components: <A HREF="../../GC/manipulating.html#function">function</A>, <A HREF="../../GC/manipulating.html#plane-mask">plane-mask</A>,<A HREF="../../GC/manipulating.html#line-width">line-width</A>,<A HREF="../../GC/manipulating.html#line-style">line-style</A>,<A HREF="../../GC/manipulating.html#cap-style">cap-style</A>,<A HREF="../../GC/manipulating.html#join-style">join-style</A>,<A HREF="../../GC/manipulating.html#fill-style">fill-style</A>,<A HREF="../../GC/manipulating.html#subwindow-mode">subwindow-mode</A>,<A HREF="../../GC/manipulating.html#clip-mask">clip-x-origin</A>,<A HREF="../../GC/manipulating.html#clip-mask">clip-y-origin</A>, and<A HREF="../../GC/manipulating.html#clip-mask">clip-mask</A>.It also uses these GC mode-dependent components: <A HREF="../../GC/manipulating.html#foreground">foreground</A>, <A HREF="../../GC/manipulating.html#background">background</A>,<A HREF="../../GC/manipulating.html#tile">tile</A>,<A HREF="../../GC/manipulating.html#stipple">stipple</A>,<A HREF="../../GC/manipulating.html#tile">tile-stipple-x-origin</A>,<A HREF="../../GC/manipulating.html#tile">tile-stipple-y-origin</A>,<A HREF="../../GC/manipulating.html#dashes">dash-offset</A>,and<A HREF="../../GC/manipulating.html#dashes">dash-list</A>.<P><B>XDrawArcs()</B>can generate<B>BadDrawable</B> ,<B>BadGC</B> ,and<B>BadMatch</B> errors.<H2>Diagnostics</H2><TABLE><TR><TD><B>BadDrawable</B><TD>A value for a Drawable argument does not name a defined Window or Pixmap.<TR><TD><B>BadGC</B><TD>A value for a <B><A HREF="../../my-own/gcontext.html">GContext</A></B> argument does not name a defined <B><A HREF="../../my-own/gcontext.html">GContext</A></B>.<TR><TD><B>BadMatch</B><TD>An<B><A HREF="../../window/create.html#InputClass">InputOnly</A></B>window is used as a Drawable.<TR><TD><B>BadMatch</B><TD>Some argument or pair of arguments has the correct type and range but fails to match in some other way required by the request. </TABLE><H2>See also</H2><B><A HREF="XDrawArcs.html">XDrawArc()</A></B>,<B><A HREF="XDrawRectangle.html">XDrawRectangle()</A></B>,<B><A HREF="XDrawPoint.html">XDrawPoint()</A></B>,"<A HREF="arcs.html">Drawing Single and Multiple Arcs</A>".<HR><ADDRESS><A HREF="http://tronche.com/">Christophe Tronche</A>, <A HREF="mailto:ch.tronche@computer.org">ch.tronche@computer.org</A></ADDRESS></BODY></HTML>⌨️ 快捷键说明
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