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Andreas Boll	ecd5c7c	2012-06-12 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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				5	<title>Mesa EGL</title>
				6	<link rel="stylesheet" type="text/css" href="mesa.css">
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Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	8	<body>
				9
Andreas Boll	b5da52a	2012-09-18 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 Wu	ada4605	2010-01-21 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
				20	about EGL can be found at
Eric Engestrom	30cf9ff	2017-02-09 02:10:17 +0000	[diff] [blame]	21	<a href="https://www.khronos.org/egl/">
				22	https://www.khronos.org/egl/</a>.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	23
				24	<p>The Mesa's implementation of EGL uses a driver architecture. The main
				25	library (<code>libEGL</code>) is window system neutral. It provides the EGL
				26	API entry points and helper functions for use by the drivers. Drivers are
				27	dynamically loaded by the main library and most of the EGL API calls are
				28	directly dispatched to the drivers.</p>
				29
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	30	<p>The driver in use decides the window system to support.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	31
				32	<h2>Build EGL</h2>
				33
				34	<ol>
				35	<li>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	36	<p>Run <code>configure</code> with the desired client APIs and enable
				37	the driver for your hardware. For example</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	38
				39	<pre>
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	40	$ ./configure --enable-gles1 --enable-gles2 \
				41	--with-dri-drivers=... \
				42	--with-gallium-drivers=...
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	43	</pre>
				44
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	45	<p>The main library and OpenGL is enabled by default. The first two options
				46	above enables <a href="opengles.html">OpenGL ES 1.x and 2.x</a>. The last two
Eric Engestrom	077879c	2017-02-26 23:58:03 +0000	[diff] [blame]	47	options enables the listed classic and Gallium drivers respectively.</p>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	48
Chia-I Wu	ada4605	2010-01-21 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 Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	55	<code>libGL</code>, <code>libGLESv1_CM</code>, <code>libGLESv2</code>, and one
				56	or more EGL drivers.</p>
Chia-I Wu	ada4605	2010-01-21 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
				61	time</p>
				62
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	63	<dl>
				64	<dt><code>--enable-egl</code></dt>
				65	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	66
				67	<p>By default, EGL is enabled. When disabled, the main library and the drivers
				68	will not be built.</p>
				69
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	70	</dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	71
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	72	<dt><code>--with-egl-driver-dir</code></dt>
				73	<dd>
Chia-I Wu	a6342af	2010-01-26 10:54:45 +0800	[diff] [blame]	74
				75	<p>The directory EGL drivers should be installed to. If not specified, EGL
				76	drivers will be installed to <code>${libdir}/egl</code>.</p>
				77
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	78	</dd>
Chia-I Wu	a6342af	2010-01-26 10:54:45 +0800	[diff] [blame]	79
Emil Velikov	73682f8	2016-11-25 18:34:03 +0000	[diff] [blame]	80	<dt><code>--with-platforms</code></dt>
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	81	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	82
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	83	<p>List the platforms (window systems) to support. Its argument is a comma
Emil Velikov	73682f8	2016-11-25 18:34:03 +0000	[diff] [blame]	84	separated string such as <code>--with-platforms=x11,drm</code>. It decides
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	85	the platforms a driver may support. The first listed platform is also used by
Emil Velikov	73682f8	2016-11-25 18:34:03 +0000	[diff] [blame]	86	the main library to decide the native platform.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	87
Chia-I Wu	e7424d7	2010-09-19 16:54:39 +0800	[diff] [blame]	88	<p>The available platforms are <code>x11</code>, <code>drm</code>,
Emil Velikov	b0a9299	2015-07-10 00:16:21 +0100	[diff] [blame]	89	<code>wayland</code>, <code>surfaceless</code>, <code>android</code>,
Nicolas Boichat	a9b2b5e	2016-05-24 13:55:20 +0800	[diff] [blame]	90	and <code>haiku</code>.
