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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glXUseXFont">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glXUseXFont</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glXUseXFont</refname>
<refpurpose>create bitmap display lists from an X font</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glXUseXFont</function></funcdef>
<paramdef>Font <parameter>font</parameter></paramdef>
<paramdef>int <parameter>first</parameter></paramdef>
<paramdef>int <parameter>count</parameter></paramdef>
<paramdef>int <parameter>listBase</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>font</parameter></term>
<listitem>
<para>
Specifies the font from which character glyphs are to be taken.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>first</parameter></term>
<listitem>
<para>
Specifies the index of the first glyph to be taken.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>count</parameter></term>
<listitem>
<para>
Specifies the number of glyphs to be taken.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>listBase</parameter></term>
<listitem>
<para>
Specifies the index of the first display list to be generated.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glXUseXFont</function> generates <parameter>count</parameter> display lists,
named <parameter>listBase</parameter> through
<inlineequation><mml:math>
<!-- eqn: listBase + count - 1:-->
<mml:mrow>
<mml:mi mathvariant="italic">listBase</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">count</mml:mi>
<mml:mo>-</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:math></inlineequation>,
each containing a single <citerefentry><refentrytitle>glBitmap</refentrytitle></citerefentry> command.
The parameters of the <citerefentry><refentrytitle>glBitmap</refentrytitle></citerefentry> command of display list
<inlineequation><mml:math>
<!-- eqn: listBase + i:-->
<mml:mrow>
<mml:mi mathvariant="italic">listBase</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">i</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
are derived from glyph
<inlineequation><mml:math>
<!-- eqn: first + i:-->
<mml:mrow>
<mml:mi mathvariant="italic">first</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">i</mml:mi>
</mml:mrow>
</mml:math></inlineequation>.
Bitmap parameters
<inlineequation><mml:math><mml:mi mathvariant="italic">xorig</mml:mi></mml:math></inlineequation>,
<inlineequation><mml:math><mml:mi mathvariant="italic">yorig</mml:mi></mml:math></inlineequation>,
<inlineequation><mml:math><mml:mi mathvariant="italic">width</mml:mi></mml:math></inlineequation>,
and
<inlineequation><mml:math><mml:mi mathvariant="italic">height</mml:mi></mml:math></inlineequation>
are computed from font metrics as
<inlineequation><mml:math>
<!-- eqn: descent-1:-->
<mml:mrow>
<mml:mi mathvariant="italic">descent</mml:mi>
<mml:mo>-</mml:mo>
<mml:mn>1</mml:mn>
</mml:mrow>
</mml:math></inlineequation>,
<inlineequation><mml:math>
<!-- eqn: -lbearing:-->
<mml:mrow>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">lbearing</mml:mi>
</mml:mrow>
</mml:math></inlineequation>,
<inlineequation><mml:math>
<!-- eqn: rbearing - lbearing:-->
<mml:mrow>
<mml:mi mathvariant="italic">rbearing</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">lbearing</mml:mi>
</mml:mrow>
</mml:math></inlineequation>,
and
<inlineequation><mml:math>
<!-- eqn: ascent+descent:-->
<mml:mrow>
<mml:mi mathvariant="italic">ascent</mml:mi>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">descent</mml:mi>
</mml:mrow>
</mml:math></inlineequation>,
respectively.
<inlineequation><mml:math><mml:mi mathvariant="italic">xmove</mml:mi></mml:math></inlineequation>
is taken from the glyph's
<inlineequation><mml:math><mml:mi mathvariant="italic">width</mml:mi></mml:math></inlineequation>
metric,
and
<inlineequation><mml:math><mml:mi mathvariant="italic">ymove</mml:mi></mml:math></inlineequation>
is set to zero.
Finally,
the glyph's image is converted to the appropriate format for <citerefentry><refentrytitle>glBitmap</refentrytitle></citerefentry>.
</para>
<para>
Using <function>glXUseXFont</function> may be more efficient than accessing the X font and generating
the display lists explicitly,
both because the display lists are created on the server without requiring
a round trip of the glyph data,
and because the server may choose to delay the creation of each
bitmap until it is accessed.
</para>
<para>
Empty display lists are created for all glyphs that are requested and
are not defined in <parameter>font</parameter>.
<function>glXUseXFont</function> is ignored if there is no current GLX context.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>BadFont</constant> is generated if <parameter>font</parameter> is not a valid font.
</para>
<para>
<constant>GLXBadContextState</constant> is generated if the current GLX context is
in display-list construction mode.
</para>
<para>
<constant>GLXBadCurrentWindow</constant> is generated if the drawable associated
with the current context of the calling thread is a window, and that
window is no longer valid.
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glBitmap</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glXMakeCurrent</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>