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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:base="" xml:id="eglCreatePbufferFromClientBuffer">
<info>
<copyright>
<year>2003-2014</year>
<holder>The Khronos Group Inc.</holder>
</copyright>
</info>
<refmeta>
<refentrytitle>eglCreatePbufferFromClientBuffer</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>eglCreatePbufferFromClientBuffer</refname>
<refpurpose>
create a new <acronym>EGL</acronym> pixel buffer surface
bound to an OpenVG image
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>EGLSurface <function>eglCreatePbufferFromClientBuffer</function></funcdef>
<paramdef>EGLDisplay <parameter>display</parameter></paramdef>
<paramdef>EGLenum <parameter>buftype</parameter></paramdef>
<paramdef>EGLClientBuffer <parameter>buffer</parameter></paramdef>
<paramdef>EGLConfig <parameter>config</parameter></paramdef>
<paramdef>EGLint const * <parameter>attrib_list</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>buftype</parameter></term>
<listitem>
<para>
Specifies the type of client API buffer to be bound.
Must be <constant>EGL_OPENVG_IMAGE</constant>,
corresponding to an OpenVG <type>VGImage</type>
buffer.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>buffer</parameter></term>
<listitem>
<para>
Specifies the OpenVG <type>VGImage</type> handle of
the buffer to be bound.
</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 surface.
</para></listitem>
</varlistentry>
<varlistentry>
<term><parameter>attrib_list</parameter></term>
<listitem><para>
Specifies pixel buffer surface attributes.
May be <constant>NULL</constant> or empty
(first attribute is <constant>EGL_NONE</constant>).
</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 xml:id="description"><title>Description</title>
<para>
<function>eglCreatePbufferFromClientBuffer</function> creates an
off-screen pixel buffer surface and returns its handle. If
<function>eglCreatePbufferFromClientBuffer</function> fails to create
a pixel buffer surface, <constant>EGL_NO_SURFACE</constant>
is returned.
</para>
<para>
The new pixel buffer surface is similar to a pixel buffer
created with
<citerefentry><refentrytitle>eglCreatePbufferSurface</refentrytitle></citerefentry>,
but storage for the color buffer is provided by a client API
buffer. Other buffer required by
<parameter>config</parameter>, such as depth, stencil, and
alpha mask, are allocated by EGL.
</para>
<para>
<parameter>buftype</parameter> must be
<constant>EGL_OPENVG_IMAGE</constant>, corresponding to an
OpenVG <type>VGImage</type> buffer.
<parameter>buffer</parameter> must be a valid
<type>VGImage</type> handle in the current OpenVG context,
cast into the type <type>EGLClientBuffer</type>.
</para>
<para>
The height, width,, OpenVG alpha format, and OpenVG
colorspace (surface attributes
<constant>EGL_HEIGHT</constant>,
<constant>EGL_WIDTH</constant>,
<constant>EGL_VG_ALPHA_FORMAT</constant>, and
<constant>EGL_VG_COLORSPACE</constant>, respectively) of the
resulting surface are determined by the size and format of
<parameter>buffer</parameter>.
</para>
<para>
Surface attributes are specified as a list of
attribute-value pairs, terminated with
<constant>EGL_NONE</constant>. Accepted attributes are:
</para>
<variablelist>
<varlistentry>
<term><constant>EGL_MIPMAP_TEXTURE</constant></term>
<listitem>
<para>
Specifies whether storage for mipmaps should be
allocated. Space for mipmaps will be set aside if
the attribute value is <constant>EGL_TRUE</constant>
and <constant>EGL_TEXTURE_FORMAT</constant> is not
<constant>EGL_NO_TEXTURE</constant>. The default
value is <constant>EGL_FALSE</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EGL_TEXTURE_FORMAT</constant></term>
<listitem>
<para>
Specifies the format of the texture that will be
created when a pbuffer is bound to a texture map.
