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<HTML><HEAD><TITLE>Xlib Programming Manual: XQueryTextExtents</TITLE></HEAD><BODY><H1 ALIGN=center>XQueryTextExtents</H1><H2>Syntax</H2><!.IN "XQueryTextExtents" "" "@DEF@"><CODE><PRE>XQueryTextExtents(<B>display</B>, <B>font_ID</B>, <B>string</B>, <B>nchars</B>, <B>direction_return</B>, <B>font_ascent_return</B>, <B>font_descent_return</B>, <B>overall_return</B>) <A HREF="../../display/opening.html#Display">Display</A> *<B>display</B>; XID <B>font_ID</B>; char *<B>string</B>; int <B>nchars</B>; int *<B>direction_return</B>; int *<B>font_ascent_return</B>, *<B>font_descent_return</B>; <A HREF="./#XCharStruct">XCharStruct</A> *<B>overall_return</B>;</PRE></CODE><H2>Arguments</H2><TABLE><TR><TD> <B>display</B><TD> Specifies the connection to the X server.<TR><TD> <B>font_ID</B><TD> Specifies either the font ID or the <B><A HREF="/toto/GContext.html">GContext</A></B>ID that contains the font.<TR><TD> <B>string</B><TD> Specifies the character string.<TR><TD> <B>nchars</B><TD> Specifies the number of characters in the character string.<TR><TD> <B>direction_return</B><TD> Returns the value of the direction hint(<B>FontLeftToRight</B>or<B>FontRightToLeft</B>).<TR><TD> <B>font_ascent_return</B><TD> Returns the font ascent.<TR><TD> <B>font_descent_return</B><TD> Returns the font descent.<TR><TD> <B>overall_return</B><TD> Returns the overall size in the specified<A HREF="./#XCharStruct">XCharStruct</A> structure.</TABLE><H2>Description</H2>The<B>XQueryTextExtents()</B>function returns the bounding box of the specified 8-bitcharacter string in the specified font or the font contained in thespecified GC.This function queries the X server and, therefore, suffer the round-tripoverhead that is avoided by<B><A HREF="XTextExtents.html">XTextExtents()</A></B>.The function returns a<A HREF="./#XCharStruct">XCharStruct</A> structure, whose members are set to the values as follows.<P>The ascent member is set to the maximum of the ascent metrics of all characters in the string.The descent member is set to the maximum of the descent metrics.The width member is set to the sum of the character-width metrics of all characters in the string.For each character in the string,let W be the sum of the character-width metrics of all characters precedingit in the string.Let L be the left-side-bearing metric of the character plus W.Let R be the right-side-bearing metric of the character plus W.The lbearing member is set to the minimum L of all characters in the string.The rbearing member is set to the maximum R.<P>For fonts defined with linear indexing rather than 2-byte matrix indexing,each <A HREF="./#XChar2b">XChar2b</A> structure is interpreted as a 16-bit number with byte1 as the most-significant byte.If the font has no defined default character,undefined characters in the string are taken to have all zero metrics.<P>Characters with all zero metrics are ignored.If the font has no defined default_char,the undefined characters in the string are also ignored.<P><B>XQueryTextExtents()</B>can generate<B>BadFont</B>and<B>BadGC</B> errors.<H2>Diagnostics</H2><TABLE><TR><TD><B>BadFont</B><TD>A value for a font argument does not name a defined font (or, in some cases, <B><A HREF="../GContext.html">GContext</A></B>).<TR><TD><B>BadGC</B><TD>A value for a <B><A HREF="../GContext.html">GContext</A></B> argument does not name a defined <B><A HREF="../GContext.html">GContext</A></B>.</TABLE><H2>See also</H2><B><A HREF="XLoadFont.html">XLoadFont()</A></B>,<B><A HREF="XQueryTextExtents16.html">XQueryTextExtents16()</A></B>,<B><A HREF="XTextExtents.html">XTextExtents()</A></B>,<B><A HREF="XTextExtents16.html">XTextExtents16()</A></B>,<B><A HREF="XTextWidth.html">XTextWidth()</A></B>,"<A HREF="computing-logical-extent.html">Computing Logical Extents</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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