<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:base="" xml:id="eglSwapBuffers">
    <info>
         <copyright>
             <year>2003-2014</year>
             <holder>The Khronos Group Inc.</holder>
         </copyright>
    </info>
    <refmeta>
        <refentrytitle>eglSwapBuffers</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>eglSwapBuffers</refname>
        <refpurpose>
            post <acronym>EGL</acronym> surface color buffer to a native window
        </refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>EGLBoolean <function>eglSwapBuffers</function></funcdef>
                <paramdef>EGLDisplay <parameter>display</parameter></paramdef>
                <paramdef>EGLSurface <parameter>surface</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
            <varlistentry>
                <term><parameter>display</parameter></term>
                <listitem>
                    <para>
                        Specifies the EGL display connection.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><parameter>surface</parameter></term>
                <listitem>
                    <para>
                        Specifies the EGL drawing surface whose buffers are to be swapped.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            If <parameter>surface</parameter> is a back-buffered window
            surface, <function>eglSwapBuffers</function> then the color
            buffer is copied (posted) native window associated with that
            surface. If <parameter>surface</parameter> is a single-buffered
            window, pixmap, or pixel buffer surface,
            <function>eglSwapBuffers</function> has no effect.
        </para>
        <para>
            The contents of ancillary buffers are always undefined after
            calling <function>eglSwapBuffers</function>. The contents of the
            color buffer are undefined if the value of the
            <constant>EGL_SWAP_BEHAVIOR</constant> attribute of
            <parameter>surface</parameter> is not
            <constant>EGL_BUFFER_PRESERVED</constant>. The value of
            <constant>EGL_SWAP_BEHAVIOR</constant> can be set for some
            surfaces using
            <citerefentry><refentrytitle>eglSurfaceAttrib</refentrytitle></citerefentry>.
            <constant>EGL_SWAP_BEHAVIOR</constant> applies only to the color
            buffer. EGL has no way to specify or query whether or not
            ancillary buffers are preserved, and applications should not
            rely on this behavior.
        </para>
        <para>
            <function>eglSwapBuffers</function> performs an implicit
            flush operation on the context (<function>glFlush</function>
            for an OpenGL ES or OpenGL context,
            <function>vgFlush</function> for an OpenVG context) bound to
            <parameter>surface</parameter> before swapping. Subsequent
            client API commands may be issued on that context
            immediately after calling
            <function>eglSwapBuffers</function>, but are not executed
            until the buffer exchange is completed.
        </para>
    </refsect1>
    <refsect1 xml:id="resize"><title>Native Window Resizing</title>
        <para>
            If the native window corresponding to
            <parameter>surface</parameter> has been resized prior to the
            swap, <parameter>surface</parameter> must be resized to match.
            <parameter>surface</parameter> will normally be resized by the
            EGL implementation at the time the native window is resized. If
            the implementation cannot do this transparently to the client,
            then <function>eglSwapBuffers</function> must detect the change
            and resize surface prior to copying its pixels to the native
            window. If <parameter>surface</parameter> shrinks as a result of
            resizing, some rendered pixels are lost. If
            <parameter>surface</parameter> grows, the newly allocated buffer
            contents are undefined. The resizing behavior described here
            only maintains consistency of EGL surfaces and native windows;
            clients are still responsible for detecting window size changes
            (using platform-specific means) and changing their viewport and
            scissor regions accordingly.
        </para>
    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
        <para>
            Attribute <constant>EGL_SWAP_BEHAVIOR</constant> is supported
            only if the EGL version is 1.2 or greater. In earlier versions,
            behavior is as though the attribute exists, and always has the
            value <constant>EGL_BUFFER_DESTROYED</constant>.
        </para>
        <para>
            The EGL 1.4 specification was updated to acknowledge that
            ancillary buffers are not necessarily preserved after a swap,
            and that the <constant>EGL_SWAP_BEHAVIOR</constant> attribute
            applies only to the color buffer. This change in the
            specification acknowledged the behavior of many shipping
            implementations, and is not intended to result in behavior
            changes in any existing implementation.
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>EGL_FALSE</constant> is returned if swapping of the
            surface buffers fails, <constant>EGL_TRUE</constant> otherwise.
        </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>surface</parameter> is not an EGL drawing surface.
        </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 xml:id="seealso"><title>See Also</title>
        <para>
            <function>glFlush</function>,
            <citerefentry><refentrytitle>eglCopyBuffers</refentrytitle></citerefentry>,
            <function>vgFlush</function>
        </para>
    </refsect1>
    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="copyright.xml"/>
</refentry>