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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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				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 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
Andreas Boll	a73c59b	2012-09-18 19:31:28 +0200	[diff] [blame]	21	<a href="http://www.khronos.org/egl/">
Brian Paul	aeff9f9	2010-01-21 08:13:32 -0700	[diff] [blame]	22	http://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
				47	options enables the listed classic and 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
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	80	<dt><code>--with-egl-platforms</code></dt>
				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
Nathan Kidd	0691b37	2014-01-03 16:44:00 -0700	[diff] [blame]	84	separated string such as <code>--with-egl-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
				86	the main library to decide the native platform: the platform the EGL native
				87	types such as <code>EGLNativeDisplayType</code> or
				88	<code>EGLNativeWindowType</code> defined for.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	89
Chia-I Wu	e7424d7	2010-09-19 16:54:39 +0800	[diff] [blame]	90	<p>The available platforms are <code>x11</code>, <code>drm</code>,
Emil Velikov	b0a9299	2015-07-10 00:16:21 +0100	[diff] [blame]	91	<code>wayland</code>, <code>surfaceless</code>, <code>android</code>,
				92	and <code>haiku</code>. The <code>android</code> platform
Emil Velikov	55029b2	2015-03-14 22:36:29 +0000	[diff] [blame]	93	can only be built as a system component, part of AOSP, while the
Emil Velikov	b0a9299	2015-07-10 00:16:21 +0100	[diff] [blame]	94	<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>
				133	<dt><code>EGL_DRIVERS_PATH</code></dt>
				134	<dd>
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	135
				136	<p>By default, the main library will look for drivers in the directory where
				137	the drivers are installed to. This variable specifies a list of
				138	colon-separated directories where the main library will look for drivers, in
Chia-I Wu	6fd8b6a	2010-02-02 16:47:53 +0800	[diff] [blame]	139	addition to the default directory. This variable is ignored for setuid/setgid
				140	binaries.</p>
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	141
Chia-I Wu	cba7786	2011-01-04 00:53:19 +0800	[diff] [blame]	142	<p>This variable is usually set to test an uninstalled build. For example, one
				143	may set</p>
				144
				145	<pre>
				146	$ export LD_LIBRARY_PATH=$mesa/lib
				147	$ export EGL_DRIVERS_PATH=$mesa/lib/egl
				148	</pre>
				149
				150	<p>to test a build without installation</p>
				151
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	152	</dd>
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	153
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	154	<dt><code>EGL_DRIVER</code></dt>
				155	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	156
Chia-I Wu	c98ea26	2011-01-07 16:30:08 +0800	[diff] [blame]	157	<p>This variable specifies a full path to or the name of an EGL driver. It
				158	forces the specified EGL driver to be loaded. It comes in handy when one wants
				159	to test a specific driver. This variable is ignored for setuid/setgid
				160	binaries.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	161
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	162	</dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	163
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	164	<dt><code>EGL_PLATFORM</code></dt>
				165	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	166
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	167	<p>This variable specifies the native platform. The valid values are the same
				168	as those for <code>--with-egl-platforms</code>. When the variable is not set,
				169	the main library uses the first platform listed in
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	170	<code>--with-egl-platforms</code> as the native platform.</p>
				171
				172	<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
				173	create displays for non-native platforms. These extensions are usually used by
				174	applications that support non-native platforms. Setting this variable is
				175	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]	176
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	177	</dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	178
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	179	<dt><code>EGL_LOG_LEVEL</code></dt>
				180	<dd>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	181
				182	<p>This changes the log level of the main library and the drivers. The valid
				183	values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
				184	<code>fatal</code>.</p>
				185
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	186	</dd>
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	187	</dl>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	188
				189	<h2>EGL Drivers</h2>
				190
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	191	<dl>
				192	<dt><code>egl_dri2</code></dt>
				193	<dd>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	194
				195	<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]	196	It functions as a DRI driver loader. For <code>x11</code> support, it talks to
				197	the X server directly using (XCB-)DRI2 protocol.</p>
				198
				199	<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]	200
