Move function pointer loading into platform-specific class.

This way it will be possible decouple the main library from
platform-specific GLX/WGL/CGL/EGL... API.

doc/platform.dox

@@ -263,25 +263,25 @@ MyApplication::MyApplication(int& argc, char** argv): Platform::Application(argc
 @section platform-custom Using custom platform toolkits
 
 In case you want to use some not-yet-supported toolkit or you don't want to use
-the wrappers in @ref Platform namespace, you can initialize %Magnum manually.
-All you need is to create OpenGL context and then create instance of
-@ref Context class, which will take care of proper initialization and feature
-detection. The instance must be alive for whole application lifetime. Example
-`main()` function with manual initialization:
+the application wrappers in @ref Platform namespace, you can initialize %Magnum
+manually. First create OpenGL context and then create instance of
+@ref Platform::Context class, which will take care of proper initialization and
+feature detection. The instance must be alive for whole application lifetime.
+Example `main()` function with manual initialization:
 @code
 int main(int argc, char** argv) {
     // Create OpenGL context ...
 
     {
         // Initialize Magnum
-        Context context;
+        Platform::Context context;
 
-        // open window, enter main loop...
+        // Open window, enter main loop ...
 
         // Magnum context gets destroyed
     }
 
-    // delete OpenGL context ...
+    // Delete OpenGL context ...
 
     return 0;
 }

src/Magnum/Context.cpp

@@ -294,17 +294,9 @@ const std::vector<Extension>& Extension::extensions(Version version) {
 
 Context* Context::_current = nullptr;
 
-Context::Context() {
-    #ifndef MAGNUM_TARGET_GLES
-    /* Init glLoadGen. Ignore functions that failed to load (described by
-       `ogl_LOAD_SUCCEEDED + n` return code), as we requested the latest OpenGL
-       with many vendor extensions and there won't ever be a driver supporting
-       everything possible. */
-    if(ogl_LoadFunctions() == ogl_LOAD_FAILED) {
-        Error() << "ExtensionWrangler: cannot initialize glLoadGen";
-        std::exit(64);
-    }
-    #endif
+Context::Context(void functionLoader()) {
+    /* Load GL function pointers */
+    if(functionLoader) functionLoader();
 
     /* Get version */
     #if defined(MAGNUM_TARGET_GLES) && !defined(MAGNUM_TARGET_GLES2)

src/Magnum/Context.h

@@ -42,9 +42,8 @@
 
 namespace Magnum {
 
-namespace Implementation {
-    struct State;
-}
+namespace Implementation { struct State; }
+namespace Platform { class Context; }
 
 /**
 @brief Run-time information about OpenGL extension
@@ -88,11 +87,15 @@ class MAGNUM_EXPORT Extension {
 
 Provides access to version and extension information. Instance available
 through @ref Context::current() is automatically created during construction of
-*Application classes in @ref Platform namespace. You can safely assume that the
-instance is available during whole lifetime of *Application object. See
-@ref platform documentation for more information about engine setup.
+`*Application` classes in @ref Platform namespace. You can safely assume that
+the instance is available during whole lifetime of `*Application` object. It's
+also possible to create the context without using any `*Application` class
+using @ref Platform::Context subclass, see @ref platform documentation for more
+information.
 */
 class MAGNUM_EXPORT Context {
+    friend class Platform::Context;
+
     public:
         /**
          * @brief %Context flag
@@ -199,17 +202,6 @@ class MAGNUM_EXPORT Context {
          */
         typedef Containers::EnumSet<DetectedDriver> DetectedDrivers;
 
-        /**
-         * @brief Constructor
-         *
-         * Does initial setup, detects available features and enables them
-         * throughout the engine.
-         * @see @fn_gl{Get} with @def_gl{MAJOR_VERSION}, @def_gl{MINOR_VERSION},
-         *      @def_gl{CONTEXT_FLAGS}, @def_gl{NUM_EXTENSIONS},
-         *      @fn_gl{GetString} with @def_gl{EXTENSIONS}
-         */
-        explicit Context();
-
         /** @brief Copying is not allowed */
         Context(const Context&) = delete;
 
@@ -478,6 +470,8 @@ class MAGNUM_EXPORT Context {
     private:
         static Context* _current;
 
+        explicit Context(void functionLoader());
+
         MAGNUM_LOCAL void setupDriverWorkarounds();
 
         Version _version;

src/Magnum/Platform/AbstractXApplication.cpp

@@ -27,7 +27,7 @@
 
 #include <Corrade/Utility/utilities.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 #include "Magnum/Version.h"
 
 #include "Implementation/AbstractContextHandler.h"
@@ -95,7 +95,7 @@ bool AbstractXApplication::tryCreateContext(const Configuration& configuration)
     /* Set OpenGL context as current */
     contextHandler->makeCurrent();
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/AbstractXApplication.h

