Mesa EGL
========

The current version of EGL in Mesa implements EGL 1.4. More information
about EGL can be found at https://www.khronos.org/egl/.

The Mesa's implementation of EGL uses a driver architecture. The main
library (``libEGL``) is window system neutral. It provides the EGL API
entry points and helper functions for use by the drivers. Drivers are
dynamically loaded by the main library and most of the EGL API calls are
directly dispatched to the drivers.

The driver in use decides the window system to support.

Build EGL
---------

#. Run ``configure`` with the desired client APIs and enable the driver
   for your hardware. For example

   .. code-block:: bash

         $ ./configure --enable-gles1 --enable-gles2 \
                       --with-dri-drivers=... \
                       --with-gallium-drivers=...

   The main library and OpenGL is enabled by default. The first two
   options above enables `OpenGL ES 1.x and 2.x <opengles.html>`__. The
   last two options enables the listed classic and Gallium drivers
   respectively.

#. Build and install Mesa as usual.

In the given example, it will build and install ``libEGL``, ``libGL``,
``libGLESv1_CM``, ``libGLESv2``, and one or more EGL drivers.

Configure Options
~~~~~~~~~~~~~~~~~

There are several options that control the build of EGL at configuration
time

``--enable-egl``
    By default, EGL is enabled. When disabled, the main library and the
    drivers will not be built.

``--with-egl-driver-dir``
    The directory EGL drivers should be installed to. If not specified,
    EGL drivers will be installed to ``${libdir}/egl``.

``--with-platforms``
    List the platforms (window systems) to support. Its argument is a
    comma separated string such as ``--with-platforms=x11,drm``. 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 available platforms are ``x11``, ``drm``, ``wayland``,
    ``surfaceless``, ``android``, and ``haiku``. The ``android``
    platform can either be built as a system component, part of AOSP,
    using ``Android.mk`` files, or cross-compiled using appropriate
    ``configure`` options. The ``haiku`` platform can only be built with
    SCons. Unless for special needs, the build system should select the
    right platforms automatically.

``--enable-gles1``
   .. See --enable-gles2

``--enable-gles2``
    These options enable OpenGL ES support in OpenGL. The result is one
    big internal library that supports multiple APIs.

``--enable-shared-glapi``
    By default, ``libGL`` has its own copy of ``libglapi``. This options
    makes ``libGL`` use the shared ``libglapi``. This is required if
    applications mix OpenGL and OpenGL ES.

Use EGL
-------

Demos
~~~~~

There are demos for the client APIs supported by EGL. They can be found
in mesa/demos repository.

Environment Variables
~~~~~~~~~~~~~~~~~~~~~

There are several environment variables that control the behavior of EGL
at runtime

``EGL_PLATFORM``
    This variable specifies the native platform. The valid values are
    the same as those for ``--with-platforms``. When the variable is not
    set, the main library uses the first platform listed in
    ``--with-platforms`` as the native platform.

    Extensions like ``EGL_MESA_drm_display`` 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.

``EGL_LOG_LEVEL``
    This changes the log level of the main library and the drivers. The
    valid values are: ``debug``, ``info``, ``warning``, and ``fatal``.

EGL Drivers
-----------

``egl_dri2``
    This driver supports both ``x11`` and ``drm`` platforms. It
    functions as a DRI driver loader. For ``x11`` support, it talks to
    the X server directly using (XCB-)DRI2 protocol.

    This driver can share DRI drivers with ``libGL``.