workbench/libs/mesa/docs/opengles.html

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   3 <title>OpenGL ES</title>
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   9 <h1>OpenGL ES</h1>
  10
  11 <p>Mesa implements OpenGL ES 1.1 and OpenGL ES 2.0.  More informations about
  12 OpenGL ES can be found at <a href="http://www.khronos.org/opengles/"
  13 target="_parent"> http://www.khronos.org/opengles/</a>.</p>
  14
  15 <p>OpenGL ES depends on a working EGL implementation.  Please refer to
  16 <a href="egl.html">Mesa EGL</a> for more information about EGL.</p>
  17
  18 <h2>Build the Libraries</h2>
  19 <ol>
  20 <li>Run <code>configure</code> with <code>--enable-gles1 --enable-gles2</code> and enable the Gallium driver for your hardware.</li>
  21 <li>Build and install Mesa as usual.</li>
  22 </ol>
  23
  24 Alternatively, if XCB-DRI2 is installed on the system, one can use
  25 <code>egl_dri2</code> EGL driver with OpenGL|ES-enabled DRI drivers
  26
  27 <ol>
  28 <li>Run <code>configure</code> with <code>--enable-gles1 --enable-gles2</code>.</li>
  29 <li>Build and install Mesa as usual.</li>
  30 </ol>
  31
  32 <p>Both methods will install libGLESv1_CM, libGLESv2, libEGL, and one or more
  33 EGL drivers for your hardware.</p>
  34
  35 <h2>Run the Demos</h2>
  36
  37 <p>There are some demos in <code>mesa/demos</code> repository.</p>
  38
  39 <h2>Developers</h2>
  40
  41 <h3>Dispatch Table</h3>
  42
  43 <p>OpenGL ES has an additional indirection when dispatching fucntions</p>
  44
  45 <pre>
  46   Mesa:       glFoo() --&gt; _mesa_Foo()
  47   OpenGL ES:  glFoo() --&gt; _es_Foo() --&gt; _mesa_Foo()
  48 </pre>
  49
  50 <p>The indirection serves several purposes</p>
  51
  52 <ul>
  53 <li>When a function is in Mesa and the type matches, it checks the arguments and calls the Mesa function.</li>
  54 <li>When a function is in Mesa but the type mismatches, it checks and converts the arguments before calling the Mesa function.</li>
  55 <li>When a function is not available in Mesa, or accepts arguments that are not available in OpenGL, it provides its own implementation.</li>
  56 </ul>
  57
  58 <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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