magnum/doc/platform.dox

/*
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    Copyright © 2010, 2011, 2012, 2013 Vladimír Vondruš <mosra@centrum.cz>

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namespace Magnum { namespace Platform {
/** @page platform Platform support

@brief Integration into windowing toolkits and creation of windowless contexts

@tableofcontents

Platform namespace provides classes integrating %Magnum engine into various
toolkits, both windowed and windowless. All the classes have common API to
achieve static polymorphism, so basically you can use different toolkits on
different platforms and the only thing you need to change is the class name,
everything else is the same.

Basic usage is to subclass the chosen `*Application` class and implement
required methods.

@section platform-windowed Windowed applications

Windowed applications provide a window and keyboard and mouse handling. The
most basic toolkit (and toolkit available on most platforms) is GLUT, which is
is implemented in GlutApplication. As said above, the usage is similar for all
toolkits, you must provide two-argument constructor and implement at least
@ref GlutApplication::viewportEvent() "viewportEvent()" and
@ref GlutApplication::drawEvent() "drawEvent()".

Barebone application implementation which will just clear the window to dark
blue color:
@code
#include <DefaultFramebuffer.h>
#include <Renderer.h>
#include <Platform/GlutApplication.h>

using namespace Magnum;

class MyApplication: public Platform::GlutApplication {
    public:
        MyApplication(const Arguments& arguments);

        void viewportEvent(const Vector2i& viewport) override;
        void drawEvent() override;
};

MyApplication::MyApplication(const Arguments& arguments): Platform::GlutApplication(arguments) {
    // Set clear color to dark blue
    Renderer::setClearColor({0.0f, 0.0f, 0.4f});
}

void MyApplication::viewportEvent(const Vector2i& size) {
    // Resize the framebuffer to new window size
    defaultFramebuffer.setViewport({{}, size});
}

void MyApplication::drawEvent() {
    // Clear the window
    defaultFramebuffer.clear(DefaultFramebuffer::Clear::Color);

    // The context is double-buffered, swap buffers
    swapBuffers();
}

// main() function implementation
MAGNUM_GLUTAPPLICATION_MAIN(MyApplication)
@endcode

@section platform-windowless Windowless applications

Windowless applications provide just a context for ofscreen rendering or
performing tasks on GPU. There is not yet any platform-independent toolkit
which could handle this in portable way, thus you have to use platform-specific
ones. As example we use WindowlessGlxApplication, you need to implement just
@ref WindowlessGlxApplication::exec() "exec()" function.

Barebone application which will just print out current OpenGL version and
renderer string and exits:
@code
#include <Context.h>
#include <Platform/WindowlessGlxApplication.h>

using namespace Magnum;

class MyApplication: public Platform::WindowlessGlxApplication {
    public:
        MyApplication(const Arguments& arguments);

        int exec() override;
};

MyApplication::MyApplication(const Arguments& arguments): Platform::WindowlessGlxApplication(arguments) {}

int MyApplication::exec() {
    Debug() << "OpenGL version:" << Context::current()->versionString();
    Debug() << "OpenGL renderer:" << Context::current()->rendererString();

    // Exit with success
    return 0;
}

// main() function implementation
MAGNUM_WINDOWLESSGLXAPPLICATION_MAIN(MyApplication)
@endcode

@section platform-compilation Compilation with CMake

Barebone compilation consists just of finding %Magnum library with required
`*Application` component, compilation of the executable and linking the
libraries to it:
@code
find_package(Magnum REQUIRED GlutApplication)

include_directories(${MAGNUM_INCLUDE_DIRS})

add_executable(myapplication MyApplication.cpp)
target_link_libraries(myapplication
    ${MAGNUM_LIBRARIES}
    ${MAGNUM_GLUTAPPLICATION_LIBRARIES})
@endcode

@section platform-configuration Specifying configuration

By default the application is created with some reasonable defaults (e.g.
window size 800x600 pixels). If you want something else, you can pass
@ref GlutApplication::Configuration "Configuration" instance to application
constructor. Using method chaining it can be done conveniently like this:
@code
MyApplication::MyApplication(int& argc, char** argv):
    Platform::GlutApplication(argc, argv, (new Configuration)
        ->setTitle("My Application")->setSize({800, 600}) {
    // ...
}
@endcode

However, sometimes you would need to configure the application based on some
configuration file or system introspection. In that case you can pass `nullptr`
instead of Configuration instance and then specify it later with
@ref GlutApplication::createContext() "createContext()":
@code
MyApplication::MyApplication(int& argc, char** argv): Platform::GlutApplication(argc, argv, nullptr) {
    // ...

    createContext((new Configuration)
        ->setTitle("My Application")
        ->setSize(size));

    // ...
}
@endcode

The configuration passed to constructor and @ref GlutApplication::createContext() "createContext()"
is automaticall deleted afterwards and if the context creation fails, the
application exits. However, it is also possible to negotiate the context using
@ref GlutApplication::tryCreateContext() "tryCreateContext()". The major
difference is that this function returns `false` instead of exiting and it
doesn't delete the configuration afterwards so you can reuse it. You can for
example try enabling MSAA and if the context creation fails, fall back to
no-AA rendering:
@code
MyApplication::MyApplication(int& argc, char** argv): Platform::GlutApplication(argc, argv, nullptr) {
    // ...

    auto conf = new Configuration;
    conf->setTitle("My Application")
        ->setSampleCount(16);

    if(!tryCreateContext(conf))
        createContext(conf->setSampleCount(0));
    else delete conf;

    // ...
}
@endcode

*/
}}