@@ -41,6 +41,7 @@
 
 #include "Magnum/Magnum.h"
 #include "Magnum/Math/Vector2.h"
+#include "Magnum/Platform/Platform.h"
 
 namespace Magnum {
 
@@ -183,7 +184,7 @@ class AbstractXApplication {
 
         Implementation::AbstractContextHandler<Configuration, Display*, VisualID, Window>* contextHandler;
 
-        Context* c;
+        Platform::Context* c;
 
         /** @todo Get this from the created window */
         Vector2i viewportSize;

src/Magnum/Platform/AndroidApplication.cpp

@@ -28,7 +28,7 @@
 #include <Corrade/Utility/AndroidStreamBuffer.h>
 #include <Corrade/Utility/Debug.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 
 #include "Implementation/Egl.h"
 
@@ -136,7 +136,7 @@ bool AndroidApplication::tryCreateContext(const Configuration& configuration) {
     /* Make the context current */
     CORRADE_INTERNAL_ASSERT_OUTPUT(eglMakeCurrent(_display, _surface, _surface, _context));
 
-    _c.reset(new Context);
+    _c.reset(new Platform::Context);
     return true;
 }
 

src/Magnum/Platform/AndroidApplication.h

@@ -306,7 +306,7 @@ class AndroidApplication {
         EGLSurface _surface;
         EGLContext _context;
 
-        std::unique_ptr<Context> _c;
+        std::unique_ptr<Platform::Context> _c;
         std::unique_ptr<LogOutput> _logOutput;
 
         CORRADE_ENUMSET_FRIEND_OPERATORS(Flags)

src/Magnum/Platform/CMakeLists.txt

@@ -25,6 +25,7 @@
 
 # Headers
 set(MagnumPlatform_HEADERS
+    Context.h
     Platform.h
     Screen.h
     ScreenedApplication.h

src/Magnum/Platform/Context.h

@@ -0,0 +1,79 @@
+#ifndef Magnum_Platform_Context_h
+#define Magnum_Platform_Context_h
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013, 2014
+              Vladimír Vondruš <mosra@centrum.cz>
+
+    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.
+*/
+
+#include <Corrade/Utility/Debug.h>
+
+#include "Magnum/Context.h"
+#include "Magnum/OpenGL.h"
+
+namespace Magnum { namespace Platform {
+
+/**
+@brief Platform-specific context
+
+In most cases not needed to be used directly as the initialization is done
+automatically in `*Application` classes. See @ref platform for more
+information.
+*/
+class Context: public Magnum::Context {
+    public:
+        /**
+         * @brief Constructor
+         *
+         * Does initial setup, loads OpenGL function pointers using
+         * platform-specific API, detects available features and enables them
+         * throughout the engine.
+         * @see @fn_gl{Get} with @def_gl{MAJOR_VERSION}, @def_gl{MINOR_VERSION},
+         *      @def_gl{CONTEXT_FLAGS}, @def_gl{NUM_EXTENSIONS},
+         *      @fn_gl{GetString} with @def_gl{EXTENSIONS}
+         */
+        explicit Context():
+            #ifndef MAGNUM_TARGET_GLES
+            Magnum::Context{functionLoader} {}
+            #else
+            Magnum::Context{nullptr} {}
+            #endif
+
+    private:
+        #ifndef MAGNUM_TARGET_GLES
+        void functionLoader() {
+            /* Init glLoadGen. Ignore functions that failed to load (described
+               by `ogl_LOAD_SUCCEEDED + n` return code), as we requested the
+               latest OpenGL with many vendor extensions and there won't ever
+               everything possible. */
+            if(ogl_LoadFunctions() == ogl_LOAD_FAILED) {
+                Error() << "ExtensionWrangler: cannot initialize glLoadGen";
+                std::exit(64);
+            }
+        }
+        #endif
+
+};
+
+}}
+
+#endif

src/Magnum/Platform/GlutApplication.cpp

@@ -27,8 +27,8 @@
 
 #include <tuple>
 
-#include "Magnum/Context.h"
 #include "Magnum/Version.h"
+#include "Magnum/Platform/Context.h"
 #include "Magnum/Platform/ScreenedApplication.hpp"
 
 namespace Magnum { namespace Platform {
@@ -96,7 +96,7 @@ bool GlutApplication::tryCreateContext(const Configuration& configuration) {
     glutMotionFunc(staticMouseMoveEvent);
     glutDisplayFunc(staticDrawEvent);
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/GlutApplication.h

@@ -267,7 +267,7 @@ class GlutApplication {
 
         static GlutApplication* instance;
 
-        Context* c;
+        Platform::Context* c;
 };
 
