text: #ifndef Magnum_Platform_WindowlessEglApplication_h
  #define Magnum_Platform_WindowlessEglApplication_h
  /*
      This file is part of Magnum.
  
      Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
                  2020 Vladimír Vondruš <mosra@centrum.cz>
      Copyright © 2020 Erik Wijmans <etw@gatech.edu>
  
      Permission is hereby granted, free of charge, to any person obtaining a
      copy of this software and associated documentation files (the "Software"),
      to deal in the Software without restriction, including without limitation
      the rights to use, copy, modify, merge, publish, distribute, sublicense,
      and/or sell copies of the Software, and to permit persons to whom the
      Software is furnished to do so, subject to the following conditions:
  
      The above copyright notice and this permission notice shall be included
      in all copies or substantial portions of the Software.
  
      THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
      THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
      FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
      DEALINGS IN THE SOFTWARE.
  */
  
  /** @file
   * @brief Class @ref Magnum::Platform::WindowlessEglApplication, @ref Magnum::Platform::WindowlessEglContext, macro @ref MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN()
   */
  
  #include "Magnum/configure.h"
  
  #ifdef MAGNUM_TARGET_GL
  #include <EGL/egl.h>
  #include <EGL/eglext.h>
  /* undef Xlib nonsense to avoid conflicts */
  #undef Always
  #undef Bool
  #undef Complex
  #undef None
  #undef Status
  #include <Corrade/Containers/EnumSet.h>
  #include <Corrade/Containers/Pointer.h>
  
  #ifndef DOXYGEN_GENERATING_OUTPUT
  /* Unfortunately Xlib *needs* the Bool type, so provide a typedef instead */
  typedef int Bool;
  #endif
  
  #include "Magnum/Magnum.h"
  #include "Magnum/GL/OpenGL.h"
  #include "Magnum/Tags.h"
  #include "Magnum/Platform/Platform.h"
  
  namespace Magnum { namespace Platform {
  
  /**
  @brief Windowless EGL context
  
  @m_keywords{WindowlessGLContext EGL}
  
  GL context using EGL without any windowing system, used in
  @ref WindowlessEglApplication. Does not have any default framebuffer.
  
  Meant to be used when there is a need to manage (multiple) GL contexts
  manually. See @ref platform-windowless-contexts for more information. If no
  other application header is included, this class is also aliased to
  @cpp Platform::WindowlessGLContext @ce.
  
  @note This class is available only if Magnum is compiled with
      @ref MAGNUM_TARGET_GL enabled (done by default). See @ref building-features
      for more information.
  */
  class WindowlessEglContext {
      public:
          class Configuration;
  
          /**
           * @brief Constructor
           * @param configuration Context configuration
           * @param context       Optional Magnum context instance constructed
           *      using @ref NoCreate to manage driver workarounds
           *
           * Once the context is created, make it current using @ref makeCurrent()
           * and create @ref Platform::GLContext instance to be able to use
           * Magnum.
           * @see @ref isCreated()
           */
          explicit WindowlessEglContext(const Configuration& configuration, GLContext* context = nullptr);
  
          /**
           * @brief Construct without creating the context
           *
           * Move a instance with created context over to make it usable.
           */
          explicit WindowlessEglContext(NoCreateT) {}
  
          /** @brief Copying is not allowed */
          WindowlessEglContext(const WindowlessEglContext&) = delete;
  
          /** @brief Move constructor */
          WindowlessEglContext(WindowlessEglContext&& other);
  
          /** @brief Copying is not allowed */
          WindowlessEglContext& operator=(const WindowlessEglContext&) = delete;
  
          /** @brief Move assignment */
          WindowlessEglContext& operator=(WindowlessEglContext&& other);
  
          /**
           * @brief Destructor
           *
           * Destroys the context, if any.
           */
          ~WindowlessEglContext();
  
          /** @brief Whether the context is created */
          bool isCreated() const { return _context; }
  
          /**
           * @brief Make the context current
           *
           * Prints error message and returns @cpp false @ce on failure,
           * otherwise returns @cpp true @ce.
           */
          bool makeCurrent();
  
