sdk/docs/man/eglQuerySurface.xml

<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:base="" xml:id="eglQuerySurface">
    <info>
         <copyright>
             <year>2003-2018</year>
             <holder>The Khronos Group Inc.</holder>
         </copyright>
    </info>
    <refmeta>
        <refentrytitle>eglQuerySurface</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>eglQuerySurface</refname>
        <refpurpose>
            return <acronym>EGL</acronym> surface information
        </refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>EGLBoolean <function>eglQuerySurface</function></funcdef>
                <paramdef>EGLDisplay <parameter>display</parameter></paramdef>
                <paramdef>EGLSurface <parameter>surface</parameter></paramdef>
                <paramdef>EGLint <parameter>attribute</parameter></paramdef>
                <paramdef>EGLint * <parameter>value</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 surface to query.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><parameter>attribute</parameter></term>
                <listitem>
                    <para>
                        Specifies the EGL surface attribute to be returned.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><parameter>value</parameter></term>
                <listitem>
                    <para>
                        Returns the requested value.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            <function>eglQuerySurface</function> returns in
            <parameter>value</parameter> the value of
            <parameter>attribute</parameter> for <parameter>surface</parameter>.
            <parameter>attribute</parameter> can be one of the following:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>EGL_CONFIG_ID</constant></term>
                <listitem><para>
                    Returns the ID of the EGL frame buffer configuration
                    with respect to which the surface was created.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_GL_COLORSPACE</constant></term>
                <listitem><para>
                    Returns the color space used by OpenGL and OpenGL ES
                    when rendering to the surface, either
                    <constant>EGL_GL_COLORSPACE_SRGB</constant> or
                    <constant>EGL_GL_COLORSPACE_LINEAR</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_HEIGHT</constant></term>
                <listitem><para>
                    Returns the height of the surface in pixels.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_HORIZONTAL_RESOLUTION</constant></term>
                <listitem><para>
                    Returns the horizontal dot pitch of the display on
                    which a window surface is visible. The value
                    returned is equal to the actual dot pitch, in
                    pixels/meter, multiplied by the constant value
                    <constant>EGL_DISPLAY_SCALING</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_LARGEST_PBUFFER</constant></term>
                <listitem><para>
                    Returns the same attribute value specified when the
                    surface was created with
                    <citerefentry><refentrytitle>eglCreatePbufferSurface</refentrytitle></citerefentry>.
                    For a window or pixmap surface,
                    <parameter>value</parameter> is not modified.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_MIPMAP_LEVEL</constant></term>
                <listitem><para>
                    Returns which level of the mipmap to render to, if
                    texture has mipmaps.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_MIPMAP_TEXTURE</constant></term>
                <listitem><para>
                    Returns <constant>EGL_TRUE</constant> if texture has
                    mipmaps, <constant>EGL_FALSE</constant> otherwise.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_MULTISAMPLE_RESOLVE</constant></term>
                <listitem>
                <para>
                    Returns the filter used when resolving the
                    multisample buffer. The filter may be either
                    <constant>EGL_MULTISAMPLE_RESOLVE_DEFAULT</constant>
                    or <constant>EGL_MULTISAMPLE_RESOLVE_BOX</constant>,
                    as described for
                    <citerefentry><refentrytitle>eglSurfaceAttrib</refentrytitle></citerefentry>.
                </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_PIXEL_ASPECT_RATIO</constant></term>
                <listitem><para>
                    Returns the aspect ratio of an individual pixel (the
                    ratio of a pixel's width to its height). The value
                    returned is equal to the actual aspect ratio
                    multiplied by the constant value
                    <constant>EGL_DISPLAY_SCALING</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_RENDER_BUFFER</constant></term>
                <listitem><para>
                    Returns the buffer which client API rendering is
                    requested to use. For a window surface, this is the
                    same attribute value specified when the surface was
                    created. For a pbuffer surface, it is always
                    <constant>EGL_BACK_BUFFER</constant>. For a pixmap
                    surface, it is always
                    <constant>EGL_SINGLE_BUFFER</constant>. To determine
                    the actual buffer being rendered to by a context,
                    call
                    <citerefentry><refentrytitle>eglQueryContext</refentrytitle></citerefentry>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_SWAP_BEHAVIOR</constant></term>
                <listitem><para>
                    Returns the effect on the color buffer when posting
                    a surface with
                    <citerefentry><refentrytitle>eglSwapBuffers</refentrytitle></citerefentry>.
