Source code of Windows XP (NT5)
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/*************************************************************************
Module: DeskSwitch.c
Copyright (C) 1997-2000 by Microsoft Corporation. All rights reserved.
*************************************************************************/
#ifdef _WIN32_IE
#undef _WIN32_IE
#endif
#define _WIN32_IE 0x0600
#include <shlwapi.h> // for IsOS
#include <shlwapip.h> // for IsOS
////////////////////////////////////////////////////////////////////////////
// Helper functions and globals for detecting desktop switch
//
// Usage: Call InitWatchDeskSwitch() with an hWnd and message during
// initialization. The message will be posted to hWnd whenever
// a desktop switch has occurred. When the message is received
// the desktop switch has taken place already.
//
// Call TermWatchDeskSwitch() to stop watching for desktop
// switches.
////////////////////////////////////////////////////////////////////////////
HANDLE g_hDesktopSwitchThread = 0;
HANDLE g_hDesktopSwitchEvent = 0;
HANDLE g_hTerminateEvent = 0;
typedef struct MsgInfo {
HWND hWnd;
DWORD dwMsg;
DWORD dwTIDMain;
DWORD fPostMultiple;
} MSG_INFO;
MSG_INFO g_MsgInfo;
void Cleanup()
{
if (g_hDesktopSwitchEvent)
{
CloseHandle(g_hDesktopSwitchEvent);
g_hDesktopSwitchEvent = 0;
}
if (g_hTerminateEvent)
{
CloseHandle(g_hTerminateEvent);
g_hTerminateEvent = 0;
}
}
#ifndef DESKTOP_ACCESSDENIED
#define DESKTOP_ACCESSDENIED 0
#define DESKTOP_DEFAULT 1
#define DESKTOP_SCREENSAVER 2
#define DESKTOP_WINLOGON 3
#define DESKTOP_TESTDISPLAY 4
#define DESKTOP_OTHER 5
#endif
int GetDesktopType()
{
HDESK hdesk;
TCHAR szName[100];
DWORD nl;
int iCurrentDesktop = DESKTOP_OTHER;
hdesk = OpenInputDesktop(0, FALSE, MAXIMUM_ALLOWED);
if (!hdesk)
{
hdesk = OpenDesktop(TEXT("Winlogon"), 0, FALSE, MAXIMUM_ALLOWED);
if (!hdesk)
{
// fails when ap has insufficient permission on secure desktop
return DESKTOP_ACCESSDENIED;
}
}
GetUserObjectInformation(hdesk, UOI_NAME, szName, 100, &nl);
CloseDesktop(hdesk);
if (!lstrcmpi(szName, TEXT("Default")))
{
iCurrentDesktop = DESKTOP_DEFAULT;
} else if (!lstrcmpi(szName, TEXT("Winlogon")))
{
iCurrentDesktop = DESKTOP_WINLOGON;
}
return iCurrentDesktop;
}
// WatchDesktopProc - waits indefinitely for a desktop switch. When
// it gets one, it posts a message to the window
// specified in InitWatchDeskSwitch. It also waits
// on an event that signals the procedure to exit.
//
DWORD WatchDesktopProc(LPVOID pvData)
{
BOOL fCont = TRUE;
DWORD dwEventIndex;
HANDLE ahEvents[2];
int iDesktopT, iCurrentDesktop = GetDesktopType();
SetThreadDesktop(GetThreadDesktop(g_MsgInfo.dwTIDMain));
ahEvents[0] = g_hDesktopSwitchEvent;
ahEvents[1] = g_hTerminateEvent;
while (fCont)
{
iDesktopT = GetDesktopType();
if (iDesktopT == iCurrentDesktop)
{
DBPRINTF(TEXT("Wait for desktop switch or exit on desktop = %d\r\n"), iCurrentDesktop);
dwEventIndex = WaitForMultipleObjects(2, ahEvents, FALSE, INFINITE);
dwEventIndex -= WAIT_OBJECT_0;
} else
{
// missed a desktop switch so handle it
dwEventIndex = 0;
}
switch (dwEventIndex)
{
case 0:
// With a FUS there is a spurious switch to Winlogon
iDesktopT = GetDesktopType();
DBPRINTF(TEXT("desktop switch from %d to %d\r\n"), iCurrentDesktop, iDesktopT);
if (iDesktopT != iCurrentDesktop)
{
iCurrentDesktop = iDesktopT;
// Handle desk switch event
DBPRINTF(TEXT("WatchDesktopProc: PostMessage(0x%x, %d...) desktop %d\r\n"), g_MsgInfo.hWnd, g_MsgInfo.dwMsg, iCurrentDesktop);
PostMessage(g_MsgInfo.hWnd, g_MsgInfo.dwMsg, iCurrentDesktop, 0);
} else DBPRINTF(TEXT("WatchDesktopProc: Ignore switch to %d\r\n"), iDesktopT);
break;
case 1:
// Handle terminate thread event
fCont = FALSE;
DBPRINTF(TEXT("WatchDesktopProc: got terminate event\r\n"));
break;
default:
// Unexpected event
fCont = FALSE;
DBPRINTF(TEXT("WatchDesktopProc unexpected event %d\r\n"), dwEventIndex + WAIT_OBJECT_0);
break;
}
}
Cleanup();
DBPRINTF(TEXT("WatchDesktopProc returning...\r\n"));
return 0;
}
// InitWatchDeskSwitch - starts a thread to watch for desktop switches
//
// hWnd [in] - window handle to post message to
// dwMsg [in] - message to post on desktop switch
//
// Call this function after the window has been created whenever it
// is to wait for a desktop switch.
