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gerrit-public.fairphone.software / platform / external / mesa3d / 0ee366960c32067b528077c49362c468364d0206 / . / 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">
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Erik Faye-Lund6e0e5502019-05-06 13:13:11 +0200[diff] [blame]5 <title>EGL</title>
Andreas Bollecd5c7c2012-06-12 09:05:03 +0200[diff] [blame]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">
Erik Faye-Lundecdab0d2019-05-06 13:26:47 +0200[diff] [blame]11 The Mesa 3D Graphics Library
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]12</div>
13
14<iframe src="contents.html"></iframe>
15<div class="content">
16
Erik Faye-Lund6e0e5502019-05-06 13:13:11 +0200[diff] [blame]17<h1>EGL</h1>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]18
19<p>The current version of EGL in Mesa implements EGL 1.4. More information
20about EGL can be found at
Eric Engestrom30cf9ff2017-02-09 02:10:17 +0000[diff] [blame]21<a href="https://www.khronos.org/egl/">
22https://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>
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]36<p>Configure your build 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>
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]40$ meson configure \
41 -D egl=true \
42 -D gles1=true \
43 -D gles2=true \
44 -D dri-drivers=... \
45 -D gallium-drivers=...
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]46</pre>
47
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]48<p>The main library and OpenGL is enabled by default. The first two options
49above enables <a href="opengles.html">OpenGL ES 1.x and 2.x</a>. The last two
Eric Engestrom077879c2017-02-26 23:58:03 +0000[diff] [blame]50options enables the listed classic and Gallium drivers respectively.</p>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]51
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]52</li>
53
54<li>Build and install Mesa as usual.</li>
55</ol>
56
57<p>In the given example, it will build and install <code>libEGL</code>,
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]58<code>libGL</code>, <code>libGLESv1_CM</code>, <code>libGLESv2</code>, and one
59or more EGL drivers.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]60
61<h3>Configure Options</h3>
62
63<p>There are several options that control the build of EGL at configuration
64time</p>
65
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]66<dl>
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]67<dt><code>-D egl=true</code></dt>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]68<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]69
70<p>By default, EGL is enabled. When disabled, the main library and the drivers
71will not be built.</p>
72
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]73</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]74
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]75<dt><code>-D platforms=...</code></dt>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]76<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]77
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]78<p>List the platforms (window systems) to support. Its argument is a comma
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]79separated string such as <code>-D platforms=x11,drm</code>. It decides
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]80the platforms a driver may support. The first listed platform is also used by
Emil Velikov73682f82016-11-25 18:34:03 +0000[diff] [blame]81the main library to decide the native platform.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]82
Chia-I Wue7424d72010-09-19 16:54:39 +0800[diff] [blame]83<p>The available platforms are <code>x11</code>, <code>drm</code>,
Emil Velikovb0a92992015-07-10 00:16:21 +0100[diff] [blame]84<code>wayland</code>, <code>surfaceless</code>, <code>android</code>,
Nicolas Boichata9b2b5e2016-05-24 13:55:20 +0800[diff] [blame]85and <code>haiku</code>.
86The <code>android</code> platform can either be built as a system
87component, part of AOSP, using <code>Android.mk</code> files, or
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]88cross-compiled using appropriate options.
Eric Engestromfe73c742019-04-24 13:19:24 +0100[diff] [blame]89The <code>haiku</code> platform can only be built with SCons or Meson.
Emil Velikov55029b22015-03-14 22:36:29 +0000[diff] [blame]90Unless for special needs, the build system should
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]91select the right platforms automatically.</p>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]92
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]93</dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]94
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]95<dt><code>-D gles1=true</code></dt>
96<dt><code>-D gles2=true</code></dt>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]97<dd>
Chia-I Wu2e3c4e42010-05-07 14:13:08 +0800[diff] [blame]98
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]99<p>These options enable OpenGL ES support in OpenGL. The result is one big
100internal library that supports multiple APIs.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]101
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]102</dd>
Chia-I Wua1306f42010-01-22 15:51:51 +0800[diff] [blame]103
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]104<dt><code>-D shared-glapi=true</code></dt>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]105<dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]106
Chia-I Wu8eea0502011-06-20 11:14:56 +0900[diff] [blame]107<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
108This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
109is required if applications mix OpenGL and OpenGL ES.</p>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]110
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]111</dd>
Chia-I Wuc6320c52010-10-28 17:25:07 +0800[diff] [blame]112
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]113</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]114
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]115<h2>Use EGL</h2>
116
Chia-I Wu411bba32010-06-11 12:47:14 +0800[diff] [blame]117<h3>Demos</h3>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]118
Chia-I Wu411bba32010-06-11 12:47:14 +0800[diff] [blame]119<p>There are demos for the client APIs supported by EGL. They can be found in
120mesa/demos repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]121
122<h3>Environment Variables</h3>
123
124<p>There are several environment variables that control the behavior of EGL at
125runtime</p>
126
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]127<dl>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]128<dt><code>EGL_PLATFORM</code></dt>
129<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]130
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]131<p>This variable specifies the native platform. The valid values are the same
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]132as those for <code>-D platforms=...</code>. When the variable is not set,
Chia-I Wub365b152010-07-03 17:18:40 +0800[diff] [blame]133the main library uses the first platform listed in
Eric Engestrom46d68832019-04-24 13:16:57 +0100[diff] [blame]134<code>-D platforms=...</code> as the native platform.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]135
136<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
137create displays for non-native platforms. These extensions are usually used by
138applications that support non-native platforms. Setting this variable is
139probably required only for some of the demos found in mesa/demo repository.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]140
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]141</dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]142
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]143<dt><code>EGL_LOG_LEVEL</code></dt>
144<dd>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]145
146<p>This changes the log level of the main library and the drivers. The valid
147values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
148<code>fatal</code>.</p>
149
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]150</dd>
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]151</dl>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]152
153<h2>EGL Drivers</h2>
154
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]155<dl>
156<dt><code>egl_dri2</code></dt>
157<dd>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]158
159<p>This driver supports both <code>x11</code> and <code>drm</code> platforms.
