Window flickering | GameDev.net

The windows are child windows that have their procs modified so that you can move them around, by selecting the top part of the window (top 20 pixels). But when you do, i get horrible flickering, i guess due to me calling InvalidateRect whenever the window is moved. I need to called invalidate, to clear the background of previous line drawing. I have pasted the whole app below, which is just a simplified version of my current app, to help make the problem clearer. could someone give me some ideas on how to reduce the flickering? and on a side not, when the user moves the window quickly, the cursor becomes in the incorrect place for detecting whether or not the user wants to move the window, ie not in that 20 pixel marking area, any ideas on this issue too?


#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
LRESULT CALLBACK EventProc (HWND, UINT, WPARAM, LPARAM) ;
HWND CreateEventWindow();

HINSTANCE		hInstance;
HWND			hApp ;
HWND			SelWin;

int WINAPI WinMain (HINSTANCE _hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("HelloWin") ;
     MSG          msg ;
     WNDCLASS     wndclass ;
	 hInstance = _hInstance;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("This program requires Windows NT!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }
     
     hApp = CreateWindow (szAppName,                  // window class name
                          TEXT ("The Hello Program"), // window caption
                          WS_OVERLAPPEDWINDOW,        // window style
                          CW_USEDEFAULT,              // initial x position
                          CW_USEDEFAULT,              // initial y position
                          CW_USEDEFAULT,              // initial x size
                          CW_USEDEFAULT,              // initial y size
                          NULL,                       // parent window handle
                          NULL,                       // window menu handle
                          hInstance,                  // program instance handle
                          NULL) ;                     // creation parameters
     
     ShowWindow (hApp, iCmdShow) ;
     UpdateWindow (hApp) ;

	HWND Event1 =  CreateEventWindow();
	CreateWindowEx(WS_EX_WINDOWEDGE , L"static", L"Node1", WS_CHILD | WS_VISIBLE | SS_CENTER, 0, 0, 198, 20, Event1, (HMENU) 0, hInstance, NULL);
	CreateWindowEx(WS_EX_CLIENTEDGE , L"static", L"Node2", WS_CHILD | WS_VISIBLE | SS_CENTER, 0, 20, 198, 20, Event1, (HMENU) 0, hInstance, NULL);
	CreateWindowEx(WS_EX_CLIENTEDGE , L"static", L"Node3", WS_CHILD | WS_VISIBLE | SS_CENTER, 0, 40, 198, 20, Event1, (HMENU) 0, hInstance, NULL);
	CreateWindowEx(WS_EX_CLIENTEDGE , L"static", L"Node4", WS_CHILD | WS_VISIBLE | SS_CENTER, 0, 60, 198, 20, Event1, (HMENU) 0, hInstance, NULL);
	SetWindowPos(Event1, 0, 500, 500, 200, 80, 0 );

	//this code just enbles the first inital line
	SelWin = HWND(1);
	SendMessage(Event1, WM_MOUSEMOVE, 0, 0);
	SelWin = 0;

     
     while (GetMessage (&msg, NULL, 0, 0))
     {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
     }
     return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     HDC         hdc ;
     PAINTSTRUCT ps ;
     RECT        r ;
     
     switch (message)
     {
     case WM_CREATE:
          return 0 ;

     case WM_DESTROY:
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

LRESULT CALLBACK EventProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	int MX, MY;
	POINT p;
	RECT r;
	HDC    hdc ;
   

     switch (message)
     {
		 case WM_CREATE:
			  return 0 ;
	     
		 case WM_DESTROY:
			  return 0 ;

		 case WM_LBUTTONDOWN:
			 if(HIWORD(lParam) <= 20 )
				 SelWin = hwnd;
			 return 0;

		 case WM_MOUSEMOVE:
			  if(SelWin != 0)
				{
				hdc = GetDC (hApp) ;
				InvalidateRect(hApp, NULL, 0);		//clear background of previous lines

				p.x = LOWORD(lParam); p.y =  HIWORD(lParam);	//p is in Event client coordiantes
				ClientToScreen(hwnd, &p);						//p is now in screen
				ScreenToClient(hApp, &p);						//p is now in hApps client

				SetWindowPos(SelWin, 0,							//set the centre of the window at the mouse pos
				  p.x - 100, 
				  p.y - 10, 0, 0, SWP_NOSIZE);

				GetWindowRect( hwnd, &r);						//draw a line from 0,0 to window corner
				p.x = r.left; p.y = r.top;
				ScreenToClient(hApp, &p);
				MoveToEx  (hdc, 0,	0, NULL) ;
				LineTo    (hdc, p.x,	p.y) ;
				ReleaseDC (hApp, hdc) ;
				}
			 return 0;

		  case WM_LBUTTONUP:
			 SelWin = 0;
			 return 0;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

 HWND CreateEventWindow()
 {
	WNDCLASS		wndclass ;
	HWND			Handle;
	 
	 wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
	 wndclass.lpfnWndProc   = EventProc ;
	 wndclass.cbClsExtra    = 0 ;
	 wndclass.cbWndExtra    = 0 ;
	 wndclass.hInstance     = hInstance ;
	 wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
	 wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
	 wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
	 wndclass.lpszMenuName  = NULL ;
	 wndclass.lpszClassName = L"Event" ;

	 if (!RegisterClass (&wndclass))
	 {
		  //class already registered // ** need to fix this, no check for register failure **
	 }
	 
	 Handle = CreateWindow (L"Event",			
						  L"",				
						  WS_CHILD | WS_BORDER, 
						  300,						 
						  300,						
						  200,              
						  20,              
						  hApp,                     
						  0,                     
						  hInstance,                
						  0) ;    

	 if(!Handle)
		MessageBox(NULL, L"Window creation failure", L"win", NULL);
	 
	 ShowWindow (Handle, SW_SHOWNORMAL) ;
	 UpdateWindow (Handle) ;

	 return Handle;
 }

Topic Locked