//
void InitWatchDeskSwitch(HWND hWnd, DWORD dwMsg)
{
DWORD dwTID;
if (g_hDesktopSwitchThread || g_hDesktopSwitchEvent)
return; // don't do this again if it's already running
// Create an unnamed event used to signal the thread to terminate
g_hTerminateEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
// and open the desktop switch event. If utility manager is
// running then we will wait on it's desktop switch event otherwise
// wait on the system desktop switch event. If waiting on utilman
// then only post one switch message.
g_hDesktopSwitchEvent = OpenEvent(SYNCHRONIZE
, FALSE
, TEXT("UtilMan_DesktopSwitch"));
g_MsgInfo.fPostMultiple = FALSE;
if (!g_hDesktopSwitchEvent)
{
g_hDesktopSwitchEvent = OpenEvent(SYNCHRONIZE
, FALSE
, TEXT("WinSta0_DesktopSwitch"));
g_MsgInfo.fPostMultiple = TRUE;
}
if (g_hDesktopSwitchEvent && g_hTerminateEvent)
{
g_MsgInfo.hWnd = hWnd;
g_MsgInfo.dwMsg = dwMsg;
g_MsgInfo.dwTIDMain = GetCurrentThreadId();
DBPRINTF(TEXT("InitWatchDeskSwitch(0x%x, %d, %d)\r\n"), g_MsgInfo.hWnd, g_MsgInfo.dwMsg, g_MsgInfo.dwTIDMain);
g_hDesktopSwitchThread = CreateThread(
NULL, 0
, WatchDesktopProc
, &g_MsgInfo, 0
, &dwTID);
}
// cleanup if failed to create thread
if (!g_hDesktopSwitchThread)
{
DBPRINTF(TEXT("InitWatchDeskSwitch failed!\r\n"));
Cleanup();
}
}
// TermWatchDeskSwitch - cleans up after a desktop switch
//
// Call this function to terminate the thread that is watching
// for desktop switches (if it is running) and to clean up the
// event handle.
//
void TermWatchDeskSwitch()
{
DBPRINTF(TEXT("TermWatchDeskSwitch...\r\n"));
if (g_hDesktopSwitchThread)
{
SetEvent(g_hTerminateEvent);
DBPRINTF(TEXT("TermWatchDeskSwitch: SetEvent(0x%x)\r\n"), g_hDesktopSwitchThread);
g_hDesktopSwitchThread = 0;
} else DBPRINTF(TEXT("TermWatchDeskSwitch: g_hDesktopSwitchThread = 0\r\n"));
}
////////////////////////////////////////////////////////////////////////////
// helper functions for detecting if UtilMan is running (in
// which case this applets is being managed by it)
////////////////////////////////////////////////////////////////////////////
__inline BOOL IsUtilManRunning()
{
HANDLE hEvent = OpenEvent(SYNCHRONIZE, FALSE, TEXT("UtilityManagerIsActiveEvent"));
if (hEvent != NULL)
{
CloseHandle(hEvent);
return TRUE;
}
return FALSE;
}
__inline BOOL CanLockDesktopWithoutDisconnect()
{
// This function may have to change if UI is added to Whistler that
// allows switching users for computers that are part of a domain.
// For now, domain users may have FUS enabled because TS allows remote
// logon which can result in multiple sessions on a machine (a form
// of FUS) even though Start/Logoff doesn't allow the "Switch User"
// option. In this case, the user can lock their desktop without
// causing their session to disconnect. If FUS is explicitly off
// in the registry then "Switch User" is not a Logoff option nor can
// a remote logon happen and the user can lock their desktop without
// causing their session to disconnect.
return (IsOS(OS_DOMAINMEMBER) || !IsOS(OS_FASTUSERSWITCHING));
}
////////////////////////////////////////////////////////////////////////////
// RunSecure - helper function to tell accessibility UI when to run secure
// (no help, no active URL links, etc...). Accessibility UI
// should run in secure mode if it is running on the winlogon
// desktop or as SYSTEM.
////////////////////////////////////////////////////////////////////////////
BOOL RunSecure(DWORD dwDesktop)
{
BOOL fOK = FALSE;
BOOL fIsLocalSystem = FALSE;
SID_IDENTIFIER_AUTHORITY siaLocalSystem = SECURITY_NT_AUTHORITY;
PSID psidSystem = 0;
if (dwDesktop == DESKTOP_WINLOGON)
return TRUE;
if (AllocateAndInitializeSid(&siaLocalSystem,
1,
SECURITY_LOCAL_SYSTEM_RID,
0, 0, 0, 0, 0, 0, 0,
&psidSystem) && psidSystem)
{
fOK = CheckTokenMembership(NULL, psidSystem, &fIsLocalSystem);
FreeSid(psidSystem);
}
return (fOK && fIsLocalSystem);
}