[host] windows: use event to gracefully signal exit

This allows the process to be terminated without resorting to
TerminateProcess. With some fixes, this allows the notification icon to be
removed when the service is restarted.

Furthermore, instead of sending WM_DESTROY to fool the window into believing
it's being destroyed, we actually call DestroyWindow now.

host/platform/Windows/CMakeLists.txt

@@ -28,6 +28,7 @@ target_link_libraries(platform_Windows
 	psapi
 	shlwapi
 	powrprof
+	rpcrt4
 )
 
 target_include_directories(platform_Windows

host/platform/Windows/src/platform.c

@@ -57,6 +57,9 @@ struct AppState
   NOTIFYICONDATA iconData;
   UINT           trayRestartMsg;
   HMENU          trayMenu;
+
+  HANDLE         exitThreadEvent;
+  LGThread     * exitThread;
 };
 
 static struct AppState app = {0};
@@ -212,6 +215,7 @@ LRESULT CALLBACK DummyWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
   switch(msg)
   {
     case WM_DESTROY:
+      Shell_NotifyIcon(NIM_DELETE, &app.iconData);
       PostQuitMessage(0);
       break;
 
@@ -264,12 +268,31 @@ static int appThread(void * opaque)
 {
   RegisterTrayIcon();
   int result = app_main(app.argc, app.argv);
-
-  Shell_NotifyIcon(NIM_DELETE, &app.iconData);
-  SendMessage(app.messageWnd, WM_DESTROY, 0, 0);
+  DestroyWindow(app.messageWnd);
   return result;
 }
 
+static int exitThread(void * opaque)
+{
+  HANDLE handles[2] = { (HANDLE) opaque, app.exitThreadEvent };
+
+  switch (WaitForMultipleObjects(2, handles, FALSE, INFINITE))
+  {
+    case WAIT_OBJECT_0:
+      DEBUG_INFO("Received exit event");
+      SendMessage(app.messageWnd, WM_CLOSE, 0, 0);
+      break;
+
+    case WAIT_OBJECT_0 + 1:
+      break;
+
+    case WAIT_FAILED:
+      DEBUG_ERROR("WaitForMultipleObjects failed: 0x%lx", GetLastError());
+  }
+
+  return 0;
+}
+
 LRESULT sendAppMessage(UINT Msg, WPARAM wParam, LPARAM lParam)
 {
   return SendMessage(app.messageWnd, Msg, wParam, lParam);
@@ -362,6 +385,13 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
       .type           = OPTION_TYPE_STRING,
       .value.x_string = logFilePath
     },
+    {
+      .module         = "os",
+      .name           = "exitEvent",
+      .description    = "Exit when the specified event is signaled",
+      .type           = OPTION_TYPE_STRING,
+      .value.x_string = ""
+    },
     {0}
   };
 
@@ -404,6 +434,8 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
 
   app.messageWnd = CreateWindowEx(0, MAKEINTATOM(class), NULL, 0, 0, 0, 0, 0, NULL, NULL, hInstance, NULL);
 
+  app.exitThreadEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
+
   // this is needed so that unprivileged processes can send us this message
   _ChangeWindowMessageFilterEx = (PChangeWindowMessageFilterEx)GetProcAddress(user32, "ChangeWindowMessageFilterEx");
   if (_ChangeWindowMessageFilterEx)
@@ -449,12 +481,20 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
 shutdown:
   DestroyMenu(app.trayMenu);
   app_shutdown();
+  SetEvent(app.exitThreadEvent);
+
   if (!lgJoinThread(thread, &result))
   {
     DEBUG_ERROR("Failed to join the main application thread");
     result = LG_HOST_EXIT_FAILED;
   }
 
+  if (app.exitThread && !lgJoinThread(app.exitThread, &result))
+  {
+    DEBUG_ERROR("Failed to join the exit thread");
+    result = LG_HOST_EXIT_FAILED;
+  }
+
 finish:
 
   for(int i = 0; i < app.argc; ++i)
@@ -518,6 +558,19 @@ bool app_init(void)
   // try to boost the scheduler priority
   boostPriority();
 
