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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 xml:base="" id="eglMakeCurrent">
<refentryinfo>
<copyright>
<year>2003-2014</year>
<holder>The Khronos Group Inc.</holder>
</copyright>
</refentryinfo>
<refmeta>
<refentrytitle>eglMakeCurrent</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>eglMakeCurrent</refname>
<refpurpose>
attach an EGL rendering context to EGL surfaces
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>EGLBoolean <function>eglMakeCurrent</function></funcdef>
<paramdef>EGLDisplay <parameter>display</parameter></paramdef>
<paramdef>EGLSurface <parameter>draw</parameter></paramdef>
<paramdef>EGLSurface <parameter>read</parameter></paramdef>
<paramdef>EGLContext <parameter>context</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>display</parameter></term>
<listitem>
<para>Specifies the <acronym>EGL</acronym> display connection.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>draw</parameter></term>
<listitem>
<para>Specifies the <acronym>EGL</acronym> draw surface.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>read</parameter></term>
<listitem>
<para>Specifies the <acronym>EGL</acronym> read surface.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>context</parameter></term>
<listitem>
<para>Specifies the <acronym>EGL</acronym> rendering context
to be attached to the surfaces.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>eglMakeCurrent</function> binds <parameter>context</parameter>
to the current rendering thread and to the <parameter>draw</parameter>
and <parameter>read</parameter> surfaces. <parameter>draw</parameter>
is used for all GL operations except for any pixel data read back
(<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>),
which is taken from the frame buffer values of
<parameter>read</parameter>.
</para>
<para>
If the calling thread has already a current rendering context, that
context is flushed and marked as no longer current.
</para>
<para>
The first time that <parameter>context</parameter> is made current,
the viewport and scissor dimensions are set to the size of the
<parameter>draw</parameter> surface. The viewport and
scissor are not modified when <parameter>context</parameter> is
subsequently made current.
</para>
<para>
To release the current context without assigning a new one, call
<function>eglMakeCurrent</function> with <parameter>draw</parameter>
and <parameter>read</parameter> set to
<constant>EGL_NO_SURFACE</constant> and <parameter>context</parameter>
set to <constant>EGL_NO_CONTEXT</constant>.
</para>
<para>
Use
<citerefentry><refentrytitle>eglGetCurrentContext</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetCurrentDisplay</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>eglGetCurrentSurface</refentrytitle></citerefentry>
to query the current rendering context and associated display connection and surfaces.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>EGL_FALSE</constant> is returned on failure,
<constant>EGL_TRUE</constant> otherwise. If <constant>EGL_FALSE</constant>
is returned, the previously current rendering context and
surfaces (if any) remain unchanged.
</para>
<para>
<constant>EGL_BAD_DISPLAY</constant> is generated if
<parameter>display</parameter> is not an EGL display connection.
</para>
<para>
<constant>EGL_NOT_INITIALIZED</constant> is generated if
<parameter>display</parameter> has not been initialized.
</para>
<para>
<constant>EGL_BAD_SURFACE</constant> is generated if
<parameter>draw</parameter> or <parameter>read</parameter> is not an
EGL surface.
</para>
<para>
<constant>EGL_BAD_CONTEXT</constant> is generated if
<parameter>context</parameter> is not an EGL rendering context.
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if
<parameter>draw</parameter> or
<parameter>read</parameter>
are not compatible with
<parameter>context</parameter>, or if
<parameter>context</parameter> is set to
<constant>EGL_NO_CONTEXT</constant> and
<parameter>draw</parameter> or
<parameter>read</parameter>
are not set to
<constant>EGL_NO_SURFACE</constant>, or if
<parameter>draw</parameter> or
<parameter>read</parameter> are set to
<constant>EGL_NO_SURFACE</constant> and
<parameter>context</parameter> is not set to
<constant>EGL_NO_CONTEXT</constant>.
</para>
<para>
<constant>EGL_BAD_ACCESS</constant> is generated if
<parameter>context</parameter>
is current to some other thread.
</para>
<para>
<constant>EGL_BAD_NATIVE_PIXMAP</constant> may be generated if
a native pixmap underlying either
<parameter>draw</parameter> or
<parameter>read</parameter>
is no longer valid.
</para>
<para>
<constant>EGL_BAD_NATIVE_WINDOW</constant> may be generated if
a native window underlying either
<parameter>draw</parameter> or
<parameter>read</parameter>
is no longer valid.
</para>
<para>
<constant>EGL_BAD_CURRENT_SURFACE</constant> is generated if
the previous context has unflushed commands and the previous surface
is no longer valid.
</para>
<para>
<constant>EGL_BAD_ALLOC</constant> may be generated if
allocation of ancillary buffers for <parameter>draw</parameter> or
<parameter>read</parameter> were delayed until
<function>eglMakeCurrent</function> is called, and there are not
enough resources to allocate them.
</para>
<para>
<constant>EGL_CONTEXT_LOST</constant> is generated if a power management
event has occurred. The application must destroy all contexts and
reinitialise OpenGL ES state and objects to continue rendering.
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglCreateContext</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglCreatePbufferSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglCreatePixmapSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglCreateWindowSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetCurrentContext</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetCurrentDisplay</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetCurrentSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetDisplay</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglInitialize</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect3 id="Copyright"><title></title>
<!-- Content included from copyright.inc.xsl -->
<imageobject>
<imagedata fileref="KhronosLogo.jpg" format="jpg" />
</imageobject>
<para />
</refsect3>
</refentry>
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