          /**
           * @brief Underlying OpenGL context
           * @m_since{2020,06}
           *
           * Use in case you need to call EGL functionality directly or in order
           * to create a shared context. Returns @cpp nullptr @ce in case the
           * context was not created yet.
           * @see @ref Configuration::setSharedContext()
           */
          EGLContext glContext() { return _context; }
  
      private:
          #ifndef MAGNUM_TARGET_WEBGL
          bool _sharedContext = false;
          #endif
          EGLDisplay _display{};
          EGLContext _context{};
          #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_WEBGL)
          /* Needed only by SwiftShader, using EGL_NO_SURFACE everywhere else */
          EGLSurface _surface = EGL_NO_SURFACE;
          #endif
  };
  
  /**
  @brief Configuration
  
  @see @ref WindowlessEglContext(),
      @ref WindowlessEglApplication::WindowlessEglApplication(),
      @ref WindowlessEglApplication::createContext(),
      @ref WindowlessEglApplication::tryCreateContext()
  */
  class WindowlessEglContext::Configuration {
      public:
          #ifndef MAGNUM_TARGET_WEBGL
          /**
           * @brief Context flag
           *
           * @see @ref Flags, @ref setFlags(), @ref GL::Context::Flag
           * @requires_gles Context flags are not available in WebGL.
           */
          enum class Flag: int {
              #ifndef MAGNUM_TARGET_GLES
              /**
               * Forward compatible context
               *
               * @requires_gl Core/compatibility profile distinction and forward
               *      compatibility applies only to desktop GL.
               */
              ForwardCompatible = EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR,
              #endif
  
              /**
               * Debug context. Enabled automatically if the
               * `--magnum-gpu-validation` @ref GL-Context-command-line "command-line option"
               * is present.
               */
              Debug = EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR
          };
  
          /**
           * @brief Context flags
           *
           * @see @ref setFlags(), @ref Context::Flags
           * @requires_gles Context flags are not available in WebGL.
           */
          #ifndef DOXYGEN_GENERATING_OUTPUT
          typedef Containers::EnumSet<Flag, EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR
              #ifndef MAGNUM_TARGET_GLES
              |EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR
              #endif
              > Flags;
          #else
          typedef Containers::EnumSet<Flag> Flags;
          #endif
          #endif
  
          /*implicit*/ Configuration();
  
          #ifndef MAGNUM_TARGET_WEBGL
          /**
           * @brief Context flags
           *
           * @requires_gles Context flags are not available in WebGL.
           */
          Flags flags() const { return _flags; }
  
          /**
           * @brief Set context flags
           * @return Reference to self (for method chaining)
           *
           * Default is @ref Flag::ForwardCompatible on desktop GL and no flags
           * on OpenGL ES.
           * @see @ref addFlags(), @ref clearFlags(), @ref GL::Context::flags()
           * @requires_gles Context flags are not available in WebGL.
           */
          Configuration& setFlags(Flags flags) {
              _flags = flags;
              return *this;
          }
  
          /**
           * @brief Add context flags
           * @return Reference to self (for method chaining)
           *
           * Unlike @ref setFlags(), ORs the flags with existing instead of
           * replacing them. Useful for preserving the defaults.
           * @see @ref clearFlags()
           * @requires_gles Context flags are not available in WebGL.
           */
          Configuration& addFlags(Flags flags) {
              _flags |= flags;
              return *this;
          }
  
          /**
           * @brief Clear context flags
           * @return Reference to self (for method chaining)
           *
           * Unlike @ref setFlags(), ANDs the inverse of @p flags with existing
           * instead of replacing them. Useful for removing default flags.
           * @see @ref addFlags()
           * @requires_gles Context flags are not available in WebGL.
           */
          Configuration& clearFlags(Flags flags) {
              _flags &= ~flags;
              return *this;
          }
  
          /**
           * @brief Device ID to use
           * @m_since{2019,10}
           *
           * @requires_gles Device selection is not available in WebGL.
           */
          UnsignedInt device() const { return _device; }
  
          /**
           * @brief Set device ID to use
           * @return Reference to self (for method chaining)
           * @m_since{2019,10}
           *
           * The device ID is expected to be smaller than the count of devices
           * reported by EGL. When using @ref WindowlessEglApplication, this is
           * also exposed as a `--magnum-device` command-line option and a
           * `MAGNUM_DEVICE` environment variable. If @ref setSharedContext() is
           * set, this value is ignored and the device is picked to be the same
           * as in the shared context instead.
           *
           * By default it's set to @cpp 0 @ce, taking the first found EGL
           * device.
           * @see @ref setCudaDevice()
           * @requires_gles Device selection is not available in WebGL.
           */
          Configuration& setDevice(UnsignedInt id) {
              _device = id;
              return *this;
          }
  
