case SCREEN_OPENGL:
		// Clear drawing area. Some drivers (on Linux) have more than 2 buffers and the screen might
		// be dirty because of other programs.
		glClearColor (0.0f, 0.0f, 0.0f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		if (sdl.opengl.pixel_buffer_object) {
			glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT);
			glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT, 0);
			GLboolean a = glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_EXT);
			if (a == GL_FALSE) LOG_MSG("HELP");
			return;