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<concept id="GUID-FFA5956E-0632-42F5-A2F9-0503888EF72B" xml:lang="en"><title>EGL
Reference Implementation Component</title><shortdesc>The EGL Reference Implementation component implements the minimum
EGL functionality to support OpenWF composition. It does not implement the
EGL functionality required to support the use of the Khronos rendering APIs,
such as OpenGL ES and OpenVG. Typically device creators replace the reference
implementation with a fully functional implementation of their own. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p><b>Target audience</b>: Device creators. </p>
<section id="GUID-3400F826-F4A6-4BCA-BF98-9CD941532B8A"><title>Implemented
APIs</title><p>The EGL Reference Implementation implements the following EGL
1.4 APIs: </p><ul>
<li><codeph>eglGetError()</codeph></li>
<li><codeph>eglGetDisplay()</codeph></li>
<li><codeph>eglInitialize()</codeph></li>
<li><codeph>eglTerminate()</codeph></li>
<li><codeph>eglReleaseThread()</codeph></li>
<li><codeph>eglQueryString()</codeph></li>
<li><codeph>eglGetProcAddress()</codeph></li>
</ul><p>The EGL Reference Implementation also implements the following reusable
sync extension functions:</p><ul>
<li><codeph>eglCreateSyncKHR()</codeph></li>
<li><codeph>eglDestroySyncKHR()</codeph></li>
<li><codeph>eglClientWaitSyncKHR()</codeph></li>
<li><codeph>eglSignalSyncKHR()</codeph></li>
<li><codeph>eglGetSyncAttribKHR()</codeph></li>
</ul><p>The Reference Implementation implements <codeph>eglGetProcAddress()</codeph> ,
which supports retrieving OpenWF-C extension functions. </p><p>Calling any
of the unsupported APIs panics the client with the <codeph>EEglPanicNotSupported</codeph> panic
code and the return value and EGL error code are undefined. This behavior
deliberately does not conform to the EGL specification. It is intended to
make it easy to detect errors in the platform configuration—for example, where
the intention was to use a fully-functional EGL implementation instead of
the Reference Implementation.</p></section>
<section id="GUID-264ED891-CB0A-4D6D-8640-8A11A9BD79A5"><title>Implementation-specific
information</title><p>The Reference Implementation returns the following implementation-specific
strings: </p><table id="GUID-EAEA383C-E4ED-4C11-A957-6EFFEECDE6BD">
<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>
<thead>
<row>
<entry valign="top">String</entry>
<entry valign="top">Value</entry>
</row>
</thead>
<tbody>
<row>
<entry>EGL_CLIENT_APIS</entry>
<entry>“”</entry>
</row>
<row>
<entry>EGL_EXTENSIONS</entry>
<entry>“EGL_KHR_reusable_sync”</entry>
</row>
<row>
<entry>EGL_VENDOR</entry>
<entry>“Nokia”</entry>
</row>
<row>
<entry>EGL_VERSION</entry>
<entry>“1.4 Reference EGL”</entry>
</row>
</tbody>
</tgroup>
</table></section>
<section id="GUID-CD9221D3-55FC-479B-A3DE-B28BBF32DAC0"><title>Private
signaling function</title><p>Both applications and middleware APIs, such as
OpenWF-C may need to signal on the EGL sync object. However, once the middleware
API calls the standard <codeph>eglSignalSyncKHR()</codeph> signaling function
and obtains the error code using <codeph>eglGetError()</codeph>, the error
code is not available to the application. </p><p>The EGL reference implementation
therefore has the following private signaling function, which returns the
error code instead of generating an EGL error. This enables the OpenWF implementation
to signal the sync object and get the error code without setting
the EGL error. This means that from the application level, the normal EGL
error behavior is maintained.</p><codeblock xml:space="preserve">EGLint egl_Private_SignalSyncNOK(
              EGLDisplay dpy,
              EGLSyncKHR sync,
              EGLenum mode)</codeblock><p>The extension name of this private
signal function is <codeph>EGL_NOK__private__signal_sync</codeph>, which can
be obtained using <codeph>eglQueryString()</codeph>. </p><p>When the same
vendor implements both EGL and OpenWF-C, the vendor might implement a different
solution.</p> </section>
<section id="GUID-8ED3006D-56A3-4512-A1A8-0E88149C236B"><title>Thread handling</title><p>The
Reference Implementation allows the supported EGL APIs to be used from multiple
threads within the same process. The Reference Implementation maintains the
process and thread state in order to conform to the correct behavior described
in the EGL specification. Access to process-wide objects is serialized and
protected by mutex to prevent race conditions.</p><p>The Reference Implementation
uses its own heap to allow the creation, access and destruction of process-wide
objects from any thread. This includes the <codeph>EGLDisplay</codeph> and <codeph>EGLSync</codeph> objects.
