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gerrit-public.fairphone.software / platform / external / mesa3d / 76d4f9e404697d82eb266a1652f95acee18fec61 / . / docs / egl.html
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Andreas Bollecd5c7c2012-06-12 09:05:03 +0200[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2<html lang="en">
3<head>
4 <meta http-equiv="content-type" content="text/html; charset=utf-8">
5 <title>Mesa EGL</title>
6 <link rel="stylesheet" type="text/css" href="mesa.css">
7</head>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]8<body>
9
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]10<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 +0800[diff] [blame]17<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 +0200[diff] [blame]21<a href="http://www.khronos.org/egl/">
Brian Paulaeff9f92010-01-21 08:13:32 -0700[diff] [blame]22http://www.khronos.org/egl/</a>.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]23
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 +0800[diff] [blame]30<p>The driver in use decides the window system to support.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]31
32<h2>Build EGL</h2>
33
34<ol>
35<li>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]36<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 +0800[diff] [blame]38
39<pre>
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]40 $ ./configure --enable-gles1 --enable-gles2 \
41 --with-dri-drivers=... \
42 --with-gallium-drivers=...
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]43</pre>
44
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]45<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 +0800[diff] [blame]48
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]49</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 +0900[diff] [blame]55<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 +0800[diff] [blame]57
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 +0200[diff] [blame^]63<dl>
64<dt><code>--enable-egl</code></dt>
65<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]66
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 +0200[diff] [blame^]70</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]71
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]72<dt><code>--with-egl-driver-dir</code></dt>
73<dd>
Chia-I Wua6342af2010-01-26 10:54:45 +0800[diff] [blame]74
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 +0200[diff] [blame^]78</dd>
Chia-I Wua6342af2010-01-26 10:54:45 +0800[diff] [blame]79
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]80<dt><code>--enable-gallium-egl</code></dt>
81<dd>
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]82
83<p>Enable the optional <code>egl_gallium</code> driver.</p>
84
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]85</dd>
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]86
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]87<dt><code>--with-egl-platforms</code></dt>
88<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]89
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]90<p>List the platforms (window systems) to support. Its argument is a comma
Chia-I Wue7424d72010-09-19 16:54:39 +0800[diff] [blame]91seprated string such as <code>--with-egl-platforms=x11,drm</code>. It decides
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]92the platforms a driver may support. The first listed platform is also used by
93the main library to decide the native platform: the platform the EGL native
94types such as <code>EGLNativeDisplayType</code> or
95<code>EGLNativeWindowType</code> defined for.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]96
Chia-I Wue7424d72010-09-19 16:54:39 +0800[diff] [blame]97<p>The available platforms are <code>x11</code>, <code>drm</code>,
Chia-I Wuda39d5d2010-06-17 16:07:46 +0800[diff] [blame]98<code>fbdev</code>, and <code>gdi</code>. The <code>gdi</code> platform can
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]99only be built with SCons. Unless for special needs, the build system should
100select the right platforms automatically.</p>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]101
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]102</dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]103
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]104<dt><code>--enable-gles1</code></dt>
105<dt><code>--enable-gles2</code></dt>
106<dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]107
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]108<p>These options enable OpenGL ES support in OpenGL. The result is one big
109internal library that supports multiple APIs.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]110
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]111</dd>
Chia-I Wua1306f42010-01-22 15:51:51 +0800[diff] [blame]112
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]113<dt><code>--enable-shared-glapi</code></dt>
114<dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]115
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]116<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
117This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
118is required if applications mix OpenGL and OpenGL ES.</p>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]119
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]120</dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]121
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]122<dt><code>--enable-openvg</code></dt>
123<dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]124
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]125<p>OpenVG must be explicitly enabled by this option.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]126
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]127</dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]128
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]129</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]130
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]131<h2>Use EGL</h2>
132
Chia-I Wu411bba32010-06-11 12:47:14 +0800[diff] [blame]133<h3>Demos</h3>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]134
Chia-I Wu411bba32010-06-11 12:47:14 +0800[diff] [blame]135<p>There are demos for the client APIs supported by EGL. They can be found in