          /**
           * @brief CUDA device ID to use
           * @m_since{2020,06}
           *
           * @requires_gles Device selection is not available in WebGL.
           */
          UnsignedInt cudaDevice() const { return _cudaDevice; }
  
          /**
           * @brief Set the CUDA device ID to use
           * @return Reference to self (for method chaining)
           * @m_since{2020,06}
           *
           * If a device with given CUDA ID is not found, context creation fails.
           * When using @ref WindowlessEglApplication, this is also exposed as a
           * `--magnum-cuda-device` command-line option and a
           * `MAGNUM_CUDA_DEVICE` environment variable. If @ref setSharedContext()
           * is set, this value is ignored and the device is picked to be the
           * same as in the shared context instead.
           *
           * If a CUDA device is set, it takes precedence over the device ID set
           * with @ref setDevice(). By default it's set to @cpp 0xffffffffu @ce,
           * indicating that @ref setDevice() is used instead.
           * @requires_gles Device selection is not available in WebGL.
           */
          Configuration& setCudaDevice(UnsignedInt id) {
              _cudaDevice = id;
              return *this;
          }
  
          /**
           * @brief Create a shared context
           * @return Reference to self (for method chaining)
           * @m_since{2020,06}
           *
           * When set, the created context will share a subset of OpenGL objects
           * with @p context and its associated @p display, instead of being
           * independent. Many caveats and limitations apply to shared OpenGL
           * contexts, please consult the OpenGL specification for details.
           * Default is `EGL_NO_CONTEXT`, i.e. no sharing. See
           * @ref Platform-WindowlessEglApplication-shared-contexts for more
           * information.
           * @see @ref WindowlessEglContext::glContext(),
           *      @ref WindowlessEglApplication::glContext()
           * @requires_gles Context sharing is not available in WebGL.
           */
          Configuration& setSharedContext(EGLDisplay display, EGLContext context);
  
          /**
           * @brief Shared display
           * @m_since{2020,06}
           *
           * @requires_gles Context sharing is not available in WebGL.
           */
          EGLContext sharedDisplay() const { return _sharedDisplay; }
  
          /**
           * @brief Shared context
           * @m_since{2020,06}
           *
           * @requires_gles Context sharing is not available in WebGL.
           */
          EGLContext sharedContext() const { return _sharedContext; }
          #endif
  
      private:
          #ifndef MAGNUM_TARGET_WEBGL
          Flags _flags;
          UnsignedInt _device;
          /* Assumes that you can't have 2^32 - 1 GPUs */
          UnsignedInt _cudaDevice = ~UnsignedInt{};
          EGLDisplay _sharedDisplay = EGL_NO_DISPLAY;
          EGLContext _sharedContext = EGL_NO_CONTEXT;
          #endif
  };
  
  #ifndef MAGNUM_TARGET_WEBGL
  CORRADE_ENUMSET_OPERATORS(WindowlessEglContext::Configuration::Flags)
  #endif
  
  /**
  @brief Windowless EGL application
  
  @m_keywords{WindowlessApplication EGL}
  
  Application for offscreen rendering using @ref WindowlessEglContext. This
  application library is in theory available for all platforms for which EGL
  works (Linux desktop or ES, @ref CORRADE_TARGET_IOS "iOS",
  @ref CORRADE_TARGET_ANDROID "Android" and also
  @ref CORRADE_TARGET_EMSCRIPTEN "Emscripten"). See other
  `Windowless*Application` classes for an alternative.
  
  @section Platform-WindowlessEglApplication-bootstrap Bootstrap application
  
  Fully contained windowless application using @ref WindowlessEglApplication
  along with CMake setup is available in `windowless` branch of
  [Magnum Bootstrap](https://github.com/mosra/magnum-bootstrap) repository,
  download it as [tar.gz](https://github.com/mosra/magnum-bootstrap/archive/windowless.tar.gz)
  or [zip](https://github.com/mosra/magnum-bootstrap/archive/windowless.zip)
  file. After extracting the downloaded archive you can build and run the
  application with these four commands:
  
  @code{.sh}
  mkdir build && cd build
  cmake ..
  cmake --build .
  ./src/MyApplication # or ./src/Debug/MyApplication
  @endcode
  
  See @ref cmake for more information.
  
