New focus management interface

focus-in-hook and focus-out-hook don't accurately reflect actual
user-visible focus states.  Add a new focus interface and mark the old
one obsolete.

* doc/lispref/frames.texi (Input Focus): Document new focus
functions.  Remove references to the now-obsolete focus hooks.

* lisp/frame.el (frame-focus-state): New function.
(after-focus-change-function): New variable.
(focus-in-hook, focus-out-hook): Move to lisp from C;
mark obsolete.

* lisp/term/xterm.el (xterm-translate-focus-in)
(xterm-translate-focus-out): Track tty focus in `tty-focus-state'
terminal parameter; call `after-focus-change-function'.
(xterm--suspend-tty-function): New function.

* src/frame.c (Fhandle_switch_frame): Update docstring; don't call
focus hooks.
(focus-in-hook, focus-out-hook): Remove: moved to lisp.
(syms_of_frame): Remove unread_switch_frame; add
Vunread_switch_frame.

* src/keyboard.c:
(Finternal_handle_focus_in): New function.
(make_lispy_event): Always report focus events to lisp; don't
translate them to switch events sometimes.  Lisp can take care of
creating synthetic switch-frame events via
`internal-handle-focus-in'.

* src/w32term.c (x_focus_changed): Remove switch-avoidance logic:
just directly report focus changes to lisp.

* src/xterm.c (x_focus_changed): Remove switch-avoidance logic:
just directly report focus changes to lisp.

4 files changed, 32 insertions, 82 deletions

diff --git a/src/frame.c b/src/frame.c
index da82621b8a0..bf0269292d6 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1455,23 +1455,15 @@ This function returns FRAME, or nil if FRAME has been deleted.  */)
 DEFUN ("handle-switch-frame", Fhandle_switch_frame, Shandle_switch_frame, 1, 1, "^e",
        doc: /* Handle a switch-frame event EVENT.
 Switch-frame events are usually bound to this function.
-A switch-frame event tells Emacs that the window manager has requested
-that the user's events be directed to the frame mentioned in the event.
-This function selects the selected window of the frame of EVENT.
-
-If EVENT is frame object, handle it as if it were a switch-frame event
-to that frame.  */)
+A switch-frame event is an event Emacs sends itself to
+indicate that input is arriving in a new frame. It does not
+necessarily represent user-visible input focus.  */)
   (Lisp_Object event)
 {
-  Lisp_Object value;
-
   /* Preserve prefix arg that the command loop just cleared.  */
   kset_prefix_arg (current_kboard, Vcurrent_prefix_arg);
   run_hook (Qmouse_leave_buffer_hook);
-  /* `switch-frame' implies a focus in.  */
-  value = do_switch_frame (event, 0, 0, Qnil);
-  call1 (intern ("handle-focus-in"), event);
-  return value;
+  return do_switch_frame (event, 0, 0, Qnil);
 }
 
 DEFUN ("selected-frame", Fselected_frame, Sselected_frame, 0, 0, 0,
@@ -5888,15 +5880,6 @@ when the mouse is over clickable text.  */);
 The pointer becomes visible again when the mouse is moved.  */);
   Vmake_pointer_invisible = Qt;
 
-  DEFVAR_LISP ("focus-in-hook", Vfocus_in_hook,
-               doc: /* Normal hook run when a frame gains input focus.
-The frame gaining focus is selected at the time this hook is run.  */);
-  Vfocus_in_hook = Qnil;
-
-  DEFVAR_LISP ("focus-out-hook", Vfocus_out_hook,
-               doc: /* Normal hook run when all frames lost input focus.  */);
-  Vfocus_out_hook = Qnil;
-
   DEFVAR_LISP ("move-frame-functions", Vmove_frame_functions,
                doc: /* Functions run after a frame was moved.
 The functions are run with one arg, the frame that moved.  */);
diff --git a/src/keyboard.c b/src/keyboard.c
index c9e069c8653..84acb247228 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -5331,45 +5331,10 @@ make_lispy_event (struct input_event *event)
       }
 
     case FOCUS_IN_EVENT:
-      {
-        /* Notification of a FocusIn event.  The frame receiving the
-           focus is in event->frame_or_window.  Generate a
-           switch-frame event if necessary.  */
-
-        Lisp_Object frame = event->frame_or_window;
-        Lisp_Object focus = FRAME_FOCUS_FRAME (XFRAME (frame));
-        if (FRAMEP (focus))
-          frame = focus;
-        bool switching
-          = (
-#ifdef HAVE_X11
-            ! NILP (event->arg)
-            &&
-#endif
-            !EQ (frame, internal_last_event_frame)
-            && !EQ (frame, selected_frame));
-        internal_last_event_frame = frame;
-
-        return (switching ? make_lispy_switch_frame (frame)
-                : make_lispy_focus_in (frame));
-      }
+        return make_lispy_focus_in (event->frame_or_window);
 
