xref: /third_party/EGL/sdk/docs/man/docbook4/eglCreateContext.xml (revision 02f4aeb0)

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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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<refentry xml:base="" id="eglCreateContext">
    <refentryinfo>
         <copyright>
             <year>2003-2014</year>
             <holder>The Khronos Group Inc.</holder>
         </copyright>
    </refentryinfo>
    <refmeta>
        <refentrytitle>eglCreateContext</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>eglCreateContext</refname>
        <refpurpose>
            create a new <acronym>EGL</acronym> rendering context
        </refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>EGLContext <function>eglCreateContext</function></funcdef>
                <paramdef>EGLDisplay <parameter>display</parameter></paramdef>
                <paramdef>EGLConfig <parameter>config</parameter></paramdef>
                <paramdef>EGLContext <parameter>share_context</parameter></paramdef>
                <paramdef>EGLint const * <parameter>attrib_list</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>config</parameter></term>
                <listitem><para>Specifies the EGL frame buffer configuration that
                    defines the frame buffer resource available to the rendering context.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><parameter>share_context</parameter></term>
                <listitem><para>
                    Specifies another
                    <acronym>EGL</acronym>
                    rendering context with which to share data, as
                    defined by the client API corresponding to the
                    contexts. Data is also shared with all other
                    contexts with which
                    <parameter>share_context</parameter> shares data.
                    <constant>EGL_NO_CONTEXT</constant> indicates that
                    no sharing is to take place.
                </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><parameter>attrib_list</parameter></term>
                <listitem><para>
                    Specifies attributes and attribute values for the
                    context being created. Only the attribute
                    <constant>EGL_CONTEXT_CLIENT_VERSION</constant> may
                    be specified.
                </para></listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>eglCreateContext</function> creates an EGL
            rendering context for the current rendering API (as set with
            <function>eglBindAPI</function>) and returns a handle to the
            context. The context can then be used to render into an EGL
            drawing surface. If <function>eglCreateContext</function>
            fails to create a rendering context,
            <constant>EGL_NO_CONTEXT</constant> is returned.
        </para>
        <para>
            If <parameter>share_context</parameter> is not
            <constant>EGL_NO_CONTEXT</constant>, then all shareable data
            in the context (as defined by the client API specification
            for the current rendering API) are shared by context
            <parameter>share_context</parameter>, all other contexts
            <parameter>share_context</parameter> already shares with,
            and the newly created context. An arbitrary number of
            rendering contexts can share data. However, all rendering
            contexts that share data must themselves exist in the same
            address space. Two rendering contexts share an address space
            if both are owned by a single process.
        </para>
        <para>
            <parameter>attrib_list</parameter> specifies a list of
            attributes for the context. The list has the same structure
            as described for <function>eglChooseConfig</function>. The
            attributes and attribute values which may be specified are
            as follows:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>EGL_CONTEXT_CLIENT_VERSION</constant></term>
                <listitem><para>
                    Must be followed by an integer that determines which
                    version of an OpenGL ES context to create. A value
                    of 1 specifies creation of an OpenGL ES 1.x context.
                    An attribute value of 2 specifies creation of an
                    OpenGL ES 2.x context. The default value is 1. This
                    attribute can only be specified when creating a
                    OpenGL ES context (e.g. when the current rendering
                    API is <constant>EGL_OPENGL_ES_API</constant>).
                </para></listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            The current rendering API is only respected if the EGL
            version is 1.2 or greater. Otherwise, an OpenGL ES context
            will always be created.
        </para>
        <para>
            The <constant>EGL_CONTEXT_CLIENT_VERSION</constant>
            attribute is only supported if the EGL version is 1.3 or
            greater.
        </para>
        <para>
            A <firstterm>process</firstterm> is a single execution environment,
            implemented in a single address space, consisting of one or more threads.
        </para>
        <para>
            A <firstterm>thread</firstterm> is one of a set of subprocesses that
            share a single address space, but maintain separate program counters,
            stack spaces, and other related global data.
            A thread is the only member of its subprocess group is equivalent to a
            process.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>EGL_NO_CONTEXT</constant> is returned if creation of
            the context fails.
        </para>
        <para>
            <constant>EGL_BAD_MATCH</constant> is generated if the
            current rendering API is <constant>EGL_NONE</constant> (this
            can only arise in an EGL implementation which does not
            support OpenGL ES, prior to the first call to
            <function>eglBindAPI</function>).
        </para>
        <para>
            <constant>EGL_BAD_MATCH</constant> is generated if the
            server context state for
            <parameter>share_context</parameter> exists in an address
            space which cannot be shared with the newly created context,
            if <parameter>share_context</parameter> was created on a
            different display than the one referenced by
            <parameter>config</parameter>, or if the contexts are
            otherwise incompatible.
        </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_CONFIG</constant> is generated if
            <parameter>config</parameter> is not an EGL frame buffer
            configuration, or does not support the current rendering
            API. This includes requesting creation of an OpenGL ES 1.x
            context when the <constant>EGL_RENDERABLE_TYPE</constant>
            attribute of <parameter>config</parameter> does not contain
            <constant>EGL_OPENGL_ES_BIT</constant>, or creation of an
            OpenGL ES 2.x context when the attribute does not contain
            <constant>EGL_OPENGL_ES2_BIT</constant>.
        </para>
        <para>
            <constant>EGL_BAD_CONTEXT</constant> is generated if
            <parameter>share_context</parameter> is not an EGL rendering
            context of the same client API type as the newly created
            context and is not <constant>EGL_NO_CONTEXT</constant>.
        </para>
        <para>
            <constant>EGL_BAD_ATTRIBUTE</constant> is generated if
            <parameter>attrib_list</parameter> contains an invalid
            context attribute or if an attribute is not recognized or
            out of range. Note that attribute
            <constant>EGL_CONTEXT_CLIENT_VERSION</constant> is
            only valid when the current rendering API is
            <constant>EGL_OPENGL_ES_API</constant>.
        </para>
        <para>
            <constant>EGL_BAD_ALLOC</constant> is generated if there are not
            enough resources to allocate the new context.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>eglDestroyContext</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglChooseConfig</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglGetConfigs</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglMakeCurrent</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>