  @section Platform-WindowlessEglApplication-bootstrap-emscripten Bootstrap application for Emscripten
  
  Fully contained windowless application together with Emscripten support along
  with full HTML markup and CMake setup is available in `windowless-emscripten`
  branch of [Magnum Bootstrap](https://github.com/mosra/magnum-bootstrap)
  repository, download it as [tar.gz](https://github.com/mosra/magnum-bootstrap/archive/windowless-emscripten.tar.gz)
  or [zip](https://github.com/mosra/magnum-bootstrap/archive/windowless-emscripten.zip)
  file. After extracting the downloaded archive, you can do the desktop build in
  the same way as above. For the Emscripten build you also need to put the
  contents of toolchains repository from https://github.com/mosra/toolchains
  in `toolchains/` subdirectory. There are two toolchain files. The
  `generic/Emscripten.cmake` is for the classical (asm.js) build, the
  `generic/Emscripten-wasm.cmake` is for WebAssembly build. Don't forget to adapt
  `EMSCRIPTEN_PREFIX` variable in `toolchains/generic/Emscripten*.cmake` to path
  where Emscripten is installed; you can also pass it explicitly on command-line
  using `-DEMSCRIPTEN_PREFIX`. Default is `/usr/emscripten`.
  
  Then create build directory and run `cmake` and build/install commands in it.
  Set `CMAKE_PREFIX_PATH` to where you have all the dependencies installed, set
  `CMAKE_INSTALL_PREFIX` to have the files installed in proper location (a
  webserver, e.g.  `/srv/http/emscripten`).
  
  @code{.sh}
  mkdir build-emscripten && cd build-emscripten
  cmake .. \
      -DCMAKE_TOOLCHAIN_FILE="../toolchains/generic/Emscripten.cmake" \
      -DCMAKE_PREFIX_PATH=/usr/lib/emscripten/system \
      -DCMAKE_INSTALL_PREFIX=/srv/http/emscripten
  cmake --build .
  cmake --build . --target install
  @endcode
  
  You can then open `MyApplication.html` in your browser (through a webserver,
  e.g. http://localhost/emscripten/MyApplication.html).
  
  Detailed information about deployment for Emscripten and all needed boilerplate
  together with a troubleshooting guide is available in @ref platforms-html5.
  
  @section Platform-WindowlessEglApplication-usage General usage
  
  This application library is built if `WITH_WINDOWLESSEGLAPPLICATION` is enabled
  when building Magnum. To use this library from CMake, put [FindEGL.cmake](https://github.com/mosra/magnum/blob/master/modules/FindEGL.cmake)
  into your `modules/` directory, request the `WindowlessEglApplication`
  component of the `Magnum` package and link to the
  `Magnum::WindowlessEglApplication` target:
  
  @code{.cmake}
  find_package(Magnum REQUIRED WindowlessEglApplication)
  
  # ...
  target_link_libraries(your-app PRIVATE Magnum::WindowlessEglApplication)
  @endcode
  
  Additionally, if you're using Magnum as a CMake subproject, do the following
  * *before* calling @cmake find_package() @ce to ensure it's enabled, as the
  library is not built by default:
  
  @code{.cmake}
  set(WITH_WINDOWLESSEGLAPPLICATION ON CACHE BOOL "" FORCE)
  add_subdirectory(magnum EXCLUDE_FROM_ALL)
  @endcode
  
  If no other application is requested, you can also use the generic
  `Magnum::WindowlessApplication` alias to simplify porting. Again, see
  @ref building and @ref cmake for more information.
  
  Place your code into @ref exec(). The subclass can be then used in main
  function using @ref MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN() macro. See
  @ref platform for more information.
  
  @code{.cpp}
  class MyApplication: public Platform::WindowlessEglApplication {
      // implement required methods...
  };
  MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN(MyApplication)
  @endcode
  
  If no other application header is included, this class is also aliased to
  @cpp Platform::WindowlessApplication @ce and the macro is aliased to
  @cpp MAGNUM_WINDOWLESSAPPLICATION_MAIN() @ce to simplify porting.
  