 /**

src/Magnum/Platform/NaClApplication.cpp

@@ -114,7 +114,7 @@ bool NaClApplication::tryCreateContext(const Configuration& configuration) {
     RequestInputEvents(PP_INPUTEVENT_CLASS_MOUSE|PP_INPUTEVENT_CLASS_WHEEL);
     RequestFilteringInputEvents(PP_INPUTEVENT_CLASS_KEYBOARD);
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/NaClApplication.h

@@ -379,7 +379,7 @@ class NaClApplication: public pp::Instance, public pp::Graphics3DClient, public
 
         pp::Graphics3D* graphics;
         pp::Fullscreen* fullscreen;
-        Context* c;
+        Platform::Context* c;
         Vector2i viewportSize;
         Flags flags;
 

src/Magnum/Platform/Platform.h

@@ -33,6 +33,7 @@ namespace Magnum { namespace Platform {
 
 template<class> class BasicScreen;
 template<class> class BasicScreenedApplication;
+class Context;
 
 }}
 

src/Magnum/Platform/Sdl2Application.cpp

@@ -31,7 +31,7 @@
 #include <emscripten/emscripten.h>
 #endif
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 #include "Magnum/Version.h"
 #include "Magnum/Platform/ScreenedApplication.hpp"
 
@@ -198,7 +198,7 @@ bool Sdl2Application::tryCreateContext(const Configuration& configuration) {
     context = SDL_SetVideoMode(configuration.size().x(), configuration.size().y(), 24, SDL_OPENGL|SDL_HWSURFACE|SDL_DOUBLEBUF);
     #endif
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/Sdl2Application.h

@@ -406,7 +406,7 @@ class Sdl2Application {
         SDL_Surface* context;
         #endif
 
-        Context* c;
+        Platform::Context* c;
 
         Flags flags;
 };

src/Magnum/Platform/WindowlessCglApplication.cpp

@@ -30,7 +30,7 @@
 #include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/Debug.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 
 namespace Magnum { namespace Platform {
 
@@ -113,7 +113,7 @@ bool WindowlessCglApplication::tryCreateContext(const Configuration&) {
     }
 
     cglError = CGLSetCurrentContext(context);
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/WindowlessCglApplication.h

@@ -151,7 +151,7 @@ class WindowlessCglApplication {
         CGLContextObj context;
         CGLPixelFormatObj pixelFormat;
 
-        Context* c;
+        Platform::Context* c;
 };
 
 /**

src/Magnum/Platform/WindowlessGlxApplication.cpp

@@ -28,7 +28,7 @@
 #include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/Debug.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 
 #define None 0L // redef Xlib nonsense
 
@@ -111,7 +111,7 @@ bool WindowlessGlxApplication::tryCreateContext(const Configuration&) {
         return false;
     }
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/WindowlessGlxApplication.h

@@ -40,6 +40,7 @@
 #undef Status
 
 #include "Magnum/Magnum.h"
+#include "Magnum/Platform/Context.h"
 
 namespace Magnum { namespace Platform {
 
@@ -157,7 +158,7 @@ class WindowlessGlxApplication {
         GLXContext context;
         GLXPbuffer pbuffer;
 
-        Context* c;
+        Platform::Context* c;
 };
 
 /**

src/Magnum/Platform/WindowlessNaClApplication.cpp

@@ -30,7 +30,7 @@
 #include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/NaClStreamBuffer.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 
 namespace Magnum { namespace Platform {
 
@@ -97,7 +97,7 @@ bool WindowlessNaClApplication::tryCreateContext(const Configuration&) {
 
     glSetCurrentContextPPAPI(graphics->pp_resource());
 
-    c = new Context;
+    c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/WindowlessNaClApplication.h

@@ -171,7 +171,7 @@ class WindowlessNaClApplication: public pp::Instance, public pp::Graphics3DClien
         bool Init(std::uint32_t, const char*, const char*) override;
 
         pp::Graphics3D* graphics;
-        Context* c;
+        Platform::Context* c;
         ConsoleDebugOutput* debugOutput;
 };
 

src/Magnum/Platform/WindowlessWglApplication.cpp

@@ -29,7 +29,7 @@
 #include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/Debug.h>
 
-#include "Magnum/Context.h"
+#include "Magnum/Platform/Context.h"
 
 namespace Magnum { namespace Platform {
 
@@ -114,7 +114,7 @@ bool WindowlessWglApplication::tryCreateContext(const Configuration&) {
         return false;
     }
 
-    _c = new Context;
+    _c = new Platform::Context;
     return true;
 }
 

src/Magnum/Platform/WindowlessWglApplication.h

@@ -154,7 +154,7 @@ class WindowlessWglApplication {
         HDC _deviceContext;
         HGLRC _renderingContext;
 
-        Context* _c;
+        Platform::Context* _c;
 };
 
 /**