if(this->full_screen_mode){
   ::SetWindowLongPtr(this->hWnd, GWL_EXstyle, 0);
   ::SetWindowLongPtr(this->hWnd, GWL_style, WS_EX_TOPMOST | WS_VISIBLE | WS_POPUP);
}
else{
   ::SetWindowLongPtr(this->hWnd, GWL_EXstyle, 256);
   ::SetWindowLongPtr(this->hWnd, GWL_style, WS_OVERLAPPEDWINDOW);
}

::SetWindowPos(this->hWnd, NULL, CW_USEDEFAULT, CW_USEDEFAULT, this->Get_screen_width(), 
    this->Get_screen_height(), SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED | SWP_SHOWWINDOW);

// Change window style to remove border in fullscreen modeDWORD dwStyle;if(m_thePresentParams.Windowed)	dwStyle = (WS_OVERLAPPEDWINDOW | WS_VISIBLE) & ~WS_THICKFRAME;else	dwStyle = WS_POPUP;SetWindowLongPtr(m_hWnd, GWL_STYLE, dwStyle);// Make sure the changes are flushedSetWindowPos(m_hWnd, NULL, 0, 0, 0, 0,	SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);

int WINAPI WinMain(....){	MSG msg; WNDCLASSEX wc;	HWND hWnd; DWORD dw_style;	//RegisterClass(hInstance);	wc.cbSize=sizeof(WNDCLASSEX);	wc.style=CS_HREDRAW | CS_VREDRAW;		wc.lpfnWndProc=(WNDPROC)WinProc;	wc.cbClsExtra=0;	wc.cbWndExtra=0;	wc.hInstance=hInstance;	wc.hIcon=NULL;	wc.hCursor=LoadCursor(NULL, IDC_ARROW);	wc.hbrBackground=NULL;	wc.lpszMenuName=NULL;	wc.lpszClassName=g_engine->GetWinTitle();	wc.hIconSm=NULL;	RegisterClassEx(&wc);	//at the beginning g_engine->Get_full_screen_mode() returns false, we start always in windowed mode	if(g_engine->Get_full_screen_mode())		dw_style = WS_POPUP;	else		dw_style = (WS_OVERLAPPEDWINDOW | WS_VISIBLE) & ~WS_THICKFRAME;		//window creation	hWnd=CreateWindow(		g_engine->GetWinTitle(),				//win class		g_engine->GetWinTitle(),				//title bar		dw_style,				//style		CW_USEDEFAULT,			//win x pos		CW_USEDEFAULT,			//win y pos		g_engine->Get_screen_width(),			//width		g_engine->Get_screen_height(),			//height		NULL,					//parent win		NULL,					//menu		hInstance,				//istanza applicazione		NULL);					//win parameters	if(hWnd==NULL)		return 0;		//display win	ShowWindow(hWnd, nCmdShow);	UpdateWindow(hWnd);	//Create an instance of Engine class called g_engine        g_engine = new Engine();		//Game initialization	if(!g_engine->Init(hWnd))		return 0;				bGame_Over=false;		//Message Loop	while( !bGame_Over )	{		if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))		{			TranslateMessage(&msg);			DispatchMessage(&msg);		}				g_engine->Update();		//Process game loop	} //end while true	g_engine->End();			//Game cleanup	delete g_engine;	return msg.wParam;} //WinMain end

