* src/keyboard.c: Fix bug#5803.

A long time ago, `read_key_sequence` used to read the keymaps at the
start, so if something happened between this start and the moment
the user actually hits a key, `read_key_sequence` could end up using
the wrong keymaps.  To work around this problem, the code used
`record_asynch_buffer_change` to try and trigger `read_key_sequence`
to re-read the keymaps in some known cases.

Several years ago, `read_key_sequence` was changed so as to read the keymaps
only once the user hits a key, making this machinery now redundant
(and also harmful apparently in bug#5803 because it introduces
"spurious" events).

So we here remove `record_asynch_buffer_change` and the
`BUFFER_SWITCH_EVENT` and `Qbuffer_switch` pseudo-events it generated.

* src/termhooks.h (enum event_kind): Delete `BUFFER_SWITCH_EVENT`.
* src/keyboard.c: (record_asynch_buffer_change): Delete function.
(syms_of_keyboard): Delete `Qbuffer_switch`.
(force_auto_save_soon, readable_events)
(kbd_buffer_store_buffered_event, kbd_buffer_get_event)
(make_lispy_event):
* src/xterm.c (handle_one_xevent):
* src/w32term.c (w32_read_socket):
* src/process.c (wait_reading_process_output)
(read_and_dispose_of_process_output, exec_sentinel): Simplify accordingly.

7 files changed, 1 insertions, 122 deletions

diff --git a/src/keyboard.c b/src/keyboard.c
index 49261fcc3e8..560d92c99f3 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -741,9 +741,6 @@ void
 force_auto_save_soon (void)
 {
   last_auto_save = - auto_save_interval - 1;
-  /* FIXME: What's the relationship between forcing auto-save and adding
-     a buffer-switch event?  */
-  record_asynch_buffer_change ();
 }
 #endif
 
@@ -3431,8 +3428,7 @@ readable_events (int flags)
                        && event->ie.part == scroll_bar_handle
                        && event->ie.modifiers == 0)
 #endif
-                  && !((flags & READABLE_EVENTS_FILTER_EVENTS)
-                       && event->kind == BUFFER_SWITCH_EVENT))
+                 )
                 return 1;
               event = next_kbd_event (event);
             }
@@ -3583,12 +3579,6 @@ kbd_buffer_store_buffered_event (union buffered_input_event *event,
           return;
         }
     }
-  /* Don't insert two BUFFER_SWITCH_EVENT's in a row.
-     Just ignore the second one.  */
-  else if (event->kind == BUFFER_SWITCH_EVENT
-           && kbd_fetch_ptr != kbd_store_ptr
-           && prev_kbd_event (kbd_store_ptr)->kind == BUFFER_SWITCH_EVENT)
-    return;
 
   /* Don't let the very last slot in the buffer become full,
      since that would make the two pointers equal,
@@ -3622,7 +3612,6 @@ kbd_buffer_store_buffered_event (union buffered_input_event *event,
     case ICONIFY_EVENT: ignore_event = Qiconify_frame; break;
     case DEICONIFY_EVENT: ignore_event = Qmake_frame_visible; break;
     case SELECTION_REQUEST_EVENT: ignore_event = Qselection_request; break;
-    case BUFFER_SWITCH_EVENT: ignore_event = Qbuffer_switch; break;
     default: ignore_event = Qnil; break;
     }
 
@@ -3961,7 +3950,6 @@ kbd_buffer_get_event (KBOARD **kbp,
 #ifdef HAVE_XWIDGETS
       case XWIDGET_EVENT:
 #endif
-      case BUFFER_SWITCH_EVENT:
       case SAVE_SESSION_EVENT:
       case NO_EVENT:
       case HELP_EVENT:
@@ -5341,14 +5329,6 @@ make_lispy_event (struct input_event *event)
       return list2 (Qmove_frame, list1 (event->frame_or_window));
 #endif
 
-    case BUFFER_SWITCH_EVENT:
-      {
-        /* The value doesn't matter here; only the type is tested.  */
-        Lisp_Object obj;
-        XSETBUFFER (obj, current_buffer);
-        return obj;
-      }
-
     /* Just discard these, by returning nil.
        With MULTI_KBOARD, these events are used as placeholders
        when we need to randomly delete events from the queue.
@@ -6805,41 +6785,6 @@ get_input_pending (int flags)
   return input_pending;
 }
 