				91	The <code>android</code> platform can either be built as a system
				92	component, part of AOSP, using <code>Android.mk</code> files, or
				93	cross-compiled using appropriate <code>configure</code> options.
				94	The <code>haiku</code> platform can only be built with SCons.
Emil Velikov	55029b2	2015-03-14 22:36:29 +0000	[diff] [blame]	95	Unless for special needs, the build system should
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	96	select the right platforms automatically.</p>
Chia-I Wu	2e3c4e4	2010-05-07 14:13:08 +0800	[diff] [blame]	97
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	98	</dd>
Chia-I Wu	2e3c4e4	2010-05-07 14:13:08 +0800	[diff] [blame]	99
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	100	<dt><code>--enable-gles1</code></dt>
				101	<dt><code>--enable-gles2</code></dt>
				102	<dd>
Chia-I Wu	2e3c4e4	2010-05-07 14:13:08 +0800	[diff] [blame]	103
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	104	<p>These options enable OpenGL ES support in OpenGL. The result is one big
				105	internal library that supports multiple APIs.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	106
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	107	</dd>
Chia-I Wu	a1306f4	2010-01-22 15:51:51 +0800	[diff] [blame]	108
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	109	<dt><code>--enable-shared-glapi</code></dt>
				110	<dd>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	111
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	112	<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
				113	This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
				114	is required if applications mix OpenGL and OpenGL ES.</p>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	115
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	116	</dd>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	117
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	118	</dl>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	119
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	120	<h2>Use EGL</h2>
				121
Chia-I Wu	411bba3	2010-06-11 12:47:14 +0800	[diff] [blame]	122	<h3>Demos</h3>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	123
Chia-I Wu	411bba3	2010-06-11 12:47:14 +0800	[diff] [blame]	124	<p>There are demos for the client APIs supported by EGL. They can be found in
				125	mesa/demos repository.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	126
				127	<h3>Environment Variables</h3>
				128
				129	<p>There are several environment variables that control the behavior of EGL at
				130	runtime</p>
				131
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	132	<dl>
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	133	<dt><code>EGL_PLATFORM</code></dt>
				134	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	135
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	136	<p>This variable specifies the native platform. The valid values are the same
Emil Velikov	73682f8	2016-11-25 18:34:03 +0000	[diff] [blame]	137	as those for <code>--with-platforms</code>. When the variable is not set,
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	138	the main library uses the first platform listed in
Emil Velikov	73682f8	2016-11-25 18:34:03 +0000	[diff] [blame]	139	<code>--with-platforms</code> as the native platform.</p>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	140
				141	<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
				142	create displays for non-native platforms. These extensions are usually used by
				143	applications that support non-native platforms. Setting this variable is
				144	probably required only for some of the demos found in mesa/demo repository.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	145
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	146	</dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	147
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	148	<dt><code>EGL_LOG_LEVEL</code></dt>
				149	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	150
				151	<p>This changes the log level of the main library and the drivers. The valid
				152	values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
				153	<code>fatal</code>.</p>
				154
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	155	</dd>
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	156	</dl>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	157
				158	<h2>EGL Drivers</h2>
				159
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	160	<dl>
				161	<dt><code>egl_dri2</code></dt>
				162	<dd>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	163
				164	<p>This driver supports both <code>x11</code> and <code>drm</code> platforms.