     case FOCUS_OUT_EVENT:
-      {
-#ifdef HAVE_WINDOW_SYSTEM
-
-        Display_Info *di;
-        Lisp_Object frame = event->frame_or_window;
-        bool focused = false;
-
-        for (di = x_display_list; di && ! focused; di = di->next)
-          focused = di->x_highlight_frame != 0;
-
-        return focused ? Qnil
-               : make_lispy_focus_out (frame);
-
-#endif /* HAVE_WINDOW_SYSTEM */
-      }
+        return make_lispy_focus_out (event->frame_or_window);
 
     /* A simple keystroke.  */
     case ASCII_KEYSTROKE_EVENT:
@@ -6637,6 +6602,31 @@ has the same base event type and all the specified modifiers.  */)
     error ("Invalid base event");
 }
 
+DEFUN ("internal-handle-focus-in", Finternal_handle_focus_in,
+       Sinternal_handle_focus_in, 1, 1, 0,
+       doc: /* Internally handle focus-in events, possibly generating
+an artifical switch-frame event.  */)
+     (Lisp_Object event)
+{
+  Lisp_Object frame;
+  if (!EQ (CAR_SAFE (event), Qfocus_in) ||
+      !CONSP (XCDR (event)) ||
+      !FRAMEP ((frame = XCAR (XCDR (event)))))
+    error ("invalid focus-in event");
+
+  /* Conceptually, the concept of window manager focus on a particular
+   frame and the Emacs selected frame shouldn't be related, but for a
+   long time, we automatically switched the selected frame in response
+   to focus events, so let's keep doing that.  */
+  bool switching = (!EQ (frame, internal_last_event_frame)
+                    && !EQ (frame, selected_frame));
+  internal_last_event_frame = frame;
+  if (switching || !NILP (unread_switch_frame))
+    unread_switch_frame = make_lispy_switch_frame (frame);
+
+  return Qnil;
+}
+
 /* Try to recognize SYMBOL as a modifier name.
    Return the modifier flag bit, or 0 if not recognized.  */
 
@@ -11277,6 +11267,7 @@ syms_of_keyboard (void)
   defsubr (&Scurrent_idle_time);
   defsubr (&Sevent_symbol_parse_modifiers);
   defsubr (&Sevent_convert_list);
+  defsubr (&Sinternal_handle_focus_in);
   defsubr (&Sread_key_sequence);
   defsubr (&Sread_key_sequence_vector);
   defsubr (&Srecursive_edit);
diff --git a/src/w32term.c b/src/w32term.c
index 24950dd25ec..ff0d2bf5ddb 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -2886,20 +2886,6 @@ x_focus_changed (int type, int state, struct w32_display_info *dpyinfo,
         {
           x_new_focus_frame (dpyinfo, frame);
           dpyinfo->w32_focus_event_frame = frame;
-
-          /* Don't stop displaying the initial startup message
-             for a switch-frame event we don't need.  */
-          if (NILP (Vterminal_frame)
-              && CONSP (Vframe_list)
-              && !NILP (XCDR (Vframe_list)))
-            {
-              bufp->arg = Qt;
-            }
-          else
-            {
-              bufp->arg = Qnil;
-            }
-
           bufp->kind = FOCUS_IN_EVENT;
           XSETFRAME (bufp->frame_or_window, frame);
         }
diff --git a/src/xterm.c b/src/xterm.c
index eb299c36759..decaa33670b 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -4387,16 +4387,6 @@ x_focus_changed (int type, int state, struct x_display_info *dpyinfo, struct fra
         {
           x_new_focus_frame (dpyinfo, frame);
           dpyinfo->x_focus_event_frame = frame;
-
-          /* Don't stop displaying the initial startup message
-             for a switch-frame event we don't need.  */
-          /* When run as a daemon, Vterminal_frame is always NIL.  */
-          bufp->arg = (((NILP (Vterminal_frame)
-                         || ! FRAME_X_P (XFRAME (Vterminal_frame))
-                         || EQ (Fdaemonp (), Qt))
-                        && CONSP (Vframe_list)
-                        && !NILP (XCDR (Vframe_list)))
-                       ? Qt : Qnil);
           bufp->kind = FOCUS_IN_EVENT;
           XSETFRAME (bufp->frame_or_window, frame);
         }