关于win32 programming中的视口和窗口！

1 什么叫设备坐标，什么叫逻辑坐标？

言语无用，程序说话！

#include <windows.h>

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

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

     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 ;
     }
    
     hwnd = 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 (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;
    
     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 ;
      static int cxClient,cyClient;
     switch (message)
     {
               
     case WM_SIZE:
   cxClient = LOWORD(lParam);
   cyClient = HIWORD(lParam);
         return 0;
  case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;
        
    SetViewportOrgEx(hdc,cxClient/2,cyClient/2,NULL);

    TextOut(hdc,0,0,TEXT("Hello,Windows 98!"),17);

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

第一，TextOut函数是以逻辑坐标为单位的；

第二，SetViewportOrgEx(hdc,cxClient/2,cyClient/2,NULL)；这条语句的字面

意思是把视口原点设在客户区的中央；

第三，事实是：文本将显示在客户区的中央；

结论：逻辑点（0，0）也被放在了中央。

把SetViewportOrgEx(hdc,cxClient/2,cyClient/2,NULL)；这句换成：

SetWindowOrgEx(hdc,-cxClient/2,-cyClient/2, NULL); 取得的效果与上句相同。

第一，此句的字面意思是：把窗口的原点设在(-cxClient/2,-cyClient/2) 上；

第二，其实字面意思太过于误导原意，什么狗屁窗口，视口，只要记住：

        SetWindowOrgEx使原来的X轴右移-cxClient/2,Y轴下移-cyClient/2

看这个：

       SetViewportOrgEx(hdc,cxClient/2,cyClient/2,NULL);

       SetWindowOrgEx(hdc,-cxClient/2,-cyClient/2,NULL);

看好了吧！！！

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