-/* Put a BUFFER_SWITCH_EVENT in the buffer
-   so that read_key_sequence will notice the new current buffer.  */
-
-void
-record_asynch_buffer_change (void)
-{
-  /* We don't need a buffer-switch event unless Emacs is waiting for input.
-     The purpose of the event is to make read_key_sequence look up the
-     keymaps again.  If we aren't in read_key_sequence, we don't need one,
-     and the event could cause trouble by messing up (input-pending-p).
-     Note: Fwaiting_for_user_input_p always returns nil when async
-     subprocesses aren't supported.  */
-  if (!NILP (Fwaiting_for_user_input_p ()))
-    {
-      struct input_event event;
-
-      EVENT_INIT (event);
-      event.kind = BUFFER_SWITCH_EVENT;
-      event.frame_or_window = Qnil;
-      event.arg = Qnil;
-
-      /* Make sure no interrupt happens while storing the event.  */
-#ifdef USABLE_SIGIO
-      if (interrupt_input)
-        kbd_buffer_store_event (&event);
-      else
-#endif
-        {
-          stop_polling ();
-          kbd_buffer_store_event (&event);
-          start_polling ();
-        }
-    }
-}
-
 /* Read any terminal input already buffered up by the system
    into the kbd_buffer, but do not wait.
 
@@ -11573,8 +11518,6 @@ syms_of_keyboard (void)
   /* Menu and tool bar item parts.  */
   DEFSYM (Qmenu_enable, "menu-enable");
 
-  DEFSYM (Qbuffer_switch, "buffer-switch");
-
 #ifdef HAVE_NTGUI
   DEFSYM (Qlanguage_change, "language-change");
   DEFSYM (Qend_session, "end-session");
diff --git a/src/keyboard.h b/src/keyboard.h
index 41da3a6bf44..24e9a007888 100644
--- a/src/keyboard.h
+++ b/src/keyboard.h
@@ -446,7 +446,6 @@ extern void push_kboard (struct kboard *);
 extern void push_frame_kboard (struct frame *);
 extern void pop_kboard (void);
 extern void temporarily_switch_to_single_kboard (struct frame *);
-extern void record_asynch_buffer_change (void);
 extern void input_poll_signal (int);
 extern void start_polling (void);
 extern void stop_polling (void);
diff --git a/src/process.c b/src/process.c
index bf64ead24e5..48b727d9e3b 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5333,14 +5333,6 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
 
               timer_delay = timer_check ();
 
-              /* If a timer has run, this might have changed buffers
-                 an alike.  Make read_key_sequence aware of that.  */
-              if (timers_run != old_timers_run
-                  && (old_buffer != current_buffer
-                      || !EQ (old_window, selected_window))
-                  && waiting_for_user_input_p == -1)
-                record_asynch_buffer_change ();
-
               if (timers_run != old_timers_run && do_display)
                 /* We must retry, since a timer may have requeued itself
                    and that could alter the time_delay.  */
@@ -5706,14 +5698,6 @@ wait_reading_process_output (intmax_t time_limit, int nsecs, int read_kbd,
                 leave = true;
             }
 
-          /* If a timer has run, this might have changed buffers
-             an alike.  Make read_key_sequence aware of that.  */
-          if (timers_run != old_timers_run
-              && waiting_for_user_input_p == -1
-              && (old_buffer != current_buffer
-              || !EQ (old_window, selected_window)))
-            record_asynch_buffer_change ();
-
           if (leave)
             break;
         }
@@ -6213,18 +6197,6 @@ read_and_dispose_of_process_output (struct Lisp_Process *p, char *chars,
   /* Restore waiting_for_user_input_p as it was
      when we were called, in case the filter clobbered it.  */
   waiting_for_user_input_p = waiting;
-
-#if 0 /* Call record_asynch_buffer_change unconditionally,
-         because we might have changed minor modes or other things
-         that affect key bindings.  */
-  if (! EQ (Fcurrent_buffer (), obuffer)
-      || ! EQ (current_buffer->keymap, okeymap))
-#endif
-    /* But do it only if the caller is actually going to read events.
-       Otherwise there's no need to make him wake up, and it could
-       cause trouble (for example it would make sit_for return).  */
-    if (waiting_for_user_input_p == -1)
-      record_asynch_buffer_change ();
 }
 
 DEFUN ("internal-default-process-filter", Finternal_default_process_filter,
@@ -7390,16 +7362,6 @@ exec_sentinel (Lisp_Object proc, Lisp_Object reason)
      when we were called, in case the filter clobbered it.  */
   waiting_for_user_input_p = waiting;
 