 The heap is created in a local chunk.</p><p>For simplicity, the Reference
Implementation supports only one display: <codeph>EGL_DEFAULT_DISPLAY</codeph>.
 A request to obtain any other <codeph>EGLDisplay</codeph> returns <codeph>EGL_NO_DISPLAY</codeph>. <codeph>EGLDisplay</codeph> is
a process-wide resource that can be accessed from any thread. Its behavior
follows the EGL specification for <codeph>eglGetDisplay()</codeph>, <codeph>eglInitialize()</codeph> and <codeph>eglTerminate()</codeph>.</p><p>Each
client thread can have its own EGL error. Error handling and thread state
management follows the EGL specification for <codeph>eglGetError()</codeph> and <codeph>eglReleaseThread()</codeph>.</p></section>
<section id="GUID-8B9FB71D-8DC8-4944-9DA8-AEC821C1041D"><title>DLL summary</title><table id="GUID-80E05C78-5FD4-5489-A1DA-A759EB7F9530">
<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>
<thead>
<row>
<entry>DLL</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><filepath>libegl_ref.dll</filepath> </entry>
<entry>The EGL reference implementation. </entry>
</row>
<row>
<entry><filepath>libEGL.dll</filepath></entry>
<entry>In the emulator, this provides a mechanism that switches among different
EGL implementation DLLs used in different scenarios, including the Reference
Implementation mentioned above. For ARM builds, the file above is renamed
to this during the ROM build process. This is controlled by IBY files.</entry>
</row>
</tbody>
</tgroup>
</table><p>To allow different EGL implementations to be used on a platform,
the Reference Implementation is built with a target name of <filepath>libegl_ref.dll</filepath>.
However, EGL Clients should link their code against <filepath>libEGL.lib</filepath>.</p></section>
<section id="GUID-0685C8AA-5F35-49B7-BF02-C147BCDCCE89"><title>Enabling the
EGL Reference Implementation</title><p><b>Emulator</b></p><p>To enable the
ScreenPlay OpenWF-C components and the EGL Reference Implementation in the
emulator, add the following lines to the <filepath>\epoc32\data\epoc.ini</filepath> file:</p><codeblock xml:space="preserve">SYMBIAN_GRAPHICS_USE_OPENWF
SYMBIAN_GRAPHICS_USE_EGL_REF</codeblock><p><b>PlatSim
and Hardware</b></p><p>To build the EGL
Reference Implementation component in the ROM image for PlatSim or other hardware
platforms, use the following arguments to the <codeph>buildrom</codeph> command:</p><codeblock xml:space="preserve">buildrom -DSYMBIAN_GRAPHICS_USE_OPENWF -DSYMBIAN_GRAPHICS_USE_EGL_REF ...</codeblock><p>Existing ROM build tools have a mechanism
to select a specific EGL implementation in a ROM image and rename it to <filepath>libEGL.dll</filepath>.
The generic <filepath>egl.iby</filepath> file which is part of EGL interface
component uses the <codeph>EGL_DRV</codeph> macro to perform the selection.
 For more information, refer to <xref href="GUID-946E64D6-3E5D-5264-AD5D-29D3AD296543.dita">Selection
of Adaptations</xref>. </p></section>
</conbody><related-links>
<link href="GUID-DEA883D0-7C53-407A-AC5D-0A3208E667C7.dita">
<linktext>EGL Reusable Sync Extension</linktext></link>
<link href="GUID-A5914CFF-6F86-53E8-9928-36D3379835B1.dita"><linktext>EGL Interface
Overview</linktext></link>
</related-links></concept>