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<concept id="GUID-4A6DC7BC-4FE9-4557-8992-0EA5ACD59A4D" xml:lang="en"><title>EGL Multithreading
Requirements</title><shortdesc>This topic provides EGL implementers with information about the
EGL multithreading requirements on the Symbian platform.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p><b>Target audience</b>: Device creators.</p>
<section id="GUID-E44AB766-ED1D-49EC-8D74-AE141B2406E7"><title>Introduction</title><p>This
topic provides clarifications to the following sections of the EGL specification:</p><ul>
<li>2.3 Direct Rendering and Address Spaces</li>
<li>3.7 Rendering Context</li>
<li>3.7.3 Binding Contexts and Drawables</li>
</ul><p>For links to the relevant EGL specifications, see <xref href="GUID-A5914CFF-6F86-53E8-9928-36D3379835B1.dita">EGL
Interface Overview</xref>.</p></section>
<section id="GUID-9E17E402-DA10-4DC3-AB97-E03135310C28"><title>Number of threads
per process</title><p>An EGL implementation must support an unlimited number
of threads per process. On Symbian all threads within a process share the
same virtual address space. EGL objects that are used by multiple threads
in a process are therefore used within the address space in which they are
created, as required by the EGL specification. </p><p>With one exception,
all EGL functions and handles must be able to be used and shared
between all of the threads within the same process. The exception is the EGL
window surface as explained in <xref href="GUID-894AB487-C127-532D-852B-37CB0DEA1440.dita">Symbian-Specific
Behavior</xref>. </p><p>There is a graphics resource cost associated with
each additional thread that uses EGL. Typically only one thread within a process
uses EGL. While usage by eight threads within a process should be possible,
it is exceptional and has not been encountered in practice. Therefore you
may want to optimize your implementation for between one and eight threads.
 </p></section>
<section id="GUID-D379EFA3-D88B-4626-8F2C-18FF82BB0E47"><title>Number of current
contexts</title><p>An EGL implementation should not place arbitrary restrictions
on the number of contexts that can be made current, other than the restrictions
that are explicitly stated in the specification. For example, <codeph>eglMakeCurrent()</codeph> should
not fail with <codeph>EGL_BAD_ACCESS</codeph> when a client attempts to make
multiple OpenVG contexts current to separate threads, simply because the implementation
has a limit to the number of contexts that can be current at the same time. </p></section>
</conbody><related-links>
<link href="GUID-F094A9FA-D253-5D33-B625-A2AA0B1CE447.dita"><linktext>EGL Implementer's
Guide</linktext></link>
</related-links></concept>