136mesa/demos repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]137
138<h3>Environment Variables</h3>
139
140<p>There are several environment variables that control the behavior of EGL at
141runtime</p>
142
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]143<dl>
144<dt><code>EGL_DRIVERS_PATH</code></dt>
145<dd>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800[diff] [blame]146
147<p>By default, the main library will look for drivers in the directory where
148the drivers are installed to. This variable specifies a list of
149colon-separated directories where the main library will look for drivers, in
Chia-I Wu6fd8b6a2010-02-02 16:47:53 +0800[diff] [blame]150addition to the default directory. This variable is ignored for setuid/setgid
151binaries.</p>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800[diff] [blame]152
Chia-I Wucba77862011-01-04 00:53:19 +0800[diff] [blame]153<p>This variable is usually set to test an uninstalled build. For example, one
154may set</p>
155
156<pre>
157 $ export LD_LIBRARY_PATH=$mesa/lib
158 $ export EGL_DRIVERS_PATH=$mesa/lib/egl
159</pre>
160
161<p>to test a build without installation</p>
162
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]163</dd>
Chia-I Wu5d8646c2010-02-02 15:34:55 +0800[diff] [blame]164
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]165<dt><code>EGL_DRIVER</code></dt>
166<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]167
Chia-I Wuc98ea262011-01-07 16:30:08 +0800[diff] [blame]168<p>This variable specifies a full path to or the name of an EGL driver. It
169forces the specified EGL driver to be loaded. It comes in handy when one wants
170to test a specific driver. This variable is ignored for setuid/setgid
171binaries.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]172
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]173</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]174
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]175<dt><code>EGL_PLATFORM</code></dt>
176<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]177
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]178<p>This variable specifies the native platform. The valid values are the same
179as those for <code>--with-egl-platforms</code>. When the variable is not set,
180the main library uses the first platform listed in
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]181<code>--with-egl-platforms</code> as the native platform.</p>
182
183<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
184create displays for non-native platforms. These extensions are usually used by
185applications that support non-native platforms. Setting this variable is
186probably required only for some of the demos found in mesa/demo repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]187
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]188</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]189
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]190<dt><code>EGL_LOG_LEVEL</code></dt>
191<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]192
193<p>This changes the log level of the main library and the drivers. The valid
194values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
195<code>fatal</code>.</p>
196
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]197</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]198
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]199<dt><code>EGL_SOFTWARE</code></dt>
200<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]201
202<p>For drivers that support both hardware and software rendering, setting this
203variable to true forces the use of software rendering.</p>
204
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]205</dd>
206</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]207
208<h2>EGL Drivers</h2>
209
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]210<dl>
211<dt><code>egl_dri2</code></dt>
212<dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]213
214<p>This driver supports both <code>x11</code> and <code>drm</code> platforms.
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]215It functions as a DRI driver loader. For <code>x11</code> support, it talks to
216the X server directly using (XCB-)DRI2 protocol.</p>
217
218<p>This driver can share DRI drivers with <code>libGL</code>.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]219
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]220</dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]221
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]222<dt><code>egl_gallium</code></dt>
223<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]224
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]225<p>This driver is based on Gallium3D. It supports all rendering APIs and
226hardwares supported by Gallium3D. It is the only driver that supports OpenVG.
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]227The supported platforms are X11, DRM, FBDEV, and GDI.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]228
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]229<p>This driver comes with its own hardware drivers
230(<code>pipe_&lt;hw&gt;</code>) and client API modules
231(<code>st_&lt;api&gt;</code>).</p>
232
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]233</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]234
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]235<dt><code>egl_glx</code></dt>
236<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]237
238<p>This driver provides a wrapper to GLX. It uses exclusively GLX to implement
239the EGL API. It supports both direct and indirect rendering when the GLX does.
240It is accelerated when the GLX is. As such, it cannot provide functions that
241is not available in GLX or GLX extensions.</p>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame^]242</dd>
243</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]244
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]245<h2>Packaging</h2>
246
247<p>The ABI between the main library and its drivers are not stable. Nor is
248there a plan to stabilize it at the moment. Of the EGL drivers,
249<code>egl_gallium</code> has its own hardware drivers and client API modules.