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]160It functions as a DRI driver loader. For <code>x11</code> support, it talks to
161the X server directly using (XCB-)DRI2 protocol.</p>
162
163<p>This driver can share DRI drivers with <code>libGL</code>.</p>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]164
Andreas Boll76d4f9e2012-09-20 16:01:08 +0200[diff] [blame]165</dd>
Eric Engestrom09a6cb72018-05-23 12:46:44 +0100[diff] [blame]166</dl>
Chia-I Wu3418f742010-11-02 23:55:56 +0800[diff] [blame]167
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]168<h2>Packaging</h2>
169
170<p>The ABI between the main library and its drivers are not stable. Nor is
Jose Fonseca5564c362015-03-03 16:01:22 +0000[diff] [blame]171there a plan to stabilize it at the moment.</p>
Chia-I Wu65e8f812010-12-25 02:45:13 +0800[diff] [blame]172
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]173<h2>Developers</h2>
174
Jose Fonseca5564c362015-03-03 16:01:22 +0000[diff] [blame]175<p>The sources of the main library and drivers can be found at
176<code>src/egl/</code>.</p>
Chia-I Wu14cbf322010-01-27 23:18:22 +0800[diff] [blame]177
Chia-I Wu14cbf322010-01-27 23:18:22 +0800[diff] [blame]178<h3>Lifetime of Display Resources</h3>
179
180<p>Contexts and surfaces are examples of display resources. They might live
181longer than the display that creates them.</p>
182
183<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
184display resources should be destroyed. Similarly, when a thread is released
Nathan Kidd0691b372014-01-03 16:44:00 -0700[diff] [blame]185through <code>eglReleaseThread</code>, all current display resources should be
186released. Another way to destroy or release resources is through functions
Chia-I Wu14cbf322010-01-27 23:18:22 +0800[diff] [blame]187such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
188
189<p>When a resource that is current to some thread is destroyed, the resource
190should not be destroyed immediately. EGL requires the resource to live until
191it is no longer current. A driver usually calls
192<code>eglIs&lt;Resource&gt;Bound</code> to check if a resource is bound
193(current) to any thread in the destroy callbacks. If it is still bound, the
194resource is not destroyed.</p>
195
196<p>The main library will mark destroyed current resources as unlinked. In a
197driver's <code>MakeCurrent</code> callback,
198<code>eglIs&lt;Resource&gt;Linked</code> can then be called to check if a newly
199released resource is linked to a display. If it is not, the last reference to
200the resource is removed and the driver should destroy the resource. But it
201should be careful here because <code>MakeCurrent</code> might be called with an
202uninitialized display.</p>
203
204<p>This is the only mechanism provided by the main library to help manage the
205resources. The drivers are responsible to the correct behavior as defined by
206EGL.</p>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]207
Chia-I Wu1b2b08c2010-02-05 12:44:45 +0800[diff] [blame]208<h3><code>EGL_RENDER_BUFFER</code></h3>
209
210<p>In EGL, the color buffer a context should try to render to is decided by the
211binding surface. It should try to render to the front buffer if the binding
212surface has <code>EGL_RENDER_BUFFER</code> set to
213<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
214surface with <code>EGL_RENDER_BUFFER</code> set to
215<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
216buffer. However, the context is allowed to make the final decision as to which
217color buffer it wants to or is able to render to.</p>
218
219<p>For pbuffer surfaces, the render buffer is always
220<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
221always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
222requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
223result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
224<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
225config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
226pbuffer surfaces.</p>
227
228<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
229single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
230is desirable that a driver allocates a private color buffer for each pbuffer
231surface created. If the window system the driver supports has native pbuffers,
232or if the native pixmaps have more than one color buffers, the driver should
233carefully attach the native color buffers to the EGL surfaces, re-route them if
234required.</p>
235
236<p>There is no defined behavior as to, for example, how
237<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
238now, it is desired that the draw buffer in a client API be fixed for pixmap and
239pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
240client API renders to the specified render buffer for pixmap and pbuffer
241surfaces.</p>
242
Chia-I Wue16f5772010-02-17 19:52:29 +0800[diff] [blame]243<h3><code>EGLDisplay</code> Mutex</h3>
244
245The <code>EGLDisplay</code> will be locked before calling any of the dispatch
246functions (well, except for GetProcAddress which does not take an
247<code>EGLDisplay</code>). This guarantees that the same dispatch function will
248not be called with the sample display at the same time. If a driver has access
249to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
250should as well lock the display before using it.
251
Andreas Bollb5da52a2012-09-18 18:57:02 +0200[diff] [blame]252</div>
Chia-I Wuada46052010-01-21 15:29:14 +0800[diff] [blame]253</body>
254</html>