OPENGL: Add functionality to query OpenGL functions on runtime.

This can and will be used for future extension usage support.

Tizen changes have been untested.

backends/graphics/opengl/opengl-graphics.h

@@ -286,6 +286,21 @@ private:
 	 */
 	void initializeGLExtensions();
 
+protected:
+	/**
+	 * Query the address of an OpenGL function by name.
+	 *
+	 * This can only be used after a context has been created.
+	 * Please note that this function can return valid addresses even if the
+	 * OpenGL context does not support the function.
+	 *
+	 * @param name The name of the OpenGL function.
+	 * @return An function pointer for the requested OpenGL function or
+	 *         nullptr in case of failure.
+	 */
+	virtual void *getProcAddress(const char *name) const = 0;
+
+private:
 	/**
 	 * Try to determine the internal parameters for a given pixel format.
 	 *

backends/graphics/opengl/opengl-sys.h

@@ -54,4 +54,10 @@ using namespace Tizen::Graphics::Opengl;
 #include <GL/gl.h>
 #endif
 
+#ifdef SDL_BACKEND
+#define GLCALLCONV APIENTRY
+#else
+#define GLCALLCONV
+#endif
+
 #endif

backends/graphics/openglsdl/openglsdl-graphics.cpp

@@ -305,6 +305,10 @@ void OpenGLSdlGraphicsManager::refreshScreen() {
 #endif
 }
 
+void *OpenGLSdlGraphicsManager::getProcAddress(const char *name) const {
+	return SDL_GL_GetProcAddress(name);
+}
+
 bool OpenGLSdlGraphicsManager::setupMode(uint width, uint height) {
 	// In case we request a fullscreen mode we will use the mode the user
 	// has chosen last time or the biggest mode available.

backends/graphics/openglsdl/openglsdl-graphics.h

@@ -67,6 +67,8 @@ protected:
 	virtual bool loadVideoMode(uint requestedWidth, uint requestedHeight, const Graphics::PixelFormat &format);
 
 	virtual void refreshScreen();
+
+	virtual void *getProcAddress(const char *name) const;
 private:
 	bool setupMode(uint width, uint height);
 

backends/platform/tizen/graphics.cpp

@@ -206,3 +206,7 @@ bool TizenGraphicsManager::loadVideoMode(uint requestedWidth, uint requestedHeig
 void TizenGraphicsManager::refreshScreen() {
 	eglSwapBuffers(_eglDisplay, _eglSurface);
 }
+
+void *TizenGraphicsManager::getProcAddress(const char *name) const {
+	return eglGetProcAddress(name);
+}

backends/platform/tizen/graphics.h

@@ -63,6 +63,8 @@ protected:
 
 	void refreshScreen();
 
+	void *getProcAddress(const char *name) const;
+
 	const Graphics::Font *getFontOSD();
 
 private: