如果窗口想获取相关消息，需要注册Session的Notification，需要Wtsapi32.dll中的两个函数：WTSRegisterSessionNotification和WTSUnRegisterSessionNotification，分别在窗口创建和销毁的时候调用。

typedef BOOL (WINAPI *WTSRegisterSessionNotification)(HWND, DWORD); typedef BOOL (WINAPI *WTSUnRegisterSessionNotification)(HWND); #define WTSAPI_DLL _T("Wtsapi32.dll") #define MY_WTS_SESSION_FUNCTION(fnType, fnName, arg) / BOOL bRet = FALSE; / HMODULE hLibrary = ::LoadLibrary(WTSAPI_DLL); / if (hLibrary) / { / fnType fn / = (fnType)::GetProcAddress(hLibrary, fnName); / if (fn) / { / bRet = fn##arg; / } / ::FreeLibrary(hLibrary); / } / return bRet; BOOL MyWTSRegisterSessionNotification(HWND hWnd, DWORD dwFlag) { MY_WTS_SESSION_FUNCTION(WTSRegisterSessionNotification, "WTSRegisterSessionNotification", (hWnd, dwFlag)); } BOOL MyWTSUnRegisterSessionNotification(HWND hWnd) { MY_WTS_SESSION_FUNCTION(WTSUnRegisterSessionNotification, "WTSUnRegisterSessionNotification", (hWnd)); }

 

这样，在SESSION切换的时候，窗口就可以收到一个WM_WTSSESSION_CHANGE消息。

 

如果不依赖窗口，需要判断当前系统是否处于锁屏状态，有一段比较tricky的代码……就是试图SwitchDesktop，如果失败就认为在锁屏。

这种方法有另一个优点：可以判断ctrl+alt+delete后系统暂时“锁定”以及“解锁”的状态，而这种状态改变，窗口是没法收到WM_WTSESSIONCHANGE的。

typedef HDESK (WINAPI *PFNOPENDESKTOP)(LPSTR, DWORD, BOOL, ACCESS_MASK); typedef BOOL (WINAPI *PFNCLOSEDESKTOP)(HDESK); typedef BOOL (WINAPI *PFNSWITCHDESKTOP)(HDESK); BOOL PP_IsWorkStationLocked() { // note: we can't call OpenInputDesktop directly because it's not // available on win 9x BOOL bLocked = FALSE; // load user32.dll once only static HMODULE hUser32 = LoadLibrary(_T("user32.dll")); if (hUser32) { static PFNOPENDESKTOP fnOpenDesktop = (PFNOPENDESKTOP)GetProcAddress(hUser32, "OpenDesktopA"); static PFNCLOSEDESKTOP fnCloseDesktop = (PFNCLOSEDESKTOP)GetProcAddress(hUser32, "CloseDesktop"); static PFNSWITCHDESKTOP fnSwitchDesktop = (PFNSWITCHDESKTOP)GetProcAddress(hUser32, "SwitchDesktop"); if (fnOpenDesktop && fnCloseDesktop && fnSwitchDesktop) { HDESK hDesk = fnOpenDesktop("Default", 0, FALSE, DESKTOP_SWITCHDESKTOP); if (hDesk) { bLocked = !fnSwitchDesktop(hDesk); // cleanup fnCloseDesktop(hDesk); } } } return bLocked; }