Blame - docs/egl.html - platform/external/mesa3d

blob: a77c12fe2de8e23a5b3d02e7f3750ebf99654323 [file] [log] [blame]

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">
				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 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
				63	<ul>
				64	<li><code>--enable-egl</code>
				65
				66	<p>By default, EGL is enabled. When disabled, the main library and the drivers
				67	will not be built.</p>
				68
				69	</li>
				70
Chia-I Wu	a6342af	2010-01-26 10:54:45 +0800	[diff] [blame]	71	<li><code>--with-egl-driver-dir</code>
				72
				73	<p>The directory EGL drivers should be installed to. If not specified, EGL
				74	drivers will be installed to <code>${libdir}/egl</code>.</p>
				75
				76	</li>
				77
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	78	<li><code>--enable-gallium-egl</code>
				79
				80	<p>Enable the optional <code>egl_gallium</code> driver.</p>
				81
				82	</li>
				83
Chia-I Wu	da39d5d	2010-06-17 16:07:46 +0800	[diff] [blame]	84	<li><code>--with-egl-platforms</code>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	85
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	86	<p>List the platforms (window systems) to support. Its argument is a comma
Chia-I Wu	e7424d7	2010-09-19 16:54:39 +0800	[diff] [blame]	87	seprated 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]	88	the platforms a driver may support. The first listed platform is also used by
				89	the main library to decide the native platform: the platform the EGL native
				90	types such as <code>EGLNativeDisplayType</code> or
				91	<code>EGLNativeWindowType</code> defined for.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	92
Chia-I Wu	e7424d7	2010-09-19 16:54:39 +0800	[diff] [blame]	93	<p>The available platforms are <code>x11</code>, <code>drm</code>,
Chia-I Wu	da39d5d	2010-06-17 16:07:46 +0800	[diff] [blame]	94	<code>fbdev</code>, and <code>gdi</code>. The <code>gdi</code> platform can
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	95	only be built with SCons. Unless for special needs, the build system should
				96	select the right platforms automatically.</p>
Chia-I Wu	2e3c4e4	2010-05-07 14:13:08 +0800	[diff] [blame]	97
				98	</li>
				99
				100	<li><code>--enable-gles1</code> and <code>--enable-gles2</code>
				101
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	102	<p>These options enable OpenGL ES support in OpenGL. The result is one big
				103	internal library that supports multiple APIs.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	104
				105	</li>
Chia-I Wu	a1306f4	2010-01-22 15:51:51 +0800	[diff] [blame]	106
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	107	<li><code>--enable-shared-glapi</code>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	108
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	109	<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
				110	This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
				111	is required if applications mix OpenGL and OpenGL ES.</p>
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	112
				113	</li>
				114
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	115	<li><code>--enable-openvg</code>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	116
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	117	<p>OpenVG must be explicitly enabled by this option.</p>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	118
				119	</li>
				120
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	121	</ul>
				122
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	123	<h2>Use EGL</h2>
				124
Chia-I Wu	411bba3	2010-06-11 12:47:14 +0800	[diff] [blame]	125	<h3>Demos</h3>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	126
Chia-I Wu	411bba3	2010-06-11 12:47:14 +0800	[diff] [blame]	127	<p>There are demos for the client APIs supported by EGL. They can be found in
				128	mesa/demos repository.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	129
				130	<h3>Environment Variables</h3>
				131
				132	<p>There are several environment variables that control the behavior of EGL at
				133	runtime</p>
				134
				135	<ul>
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	136	<li><code>EGL_DRIVERS_PATH</code>