Possible values are
<constant>EGL_NO_TEXTURE</constant>,
<constant>EGL_TEXTURE_RGB</constant>, and
<constant>EGL_TEXTURE_RGBA</constant>. The default
value is <constant>EGL_NO_TEXTURE</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>EGL_TEXTURE_TARGET</constant></term>
<listitem>
<para>
Specifies the target for the texture that will be
created when the pbuffer is created with a texture
format of <constant>EGL_TEXTURE_RGB</constant> or
<constant>EGL_TEXTURE_RGBA</constant>. Possible
values are <constant>EGL_NO_TEXTURE</constant>, or
<constant>EGL_TEXTURE_2D</constant>. The default
value is <constant>EGL_NO_TEXTURE</constant>.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
Any EGL rendering context that was created with respect to
<parameter>config</parameter> can be used to render into the
surface. Use
<citerefentry><refentrytitle>eglMakeCurrent</refentrytitle></citerefentry>
to attach an EGL rendering context to the surface.
</para>
<para>
Use
<citerefentry><refentrytitle>eglQuerySurface</refentrytitle></citerefentry>
to retrieve the dimensions of the allocated pixel buffer
surface or the ID of <parameter>config</parameter>.
</para>
<para>
Use <citerefentry><refentrytitle>eglDestroySurface</refentrytitle></citerefentry>
to destroy the surface.
</para>
</refsect1>
<refsect1 xml:id="notes"><title>Notes</title>
<para>
<function>eglCreatePbufferFromClientBuffer</function> is
supported only if the EGL version is 1.2 or greater, and if
the EGL implementation supports the OpenVG client API.
</para>
<para>
Currently
<function>eglCreatePbufferFromClientBuffer</function> only
supports binding OpenVG <type>VGImage</type> buffers to
pixel buffers. While other client API resources could be
supported in the future, mechanisms such as OpenGL ES
framebuffer objects, and the family of EGL and client API
extensions for defining and using <type>EGLImageKHR</type>
images, are a more flexible and general framework to satisfy
most of the same needs.
</para>
<para>
If the value of <parameter>config</parameter> attribute
<constant>EGL_TEXTURE_FORMAT</constant> is not
<constant>EGL_NO_TEXTURE</constant>, then the pbuffer width
and height specify the size of the level zero texture image
</para>
<para>
If <constant>EGL_LARGEST_PBUFFER</constant> is specified and
if the pbuffer will be used as a texture (i.e. the value of
<constant>EGL_TEXTURE_TARGET</constant> is
<constant>EGL_TEXTURE_2D</constant>, and the value of
<constant>EGL_TEXTURE FORMAT</constant> is
<constant>EGL_TEXTURE_RGB</constant> or
<constant>EGL_TEXTURE_RGBA</constant>), then the aspect
ratio will be preserved and the new width and height will be
valid sizes for the texture target (e.g. if the underlying
OpenGL ES implementation does not support non-power-of-two
textures, both the width and height will be a power of 2).
</para>
<para>
The contents of the depth and stencil buffers may not be
preserved when rendering a texture to the pbuffer and
switching which image of the texture is rendered to (e.g.,
switching from rendering one mipmap level to rendering
another).
</para>
<para>
Binding client API buffers to EGL pbuffers create the
possibility of race conditions, and of buffers being deleted
through one API while still in use in another API. To avoid
these problems, a number of constraints apply to bound
client API buffers:
<orderedlist>
<listitem>
<para>
Bound buffers may be used exclusively by either EGL,
or the client API that originally created them. For
example, if a <type>VGImage</type> is bound to a
pbuffer, and that pbuffer is bound to any client API
rendering context, then the <type>VGImage</type> may
not be used as the explicit source or destination of
any OpenVG operation. Errors resulting from such use
are described in client API specifications.
Similarly, while a <type>VGImage</type> is in use by
OpenVG, the pbuffer it is bound to may not be made
current to any client API context using
<citerefentry><refentrytitle>eglMakeCurrent</refentrytitle></citerefentry>.
</para>
</listitem>
<listitem>
<para>
Binding a buffer creates an additional reference to
it, and implementations must respect outstanding
references when destroying objects. For example, if
a <type>VGImage</type> is bound to a pbuffer,
destroying the image with
<function>vgDestroyImage</function> will not free
the underlying buffer, because it is still in use by
EGL. However, following
<function>vgDestroyImage</function> the buffer may
only be referred to via the EGL pbuffer handle,
since the OpenVG handle to that buffer no longer
exists. Similarly, destroying the pbuffer with
<function>eglDestroySurface</function> will not free
the underlying buffer, because it is still in use by
OpenVG . However, following
<function>eglDestroySurface</function> the buffer
may only be referred to via the OpenVG
<type>VGImage</type> handle, since the EGL pbuffer
handle no longer exists.