250They are considered internal to <code>egl_gallium</code> and there is also no
251stable ABI between them. These should be kept in mind when packaging for
252distribution.</p>
253
254<p>Generally, <code>egl_dri2</code> is preferred over <code>egl_gallium</code>
255when the system already has DRI drivers. As <code>egl_gallium</code> is loaded
256before <code>egl_dri2</code> when both are available, <code>egl_gallium</code>
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]257is disabled by default.</p>
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]258
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]259<h2>Developers</h2>
260
Chia-I Wu14cbf322010-01-27 23:18:22 +0800[diff] [blame]261<p>The sources of the main library and the classic drivers can be found at
Chia-I Wu3c967a92010-01-22 16:31:43 +0800[diff] [blame]262<code>src/egl/</code>. The sources of the <code>egl</code> state tracker can
Chia-I Wu14cbf322010-01-27 23:18:22 +0800[diff] [blame]263be found at <code>src/gallium/state_trackers/egl/</code>.</p>
264
265<p>The suggested way to learn to write a EGL driver is to see how other drivers
266are written. <code>egl_glx</code> should be a good reference. It works in any
267environment that has GLX support, and it is simpler than most drivers.</p>
268
269<h3>Lifetime of Display Resources</h3>
270
271<p>Contexts and surfaces are examples of display resources. They might live
272longer than the display that creates them.</p>
273
274<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
275display resources should be destroyed. Similarly, when a thread is released
276throught <code>eglReleaseThread</code>, all current display resources should be
277released. Another way to destory or release resources is through functions
278such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
279
280<p>When a resource that is current to some thread is destroyed, the resource
281should not be destroyed immediately. EGL requires the resource to live until
282it is no longer current. A driver usually calls
283<code>eglIs&lt;Resource&gt;Bound</code> to check if a resource is bound
284(current) to any thread in the destroy callbacks. If it is still bound, the
285resource is not destroyed.</p>
286
287<p>The main library will mark destroyed current resources as unlinked. In a
288driver's <code>MakeCurrent</code> callback,
289<code>eglIs&lt;Resource&gt;Linked</code> can then be called to check if a newly
290released resource is linked to a display. If it is not, the last reference to
291the resource is removed and the driver should destroy the resource. But it
292should be careful here because <code>MakeCurrent</code> might be called with an
293uninitialized display.</p>
294
295<p>This is the only mechanism provided by the main library to help manage the
296resources. The drivers are responsible to the correct behavior as defined by
297EGL.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]298
Chia-I Wu1b2b08c2010-02-05 12:44:45 +0800[diff] [blame]299<h3><code>EGL_RENDER_BUFFER</code></h3>
300
301<p>In EGL, the color buffer a context should try to render to is decided by the
302binding surface. It should try to render to the front buffer if the binding
303surface has <code>EGL_RENDER_BUFFER</code> set to
304<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
305surface with <code>EGL_RENDER_BUFFER</code> set to
306<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
307buffer. However, the context is allowed to make the final decision as to which
308color buffer it wants to or is able to render to.</p>
309
310<p>For pbuffer surfaces, the render buffer is always
311<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
312always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
313requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
314result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
315<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
316config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
317pbuffer surfaces.</p>
318
319<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
320single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
321is desirable that a driver allocates a private color buffer for each pbuffer
322surface created. If the window system the driver supports has native pbuffers,
323or if the native pixmaps have more than one color buffers, the driver should
324carefully attach the native color buffers to the EGL surfaces, re-route them if
325required.</p>
326
327<p>There is no defined behavior as to, for example, how
328<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
329now, it is desired that the draw buffer in a client API be fixed for pixmap and
330pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
331client API renders to the specified render buffer for pixmap and pbuffer
332surfaces.</p>
333
Chia-I Wue16f5772010-02-17 19:52:29 +0800[diff] [blame]334<h3><code>EGLDisplay</code> Mutex</h3>
335
336The <code>EGLDisplay</code> will be locked before calling any of the dispatch
337functions (well, except for GetProcAddress which does not take an
338<code>EGLDisplay</code>). This guarantees that the same dispatch function will
339not be called with the sample display at the same time. If a driver has access
340to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
341should as well lock the display before using it.
342
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]343</div>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]344</body>
345</html>