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	165	It functions as a DRI driver loader. For <code>x11</code> support, it talks to
				166	the X server directly using (XCB-)DRI2 protocol.</p>
				167
				168	<p>This driver can share DRI drivers with <code>libGL</code>.</p>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	169
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	170	</dd>
Eric Engestrom	09a6cb7	2018-05-23 12:46:44 +0100	[diff] [blame^]	171	</dl>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	172
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	173	<h2>Packaging</h2>
				174
				175	<p>The ABI between the main library and its drivers are not stable. Nor is
Jose Fonseca	5564c36	2015-03-03 16:01:22 +0000	[diff] [blame]	176	there a plan to stabilize it at the moment.</p>
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	177
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	178	<h2>Developers</h2>
				179
Jose Fonseca	5564c36	2015-03-03 16:01:22 +0000	[diff] [blame]	180	<p>The sources of the main library and drivers can be found at
				181	<code>src/egl/</code>.</p>
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	182
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	183	<h3>Lifetime of Display Resources</h3>
				184
				185	<p>Contexts and surfaces are examples of display resources. They might live
				186	longer than the display that creates them.</p>
				187
				188	<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
				189	display resources should be destroyed. Similarly, when a thread is released
Nathan Kidd	0691b37	2014-01-03 16:44:00 -0700	[diff] [blame]	190	through <code>eglReleaseThread</code>, all current display resources should be
				191	released. Another way to destroy or release resources is through functions
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	192	such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
				193
				194	<p>When a resource that is current to some thread is destroyed, the resource
				195	should not be destroyed immediately. EGL requires the resource to live until
				196	it is no longer current. A driver usually calls
				197	<code>eglIs<Resource>Bound</code> to check if a resource is bound
				198	(current) to any thread in the destroy callbacks. If it is still bound, the
				199	resource is not destroyed.</p>
				200
				201	<p>The main library will mark destroyed current resources as unlinked. In a
				202	driver's <code>MakeCurrent</code> callback,
				203	<code>eglIs<Resource>Linked</code> can then be called to check if a newly
				204	released resource is linked to a display. If it is not, the last reference to
				205	the resource is removed and the driver should destroy the resource. But it
				206	should be careful here because <code>MakeCurrent</code> might be called with an
				207	uninitialized display.</p>
				208
				209	<p>This is the only mechanism provided by the main library to help manage the
				210	resources. The drivers are responsible to the correct behavior as defined by
				211	EGL.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	212
Chia-I Wu	1b2b08c	2010-02-05 12:44:45 +0800	[diff] [blame]	213	<h3><code>EGL_RENDER_BUFFER</code></h3>
				214
				215	<p>In EGL, the color buffer a context should try to render to is decided by the
				216	binding surface. It should try to render to the front buffer if the binding
				217	surface has <code>EGL_RENDER_BUFFER</code> set to
				218	<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
				219	surface with <code>EGL_RENDER_BUFFER</code> set to
				220	<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
				221	buffer. However, the context is allowed to make the final decision as to which
				222	color buffer it wants to or is able to render to.</p>
				223
				224	<p>For pbuffer surfaces, the render buffer is always
				225	<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
				226	always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
				227	requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
				228	result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
				229	<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
				230	config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
				231	pbuffer surfaces.</p>
				232
				233	<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
				234	single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
				235	is desirable that a driver allocates a private color buffer for each pbuffer
				236	surface created. If the window system the driver supports has native pbuffers,
				237	or if the native pixmaps have more than one color buffers, the driver should
				238	carefully attach the native color buffers to the EGL surfaces, re-route them if
				239	required.</p>
				240
				241	<p>There is no defined behavior as to, for example, how
				242	<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
				243	now, it is desired that the draw buffer in a client API be fixed for pixmap and
				244	pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
				245	client API renders to the specified render buffer for pixmap and pbuffer
				246	surfaces.</p>
				247
Chia-I Wu	e16f577	2010-02-17 19:52:29 +0800	[diff] [blame]	248	<h3><code>EGLDisplay</code> Mutex</h3>
				249
				250	The <code>EGLDisplay</code> will be locked before calling any of the dispatch
				251	functions (well, except for GetProcAddress which does not take an
				252	<code>EGLDisplay</code>). This guarantees that the same dispatch function will
				253	not be called with the sample display at the same time. If a driver has access
				254	to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
				255	should as well lock the display before using it.
				256
Andreas Boll	b5da52a	2012-09-18 18:57:02 +0200	[diff] [blame]	257	</div>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	258	</body>
				259	</html>