-<html>
-
-<title>Mesa EGL</title>
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
+<html lang="en">
+<head>
+ <meta http-equiv="content-type" content="text/html; charset=utf-8">
+ <title>Mesa EGL</title>
+ <link rel="stylesheet" type="text/css" href="mesa.css">
+</head>
+<body>
-<head><link rel="stylesheet" type="text/css" href="mesa.css"></head>
+<div class="header">
+ <h1>The Mesa 3D Graphics Library</h1>
+</div>
-<body>
+<iframe src="contents.html"></iframe>
+<div class="content">
<h1>Mesa EGL</h1>
<p>The current version of EGL in Mesa implements EGL 1.4. More information
about EGL can be found at
-<a href="http://www.khronos.org/egl/" target="_parent">
+<a href="http://www.khronos.org/egl/">
http://www.khronos.org/egl/</a>.</p>
<p>The Mesa's implementation of EGL uses a driver architecture. The main
dynamically loaded by the main library and most of the EGL API calls are
directly dispatched to the drivers.</p>
-<p>The driver in use decides the window system to support. For drivers that
-support hardware rendering, there are usually multiple drivers supporting the
-same window system. Each one of of them supports a certain range of graphics
-cards.</p>
+<p>The driver in use decides the window system to support.</p>
<h2>Build EGL</h2>
<ol>
<li>
-<p>Run <code>configure</code> with the desired state trackers and and enable
-the Gallium driver for your hardware. For example</p>
+<p>Run <code>configure</code> with the desired client APIs and enable
+the driver for your hardware. For example</p>
<pre>
- $ ./configure --with-state-trackers=egl,es,vega --enable-gallium-{swrast,intel}
+ $ ./configure --enable-gles1 --enable-gles2 \
+ --with-dri-drivers=... \
+ --with-gallium-drivers=...
</pre>
-<p>The main library will be enabled by default. The <code>egl</code> state
-tracker is needed by a number of EGL drivers. EGL drivers will be covered
-later. The <a href="opengles.html">es state tracker</a> provides OpenGL ES 1.x
-and 2.x and the <a href="openvg.html">vega state tracker</a> provides OpenVG
-1.x.</p>
+<p>The main library and OpenGL is enabled by default. The first two options
+above enables <a href="opengles.html">OpenGL ES 1.x and 2.x</a>. The last two
+options enables the listed classic and and Gallium drivers respectively.</p>
+
</li>
<li>Build and install Mesa as usual.</li>
</ol>
<p>In the given example, it will build and install <code>libEGL</code>,
-<code>libGLESv1_CM</code>, <code>libGLESv2</code>, <code>libOpenVG</code>, and
-one or more EGL drivers.</p>
+<code>libGL</code>, <code>libGLESv1_CM</code>, <code>libGLESv2</code>, and one
+or more EGL drivers.</p>
<h3>Configure Options</h3>
<p>There are several options that control the build of EGL at configuration
time</p>
-<ul>
-<li><code>--enable-egl</code>
+<dl>
+<dt><code>--enable-egl</code></dt>
+<dd>
<p>By default, EGL is enabled. When disabled, the main library and the drivers
will not be built.</p>
-</li>
+</dd>
-<li><code>--with-egl-driver-dir</code>
+<dt><code>--with-egl-driver-dir</code></dt>
+<dd>
<p>The directory EGL drivers should be installed to. If not specified, EGL
drivers will be installed to <code>${libdir}/egl</code>.</p>
-</li>
+</dd>
-<li><code>--with-egl-displays</code>
+<dt><code>--enable-gallium-egl</code></dt>
+<dd>
-<p>List the window system(s) to support. It is by default <code>x11</code>,
-which supports the X Window System. Its argument is a comma separated string
-like, for example, <code>--with-egl-displays=x11,kms</code>. Because an EGL
-driver decides which window system to support, this example will enable two
-(sets of) EGL drivers. One supports the X window system and the other supports
-bare KMS (kernel modesetting).</p>
+<p>Enable the optional <code>egl_gallium</code> driver.</p>
-</li>
+</dd>
-<li><code>--with-state-trackers</code>
+<dt><code>--with-egl-platforms</code></dt>
+<dd>
-<p>The argument is a comma separated string. It is usually used to specify the
-rendering APIs, like OpenGL ES or OpenVG, to build. But it should be noted
-that a number of EGL drivers depend on the <code>egl</code> state tracker.
