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！！！