docs/opengles.html


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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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  <title>OpenGL ES</title>
  <link rel="stylesheet" type="text/css" href="mesa.css">
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<body>

<div class="header">
  <h1>The Mesa 3D Graphics Library</h1>
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<h1>OpenGL ES</h1>

<p>Mesa implements OpenGL ES 1.1 and OpenGL ES 2.0.  More information about
OpenGL ES can be found at <a href="https://www.khronos.org/opengles/">
https://www.khronos.org/opengles/</a>.</p>

<p>OpenGL ES depends on a working EGL implementation.  Please refer to
<a href="egl.html">Mesa EGL</a> for more information about EGL.</p>

<h2>Build the Libraries</h2>
<ol>
<li>Run <code>meson configure</code> with <code>-D gles1=true -D gles2=true</code> and enable the Gallium driver for your hardware.</li>
<li>Build and install Mesa as usual.</li>
</ol>

Alternatively, if XCB-DRI2 is installed on the system, one can use
<code>egl_dri2</code> EGL driver with OpenGL|ES-enabled DRI drivers

<ol>
<li>Run <code>meson configure</code> with <code>-D gles1=true -D gles2=true</code>.</li>
<li>Build and install Mesa as usual.</li>
</ol>

<p>Both methods will install libGLESv1_CM, libGLESv2, libEGL, and one or more
EGL drivers for your hardware.</p>

<h2>Run the Demos</h2>

<p>There are some demos in <code>mesa/demos</code> repository.</p>

<h2>Developers</h2>

<h3>Dispatch Table</h3>

<p>OpenGL ES has an additional indirection when dispatching functions</p>

<pre>
  Mesa:       glFoo() --&gt; _mesa_Foo()
  OpenGL ES:  glFoo() --&gt; _es_Foo() --&gt; _mesa_Foo()
</pre>

<p>The indirection serves several purposes</p>

<ul>
<li>When a function is in Mesa and the type matches, it checks the arguments and calls the Mesa function.</li>
<li>When a function is in Mesa but the type mismatches, it checks and converts the arguments before calling the Mesa function.</li>
<li>When a function is not available in Mesa, or accepts arguments that are not available in OpenGL, it provides its own implementation.</li>
</ul>

<p>Other than the last case, OpenGL ES uses <code>APIspec.xml</code> to generate functions to check and/or converts the arguments.</p>

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