				137
				138	<p>By default, the main library will look for drivers in the directory where
				139	the drivers are installed to. This variable specifies a list of
				140	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]	141	addition to the default directory. This variable is ignored for setuid/setgid
				142	binaries.</p>
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	143
Chia-I Wu	cba7786	2011-01-04 00:53:19 +0800	[diff] [blame]	144	<p>This variable is usually set to test an uninstalled build. For example, one
				145	may set</p>
				146
				147	<pre>
				148	$ export LD_LIBRARY_PATH=$mesa/lib
				149	$ export EGL_DRIVERS_PATH=$mesa/lib/egl
				150	</pre>
				151
				152	<p>to test a build without installation</p>
				153
Chia-I Wu	5d8646c	2010-02-02 15:34:55 +0800	[diff] [blame]	154	</li>
				155
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	156	<li><code>EGL_DRIVER</code>
				157
Chia-I Wu	c98ea26	2011-01-07 16:30:08 +0800	[diff] [blame]	158	<p>This variable specifies a full path to or the name of an EGL driver. It
				159	forces the specified EGL driver to be loaded. It comes in handy when one wants
				160	to test a specific driver. This variable is ignored for setuid/setgid
				161	binaries.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	162
				163	</li>
				164
Chia-I Wu	da39d5d	2010-06-17 16:07:46 +0800	[diff] [blame]	165	<li><code>EGL_PLATFORM</code>
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
				177	</li>
				178
				179	<li><code>EGL_LOG_LEVEL</code>
				180
				181	<p>This changes the log level of the main library and the drivers. The valid
				182	values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
				183	<code>fatal</code>.</p>
				184
				185	</li>
				186
				187	<li><code>EGL_SOFTWARE</code>
				188
				189	<p>For drivers that support both hardware and software rendering, setting this
				190	variable to true forces the use of software rendering.</p>
				191
				192	</li>
				193	</ul>
				194
				195	<h2>EGL Drivers</h2>
				196
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	197	<ul>
Chia-I Wu	3418f74	2010-11-02 23:55:56 +0800	[diff] [blame]	198	<li><code>egl_dri2</code>
				199
				200	<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]	201	It functions as a DRI driver loader. For <code>x11</code> support, it talks to
				202	the X server directly using (XCB-)DRI2 protocol.</p>
				203
				204	<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]	205
				206	</li>
				207
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	208	<li><code>egl_gallium</code>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	209
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	210	<p>This driver is based on Gallium3D. It supports all rendering APIs and
				211	hardwares supported by Gallium3D. It is the only driver that supports OpenVG.
Chia-I Wu	c6320c5	2010-10-28 17:25:07 +0800	[diff] [blame]	212	The supported platforms are X11, DRM, FBDEV, and GDI.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	213
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	214	<p>This driver comes with its own hardware drivers
				215	(<code>pipe_<hw></code>) and client API modules
				216	(<code>st_<api></code>).</p>
				217
Chia-I Wu	b365b15	2010-07-03 17:18:40 +0800	[diff] [blame]	218	</li>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	219
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	220	<li><code>egl_glx</code>
				221
				222	<p>This driver provides a wrapper to GLX. It uses exclusively GLX to implement
				223	the EGL API. It supports both direct and indirect rendering when the GLX does.
				224	It is accelerated when the GLX is. As such, it cannot provide functions that
				225	is not available in GLX or GLX extensions.</p>
				226	</li>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	227	</ul>
				228
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	229	<h2>Packaging</h2>
				230
				231	<p>The ABI between the main library and its drivers are not stable. Nor is
				232	there a plan to stabilize it at the moment. Of the EGL drivers,
				233	<code>egl_gallium</code> has its own hardware drivers and client API modules.