-#if 0
-  if (! EQ (Fcurrent_buffer (), obuffer)
-      || ! EQ (current_buffer->keymap, okeymap))
-#endif
-    /* But do it only if the caller is actually going to read events.
-       Otherwise there's no need to make him wake up, and it could
-       cause trouble (for example it would make sit_for return).  */
-    if (waiting_for_user_input_p == -1)
-      record_asynch_buffer_change ();
-
   unbind_to (count, Qnil);
 }
 
diff --git a/src/termhooks.h b/src/termhooks.h
index 44ab14225fd..e94959ca9a3 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -159,7 +159,6 @@ enum event_kind
   SELECTION_REQUEST_EVENT,      /* Another X client wants a selection from us.
                                    See `struct selection_input_event'.  */
   SELECTION_CLEAR_EVENT,        /* Another X client cleared our selection.  */
-  BUFFER_SWITCH_EVENT,          /* A process filter has switched buffers.  */
   DELETE_WINDOW_EVENT,          /* An X client said "delete this window".  */
 #ifdef HAVE_NTGUI
   END_SESSION_EVENT,            /* The user is logging out or shutting down.  */
diff --git a/src/thread.h b/src/thread.h
index a09929fa440..9697e49f09f 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -140,7 +140,6 @@ struct thread_state
      for user-input when that process-filter was called.
      waiting_for_input cannot be used as that is by definition 0 when
      lisp code is being evalled.
-     This is also used in record_asynch_buffer_change.
      For that purpose, this must be 0
      when not inside wait_reading_process_output.  */
   int m_waiting_for_user_input_p;
diff --git a/src/w32term.c b/src/w32term.c
index dc5cd1f6997..a038e4593f4 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -4858,10 +4858,6 @@ w32_read_socket (struct terminal *terminal,
                       inev.kind = DEICONIFY_EVENT;
                       XSETFRAME (inev.frame_or_window, f);
                     }
-                  else if (!NILP (Vframe_list) && !NILP (XCDR (Vframe_list)))
-                    /* Force a redisplay sooner or later to update the
-                       frame titles in case this is the second frame.  */
-                    record_asynch_buffer_change ();
                 }
               else
                 {
@@ -5479,12 +5475,6 @@ w32_read_socket (struct terminal *terminal,
                         inev.kind = DEICONIFY_EVENT;
                         XSETFRAME (inev.frame_or_window, f);
                       }
-                    else if (! NILP (Vframe_list)
-                             && ! NILP (XCDR (Vframe_list)))
-                      /* Force a redisplay sooner or later
-                         to update the frame titles
-                         in case this is the second frame.  */
-                      record_asynch_buffer_change ();
 
                   /* Windows can send us a SIZE_MAXIMIZED message even
                      when fullscreen is fullboth.  The following is a
@@ -5532,12 +5522,6 @@ w32_read_socket (struct terminal *terminal,
                         inev.kind = DEICONIFY_EVENT;
                         XSETFRAME (inev.frame_or_window, f);
                       }
-                    else if (! NILP (Vframe_list)
-                             && ! NILP (XCDR (Vframe_list)))
-                      /* Force a redisplay sooner or later
-                         to update the frame titles
-                         in case this is the second frame.  */
-                      record_asynch_buffer_change ();
                   }
 
                   if (EQ (get_frame_param (f, Qfullscreen), Qmaximized))
@@ -5829,9 +5813,6 @@ w32_read_socket (struct terminal *terminal,
                     SET_FRAME_GARBAGED (f);
                     DebPrint (("obscured frame %p (%s) found to be visible\n",
                                f, SDATA (f->name)));
-
-                    /* Force a redisplay sooner or later.  */
-                    record_asynch_buffer_change ();
                   }
               }
           }
diff --git a/src/xterm.c b/src/xterm.c
index 0d2452de929..3de0d2e73c0 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -8383,10 +8383,6 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               inev.ie.kind = DEICONIFY_EVENT;
               XSETFRAME (inev.ie.frame_or_window, f);
             }
-          else if (! NILP (Vframe_list) && ! NILP (XCDR (Vframe_list)))
-            /* Force a redisplay sooner or later to update the
-               frame titles in case this is the second frame.  */
-            record_asynch_buffer_change ();
         }
       goto OTHER;