Magnum Windowless Emscripten Application

@ce. The JavaScript file contains event listeners which print loading status on the page. The status displayed in the remaining two @cb{.html}
@ce s, if they are available. The CSS file contains rudimentary style to avoid eye bleeding. The application prints all output (thus also @ref Corrade::Utility::Debug "Debug", @ref Corrade::Utility::Warning "Warning" and @ref Corrade::Utility::Error "Error") to the @cb{.html}
 @ce on the page. It's possible to pass command-line
arguments to @cpp main() @ce using GET URL parameters. For example,
`/app/?foo=bar&fizz&buzz=3` will go to the app as
@cb{.py} ['--foo', 'bar', '--fizz', '--buzz', '3'] @ce.
*/
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);

        #ifdef MAGNUM_BUILD_DEPRECATED
        /**
         * @copybrief WindowlessEglApplication(const Arguments&, NoCreateT)
         * @deprecated Use @ref WindowlessEglApplication(const Arguments&, NoCreateT) instead.
         */
        CORRADE_DEPRECATED("use WindowlessEglApplication(const Arguments&, NoCreateT) instead") explicit WindowlessEglApplication(const Arguments& arguments, std::nullptr_t): WindowlessEglApplication{arguments, NoCreate} {}
        #endif

        /** @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;

    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;
        std::unique_ptr _context;
};

/** @hideinitializer
@brief Entry point for windowless EGL application
@param className Class name

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

}}

#endif