  @section Platform-WindowlessEglApplication-device-selection GPU device selection
  
  The application prefers to use the @m_class{m-doc-external}
  [EGL_EXT_device_enumeration](https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_device_enumeration.txt),
  @m_class{m-doc-external} [EGL_EXT_platform_base](https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_platform_base.txt) and
  @m_class{m-doc-external} [EGL_EXT_platform_device](https://www.khronos.org/registry/EGL/extensions/EXT/EGL_EXT_platform_device.txt)
  extensions where available instead of `EGL_DEFAULT_DISPLAY` to work better on
  headless setups. The application chooses the first found device by default, you
  can override that either with @ref Configuration::setDevice() or using a
  `--magnum-device` command-line option (and the `MAGNUM_DEVICE` environment
  variable). Unfortunately EGL doesn't provide any reasonable way to enumerate or
  filter named devices, so the best you can do is checking reported device count
  printed by the `--magnum-log verbose` @ref GL-Context-command-line "command-line option",
  and then going from `0` up to figure out the desired device ID.
  
  On systems with NVIDIA GPUs and CUDA, it's possible to directly select a
  particular CUDA device, allowing for EGL and CUDA to both target the same
  physical device for a given ID. This can be chosen via the
  `--magnum-cuda-device` command-line option (and the `MAGNUM_CUDA_DEVICE`
  environment variable), which then takes precedence over `--magnum-device`. The
  same can be also specified via via @ref Configuration::setCudaDevice().
  
  @m_class{m-block m-danger}
  
  @par No EGL devices found
  @parblock
  Systems running Mesa 19.2 (which has the above extensions) that also have
  `libEGL_nvidia.so` installed (for example as a CUDA dependency) may fail
  to create the context with the following error (with additional output
  produced when the `--magnum-gpu-validation`
  @ref GL-Context-command-line "command-line option" is enabled):
  
  @m_class{m-console-wrap}
  
  @code{.shell-session}
  eglQueryDevicesEXT(): EGL_BAD_ALLOC error: In internal function: Additional INFO may be available
  eglQueryDevicesEXT(): EGL_BAD_ALLOC error: In function eglQueryDevicesEXT(), backend failed to query devices
  Platform::WindowlessEglApplication::tryCreateContext(): no EGL devices found
  @endcode
  
  This is due to the NVidia's EGL implementation failing to enumerate devices
  (because there aren't any), which then causes the GLVND wrapper to stop
  instead of enumerating the Mesa devices as well. The solution is
  whitelisting all EGL implementations except the NVidia one
  <a href="https://github.com/NVIDIA/libglvnd/blob/master/src/EGL/icd_enumeration.md">as described in the libglvnd documentation</a>
  using the `__EGL_VENDOR_LIBRARY_FILENAMES` environment variable, for example:
  
  @m_class{m-console-wrap}
  
  @code{.sh}
  __EGL_VENDOR_LIBRARY_FILENAMES=/usr/share/glvnd/egl_vendor.d/50_mesa.json ./my-application
  @endcode
  @endparblock
  
  @section Platform-WindowlessEglApplication-shared-contexts Shared EGL contexts
  
  Unlike with @ref WindowlessGlxApplication and @ref WindowlessWglApplication,
  you're expected to supply both the display and the context in
  @ref Configuration::setSharedContext(). This is done in order to ensure the
  same `EGLDisplay` is used for all shared contexts, especially when a
  non-default GPU device is selected via @ref Configuration::setDevice().
  
  Moreover, since `eglInitialize()` and `eglTerminate()` is expected to be called
  just once on a particular display, EGL initialization and termination is only
  done in the case of a non-shared @ref WindowlessEglApplication (or the first
  one created in a shared chain). Shared instances then reuse the already
  initialized `EGLDisplay` and expect that it's terminated only after all shared
  instances are gone.
  */
  class WindowlessEglApplication {
      public:
          /** @brief Application arguments */
          struct Arguments {
              /** @brief Constructor */
              /*implicit*/ constexpr Arguments(int& argc, char** argv) noexcept: argc{argc}, argv{argv}{}
  
              int& argc;      /**< @brief Argument count */
              char** argv;    /**< @brief Argument values */
          };
  
          /**
           * @brief Configuration
           *
           * @see @ref WindowlessEglApplication(), @ref createContext(),
           *      @ref tryCreateContext()
           */
          typedef WindowlessEglContext::Configuration Configuration;
  
          /**
           * @brief Default constructor
           * @param arguments     Application arguments
           * @param configuration Configuration
           *
           * Creates application with default or user-specified configuration.
           * See @ref Configuration for more information. The program exits if
           * the context cannot be created, see @ref tryCreateContext() for an
           * alternative.
           * @see @ref WindowlessEglContext
           */
          #ifdef DOXYGEN_GENERATING_OUTPUT
          explicit WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration = Configuration());
          #else
          /* To avoid "invalid use of incomplete type" */
          explicit WindowlessEglApplication(const Arguments& arguments, const Configuration& configuration);
          explicit WindowlessEglApplication(const Arguments& arguments);
          #endif
  
