位图绘制后拖放窗口时闪动现象的解决方案

 LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 PAINTSTRUCT ps;
 RECT  rect;
 
 TCHAR szHello[MAX_LOADSTRING];
 LoadString(hInst, IDS_HELLO, szHello, MAX_LOADSTRING);
 
 static HDC hdc,hMemDC,hBmpDC;
 static HBITMAP hBitmap;
 static HBITMAP hMemDCBmp;

 switch (message)
 {  
  case WM_CREATE:
   //读取资源位图
   hBitmap=LoadBitmap(hInst,MAKEINTRESOURCE(IDB_BITMAP1) );
   /*
   hBmpDC=CreateCompatibleDC(hdc);
   SelectObject(hBmpDC,hBitmap);
   */
   return 0;
  
  case WM_ERASEBKGND:    

   return 0;
  
  case WM_SIZING:  
   
   return 0;
  case WM_SIZE:  
   return 0;
  
  case WM_PAINT:
   hdc=BeginPaint(hWnd, &ps);
   {    
    GetClientRect(hWnd,&rect);
    
    //创建内存DC并将位图句柄选入 
    hBmpDC=CreateCompatibleDC(hdc);
    SelectObject(hBmpDC,hBitmap);

    //建立新一个内存DC和位图句柄
    hMemDC=::CreateCompatibleDC(hdc);
    hMemDCBmp=CreateCompatibleBitmap(hdc,rect.right-rect.left,rect.bottom-rect.top);
    
    HGDIOBJ hBjOld=::SelectObject(hMemDC,hMemDCBmp);
    
    //先在内存DC上进行整个的画刷填充
    FillRect(hMemDC,&rect,(HBRUSH)GetStockObject(WHITE_BRUSH));
    
    BitBlt(hMemDC,0,0,rect.right-rect.left,rect.bottom-rect.top,hBmpDC,0,0,SRCCOPY);
    BitBlt(hdc,0,0,rect.right-rect.left,rect.bottom-rect.top,hMemDC,0,0,SRCCOPY);
    
    //func(rect);
    SelectObject(hMemDC,hBjOld);
     
    DeleteObject(hMemDCBmp); 
    DeleteDC(hBmpDC);
    DeleteDC(hMemDC);
   }
   EndPaint(hWnd,&ps);
   
   return 0;
  
  case WM_DESTROY:
   DeleteObject(hBitmap);
   /*
   DeleteObject(hBitmap); 
   DeleteObject(hMemDCBmp); 
   DeleteDC(hBmpDC);
   DeleteDC(hMemDC);
   */
   PostQuitMessage(0);
   return 0;
  default:
   return DefWindowProc(hWnd, message, wParam, lParam);
   }
   return 0;
}