user32: Don't start explorer.exe on non-visible window stations.

dlls/user32/win.c

@@ -1620,30 +1620,35 @@ HWND WINAPI GetDesktopWindow(void)
 
     if (!thread_info->desktop)
     {
-        static const WCHAR command_line[] = {'\\','e','x','p','l','o','r','e','r','.','e','x','e',' ','/','d','e','s','k','t','o','p',0};
-        STARTUPINFOW si;
-        PROCESS_INFORMATION pi;
-        WCHAR cmdline[MAX_PATH + sizeof(command_line)/sizeof(WCHAR)];
-
-        memset( &si, 0, sizeof(si) );
-        si.cb = sizeof(si);
-        si.dwFlags = STARTF_USESTDHANDLES;
-        si.hStdInput  = 0;
-        si.hStdOutput = 0;
-        si.hStdError  = GetStdHandle( STD_ERROR_HANDLE );
-
-        GetSystemDirectoryW( cmdline, MAX_PATH );
-        lstrcatW( cmdline, command_line );
-        if (CreateProcessW( NULL, cmdline, NULL, NULL, FALSE, DETACHED_PROCESS,
-                            NULL, NULL, &si, &pi ))
-        {
-            TRACE( "started explorer pid %04x tid %04x\n", pi.dwProcessId, pi.dwThreadId );
-            WaitForInputIdle( pi.hProcess, 10000 );
-            CloseHandle( pi.hThread );
-            CloseHandle( pi.hProcess );
-
-        }
-        else WARN( "failed to start explorer, err %d\n", GetLastError() );
+        USEROBJECTFLAGS flags;
+        if (!GetUserObjectInformationW( GetProcessWindowStation(), UOI_FLAGS, &flags,
+                                        sizeof(flags), NULL ) || (flags.dwFlags & WSF_VISIBLE))
+        {
+            static const WCHAR command_line[] = {'\\','e','x','p','l','o','r','e','r','.','e','x','e',' ','/','d','e','s','k','t','o','p',0};
+            STARTUPINFOW si;
+            PROCESS_INFORMATION pi;
+            WCHAR cmdline[MAX_PATH + sizeof(command_line)/sizeof(WCHAR)];
+
+            memset( &si, 0, sizeof(si) );
+            si.cb = sizeof(si);
+            si.dwFlags = STARTF_USESTDHANDLES;
+            si.hStdInput  = 0;
+            si.hStdOutput = 0;
+            si.hStdError  = GetStdHandle( STD_ERROR_HANDLE );
+
+            GetSystemDirectoryW( cmdline, MAX_PATH );
+            lstrcatW( cmdline, command_line );
+            if (CreateProcessW( NULL, cmdline, NULL, NULL, FALSE, DETACHED_PROCESS,
+                                NULL, NULL, &si, &pi ))
+            {
+                TRACE( "started explorer pid %04x tid %04x\n", pi.dwProcessId, pi.dwThreadId );
+                WaitForInputIdle( pi.hProcess, 10000 );
+                CloseHandle( pi.hThread );
+                CloseHandle( pi.hProcess );
+            }
+            else WARN( "failed to start explorer, err %d\n", GetLastError() );
+        }
+        else TRACE( "not starting explorer since winstation is not visible\n" );
 
         SERVER_START_REQ( get_desktop_window )
         {