Engine::Engine(){	..........	this->deviceLost = false;	this->toggling_WinFullScreenMode = false;}void Engine::Shutdown(void){	bGame_Over = true;}int Engine::Init(HWND hWnd)	//D3D Initialization{	D3DDISPLAYMODE dm; this->hWnd = hWnd;	......	this->d3d->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &dm);	//this->p_d3dpp_windowedMode holds Presentation_parameters for windowed mode	ZeroMemory(&(this->p_d3dpp_windowedMode), sizeof(this->p_d3dpp_windowedMode));	this->p_d3dpp_windowedMode.Windowed = true;	this->p_d3dpp_windowedMode.SwapEffect = D3DSWAPEFFECT_DISCARD;	this->p_d3dpp_windowedMode.BackBufferFormat=D3DFMT_UNKNOWN;	this->p_d3dpp_windowedMode.PresentationInterval = D3DPRESENT_INTERVAL_ONE;	this->p_d3dpp_windowedMode.hDeviceWindow = this->hWnd;	//and this->p_d3dpp_fullScreenMode for fullscreen mode	ZeroMemory(&(this->p_d3dpp_fullScreenMode), sizeof(this->p_d3dpp_fullScreenMode));	this->p_d3dpp_fullScreenMode.Windowed = false;	this->p_d3dpp_fullScreenMode.SwapEffect = D3DSWAPEFFECT_DISCARD;	this->p_d3dpp_fullScreenMode.BackBufferFormat=dm.Format;	this->p_d3dpp_fullScreenMode.BackBufferCount = 1;	this->p_d3dpp_fullScreenMode.BackBufferWidth = this->screen_width;	this->p_d3dpp_fullScreenMode.BackBufferHeight = this->screen_height;	this->p_d3dpp_fullScreenMode.PresentationInterval = D3DPRESENT_INTERVAL_ONE;	this->p_d3dpp_fullScreenMode.hDeviceWindow = this->hWnd;		//this->p_d3dpp holds the parameters for device->Reset and device->CreateDevice	if(this->full_screen_mode){		//FULL screen mode		::ShowCursor(FALSE);		this->p_d3dpp = this->p_d3dpp_fullScreenMode;	}	else		this->p_d3dpp = this->p_d3dpp_windowedMode;	//Create device D3D device	this->d3d->CreateDevice(		D3DADAPTER_DEFAULT,		D3DDEVTYPE_HAL,		this->hWnd,		D3DCREATE_SOFTWARE_VERTEXPROCESSING,		&this->p_d3dpp,		&(this->d3ddev));	if(this->d3ddev==NULL){		MessageBox(NULL, "Engine::Init - Error creating D3D Device", "ERROR", MB_OK);		return 0;	}	.... }void Engine::ToggleScreenMode(void){	//function called if F2 key hit by user to toggle between windowed and fullcreen mode	this->full_screen_mode = !this->full_screen_mode;	this->deviceLost = true;	this->toggling_WinFullScreenMode = true;	if(this->full_screen_mode)		this->p_d3dpp = this->p_d3dpp_fullScreenMode;	else		this->p_d3dpp = this->p_d3dpp_windowedMode;}void Engine::Update(){	//Called in the window main loop at every frame	HRESULT result;	//Check if the device is lost (ALT-TAB in fullscreen mode) or user hits F2 for toggling	if(this->deviceLost)	{		result = this->d3ddev->TestCooperativeLevel();		if(result == D3DERR_DEVICELOST){			::Sleep(100);			return;		//leave Update method and go to the win main loop		} //endif(result == D3DERR_DEVICELOST)		if( (result == D3DERR_DEVICENOTRESET) || (this->toggling_WinFullScreenMode) ){			//device->Reset can be tried or user hits F2 key			//Release of all resources and call device->Reset			this->onLostDevice();						result = this->d3ddev->Reset(&this->p_d3dpp);			if(result == D3D_OK){	//Reset is OK				this->deviceLost = false;								//Try to reacquire all resources previously released				if( !this->onResetDevice() ) {					this->Shutdown(); //something wrong, shutdown and kill the application				}				if(this->toggling_WinFullScreenMode) { //if true the user press F2 for toggling mode					this->toggling_WinFullScreenMode = false;					DWORD dwStyle;					if(this->full_screen_mode){	//change style for full screen mode						dwStyle = WS_POPUP;						::ShowCursor(FALSE);					}					else{	//change win style for windowed mode						dwStyle = (WS_OVERLAPPEDWINDOW | WS_VISIBLE) & ~WS_THICKFRAME;						::ShowCursor(TRUE);					}					//change the win style and flush changes					::SetWindowLongPtr(this->hWnd, GWL_STYLE, dwStyle);						::SetWindowPos(this->hWnd, NULL, 0, 0, 0, 0,						SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);				} //endif(this->toggling_WinFullScreenMode)			}			else{ //the device->Reset goes wrong, return, leave Update method and go back to the win main loop				return;			} //endif(result == D3D_OK)		}//endif(result == D3DERR_DEVICENOTRESET)		if(result != D3D_OK){			////something wrong, shutdown and kill the application			this->Shutdown();		} //endif(result != D3D_OK)	} //endif(this->deviceLost) --- end of section that manages the devicelost and the toggle mode 	//Call the extern function Game_Run() wich update 2d objects position according to the keys hit by user	Game_Run();		//it updates objects not managed by the Engine class but managed by the extern functions	//automatically update the objects managed by the Engine class contained inside a std::list object	this->Update2D_Entities();	//Perform collision detection testing, I omitted the code	//update with 60fps timing using a stopwatch of 14ms. If from the previous call the time passed is less than 	//14ms sleep(1) and jump the code below	if (!timedUpdate.stopwatch(14)) {		Sleep(1);	}	else {  //more than 14ms passed before last call, I can write on backbuffer and present the scene		//update input devices and audio system, code omitted		//Render objects		if(this->Start_Render()) //execute this->d3ddev->BeginScene();		{			this->d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 200), 1.0f, 0); //Clear the scene			this->Start_Render2d(); //execute D3DXSprite->Begin(D3DXSPRITE_ALPHABLEND))			this->Draw2D_Entities(); //execute the D3DXSprite->Draw() for the objects managed by the Engine class contained inside a std::list object			Game_Render2d(); //extern function that does the D3DXSprite->Draw() for the objects not managed by the Engine class but managed by the extern functions			this->Stop_Render2d(); //execute D3DXSprite->End();			this->Stop_Render(); //execute the this->d3ddev->EndScene() and the this->d3ddev->Present(NULL, NULL, NULL, NULL);			//if the d3ddev->Present() get back a D3DERR_DEVICELOST =====> this->deviceLost = true;		}				//automatically remove the dead objects managed by the Engine class and contained inside a std::list object		this->Bury2D_Entities();	} //endelse} //End of Engine::Update