docs/egl.html

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   9 <h1>Mesa EGL</h1>
  10
  11 <p>The current version of EGL in Mesa implements EGL 1.4.  More information
  12 about EGL can be found at
  13 <a href="http://www.khronos.org/egl/" target="_parent">
  14 http://www.khronos.org/egl/</a>.</p>
  15
  16 <p>The Mesa's implementation of EGL uses a driver architecture.  The main
  17 library (<code>libEGL</code>) is window system neutral.  It provides the EGL
  18 API entry points and helper functions for use by the drivers.  Drivers are
  19 dynamically loaded by the main library and most of the EGL API calls are
  20 directly dispatched to the drivers.</p>
  21
  22 <p>The driver in use decides the window system to support.  For drivers that
  23 support hardware rendering, there are usually multiple drivers supporting the
  24 same window system.  Each one of of them supports a certain range of graphics
  25 cards.</p>
  26
  27 <h2>Build EGL</h2>
  28
  29 <ol>
  30 <li>
  31 <p>Run <code>configure</code> with the desired state trackers and and enable
  32 the Gallium driver for your hardware.  For example</p>
  33
  34 <pre>
  35   $ ./configure --with-state-trackers=egl_g3d,es,vega --enable-gallium-intel
  36 </pre>
  37
  38 <p>The main library will be enabled by default.  The <code>egl_g3d</code> state
  39 tracker is needed by a number of EGL drivers.  EGL drivers will be covered
  40 later.  The <a href="opengles.html">es state tracker</a> provides OpenGL ES 1.x
  41 and 2.x and the <a href="openvg.html">vega state tracker</a> provides OpenVG
  42 1.x.</p>
  43 </li>
  44
  45 <li>Build and install Mesa as usual.</li>
  46 </ol>
  47
  48 <p>In the given example, it will build and install <code>libEGL</code>,
  49 <code>libGLESv1_CM</code>, <code>libGLESv2</code>, <code>libOpenVG</code>, and
  50 one or more EGL drivers.</p>
  51
  52 <h3>Configure Options</h3>
  53
  54 <p>There are several options that control the build of EGL at configuration
  55 time</p>
  56
  57 <ul>
  58 <li><code>--enable-egl</code>
  59
  60 <p>By default, EGL is enabled.  When disabled, the main library and the drivers
  61 will not be built.</p>
  62
  63 </li>
  64
  65 <li><code>--with-egl-displays</code>
  66
  67 <p>List the window system(s) to support.  It is by default <code>x11</code>,
  68 which supports the X Window System.  Its argument is a comma separated string
  69 like, for example, <code>--with-egl-displays=x11,kms</code>.  Because an EGL
  70 driver decides which window system to support, this example will enable two
  71 (sets of) EGL drivers.  One supports the X window system and the other supports
  72 bare KMS (kernel modesetting).</p>
  73
  74 </li>
  75
  76 <li><code>--with-state-trackers</code>
  77
  78 <p>The argument is a comma separated string.  It is usually used to specify the
  79 rendering APIs, like OpenGL ES or OpenVG, to build.  But it should be noted
  80 that a number of EGL drivers depend on the <code>egl_g3d</code> state tracker.
  81 They will <em>not</em> be built without the <code>egl_g3d</code> state
  82 tracker.</p>
  83
  84 </li>
  85 </ul>
  86
  87 <h3>OpenGL</h3>
  88
  89 <p>The OpenGL state tracker is not built in the above example.  It should be
  90 noted that the classic <code>libGL</code> is not a state tracker and cannot be
  91 used with EGL (unless the EGL driver in use is <code>egl_glx</code>).  To build
  92 the OpenGL state tracker, one may append <code>glx</code> to
  93 <code>--with-state-trackers</code> and manually build
  94 <code>src/gallium/winsys/xlib/</code>.</p>
  95
  96 <h2>Use EGL</h2>
  97
  98 <p> The demos for OpenGL ES and OpenVG can be found in <code>progs/es1/</code>,
  99 <code>progs/es2/</code> and <code>progs/openvg/</code>.  You can use them to
 100 test your build.  For example,</p>
 101
 102 <pre>
 103   $ cd progs/es1/xegl
 104   $ make
 105   $ ./torus
 106 </pre>
 107
 108 <h3>Environment Variables</h3>
 109
 110 <p>There are several environment variables that control the behavior of EGL at
 111 runtime</p>
 112
 113 <ul>
 114 <li><code>EGL_DRIVER</code>
 115
 116 <p>This variable forces the specified EGL driver to be loaded.  It comes in
 117 handy when one wants to test a specific driver.</p>
 118
 119 </li>
 120
 121 <li><code>EGL_DISPLAY</code>
 122
 123 <p>When <code>EGL_DRIVER</code> is not set, the main library loads <em>all</em>
 124 EGL drivers that support a certain window system.  <code>EGL_DISPLAY</code> can
 125 be used to specify the window system and the valid values are, for example,
 126 <code>x11</code> or <code>kms</code>.  When the variable is not set, the main
 127 library defaults the value to the first window system listed in
 128 <code>--with-egl-displays</code> at configuration time.