          /**
           * @brief Constructor
           * @param arguments     Application arguments
           *
           * Unlike above, the context is not created and must be created later
           * with @ref createContext() or @ref tryCreateContext().
           */
          explicit WindowlessEglApplication(const Arguments& arguments, NoCreateT);
  
          /** @brief Copying is not allowed */
          WindowlessEglApplication(const WindowlessEglApplication&) = delete;
  
          /** @brief Moving is not allowed */
          WindowlessEglApplication(WindowlessEglApplication&&) = delete;
  
          /** @brief Copying is not allowed */
          WindowlessEglApplication& operator=(const WindowlessEglApplication&) = delete;
  
          /** @brief Moving is not allowed */
          WindowlessEglApplication& operator=(WindowlessEglApplication&&) = delete;
  
          /**
           * @brief Execute application
           * @return Value for returning from @cpp main() @ce
           *
           * See @ref MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN() for usage
           * information.
           */
          virtual int exec() = 0;
  
          /**
           * @brief Underlying OpenGL context
           * @m_since{2020,06}
           *
           * Use in case you need to call EGL functionality directly or in order
           * to create a shared context. Returns @cpp nullptr @ce in case the
           * context was not created yet.
           * @see @ref Configuration::setSharedContext()
           */
          EGLContext glContext() { return _glContext.glContext(); }
  
      protected:
          /* Nobody will need to have (and delete) WindowlessEglApplication*,
             thus this is faster than public pure virtual destructor */
          ~WindowlessEglApplication();
  
          /**
           * @brief Create context with given configuration
           *
           * Must be called if and only if the context wasn't created by the
           * constructor itself. Error message is printed and the program exits
           * if the context cannot be created, see @ref tryCreateContext() for an
           * alternative.
           * @see @ref WindowlessEglContext
           */
          #ifdef DOXYGEN_GENERATING_OUTPUT
          void createContext(const Configuration& configuration = Configuration());
          #else
          /* To avoid "invalid use of incomplete type" */
          void createContext(const Configuration& configuration);
          void createContext();
          #endif
  
          /**
           * @brief Try to create context with given configuration
           *
           * Unlike @ref createContext() returns @cpp false @ce if the context
           * cannot be created, @cpp true @ce otherwise.
           */
          bool tryCreateContext(const Configuration& configuration);
  
      private:
          WindowlessEglContext _glContext;
          Containers::Pointer<Platform::GLContext> _context;
  
          #ifndef MAGNUM_TARGET_WEBGL
          /* These are saved from command-line arguments */
          UnsignedInt _commandLineDevice;
          UnsignedInt _commandLineCudaDevice = ~UnsignedInt{};
          #endif
  };
  
  /** @hideinitializer
  @brief Entry point for windowless EGL application
  @param className Class name
  
  @m_keywords{MAGNUM_WINDOWLESSAPPLICATION_MAIN()}
  
  See @ref Magnum::Platform::WindowlessEglApplication "Platform::WindowlessEglApplication"
  for usage information. This macro abstracts out platform-specific entry point
  code and is equivalent to the following, see @ref portability-applications for
  more information.
  
  @code{.cpp}
  int main(int argc, char** argv) {
      className app({argc, argv});
      return app.exec();
  }
  @endcode
  
  When no other windowless application header is included this macro is also
  aliased to @cpp MAGNUM_WINDOWLESSAPPLICATION_MAIN() @ce.
  */
  #define MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN(className)                     \
      int main(int argc, char** argv) {                                       \
          className app({argc, argv});                                        \
          return app.exec();                                                  \
      }
  
  #ifndef DOXYGEN_GENERATING_OUTPUT
  #ifndef MAGNUM_WINDOWLESSAPPLICATION_MAIN
  typedef WindowlessEglApplication WindowlessApplication;
  typedef WindowlessEglContext WindowlessGLContext;
  #define MAGNUM_WINDOWLESSAPPLICATION_MAIN(className) MAGNUM_WINDOWLESSEGLAPPLICATION_MAIN(className)
  #else
  #undef MAGNUM_WINDOWLESSAPPLICATION_MAIN
  #endif
  #endif
  
  }}
  #else
  #error this header is available only in the OpenGL build
  #endif
  
  #endif
  