                    Swap behavior may be either
                    <constant>EGL_BUFFER_PRESERVED</constant> or
                    <constant>EGL_BUFFER_DESTROYED</constant>, as
                    described for
                    <citerefentry><refentrytitle>eglSurfaceAttrib</refentrytitle></citerefentry>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_TEXTURE_FORMAT</constant></term>
                <listitem><para>
                    Returns format of texture. Possible values are
                    <constant>EGL_NO_TEXTURE</constant>,
                    <constant>EGL_TEXTURE_RGB</constant>, and
                    <constant>EGL_TEXTURE_RGBA</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_TEXTURE_TARGET</constant></term>
                <listitem><para>
                    Returns type of texture. Possible values are
                    <constant>EGL_NO_TEXTURE</constant>, or
                    <constant>EGL_TEXTURE_2D</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_VERTICAL_RESOLUTION</constant></term>
                <listitem><para>
                    Returns the vertical dot pitch of the display on
                    which a window surface is visible. The value
                    returned is equal to the actual dot pitch, in
                    pixels/meter, multiplied by the constant value
                    <constant>EGL_DISPLAY_SCALING</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_VG_ALPHA_FORMAT</constant></term>
                <listitem><para>
                    Returns the interpretation of alpha values used by
                    OpenVG when rendering to the surface, either
                    <constant>EGL_VG_ALPHA_FORMAT_NONPRE</constant> or
                    <constant>EGL_VG_ALPHA_FORMAT_PRE</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_VG_COLORSPACE</constant></term>
                <listitem><para>
                    Returns the color space used by OpenVG when rendering to
                    the surface, either
                    <constant>EGL_VG_COLORSPACE_sRGB</constant> or
                    <constant>EGL_VG_COLORSPACE_LINEAR</constant>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>EGL_WIDTH</constant></term>
                <listitem><para>
                    Returns the width of the surface in pixels.
                </para></listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
        <para>
            Attribute <constant>EGL_GL_COLORSPACE</constant> is supported
            only if the EGL version is 1.5 or greater.
        </para>
        <para>
            Attribute <constant>EGL_MULTISAMPLE_RESOLVE</constant> is
            supported only if the EGL version is 1.4 or greater.
        </para>
        <para>
            Attributes <constant>EGL_DISPLAY_SCALING</constant>.
            <constant>EGL_HORIZONTAL_RESOLUTION</constant>,
            <constant>EGL_PIXEL_ASPECT_RATIO</constant>,
            <constant>EGL_RENDER_BUFFER</constant>,
            <constant>EGL_SWAP_BEHAVIOR</constant>, and
            <constant>EGL_VERTICAL_RESOLUTION</constant> are supported
            only if the EGL version is 1.2 or greater.
        </para>
        <para>
            Querying attributes <constant>EGL_TEXTURE_FORMAT</constant>,
            <constant>EGL_TEXTURE_TARGET</constant>,
            <constant>EGL_MIPMAP_TEXTURE</constant>, or
            <constant>EGL_MIPMAP_LEVEL</constant> for a non-pbuffer
            surface is not an error, but <parameter>value</parameter> is
            not modified.
        </para>
        <para>
            <constant>EGL_DISPLAY_SCALING</constant> is the constant
            value 10000. Floating-point values such as resolution and
            pixel aspect ratio are scaled by this value before being
            returned as integers so that sufficient precision to be
            meaningful will be retained in the returned value.
        </para>
        <para>
            For an offscreen (pbuffer or pixmap) surface, or a surface
            whose pixel dot pitch or aspect ratio are unknown, querying
            <constant>EGL_HORIZONTAL_RESOLUTION</constant>,
            <constant>EGL_PIXEL_ASPECT_RATIO</constant>, or
            <constant>EGL_VERTICAL_RESOLUTION</constant> will return the
            constant value <constant>EGL_UNKNOWN</constant> (-1).
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>EGL_FALSE</constant> is returned on failure,
            <constant>EGL_TRUE</constant> otherwise.
            <parameter>value</parameter> is not modified when
            <constant>EGL_FALSE</constant> is returned.
        </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 surface.
        </para>
        <para>
            <constant>EGL_BAD_ATTRIBUTE</constant> is generated if
            <parameter>attribute</parameter> is not a valid surface attribute.
        </para>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>eglCreatePbufferSurface</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglCreatePixmapSurface</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglCreateWindowSurface</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglSurfaceAttrib</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>eglSwapBuffers</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="copyright.xml"/>
</refentry>