Fix resetting keyboard hook state on MS-Windows

Register session notifications so Emacs is notified when the
computer is being locked, as required to reset the low level
keyboard hook state.  (Bug#69083).
* src/w32term.h:
* src/w32fns.c (setup_w32_kbdhook, remove_w32_kbdhook)
(w32_wnd_proc, globals_of_w32fns, maybe_pass_notification):
Register and manage session notifications in GUI Emacs.
* src/w32console.c (initialize_w32_display, find_ime_window):
* src/w32xfns.c (drain_message_queue): Register notifications
and reset keyboard hook state in console Emacs.
* src/w32.c (term_ntproc): Un-register session notifications
when terminating.

src/w32.c

@@ -10392,11 +10392,16 @@ check_windows_init_file (void)
     }
 }
 
+/* from w32fns.c */
+extern void remove_w32_kbdhook (void);
+
 void
 term_ntproc (int ignored)
 {
   (void)ignored;
 
+  remove_w32_kbdhook ();
+
   term_timers ();
 
   /* shutdown the socket interface if necessary */

src/w32console.c

@@ -659,6 +659,24 @@ w32_face_attributes (struct frame *f, int face_id)
   return char_attr;
 }
 
+/* The IME window is needed to receive the session notifications
+   required to reset the low level keyboard hook state.  */
+
+static BOOL CALLBACK
+find_ime_window (HWND hwnd, LPARAM arg)
+{
+  char window_class[32];
+
+  GetClassName (hwnd, window_class, sizeof (window_class));
+  if (strcmp (window_class, "IME") == 0)
+    {
+      *(HWND *) arg = hwnd;
+      return FALSE;
+    }
+  /* keep looking */
+  return TRUE;
+}
+
 void
 initialize_w32_display (struct terminal *term, int *width, int *height)
 {
@@ -818,11 +836,14 @@ initialize_w32_display (struct terminal *term, int *width, int *height)
   else
     w32_console_unicode_input = 0;
 
-  /* Setup w32_display_info structure for this frame. */
+  /* Setup w32_display_info structure for this frame.  */
   w32_initialize_display_info (build_string ("Console"));
 
+  HWND hwnd = NULL;
+  EnumThreadWindows (GetCurrentThreadId (), find_ime_window, (LPARAM) &hwnd);
+
   /* Set up the keyboard hook.  */
-  setup_w32_kbdhook ();
+  setup_w32_kbdhook (hwnd);
 }
 
 

src/w32fns.c

@@ -49,6 +49,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #ifdef WINDOWSNT
 #include <mbstring.h>
 #include <mbctype.h>	/* for _getmbcp */
+#include <wtsapi32.h>	/* for WTS(Un)RegisterSessionNotification */
 #endif /* WINDOWSNT */
 
 #if CYGWIN
@@ -204,6 +205,10 @@ typedef HRESULT (WINAPI * SetWindowTheme_Proc)
 typedef HRESULT (WINAPI * DwmSetWindowAttribute_Proc)
   (HWND hwnd, DWORD dwAttribute, IN LPCVOID pvAttribute, DWORD cbAttribute);
 
+typedef BOOL (WINAPI * WTSRegisterSessionNotification_Proc)
+  (HWND hwnd, DWORD dwFlags);
+typedef BOOL (WINAPI * WTSUnRegisterSessionNotification_Proc) (HWND hwnd);
+
 TrackMouseEvent_Proc track_mouse_event_fn = NULL;
 ImmGetCompositionString_Proc get_composition_string_fn = NULL;
 ImmGetContext_Proc get_ime_context_fn = NULL;
@@ -220,6 +225,8 @@ IsDebuggerPresent_Proc is_debugger_present = NULL;
 SetThreadDescription_Proc set_thread_description = NULL;
 SetWindowTheme_Proc SetWindowTheme_fn = NULL;
 DwmSetWindowAttribute_Proc DwmSetWindowAttribute_fn = NULL;
+WTSUnRegisterSessionNotification_Proc WTSUnRegisterSessionNotification_fn = NULL;
+WTSRegisterSessionNotification_Proc WTSRegisterSessionNotification_fn = NULL;
 
 extern AppendMenuW_Proc unicode_append_menu;
 
