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Andreas Bollecd5c7c2012-06-12 09:05:03 +02001<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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5 <title>Mesa EGL</title>
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Chia-I Wuada46052010-01-21 15:29:14 +08008<body>
9
Andreas Bollb5da52a2012-09-18 18:57:02 +020010<div class="header">
11 <h1>The Mesa 3D Graphics Library</h1>
12</div>
13
14<iframe src="contents.html"></iframe>
15<div class="content">
16
Chia-I Wuada46052010-01-21 15:29:14 +080017<h1>Mesa EGL</h1>
18
19<p>The current version of EGL in Mesa implements EGL 1.4. More information
20about EGL can be found at
Andreas Bolla73c59b2012-09-18 19:31:28 +020021<a href="http://www.khronos.org/egl/">
Brian Paulaeff9f92010-01-21 08:13:32 -070022http://www.khronos.org/egl/</a>.</p>
Chia-I Wuada46052010-01-21 15:29:14 +080023
24<p>The Mesa's implementation of EGL uses a driver architecture. The main
25library (<code>libEGL</code>) is window system neutral. It provides the EGL
26API entry points and helper functions for use by the drivers. Drivers are
27dynamically loaded by the main library and most of the EGL API calls are
28directly dispatched to the drivers.</p>
29
Chia-I Wu65e8f812010-12-25 02:45:13 +080030<p>The driver in use decides the window system to support.</p>
Chia-I Wuada46052010-01-21 15:29:14 +080031
32<h2>Build EGL</h2>
33
34<ol>
35<li>
Chia-I Wu3418f742010-11-02 23:55:56 +080036<p>Run <code>configure</code> with the desired client APIs and enable
37the driver for your hardware. For example</p>
Chia-I Wuada46052010-01-21 15:29:14 +080038
39<pre>
Chia-I Wu8eea0502011-06-20 11:14:56 +090040 $ ./configure --enable-gles1 --enable-gles2 \
41 --with-dri-drivers=... \
42 --with-gallium-drivers=...
Chia-I Wuada46052010-01-21 15:29:14 +080043</pre>
44
Chia-I Wu8eea0502011-06-20 11:14:56 +090045<p>The main library and OpenGL is enabled by default. The first two options
46above enables <a href="opengles.html">OpenGL ES 1.x and 2.x</a>. The last two
47options enables the listed classic and and Gallium drivers respectively.</p>
Chia-I Wuc6320c52010-10-28 17:25:07 +080048
Chia-I Wuada46052010-01-21 15:29:14 +080049</li>
50
51<li>Build and install Mesa as usual.</li>
52</ol>
53
54<p>In the given example, it will build and install <code>libEGL</code>,
Chia-I Wu8eea0502011-06-20 11:14:56 +090055<code>libGL</code>, <code>libGLESv1_CM</code>, <code>libGLESv2</code>, and one
56or more EGL drivers.</p>
Chia-I Wuada46052010-01-21 15:29:14 +080057
58<h3>Configure Options</h3>
59
60<p>There are several options that control the build of EGL at configuration
61time</p>
62
Andreas Boll76d4f9e2012-09-20 16:01:08 +020063<dl>
64<dt><code>--enable-egl</code></dt>
65<dd>
Chia-I Wuada46052010-01-21 15:29:14 +080066
67<p>By default, EGL is enabled. When disabled, the main library and the drivers
68will not be built.</p>
69
Andreas Boll76d4f9e2012-09-20 16:01:08 +020070</dd>
Chia-I Wuada46052010-01-21 15:29:14 +080071
Andreas Boll76d4f9e2012-09-20 16:01:08 +020072<dt><code>--with-egl-driver-dir</code></dt>
73<dd>
Chia-I Wua6342af2010-01-26 10:54:45 +080074
75<p>The directory EGL drivers should be installed to. If not specified, EGL
76drivers will be installed to <code>${libdir}/egl</code>.</p>
77
Andreas Boll76d4f9e2012-09-20 16:01:08 +020078</dd>
Chia-I Wua6342af2010-01-26 10:54:45 +080079
Andreas Boll76d4f9e2012-09-20 16:01:08 +020080<dt><code>--with-egl-platforms</code></dt>
81<dd>
Chia-I Wuada46052010-01-21 15:29:14 +080082
Chia-I Wub365b152010-07-03 17:18:40 +080083<p>List the platforms (window systems) to support. Its argument is a comma
Nathan Kidd0691b372014-01-03 16:44:00 -070084separated string such as <code>--with-egl-platforms=x11,drm</code>. It decides
Chia-I Wub365b152010-07-03 17:18:40 +080085the platforms a driver may support. The first listed platform is also used by
86the main library to decide the native platform: the platform the EGL native
87types such as <code>EGLNativeDisplayType</code> or
88<code>EGLNativeWindowType</code> defined for.</p>
Chia-I Wuada46052010-01-21 15:29:14 +080089
Chia-I Wue7424d72010-09-19 16:54:39 +080090<p>The available platforms are <code>x11</code>, <code>drm</code>,
Chia-I Wuda39d5d2010-06-17 16:07:46 +080091<code>fbdev</code>, and <code>gdi</code>. The <code>gdi</code> platform can
Chia-I Wu3418f742010-11-02 23:55:56 +080092only be built with SCons. Unless for special needs, the build system should
93select the right platforms automatically.</p>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +080094
Andreas Boll76d4f9e2012-09-20 16:01:08 +020095</dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +080096
Andreas Boll76d4f9e2012-09-20 16:01:08 +020097<dt><code>--enable-gles1</code></dt>
98<dt><code>--enable-gles2</code></dt>
99<dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800100
Chia-I Wu65e8f812010-12-25 02:45:13 +0800101<p>These options enable OpenGL ES support in OpenGL. The result is one big
102internal library that supports multiple APIs.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800103
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200104</dd>
Chia-I Wua1306f42010-01-22 15:51:51 +0800105
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200106<dt><code>--enable-shared-glapi</code></dt>
107<dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800108
Chia-I Wu8eea0502011-06-20 11:14:56 +0900109<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
110This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
111is required if applications mix OpenGL and OpenGL ES.</p>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800112
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200113</dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800114