-They will <em>not</em> be built without the <code>egl</code> state tracker.</p>
+<p>List the platforms (window systems) to support. Its argument is a comma
+seprated string such as <code>--with-egl-platforms=x11,drm</code>. It decides
+the platforms a driver may support. The first listed platform is also used by
+the main library to decide the native platform: the platform the EGL native
+types such as <code>EGLNativeDisplayType</code> or
+<code>EGLNativeWindowType</code> defined for.</p>
-</li>
+<p>The available platforms are <code>x11</code>, <code>drm</code>,
+<code>fbdev</code>, and <code>gdi</code>. The <code>gdi</code> platform can
+only be built with SCons. Unless for special needs, the build system should
+select the right platforms automatically.</p>
-<li><code>--enable-gallium-swrast</code>
+</dd>
-<p>This option is not specific to EGL. But if there is no driver for your
-hardware, or you are experiencing problems with the hardware driver, you can
-enable the swrast DRM driver. It is a dummy driver and EGL will fallback to
-software rendering automatically.</p>
+<dt><code>--enable-gles1</code></dt>
+<dt><code>--enable-gles2</code></dt>
+<dd>
-</li>
-</ul>
+<p>These options enable OpenGL ES support in OpenGL. The result is one big
+internal library that supports multiple APIs.</p>
+
+</dd>
+
+<dt><code>--enable-shared-glapi</code></dt>
+<dd>
-<h3>OpenGL</h3>
+<p>By default, <code>libGL</code> has its own copy of <code>libglapi</code>.
+This options makes <code>libGL</code> use the shared <code>libglapi</code>. This
+is required if applications mix OpenGL and OpenGL ES.</p>
-<p>The OpenGL state tracker is not built in the above example. It should be
-noted that the classic <code>libGL</code> is not a state tracker and cannot be
-used with EGL (unless the EGL driver in use is <code>egl_glx</code>). To build
-the OpenGL state tracker, one may append <code>glx</code> to
-<code>--with-state-trackers</code> and manually build
-<code>src/gallium/winsys/xlib/</code>.</p>
+</dd>
+
+<dt><code>--enable-openvg</code></dt>
+<dd>
+
+<p>OpenVG must be explicitly enabled by this option.</p>
+
+</dd>
+
+</dl>
<h2>Use EGL</h2>
-<p> The demos for OpenGL ES and OpenVG can be found in <code>progs/es1/</code>,
-<code>progs/es2/</code> and <code>progs/openvg/</code>. You can use them to
-test your build. For example,</p>
+<h3>Demos</h3>
-<pre>
- $ cd progs/es1/xegl
- $ make
- $ ./torus
-</pre>
+<p>There are demos for the client APIs supported by EGL. They can be found in
+mesa/demos repository.</p>
<h3>Environment Variables</h3>
<p>There are several environment variables that control the behavior of EGL at
runtime</p>
-<ul>
-<li><code>EGL_DRIVER</code>
+<dl>
+<dt><code>EGL_DRIVERS_PATH</code></dt>
+<dd>
-<p>This variable forces the specified EGL driver to be loaded. It comes in
-handy when one wants to test a specific driver.</p>
+<p>By default, the main library will look for drivers in the directory where
+the drivers are installed to. This variable specifies a list of
+colon-separated directories where the main library will look for drivers, in
+addition to the default directory. This variable is ignored for setuid/setgid
+binaries.</p>
-</li>
+<p>This variable is usually set to test an uninstalled build. For example, one
+may set</p>
-<li><code>EGL_DISPLAY</code>
+<pre>
+ $ export LD_LIBRARY_PATH=$mesa/lib
+ $ export EGL_DRIVERS_PATH=$mesa/lib/egl
+</pre>
-<p>When <code>EGL_DRIVER</code> is not set, the main library loads <em>all</em>
-EGL drivers that support a certain window system. <code>EGL_DISPLAY</code> can
-be used to specify the window system and the valid values are, for example,
-<code>x11</code> or <code>kms</code>. When the variable is not set, the main
-library defaults the value to the first window system listed in
-<code>--with-egl-displays</code> at configuration time.