				234	They are considered internal to <code>egl_gallium</code> and there is also no
				235	stable ABI between them. These should be kept in mind when packaging for
				236	distribution.</p>
				237
				238	<p>Generally, <code>egl_dri2</code> is preferred over <code>egl_gallium</code>
				239	when the system already has DRI drivers. As <code>egl_gallium</code> is loaded
				240	before <code>egl_dri2</code> when both are available, <code>egl_gallium</code>
Chia-I Wu	8eea050	2011-06-20 11:14:56 +0900	[diff] [blame]	241	is disabled by default.</p>
Chia-I Wu	65e8f81	2010-12-25 02:45:13 +0800	[diff] [blame]	242
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	243	<h2>Developers</h2>
				244
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	245	<p>The sources of the main library and the classic drivers can be found at
Chia-I Wu	3c967a9	2010-01-22 16:31:43 +0800	[diff] [blame]	246	<code>src/egl/</code>. The sources of the <code>egl</code> state tracker can
Chia-I Wu	14cbf32	2010-01-27 23:18:22 +0800	[diff] [blame]	247	be found at <code>src/gallium/state_trackers/egl/</code>.</p>
				248
				249	<p>The suggested way to learn to write a EGL driver is to see how other drivers
				250	are written. <code>egl_glx</code> should be a good reference. It works in any
				251	environment that has GLX support, and it is simpler than most drivers.</p>
				252
				253	<h3>Lifetime of Display Resources</h3>
				254
				255	<p>Contexts and surfaces are examples of display resources. They might live
				256	longer than the display that creates them.</p>
				257
				258	<p>In EGL, when a display is terminated through <code>eglTerminate</code>, all
				259	display resources should be destroyed. Similarly, when a thread is released
				260	throught <code>eglReleaseThread</code>, all current display resources should be
				261	released. Another way to destory or release resources is through functions
				262	such as <code>eglDestroySurface</code> or <code>eglMakeCurrent</code>.</p>
				263
				264	<p>When a resource that is current to some thread is destroyed, the resource
				265	should not be destroyed immediately. EGL requires the resource to live until
				266	it is no longer current. A driver usually calls
				267	<code>eglIs<Resource>Bound</code> to check if a resource is bound
				268	(current) to any thread in the destroy callbacks. If it is still bound, the
				269	resource is not destroyed.</p>
				270
				271	<p>The main library will mark destroyed current resources as unlinked. In a
				272	driver's <code>MakeCurrent</code> callback,
				273	<code>eglIs<Resource>Linked</code> can then be called to check if a newly
				274	released resource is linked to a display. If it is not, the last reference to
				275	the resource is removed and the driver should destroy the resource. But it
				276	should be careful here because <code>MakeCurrent</code> might be called with an
				277	uninitialized display.</p>
				278
				279	<p>This is the only mechanism provided by the main library to help manage the
				280	resources. The drivers are responsible to the correct behavior as defined by
				281	EGL.</p>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	282
Chia-I Wu	1b2b08c	2010-02-05 12:44:45 +0800	[diff] [blame]	283	<h3><code>EGL_RENDER_BUFFER</code></h3>
				284
				285	<p>In EGL, the color buffer a context should try to render to is decided by the
				286	binding surface. It should try to render to the front buffer if the binding
				287	surface has <code>EGL_RENDER_BUFFER</code> set to
				288	<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
				289	surface with <code>EGL_RENDER_BUFFER</code> set to
				290	<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
				291	buffer. However, the context is allowed to make the final decision as to which
				292	color buffer it wants to or is able to render to.</p>
				293
				294	<p>For pbuffer surfaces, the render buffer is always
				295	<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
				296	always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
				297	requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
				298	result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
				299	<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
				300	config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
				301	pbuffer surfaces.</p>
				302
				303	<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
				304	single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
				305	is desirable that a driver allocates a private color buffer for each pbuffer
				306	surface created. If the window system the driver supports has native pbuffers,
				307	or if the native pixmaps have more than one color buffers, the driver should
				308	carefully attach the native color buffers to the EGL surfaces, re-route them if
				309	required.</p>
				310
				311	<p>There is no defined behavior as to, for example, how
				312	<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
				313	now, it is desired that the draw buffer in a client API be fixed for pixmap and
				314	pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
				315	client API renders to the specified render buffer for pixmap and pbuffer
				316	surfaces.</p>
				317
Chia-I Wu	e16f577	2010-02-17 19:52:29 +0800	[diff] [blame]	318	<h3><code>EGLDisplay</code> Mutex</h3>
				319
				320	The <code>EGLDisplay</code> will be locked before calling any of the dispatch
				321	functions (well, except for GetProcAddress which does not take an
				322	<code>EGLDisplay</code>). This guarantees that the same dispatch function will
				323	not be called with the sample display at the same time. If a driver has access
				324	to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
				325	should as well lock the display before using it.
				326
Andreas Boll	b5da52a	2012-09-18 18:57:02 +0200	[diff] [blame]	327	</div>
Chia-I Wu	ada4605	2010-01-21 15:29:14 +0800	[diff] [blame]	328	</body>
				329	</html>