1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Wm_paint

Discussion in 'Win32' started by johny10151981, Oct 10, 2008.

  1. johny10151981

    johny10151981 New Member

    Joined:
    Jul 7, 2010
    Messages:
    15
    Likes Received:
    0
    Trophy Points:
    0
    the problem with below program is i want to erase background when i press the button. how it is possible and what is wrong with the program. is there anything wrong with programming stratagy. i am preparing for a big leap
    ??

    Code:
    #include <windows.h>
    HINSTANCE ghins;
    HWND ghwnd,btnHwnd;
    
    LRESULT __stdcall WndProc(HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam);
    
    
    int __stdcall WinMain(HINSTANCE hInstance,HINSTANCE hPrev,LPSTR lpCmdline,int nShowCmd)
    {
     MSG msg;
     WNDCLASS wc;
     
     ghins = hInstance;
     wc.cbClsExtra=0;
     wc.cbWndExtra=0;
     wc.hbrBackground=GetStockObject(WHITE_BRUSH);
     wc.hCursor=LoadCursor(NULL,IDC_ARROW);
     wc.hIcon=NULL;
     wc.hInstance=ghins;
     wc.lpfnWndProc=WndProc;
     wc.lpszClassName=TEXT("WM_PAINTAPPS");
     wc.lpszMenuName=NULL;
     wc.style=0;
    
     RegisterClass(&wc);
     ghwnd=CreateWindow( wc.lpszClassName,
    			   TEXT("Test Prog"),
    			   WS_OVERLAPPEDWINDOW,
    			   CW_USEDEFAULT,
    			   CW_USEDEFAULT,
    			   CW_USEDEFAULT,
    			   CW_USEDEFAULT,
    			   NULL,
    			   NULL,
    			   ghins,
    			   NULL);
    
     ShowWindow(ghwnd,nShowCmd);
     UpdateWindow(ghwnd);
     while(GetMessage(&msg,0,0,0))
     {
      TranslateMessage(&msg);
      DispatchMessage(&msg);
     }
    
     return (INT)msg.wParam;
    }
    
    
    
    LRESULT __stdcall WndProc(HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam)
    {
     HDC hdc;
     static TCHAR pStr[100];
     PAINTSTRUCT ps;
     switch(msg)
     {
    	case WM_CREATE:
    		CreateWindow(TEXT("BUTTON"),TEXT("GetDC"),WS_VISIBLE|WS_CHILD,
    			200,300,150,40,hWnd,(HMENU)3001,ghins,NULL);		
    		CreateWindow(TEXT("BUTTON"),TEXT("BeginPaint"),WS_VISIBLE|WS_CHILD,
    			355,300,150,40,hWnd,(HMENU)3002,ghins,NULL);		
    		lstrcpy(pStr,TEXT("Hello World"));
    	return 0;	
    	case WM_PAINT:
    		hdc = GetDC(hWnd);
    		TextOut (hdc, 0, 0,pStr,lstrlen(pStr)) ;
    		DeleteDC(hdc);				
    		break;
    
    	case WM_COMMAND:
    		switch(LOWORD(wParam))
    		{
    		case 3001:
    			lstrcpy(pStr,TEXT("What I"));			
    			break;
    		case 3002:
    			lstrcpy(pStr,TEXT("Know"));
    			break;
    		}
    		return 0;
    	case WM_CLOSE:
    		PostQuitMessage(0);
    		return 0;
    	
    	
     }
     	return DefWindowProc(hWnd,msg,wParam,lParam);
    }
     
  2. imported_xpi0t0s

    imported_xpi0t0s New Member

    Joined:
    Jul 18, 2008
    Messages:
    101
    Likes Received:
    0
    Trophy Points:
    0
    InvalidateRect is your friend. Also see UpdateWindow if you want the changes to take place immediately, rather than waiting for Windows to get round to validating the window (which it will eventually, but for snappy updates then you need to force it to happen).
     
  3. johny10151981

    johny10151981 New Member

    Joined:
    Jul 7, 2010
    Messages:
    15
    Likes Received:
    0
    Trophy Points:
    0
    thanks, but if my memory serves well i can say that InvalidateRect will erase Buttons from the main window too.
     
  4. imported_xpi0t0s

    imported_xpi0t0s New Member

    Joined:
    Jul 18, 2008
    Messages:
    101
    Likes Received:
    0
    Trophy Points:
    0
    It shouldn't unless you specify that the invalidated area needs blanking first. Look at the bErase parameter. If specifying that it shouldn't be blanked first still causes the buttons to flicker, try invalidating a region (InvalidateRgn perhaps) that excludes those buttons instead of the whole lot.
     

Share This Page