[host] Windows: Implemented service to launch LG as the SYSTEM user

Experimental, use at your own peril!

This commit adds the ability for the LG host to install and launch with
Windows as a system service.

To install simply run `looking-glass-host.exe InstallService` or
conversely to uninstall `looking-glass-host.exe UninstallService`.

host/platform/Windows/CMakeLists.txt

@@ -7,6 +7,7 @@ include_directories(
 
 add_library(platform_Windows STATIC
 	src/platform.c
+	src/service.c
 	src/mousehook.c
 )
 
@@ -23,6 +24,9 @@ target_link_libraries(platform_Windows
 	"${PROJECT_BINARY_DIR}/resource.o"
 	lg_common
 	capture
+
+	userenv
+	wtsapi32
 )
 
 target_include_directories(platform_Windows

host/platform/Windows/src/platform.c

@@ -18,6 +18,7 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 */
 
 #include "platform.h"
+#include "service.h"
 #include "windows/mousehook.h"
 
 #include <windows.h>
@@ -42,9 +43,11 @@ struct AppState
   int     argc;
   char ** argv;
 
-  char         executable[MAX_PATH + 1];
+  char           executable[MAX_PATH + 1];
-  HWND         messageWnd;
+  HWND           messageWnd;
-  HMENU        trayMenu;
+  NOTIFYICONDATA iconData;
+  UINT           trayRestartMsg;
+  HMENU          trayMenu;
 };
 
 static struct AppState app = {0};
@@ -54,6 +57,21 @@ HWND MessageHWND;
 typedef NTSTATUS (__stdcall *ZwSetTimerResolution_t)(ULONG RequestedResolution, BOOLEAN Set, PULONG ActualResolution);
 static ZwSetTimerResolution_t ZwSetTimerResolution = NULL;
 
+static void RegisterTrayIcon()
+{
+  // register our TrayIcon
+  if (!app.iconData.cbSize)
+  {
+    app.iconData.cbSize           = sizeof(NOTIFYICONDATA);
+    app.iconData.hWnd             = app.messageWnd;
+    app.iconData.uFlags           = NIF_ICON | NIF_MESSAGE | NIF_TIP;
+    app.iconData.uCallbackMessage = WM_TRAYICON;
+    strncpy(app.iconData.szTip, "Looking Glass (host)", sizeof(app.iconData.szTip));
+    app.iconData.hIcon            = LoadIcon(app.hInst, IDI_APPLICATION);
+  }
+  Shell_NotifyIcon(NIM_ADD, &app.iconData);
+}
+
 LRESULT CALLBACK DummyWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
   switch(msg)
@@ -99,28 +117,20 @@ LRESULT CALLBACK DummyWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
     }
 
     default:
-      return DefWindowProc(hwnd, msg, wParam, lParam);
+      if (msg == app.trayRestartMsg)
+        RegisterTrayIcon();
+      break;
   }
-  return 0;
+
+  return DefWindowProc(hwnd, msg, wParam, lParam);
 }
 
 static int appThread(void * opaque)
 {
-  // register our TrayIcon
+  RegisterTrayIcon();
-  NOTIFYICONDATA iconData =
-  {
-    .cbSize           = sizeof(NOTIFYICONDATA),
-    .hWnd             = app.messageWnd,
-    .uFlags           = NIF_ICON | NIF_MESSAGE | NIF_TIP,
-    .uCallbackMessage = WM_TRAYICON,
-    .szTip            = "Looking Glass (host)"
-  };
-  iconData.hIcon = LoadIcon(app.hInst, IDI_APPLICATION);
-  Shell_NotifyIcon(NIM_ADD, &iconData);
-
   int result = app_main(app.argc, app.argv);
 
-  Shell_NotifyIcon(NIM_DELETE, &iconData);
+  Shell_NotifyIcon(NIM_DELETE, &app.iconData);
   mouseHook_remove();
   SendMessage(app.messageWnd, WM_DESTROY, 0, 0);
   return result;
@@ -144,6 +154,21 @@ static BOOL WINAPI CtrlHandler(DWORD dwCtrlType)
 
 int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
 {
+  // convert the command line to the standard argc and argv
+  LPWSTR * wargv = CommandLineToArgvW(GetCommandLineW(), &app.argc);
+  app.argv = malloc(sizeof(char *) * app.argc);
+  for(int i = 0; i < app.argc; ++i)
+  {
+    const size_t s = (wcslen(wargv[i])+1) * 2;
+    app.argv[i] = malloc(s);
+    wcstombs(app.argv[i], wargv[i], s);
+  }
+  LocalFree(wargv);
+
+  GetModuleFileName(NULL, app.executable, sizeof(app.executable));
+  if (HandleService(app.argc, app.argv))
+    return 0;
+
   /* this is a bit of a hack but without this --help will produce no output in a windows command prompt */
   if (!IsDebuggerPresent() && AttachConsole(ATTACH_PARENT_PROCESS))
   {
@@ -183,19 +208,6 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
   option_register(options);
   free(logFilePath);
 
-  // convert the command line to the standard argc and argv
-  LPWSTR * wargv = CommandLineToArgvW(GetCommandLineW(), &app.argc);
-  app.argv = malloc(sizeof(char *) * app.argc);
-  for(int i = 0; i < app.argc; ++i)
-  {
-    const size_t s = (wcslen(wargv[i])+1) * 2;
-    app.argv[i] = malloc(s);
-    wcstombs(app.argv[i], wargv[i], s);
-  }
-  LocalFree(wargv);
-
-  GetModuleFileName(NULL, app.executable, sizeof(app.executable));
-
   // setup a handler for ctrl+c
   SetConsoleCtrlHandler(CtrlHandler, TRUE);
 
@@ -209,13 +221,18 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
   wx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);
   wx.hCursor       = LoadCursor(NULL, IDC_ARROW);
   wx.hbrBackground = (HBRUSH)COLOR_APPWORKSPACE;
-  if (!RegisterClassEx(&wx))
+  ATOM class;
+  if (!(class = RegisterClassEx(&wx)))
   {
     DEBUG_ERROR("Failed to register message window class");
     result = -1;
     goto finish;
   }
-  app.messageWnd = CreateWindowEx(0, "DUMMY_CLASS", "DUMMY_NAME", 0, 0, 0, 0, 0, HWND_MESSAGE, NULL, NULL, NULL);
+
+  app.trayRestartMsg = RegisterWindowMessage("TaskbarCreated");
+
+  app.messageWnd = CreateWindowEx(0, MAKEINTATOM(class), NULL, 0, 0, 0, 0, 0, NULL, NULL, hInstance, NULL);
+  ChangeWindowMessageFilterEx(app.messageWnd, app.trayRestartMsg, MSGFLT_ALLOW, NULL);
 
   // set the global
   MessageHWND = app.messageWnd;