</para>
</listitem>
</orderedlist>
</para>
</refsect1>
<refsect1 xml:id="errors"><title>Errors</title>
<para>
<constant>EGL_NO_SURFACE</constant> is returned if creation of
the context fails.
</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.
</para>
<para>
<constant>EGL_BAD_PARAMETER</constant> is generated if
<parameter>buftype</parameter> is not
<constant>EGL_OPENVG_IMAGE</constant>, or if
<parameter>buffer</parameter> is not a valid handle to a
<type>VGImage</type> object in the currently bound OpenVG
context.
</para>
<para>
<constant>EGL_BAD_ACCESS</constant> is generated if there is
no current OpenVG context, or if
<parameter>buffer</parameter> is already bound to another
pixel buffer or in use by OpenVG as discussed in the Notes
section above.
</para>
<para>
<constant>EGL_BAD_ACCESS</constant> is generated if the buffers
contained in <parameter>buffer</parameter> consist of any
<type>EGLImage</type> siblings.
</para>
<para>
<constant>EGL_BAD_ALLOC</constant> is generated if there are not
enough resources to allocate the new surface.
</para>
<para>
<constant>EGL_BAD_ATTRIBUTE</constant> is generated if
<parameter>attrib_list</parameter> contains an invalid pixel
buffer attribute or if an attribute value is not recognized
or out of range.
</para>
<para>
<constant>EGL_BAD_ATTRIBUTE</constant> is generated if
<parameter>attrib_list</parameter> contains any of the
attributes <constant>EGL_MIPMAP_TEXTURE</constant>,
<constant>EGL_TEXTURE_FORMAT</constant>, or
<constant>EGL_TEXTURE_TARGET</constant>, and
<parameter>config</parameter> does not support OpenGL ES
rendering (e.g. the EGL version is 1.2 or later, and the
<constant>EGL_RENDERABLE_TYPE</constant> attribute of
<parameter>config</parameter> does not include at least one
of <constant>EGL_OPENGL_ES_BIT</constant> or
<constant>EGL_OPENGL_ES2_BIT</constant>).
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if
<parameter>config</parameter> does not support rendering to
pixel buffers (the <constant>EGL_SURFACE_TYPE</constant>
attribute does not contain
<constant>EGL_PBUFFER_BIT</constant>).
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if the
buffers contained in <parameter>buffer</parameter> do not
match the bit depths for those buffers specified by
<parameter>config</parameter>.
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if the
<constant>EGL_TEXTURE_FORMAT</constant> attribute is not
<constant>EGL_NO_TEXTURE</constant>, and
<constant>EGL_WIDTH</constant> and/or
<constant>EGL_HEIGHT</constant> specify an invalid size
(e.g., the texture size is not a power of 2, and the
underlying OpenGL ES implementation does not support
non-power-of-two textures).
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if
the <constant>EGL_TEXTURE_FORMAT</constant> attribute is
<constant>EGL_NO_TEXTURE</constant>, and
<constant>EGL_TEXTURE_TARGET</constant> is something other
than <constant>EGL_NO_TEXTURE</constant>; or,
<constant>EGL_TEXTURE_FORMAT</constant> is something other
than <constant>EGL_NO_TEXTURE</constant>, and
<constant>EGL_TEXTURE_TARGET</constant> is
<constant>EGL_NO_TEXTURE</constant>.
</para>
<para>
<constant>EGL_BAD_MATCH</constant> is generated if the
implementation has additional constraints on which types of
client API buffers may be bound to pixel buffer surfaces.
For example, it is possible that the OpenVG implementation
might not support a <type>VGImage</type> being bound to a
pixel buffer which will be used as a mipmapped OpenGL ES
texture (e.g. whose <constant>EGL_MIPMAP_TEXTURE</constant>
attribute is <constant>TRUE</constant>). Any such
constraints should be documented by the implementation
release notes.
</para>
</refsect1>
<refsect1 xml:id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>eglDestroySurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglChooseConfig</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglCreatePbufferSurface</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglGetConfigs</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglMakeCurrent</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>eglQuerySurface</refentrytitle></citerefentry>
</para>
</refsect1>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="copyright.xml"/>
</refentry>
|