+<p>to test a build without installation</p>
-</li>
+</dd>
-<li><code>EGL_LOG_LEVEL</code>
+<dt><code>EGL_DRIVER</code></dt>
+<dd>
+
+<p>This variable specifies a full path to or the name of an EGL driver. It
+forces the specified EGL driver to be loaded. It comes in handy when one wants
+to test a specific driver. This variable is ignored for setuid/setgid
+binaries.</p>
+
+</dd>
+
+<dt><code>EGL_PLATFORM</code></dt>
+<dd>
+
+<p>This variable specifies the native platform. The valid values are the same
+as those for <code>--with-egl-platforms</code>. When the variable is not set,
+the main library uses the first platform listed in
+<code>--with-egl-platforms</code> as the native platform.</p>
+
+<p>Extensions like <code>EGL_MESA_drm_display</code> define new functions to
+create displays for non-native platforms. These extensions are usually used by
+applications that support non-native platforms. Setting this variable is
+probably required only for some of the demos found in mesa/demo repository.</p>
+
+</dd>
+
+<dt><code>EGL_LOG_LEVEL</code></dt>
+<dd>
<p>This changes the log level of the main library and the drivers. The valid
values are: <code>debug</code>, <code>info</code>, <code>warning</code>, and
<code>fatal</code>.</p>
-</li>
+</dd>
-<li><code>EGL_SOFTWARE</code>
+<dt><code>EGL_SOFTWARE</code></dt>
+<dd>
<p>For drivers that support both hardware and software rendering, setting this
variable to true forces the use of software rendering.</p>
-</li>
-</ul>
+</dd>
+</dl>
<h2>EGL Drivers</h2>
-<p>There are two categories of EGL drivers: Gallium and classic.</p>
+<dl>
+<dt><code>egl_dri2</code></dt>
+<dd>
+
+<p>This driver supports both <code>x11</code> and <code>drm</code> platforms.
+It functions as a DRI driver loader. For <code>x11</code> support, it talks to
+the X server directly using (XCB-)DRI2 protocol.</p>
+
+<p>This driver can share DRI drivers with <code>libGL</code>.</p>
-<p>Gallium EGL drivers supports all rendering APIs specified in EGL 1.4. The
-support for optional EGL functions and EGL extensions is usually more complete
-than the classic ones. These drivers depend on the <code>egl</code> state
-tracker to build. The available drivers are</p>
+</dd>
-<ul>
-<li><code>egl_<dpy>_i915</code></li>
-<li><code>egl_<dpy>_i965</code></li>
-<li><code>egl_<dpy>_radeon</code></li>
-<li><code>egl_<dpy>_nouveau</code></li>
-<li><code>egl_<dpy>_swrast</code></li>
-<li><code>egl_<dpy>_vmwgfx</code></li>
-</ul>
+<dt><code>egl_gallium</code></dt>
+<dd>
-<p><code><dpy></code> is given by <code>--with-egl-displays</code> at
-configuration time. There will be one EGL driver for each combination of the
-displays listed and the hardware drivers enabled.</p>
+<p>This driver is based on Gallium3D. It supports all rendering APIs and
+hardwares supported by Gallium3D. It is the only driver that supports OpenVG.
+The supported platforms are X11, DRM, FBDEV, and GDI.</p>
-<p>Classic EGL drivers, on the other hand, supports only OpenGL as its
-rendering API. They can be found under <code>src/egl/drivers/</code>. There
-are 3 of them</p>
+<p>This driver comes with its own hardware drivers
+(<code>pipe_<hw></code>) and client API modules
+(<code>st_<api></code>).</p>
-<ul>
-<li><code>egl_glx</code>
+</dd>
+
+<dt><code>egl_glx</code></dt>
+<dd>
<p>This driver provides a wrapper to GLX. It uses exclusively GLX to implement
the EGL API. It supports both direct and indirect rendering when the GLX does.