@@ -307,6 +314,7 @@ static struct
   int hook_count; /* counter, if several windows are created */
   HHOOK hook;     /* hook handle */
   HWND console;   /* console window handle */
+  HWND notified_wnd; /* window that receives session notifications */
 
   int lwindown;      /* Left Windows key currently pressed (and hooked) */
   int rwindown;      /* Right Windows key currently pressed (and hooked) */
@@ -2744,7 +2752,7 @@ funhook (int code, WPARAM w, LPARAM l)
 /* Set up the hook; can be called several times, with matching
    remove_w32_kbdhook calls.  */
 void
-setup_w32_kbdhook (void)
+setup_w32_kbdhook (HWND hwnd)
 {
   kbdhook.hook_count++;
 
@@ -2800,6 +2808,15 @@ setup_w32_kbdhook (void)
       /* Set the hook.  */
       kbdhook.hook = SetWindowsHookEx (WH_KEYBOARD_LL, funhook,
 				       GetModuleHandle (NULL), 0);
+
+      /* Register session notifications so we get notified about the
+	 computer being locked.  */
+      kbdhook.notified_wnd = NULL;
+      if (hwnd != NULL && WTSRegisterSessionNotification_fn != NULL)
+	{
+	  WTSRegisterSessionNotification_fn (hwnd, NOTIFY_FOR_THIS_SESSION);
+	  kbdhook.notified_wnd = hwnd;
+	}
     }
 }
 
@@ -2811,7 +2828,11 @@ remove_w32_kbdhook (void)
   if (kbdhook.hook_count == 0 && w32_kbdhook_active)
     {
       UnhookWindowsHookEx (kbdhook.hook);
+      if (kbdhook.notified_wnd != NULL
+	  && WTSUnRegisterSessionNotification_fn != NULL)
+	  WTSUnRegisterSessionNotification_fn (kbdhook.notified_wnd);
       kbdhook.hook = NULL;
+      kbdhook.notified_wnd = NULL;
     }
 }
 #endif	/* WINDOWSNT */
@@ -2884,13 +2905,12 @@ check_w32_winkey_state (int vkey)
     }
   return 0;
 }
-#endif	/* WINDOWSNT */
 
 /* Reset the keyboard hook state.  Locking the workstation with Win-L
    leaves the Win key(s) "down" from the hook's point of view - the
    keyup event is never seen.  Thus, this function must be called when
    the system is locked.  */
-static void
+void
 reset_w32_kbdhook_state (void)
 {
   kbdhook.lwindown = 0;
@@ -2900,6 +2920,7 @@ reset_w32_kbdhook_state (void)
   kbdhook.suppress_lone = 0;
   kbdhook.winseen = 0;
 }
+#endif	/* WINDOWSNT */
 
 /* GetKeyState and MapVirtualKey on Windows 95 do not actually distinguish
    between left and right keys as advertised.  We test for this
@@ -4129,6 +4150,47 @@ deliver_wm_chars (int do_translate, HWND hwnd, UINT msg, UINT wParam,
   return 0;
 }
 