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200115<dt><code>--enable-openvg</code></dt>
116<dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800117
Chia-I Wu8eea0502011-06-20 11:14:56 +0900118<p>OpenVG must be explicitly enabled by this option.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800119
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200120</dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800121
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200122</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800123
Chia-I Wuada46052010-01-21 15:29:14 +0800124<h2>Use EGL</h2>
125
Chia-I Wu411bba32010-06-11 12:47:14 +0800126<h3>Demos</h3>
Chia-I Wuada46052010-01-21 15:29:14 +0800127
Chia-I Wu411bba32010-06-11 12:47:14 +0800128<p>There are demos for the client APIs supported by EGL. They can be found in
129mesa/demos repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800130
131<h3>Environment Variables</h3>
132
133<p>There are several environment variables that control the behavior of EGL at
134runtime</p>
135
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200136<dl>
137<dt><code>EGL_DRIVERS_PATH</code></dt>
138<dd>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800139
140<p>By default, the main library will look for drivers in the directory where
141the drivers are installed to. This variable specifies a list of
142colon-separated directories where the main library will look for drivers, in
Chia-I Wu6fd8b6a2010-02-02 16:47:53 +0800143addition to the default directory. This variable is ignored for setuid/setgid
144binaries.</p>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800145
Chia-I Wucba77862011-01-04 00:53:19 +0800146<p>This variable is usually set to test an uninstalled build. For example, one
147may set</p>
148
149<pre>
150 $ export LD_LIBRARY_PATH=$mesa/lib
151 $ export EGL_DRIVERS_PATH=$mesa/lib/egl
152</pre>
153
154<p>to test a build without installation</p>
155
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200156</dd>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800157
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200158<dt><code>EGL_DRIVER</code></dt>
159<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800160
Chia-I Wuc98ea262011-01-07 16:30:08 +0800161<p>This variable specifies a full path to or the name of an EGL driver. It
162forces the specified EGL driver to be loaded. It comes in handy when one wants
163to test a specific driver. This variable is ignored for setuid/setgid
164binaries.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800165
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200166</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800167
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200168<dt><code>EGL_PLATFORM</code></dt>
169<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800170
Chia-I Wub365b152010-07-03 17:18:40 +0800171<p>This variable specifies the native platform. The valid values are the same
172as those for <code>--with-egl-platforms</code>. When the variable is not set,
173the main library uses the first platform listed in
Chia-I Wu3418f742010-11-02 23:55:56 +0800174<code>--with-egl-platforms</code> as the native platform.</p>
175
176<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
177create displays for non-native platforms. These extensions are usually used by
178applications that support non-native platforms. Setting this variable is
179probably required only for some of the demos found in mesa/demo repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800180
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200181</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800182
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200183<dt><code>EGL_LOG_LEVEL</code></dt>
184<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800185
186<p>This changes the log level of the main library and the drivers. The valid
187values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
188<code>fatal</code>.</p>
189
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200190</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800191
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200192<dt><code>EGL_SOFTWARE</code></dt>
193<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800194
195<p>For drivers that support both hardware and software rendering, setting this
196variable to true forces the use of software rendering.</p>
197
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200198</dd>
199</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800200
201<h2>EGL Drivers</h2>
202
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200203<dl>
204<dt><code>egl_dri2</code></dt>
205<dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800206
207<p>This driver supports both <code>x11</code> and <code>drm</code> platforms.
Chia-I Wu65e8f812010-12-25 02:45:13 +0800208It functions as a DRI driver loader. For <code>x11</code> support, it talks to
209the X server directly using (XCB-)DRI2 protocol.</p>
210
211<p>This driver can share DRI drivers with <code>libGL</code>.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800212
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200213</dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800214
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200215<dt><code>egl_gallium</code></dt>
216<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800217
Chia-I Wub365b152010-07-03 17:18:40 +0800218<p>This driver is based on Gallium3D. It supports all rendering APIs and
Nathan Kidd0691b372014-01-03 16:44:00 -0700219hardware supported by Gallium3D. It is the only driver that supports OpenVG.