 129
 130 </li>
 131
 132 <li><code>EGL_LOG_LEVEL</code>
 133
 134 <p>This changes the log level of the main library and the drivers.  The valid
 135 values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
 136 <code>fatal</code>.</p>
 137
 138 </li>
 139
 140 <li><code>EGL_SOFTWARE</code>
 141
 142 <p>For drivers that support both hardware and software rendering, setting this
 143 variable to true forces the use of software rendering.</p>
 144
 145 </li>
 146 </ul>
 147
 148 <h2>EGL Drivers</h2>
 149
 150 <p>There are two categories of EGL drivers: Gallium and classic.</p>
 151
 152 <p>Gallium EGL drivers supports all rendering APIs specified in EGL 1.4.  The
 153 support for optional EGL functions and EGL extensions is usually more complete
 154 than the classic ones.  These drivers depend on the <code>egl_g3d</code> state
 155 tracker to build.  The available drivers are</p>
 156
 157 <ul>
 158 <li><code>egl_&lt;dpy&gt;_i915</code></li>
 159 <li><code>egl_&lt;dpy&gt;_i965</code></li>
 160 <li><code>egl_&lt;dpy&gt;_radeon</code></li>
 161 <li><code>egl_&lt;dpy&gt;_nouveau</code></li>
 162 <li><code>egl_&lt;dpy&gt;_vmwgfx</code></li>
 163 </ul>
 164
 165 <p><code>&lt;dpy&gt;</code> is given by <code>--with-egl-displays</code> at
 166 configuration time.  There will be one EGL driver for each combination of the
 167 displays listed and the hardware drivers enabled.</p>
 168
 169 <p>Classic EGL drivers, on the other hand, supports only OpenGL as its
 170 rendering API.  They can be found under <code>src/egl/drivers/</code>.  There
 171 are 3 of them</p>
 172
 173 <ul>
 174 <li><code>egl_glx</code>
 175
 176 <p>This driver provides a wrapper to GLX.  It uses exclusively GLX to implement
 177 the EGL API.  It supports both direct and indirect rendering when the GLX does.
 178 It is accelerated when the GLX is.  As such, it cannot provide functions that
 179 is not available in GLX or GLX extensions.</p>
 180 </li>
 181
 182 <li><code>egl_xdri</code>
 183
 184 <p>This driver supports the X Window System as its window system.  It functions
 185 as a DRI driver loader and can load DRI/DRI2/DRISW drivers.  Unlike
 186 <code>egl_glx</code>, it has no dependency on <code>libGL</code>.  It talks to
 187 the X server directly using DRI or DRI2 protocols.  It also talks minimal GLX
 188 protocol for things like available visuals or fbconfigs.  With direct access to
 189 the DRI drivers, it has the potential to support more EGL functions that are
 190 not possible with <code>egl_glx</code>.</p>
 191
 192 </li>
 193 <li><code>egl_dri</code>
 194
 195 <p>This driver lacks maintenance and does <em>not</em> build.  It is similiar
 196 to <code>egl_xdri</code> in that it functions as a DRI driver loader.  But
 197 unlike <code>egl_xdri</code>, it supports Linux framebuffer devices as its
 198 window system and supports EGL_MESA_screen_surface extension.  It loads only
 199 DRI1 drivers.  As DRI1 drivers is phasing out, it might be better to rewrite
 200 the driver to support KMS and DRI2.</p>
 201
 202 </li>
 203 </ul>
 204
 205 <p>To use the classic drivers, one must manually set <code>EGL_DRIVER</code> at
 206 runtime.</p>
 207
 208 <h2>Developers</h2>
 209
 210 The sources of the main library and the classic drivers can be found at
 211 <code>src/egl/</code>.  The sources of the <code>egl_g3d</code> state tracker
 212 can be found at <code>src/gallium/state_trackers/egl_g3d/</code>.
 213
 214 <h3>TODOs</h3>
 215
 216 <ul>
 217 <li>Thread safety</li>
 218 <li>Pass the conformance tests</li>
 219 <li>Better automatic driver selection: <code>EGL_DISPLAY</code> loads all
 220 drivers and might eat too much memory.</li>
 221
 222 </ul>
 223
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