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OpenGL ES 1.0 and EGL 1.0 reference manual and man pages (written by
Claude Knaus, based on OpenGL SI man pages).

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.2//EN" "DTD/docbook/docbookx.dtd">

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<refentry id="eglMakeCurrent">

  <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>
    <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>
    <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>
    <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>
  </refsect1>

  <refsect1>
    <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>

</refentry>