Andreas Boll	76d4f9e	2012-09-20 16:01:08 +0200	[diff] [blame]	201	</dd>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	202
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	203	<h2>Packaging</h2>
				204
				205	<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]	206	there a plan to stabilize it at the moment.</p>
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	207
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	208	<h2>Developers</h2>
				209
Jose Fonseca	5564c36	2015-03-03 16:01:22 +0000	[diff] [blame]	210	<p>The sources of the main library and drivers can be found at
				211	<code>src/egl/</code>.</p>
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	212
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	213	<h3>Lifetime of Display Resources</h3>
				214
				215	<p>Contexts and surfaces are examples of display resources. They might live
				216	longer than the display that creates them.</p>
				217
				218	<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
				219	display resources should be destroyed. Similarly, when a thread is released
Nathan Kidd	0691b37	2014-01-03 16:44:00 -0700	[diff] [blame]	220	through <code>eglReleaseThread</code>, all current display resources should be
				221	released. Another way to destroy or release resources is through functions
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	222	such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
				223
				224	<p>When a resource that is current to some thread is destroyed, the resource
				225	should not be destroyed immediately. EGL requires the resource to live until
				226	it is no longer current. A driver usually calls
				227	<code>eglIs<Resource>Bound</code> to check if a resource is bound
				228	(current) to any thread in the destroy callbacks. If it is still bound, the
				229	resource is not destroyed.</p>
				230
				231	<p>The main library will mark destroyed current resources as unlinked. In a
				232	driver's <code>MakeCurrent</code> callback,
				233	<code>eglIs<Resource>Linked</code> can then be called to check if a newly
				234	released resource is linked to a display. If it is not, the last reference to
				235	the resource is removed and the driver should destroy the resource. But it
				236	should be careful here because <code>MakeCurrent</code> might be called with an
				237	uninitialized display.</p>
				238
				239	<p>This is the only mechanism provided by the main library to help manage the
				240	resources. The drivers are responsible to the correct behavior as defined by
				241	EGL.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	242
Chia-I Wu	1b2b08c	2010-02-05 12:44:45 +0800	[diff] [blame]	243	<h3><code>EGL_RENDER_BUFFER</code></h3>
				244
				245	<p>In EGL, the color buffer a context should try to render to is decided by the
				246	binding surface. It should try to render to the front buffer if the binding
				247	surface has <code>EGL_RENDER_BUFFER</code> set to
				248	<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
				249	surface with <code>EGL_RENDER_BUFFER</code> set to
				250	<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
				251	buffer. However, the context is allowed to make the final decision as to which
				252	color buffer it wants to or is able to render to.</p>
				253
				254	<p>For pbuffer surfaces, the render buffer is always
				255	<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
				256	always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
				257	requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
				258	result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
				259	<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
				260	config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
				261	pbuffer surfaces.</p>
				262
				263	<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
				264	single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
				265	is desirable that a driver allocates a private color buffer for each pbuffer
				266	surface created. If the window system the driver supports has native pbuffers,
				267	or if the native pixmaps have more than one color buffers, the driver should
				268	carefully attach the native color buffers to the EGL surfaces, re-route them if
				269	required.</p>
				270
				271	<p>There is no defined behavior as to, for example, how
				272	<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
				273	now, it is desired that the draw buffer in a client API be fixed for pixmap and
				274	pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
				275	client API renders to the specified render buffer for pixmap and pbuffer
				276	surfaces.</p>
				277
Chia-I Wu	e16f577	2010-02-17 19:52:29 +0800	[diff] [blame]	278	<h3><code>EGLDisplay</code> Mutex</h3>
				279
				280	The <code>EGLDisplay</code> will be locked before calling any of the dispatch
				281	functions (well, except for GetProcAddress which does not take an
				282	<code>EGLDisplay</code>). This guarantees that the same dispatch function will
				283	not be called with the sample display at the same time. If a driver has access
				284	to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
				285	should as well lock the display before using it.
				286
Andreas Boll	b5da52a	2012-09-18 18:57:02 +0200	[diff] [blame]	287	</div>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	288	</body>
				289	</html>