+/* Maybe pass session notification registration to another frame.  If
+   the frame with window handle HWND is deleted, we must pass the
+   notifications to some other frame, if they have been sent to this
+   frame before and have not already been passed on.  If there is no
+   other frame, do nothing.  */
+
+#ifdef WINDOWSNT
+static void
+maybe_pass_notification (HWND hwnd)
+{
+  if (hwnd == kbdhook.notified_wnd
+      && kbdhook.hook_count > 0 && w32_kbdhook_active)
+    {
+      Lisp_Object tail, frame;
+      struct frame *f;
+      bool found_frame = false;
+
+      FOR_EACH_FRAME (tail, frame)
+	{
+	  f = XFRAME (frame);
+	  if (FRAME_W32_P (f) && FRAME_OUTPUT_DATA (f) != NULL
+	      && FRAME_W32_WINDOW (f) != hwnd)
+	    {
+	      found_frame = true;
+	      break;
+	    }
+	}
+
+      if (found_frame && WTSUnRegisterSessionNotification_fn != NULL
+	  && WTSRegisterSessionNotification_fn != NULL)
+	{
+	  /* There is another frame, pass on the session notification.  */
+	  HWND next_wnd = FRAME_W32_WINDOW (f);
+	  WTSUnRegisterSessionNotification_fn (hwnd);
+	  WTSRegisterSessionNotification_fn (next_wnd, NOTIFY_FOR_THIS_SESSION);
+	  kbdhook.notified_wnd = next_wnd;
+	}
+    }
+}
+#endif	/* WINDOWSNT */
+
 /* Main window procedure */
 
 static LRESULT CALLBACK
@@ -5301,23 +5363,29 @@ w32_wnd_proc (HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 
 #ifdef WINDOWSNT
     case WM_CREATE:
-      setup_w32_kbdhook ();
+      setup_w32_kbdhook (hwnd);
       goto dflt;
 #endif
 
     case WM_DESTROY:
 #ifdef WINDOWSNT
+      maybe_pass_notification (hwnd);
       remove_w32_kbdhook ();
 #endif
       CoUninitialize ();
       return 0;
 
+#ifdef WINDOWSNT
     case WM_WTSSESSION_CHANGE:
       if (wParam == WTS_SESSION_LOCK)
         reset_w32_kbdhook_state ();
       goto dflt;
+#endif
 
     case WM_CLOSE:
+#ifdef WINDOWSNT
+      maybe_pass_notification (hwnd);
+#endif
       wmsg.dwModifiers = w32_get_modifiers ();
       my_post_msg (&wmsg, hwnd, msg, wParam, lParam);
       return 0;
@@ -11335,6 +11403,14 @@ globals_of_w32fns (void)
   set_thread_description = (SetThreadDescription_Proc)
     get_proc_addr (hm_kernel32, "SetThreadDescription");
 
+#ifdef WINDOWSNT
+  HMODULE wtsapi32_lib = LoadLibrary ("wtsapi32.dll");
+  WTSRegisterSessionNotification_fn = (WTSRegisterSessionNotification_Proc)
+    get_proc_addr (wtsapi32_lib, "WTSRegisterSessionNotification");
+  WTSUnRegisterSessionNotification_fn = (WTSUnRegisterSessionNotification_Proc)
+    get_proc_addr (wtsapi32_lib, "WTSUnRegisterSessionNotification");
+#endif
+
   /* Support OS dark mode on Windows 10 version 1809 and higher.
      See `w32_applytheme' which uses appropriate APIs per version of Windows.
      For future wretches who may need to understand Windows build numbers:

src/w32term.h

@@ -779,8 +779,9 @@ extern bool w32_image_rotations_p (void);
 
 #ifdef WINDOWSNT
 /* Keyboard hooks.  */
-extern void setup_w32_kbdhook (void);
+extern void setup_w32_kbdhook (HWND);
 extern void remove_w32_kbdhook (void);
+extern void reset_w32_kbdhook_state (void);
 extern int check_w32_winkey_state (int);
 #define w32_kbdhook_active (os_subtype != OS_SUBTYPE_9X)
 #else

src/w32xfns.c

@@ -413,8 +413,16 @@ drain_message_queue (void)
 
   while (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))
     {
-      if (msg.message == WM_EMACS_FILENOTIFY)
-	retval = 1;
+      switch (msg.message)
+	{
+	case WM_WTSSESSION_CHANGE:
+	  if (msg.wParam == WTS_SESSION_LOCK)
+	    reset_w32_kbdhook_state ();
+	  break;
+	case WM_EMACS_FILENOTIFY:
+	  retval = 1;
+	  break;
+	}
       TranslateMessage (&msg);
       DispatchMessage (&msg);
     }