It is accelerated when the GLX is. As such, it cannot provide functions that
is not available in GLX or GLX extensions.</p>
-</li>
-
-<li><code>egl_xdri</code>
-
-<p>This driver supports the X Window System as its window system. It functions
-as a DRI driver loader and can load DRI/DRI2/DRISW drivers. Unlike
-<code>egl_glx</code>, it has no dependency on <code>libGL</code>. It talks to
-the X server directly using DRI or DRI2 protocols. It also talks minimal GLX
-protocol for things like available visuals or fbconfigs. With direct access to
-the DRI drivers, it has the potential to support more EGL functions that are
-not possible with <code>egl_glx</code>.</p>
-
-</li>
-<li><code>egl_dri</code>
+</dd>
+</dl>
-<p>This driver lacks maintenance and does <em>not</em> build. It is similiar
-to <code>egl_xdri</code> in that it functions as a DRI driver loader. But
-unlike <code>egl_xdri</code>, it supports Linux framebuffer devices as its
-window system and supports EGL_MESA_screen_surface extension. It loads only
-DRI1 drivers. As DRI1 drivers is phasing out, it might be better to rewrite
-the driver to support KMS and DRI2.</p>
+<h2>Packaging</h2>
-</li>
-</ul>
+<p>The ABI between the main library and its drivers are not stable. Nor is
+there a plan to stabilize it at the moment. Of the EGL drivers,
+<code>egl_gallium</code> has its own hardware drivers and client API modules.
+They are considered internal to <code>egl_gallium</code> and there is also no
+stable ABI between them. These should be kept in mind when packaging for
+distribution.</p>
-<p>To use the classic drivers, one must manually set <code>EGL_DRIVER</code> at
-runtime.</p>
+<p>Generally, <code>egl_dri2</code> is preferred over <code>egl_gallium</code>
+when the system already has DRI drivers. As <code>egl_gallium</code> is loaded
+before <code>egl_dri2</code> when both are available, <code>egl_gallium</code>
+is disabled by default.</p>
<h2>Developers</h2>
resources. The drivers are responsible to the correct behavior as defined by
EGL.</p>
-<h3>TODOs</h3>
-
-<ul>
-<li>Thread safety</li>
-<li>Pass the conformance tests</li>
-<li>Better automatic driver selection: <code>EGL_DISPLAY</code> loads all
-drivers and might eat too much memory.</li>
-<li>Stop using <code>glxinit.c</code> and sources from <code>src/glx/x11/</code></li>
-
-</ul>
-
+<h3><code>EGL_RENDER_BUFFER</code></h3>
+
+<p>In EGL, the color buffer a context should try to render to is decided by the
+binding surface. It should try to render to the front buffer if the binding
+surface has <code>EGL_RENDER_BUFFER</code> set to
+<code>EGL_SINGLE_BUFFER</code>; If the same context is later bound to a
+surface with <code>EGL_RENDER_BUFFER</code> set to
+<code>EGL_BACK_BUFFER</code>, the context should try to render to the back
+buffer. However, the context is allowed to make the final decision as to which
+color buffer it wants to or is able to render to.</p>
+
+<p>For pbuffer surfaces, the render buffer is always
+<code>EGL_BACK_BUFFER</code>. And for pixmap surfaces, the render buffer is
+always <code>EGL_SINGLE_BUFFER</code>. Unlike window surfaces, EGL spec
+requires their <code>EGL_RENDER_BUFFER</code> values to be honored. As a
+result, a driver should never set <code>EGL_PIXMAP_BIT</code> or
+<code>EGL_PBUFFER_BIT</code> bits of a config if the contexts created with the
+config won't be able to honor the <code>EGL_RENDER_BUFFER</code> of pixmap or
+pbuffer surfaces.</p>
+
+<p>It should also be noted that pixmap and pbuffer surfaces are assumed to be
+single-buffered, in that <code>eglSwapBuffers</code> has no effect on them. It
+is desirable that a driver allocates a private color buffer for each pbuffer
+surface created. If the window system the driver supports has native pbuffers,
+or if the native pixmaps have more than one color buffers, the driver should
+carefully attach the native color buffers to the EGL surfaces, re-route them if
+required.</p>
+
+<p>There is no defined behavior as to, for example, how
+<code>glDrawBuffer</code> interacts with <code>EGL_RENDER_BUFFER</code>. Right
+now, it is desired that the draw buffer in a client API be fixed for pixmap and
+pbuffer surfaces. Therefore, the driver is responsible to guarantee that the
+client API renders to the specified render buffer for pixmap and pbuffer
+surfaces.</p>
+
+<h3><code>EGLDisplay</code> Mutex</h3>
+
+The <code>EGLDisplay</code> will be locked before calling any of the dispatch
+functions (well, except for GetProcAddress which does not take an
+<code>EGLDisplay</code>). This guarantees that the same dispatch function will
+not be called with the sample display at the same time. If a driver has access
+to an <code>EGLDisplay</code> without going through the EGL APIs, the driver
+should as well lock the display before using it.
+
+</div>
</body>
</html>