Chia-I Wuc6320c52010-10-28 17:25:07 +0800220The supported platforms are X11, DRM, FBDEV, and GDI.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800221
Chia-I Wu65e8f812010-12-25 02:45:13 +0800222<p>This driver comes with its own hardware drivers
223(<code>pipe_&lt;hw&gt;</code>) and client API modules
224(<code>st_&lt;api&gt;</code>).</p>
225
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200226</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800227
Chia-I Wu65e8f812010-12-25 02:45:13 +0800228<h2>Packaging</h2>
229
230<p>The ABI between the main library and its drivers are not stable. Nor is
231there a plan to stabilize it at the moment. Of the EGL drivers,
232<code>egl_gallium</code> has its own hardware drivers and client API modules.
233They are considered internal to <code>egl_gallium</code> and there is also no
234stable ABI between them. These should be kept in mind when packaging for
235distribution.</p>
236
237<p>Generally, <code>egl_dri2</code> is preferred over <code>egl_gallium</code>
238when the system already has DRI drivers. As <code>egl_gallium</code> is loaded
239before <code>egl_dri2</code> when both are available, <code>egl_gallium</code>
Chia-I Wu8eea0502011-06-20 11:14:56 +0900240is disabled by default.</p>
Chia-I Wu65e8f812010-12-25 02:45:13 +0800241
Chia-I Wuada46052010-01-21 15:29:14 +0800242<h2>Developers</h2>
243
Chia-I Wu14cbf322010-01-27 23:18:22 +0800244<p>The sources of the main library and the classic drivers can be found at
Chia-I Wu3c967a92010-01-22 16:31:43 +0800245<code>src/egl/</code>. The sources of the <code>egl</code> state tracker can
Chia-I Wu14cbf322010-01-27 23:18:22 +0800246be found at <code>src/gallium/state_trackers/egl/</code>.</p>
247
Chia-I Wu14cbf322010-01-27 23:18:22 +0800248<h3>Lifetime of Display Resources</h3>
249
250<p>Contexts and surfaces are examples of display resources. They might live
251longer than the display that creates them.</p>
252
253<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
254display resources should be destroyed. Similarly, when a thread is released
Nathan Kidd0691b372014-01-03 16:44:00 -0700255through <code>eglReleaseThread</code>, all current display resources should be
256released. Another way to destroy or release resources is through functions
Chia-I Wu14cbf322010-01-27 23:18:22 +0800257such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
258
259<p>When a resource that is current to some thread is destroyed, the resource
260should not be destroyed immediately. EGL requires the resource to live until
261it is no longer current. A driver usually calls
262<code>eglIs&lt;Resource&gt;Bound</code> to check if a resource is bound
263(current) to any thread in the destroy callbacks. If it is still bound, the
264resource is not destroyed.</p>
265
266<p>The main library will mark destroyed current resources as unlinked. In a
267driver's <code>MakeCurrent</code> callback,
268<code>eglIs&lt;Resource&gt;Linked</code> can then be called to check if a newly
269released resource is linked to a display. If it is not, the last reference to
270the resource is removed and the driver should destroy the resource. But it
271should be careful here because <code>MakeCurrent</code> might be called with an
272uninitialized display.</p>
273
274<p>This is the only mechanism provided by the main library to help manage the
275resources. The drivers are responsible to the correct behavior as defined by
276EGL.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800277
Chia-I Wu1b2b08c2010-02-05 12:44:45 +0800278<h3><code>EGL_RENDER_BUFFER</code></h3>
279
280<p>In EGL, the color buffer a context should try to render to is decided by the
281binding surface. It should try to render to the front buffer if the binding
282surface has <code>EGL_RENDER_BUFFER</code> set to
283<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
284surface with <code>EGL_RENDER_BUFFER</code> set to
285<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
286buffer. However, the context is allowed to make the final decision as to which
287color buffer it wants to or is able to render to.</p>
288
289<p>For pbuffer surfaces, the render buffer is always
290<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
291always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
292requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
293result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
294<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
295config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
296pbuffer surfaces.</p>
297
298<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
299single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
300is desirable that a driver allocates a private color buffer for each pbuffer
301surface created. If the window system the driver supports has native pbuffers,
302or if the native pixmaps have more than one color buffers, the driver should
303carefully attach the native color buffers to the EGL surfaces, re-route them if
304required.</p>
305
306<p>There is no defined behavior as to, for example, how
307<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
308now, it is desired that the draw buffer in a client API be fixed for pixmap and
309pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
310client API renders to the specified render buffer for pixmap and pbuffer
311surfaces.</p>
312
Chia-I Wue16f5772010-02-17 19:52:29 +0800313<h3><code>EGLDisplay</code> Mutex</h3>
314
315The <code>EGLDisplay</code> will be locked before calling any of the dispatch
316functions (well, except for GetProcAddress which does not take an
317<code>EGLDisplay</code>). This guarantees that the same dispatch function will
318not be called with the sample display at the same time. If a driver has access
319to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
320should as well lock the display before using it.
321
Andreas Bollb5da52a2012-09-18 18:57:02 +0200322</div>
Chia-I Wuada46052010-01-21 15:29:14 +0800323</body>
324</html>