+  // open exit signaling event
+  HANDLE exitEvent = NULL;
+  const char * exitEventName = option_get_string("os", "exitEvent");
+  if (exitEventName && exitEventName[0])
+  {
+    exitEvent = OpenEvent(SYNCHRONIZE, FALSE, exitEventName);
+    if (!exitEvent)
+      DEBUG_WARN("Failed to open exitEvent with error 0x%lx: %s", GetLastError(), exitEventName);
+  }
+
+  if (exitEvent && !lgCreateThread("exitThread", exitThread, exitEvent, &app.exitThread))
+    DEBUG_ERROR("Failed to create the exit thread");
+
   return true;
 }
 

host/platform/Windows/src/service.c

@@ -50,6 +50,8 @@ struct Service
   FILE * logFile;
   bool   running;
   HANDLE process;
+  HANDLE exitEvent;
+  char   exitEventName[64];
 };
 
 struct Service service = { 0 };
@@ -311,10 +313,19 @@ void Launch(void)
     .lpDesktop   = "WinSta0\\Default"
   };
 
+  char * cmdline = NULL;
+  char cmdbuf[128];
+  if (service.exitEvent)
+  {
+    snprintf(cmdbuf, sizeof(cmdbuf), "looking-glass-host.exe os:exitEvent=%s",
+      service.exitEventName);
+    cmdline = cmdbuf;
+  }
+
   if (!f_CreateProcessAsUserA(
       hToken,
       os_getExecutable(),
-      NULL,
+      cmdline,
       NULL,
       NULL,
       FALSE,
@@ -643,6 +654,21 @@ VOID WINAPI SvcMain(DWORD dwArgc, LPTSTR *lpszArgv)
 
   ReportSvcStatus(SERVICE_RUNNING, NO_ERROR, 0);
 
+  UUID uuid;
+  RPC_CSTR uuidStr;
+  UuidCreate(&uuid);
+
+  if (UuidToString(&uuid, &uuidStr) == RPC_S_OK)
+  {
+    strcpy(service.exitEventName, "Global\\");
+    strcat(service.exitEventName, (const char*) uuidStr);
+    RpcStringFree(&uuidStr);
+
+    service.exitEvent = CreateEvent(NULL, FALSE, FALSE, service.exitEventName);
+    if (!service.exitEvent)
+      doLog("Failed to create exit event: 0x%lx\n", GetLastError());
+  }
+
   int failCount = 0;
   while(1)
   {
@@ -734,16 +760,36 @@ VOID WINAPI SvcMain(DWORD dwArgc, LPTSTR *lpszArgv)
   }
 
   stopped:
+  if (service.running)
+  {
+    SetEvent(service.exitEvent);
+    switch (WaitForSingleObject(service.process, 1000))
+    {
+      case WAIT_OBJECT_0:
+        service.running = false;
+        break;
+      case WAIT_TIMEOUT:
+        doLog("Host application failed to exit in 1 second\n");
+        break;
+      case WAIT_FAILED:
+        doLog("WaitForSingleObject failed: 0x%lx\n", GetLastError());
+        break;
+    }
+
     if (service.running)
     {
       doLog("Terminating the host application\n");
       if (TerminateProcess(service.process, LG_HOST_EXIT_KILLED))
       {
-      while(WaitForSingleObject(service.process, INFINITE) != WAIT_OBJECT_0) {}
+        if (WaitForSingleObject(service.process, INFINITE) == WAIT_OBJECT_0)
           doLog("Host application terminated\n");
+        else
+          doLog("WaitForSingleObject failed: 0x%lx\n", GetLastError());
       }
       else
         doLog("Failed to terminate the host application\n");
+    }
+
     CloseHandle(service.process);
     service.process = NULL;
   }