Re: local keymap patch for key-binding

[David Kastrup]

Chong Yidong <address@hidden> writes:

> David Kastrup <address@hidden> writes:
>
>> It does too little.  Check out what read-key-sequence (defined in
>> keyboard.c) does with regard to mouse events (EVENT_HAS_PARAMETERS).
>> The problem is that read-key-sequence does such a load of other stuff
>> that it is hard to extract the material and transfer it to
>> key-binding.
>>
>> The problem is that keymaps may be provided by text properties and
>> overlays, and by keymap properties on strings that display as the
>> display or before-string or after-string properties of text properties
>> or overlays.
>
> I just verified that my patch truly works for keymaps on display
> strings, text properties, and overlays.  For example, with
>
> (with-output-to-temp-buffer "Testo"
>   (set-buffer "Testo")
>   (erase-buffer)
>   (let* ((map (make-sparse-keymap))
>        (str (propertize "foostring" 'keymap map 'mouse-face 'highlight))
>        ovr)
>     (define-key map [mouse-1] 'delete-window)
>     (insert "1234567890")
>     (setq ovr (make-overlay 2 3))
>     (overlay-put ovr 'keymap map)
>     (overlay-put ovr 'mouse-face 'highlight)
>     (put-text-property 5 6 'display str)
>     (put-text-property 8 9 'keymap map)
>     (put-text-property 8 9 'mouse-face 'highlight)))
>
> C-h k followed by mouse-1 on the overlay, display string, or text
> propertized region all report the correct action for the given local
> keymap.

Uh, C-h k has extra code doing this sort of lookup.  It does not rely
on key-binding.  So you should not test this with C-h k unless you
have previously dumbed it down with
(defun string-key-binding (&rest ignore) nil)
after help.el has been loaded.

> The reason is that the mouse event passed to `key-binding' contains
> all the information you need to reconstruct the binding directly
> (including whether or not the object we are looking at is a buffer
> position or a string.)
>
> So it seems like there's no problem.

Amazing.  Do you have an idea why the stuff in read-key-sequence
concerning mouse related maps appears so much more complicated?  Or is
it just me?  Some complication, of course, is due to read-key-sequence
having to _assemble_ a key sequence instead of merely looking it up.
But still...

Concretely, we have the following in keyboard.c concerning mouse
events, and I'll add my own comments with // in between.

      if (EVENT_HAS_PARAMETERS (key))
        {
          Lisp_Object kind;
          Lisp_Object string;

          kind = EVENT_HEAD_KIND (EVENT_HEAD (key));
          if (EQ (kind, Qmouse_click))
            {
              Lisp_Object window, posn;

              window = POSN_WINDOW      (EVENT_START (key));
              posn   = POSN_POSN (EVENT_START (key));

// Fake prefixes probably not relevant for keybinding-lookup
              if (CONSP (posn)
                  || (!NILP (fake_prefixed_keys)
                      && !NILP (Fmemq (key, fake_prefixed_keys))))
                {
// elided
                }

              /* Key sequences beginning with mouse clicks are
                 read using the keymaps in the buffer clicked on,
                 not the current buffer.  If we're at the
                 beginning of a key sequence, switch buffers.  */

// Do you change the buffer accordingly in your patch?

              if (last_real_key_start == 0
                  && WINDOWP (window)
                  && BUFFERP (XWINDOW (window)->buffer)
                  && XBUFFER (XWINDOW (window)->buffer) != current_buffer)
                {
                  XVECTOR (raw_keybuf)->contents[raw_keybuf_count++] = key;
                  keybuf[t] = key;
                  mock_input = t + 1;

                  /* Arrange to go back to the original buffer once we're
                     done reading the key sequence.  Note that we can't
                     use save_excursion_{save,restore} here, because they
                     save point as well as the current buffer; we don't
                     want to save point, because redisplay may change it,
                     to accommodate a Fset_window_start or something.  We
                     don't want to do this at the top of the function,
                     because we may get input from a subprocess which
                     wants to change the selected window and stuff (say,
                     emacsclient).  */
                  record_unwind_protect (Fset_buffer, Fcurrent_buffer ());

                  if (! FRAME_LIVE_P (XFRAME (selected_frame)))
                    Fkill_emacs (Qnil);
                  set_buffer_internal (XBUFFER (XWINDOW (window)->buffer));
                  orig_local_map = get_local_map (PT, current_buffer,
                                                  Qlocal_map);
                  orig_keymap = get_local_map (PT, current_buffer, Qkeymap);
                  goto replay_sequence;

// This starts the whole lookup sequence with new values for local-map
// and, well, I don't quite understand what Qkeymap is.
                }

              /* For a mouse click, get the local text-property keymap
                 of the place clicked on, rather than point.  */
              if (last_real_key_start == 0
                  && CONSP (XCDR (key))
                  && ! localized_local_map)
                {
                  Lisp_Object map_here, start, pos;

                  localized_local_map = 1;
                  start = EVENT_START (key);

                  if (CONSP (start) && POSN_INBUFFER_P (start))
                    {
                      pos = POSN_BUFFER_POSN (start);
                      if (INTEGERP (pos)
                          && XINT (pos) >= BEG && XINT (pos) <= Z)
                        {
                          map_here = get_local_map (XINT (pos),
                                                    current_buffer, Qlocal_map);
                          if (!EQ (map_here, orig_local_map))
                            {
                              orig_local_map = map_here;
                              keybuf[t] = key;
                              mock_input = t + 1;

                              goto replay_sequence;
                            }
                          map_here = get_local_map (XINT (pos),
                                                     current_buffer, Qkeymap);
                          if (!EQ (map_here, orig_keymap))
                            {
                              orig_keymap = map_here;
                              keybuf[t] = key;
                              mock_input = t + 1;

                              goto replay_sequence;
                            }
                        }
                    }
                }

// Another class of events: but they mostly don't require looking in
// other maps

              /* Expand mode-line and scroll-bar events into two events:
                 use posn as a fake prefix key.  */
              if (SYMBOLP (posn)
                  && (NILP (fake_prefixed_keys)
                      || NILP (Fmemq (key, fake_prefixed_keys))))
                {
                  if (t + 1 >= bufsize)
                    error ("Key sequence too long");

                  keybuf[t]     = posn;
                  keybuf[t + 1] = key;
                  mock_input    = t + 2;

                  /* Record that a fake prefix key has been generated
                     for KEY.  Don't modify the event; this would
                     prevent proper action when the event is pushed
                     back into unread-command-events.  */
                  fake_prefixed_keys = Fcons (key, fake_prefixed_keys);

// Except in the following case:

                  /* If on a mode line string with a local keymap,
                     reconsider the key sequence with that keymap.  */
                  if (string = POSN_STRING (EVENT_START (key)),
                      (CONSP (string) && STRINGP (XCAR (string))))
                    {
                      Lisp_Object pos, map, map2;

                      pos = XCDR (string);
                      string = XCAR (string);
                      if (XINT (pos) >= 0
                          && XINT (pos) < SCHARS (string))
                        {
                          map = Fget_text_property (pos, Qlocal_map, string);
                          if (!NILP (map))
                            orig_local_map = map;
                          map2 = Fget_text_property (pos, Qkeymap, string);
                          if (!NILP (map2))
                            orig_keymap = map2;
                          if (!NILP (map) || !NILP (map2))
                            goto replay_sequence;
                        }
                    }

                  goto replay_key;
                }
              else if (NILP (from_string)
                       && (string = POSN_STRING (EVENT_START (key)),
                           (CONSP (string) && STRINGP (XCAR (string)))))
                {
                  /* For a click on a string, i.e. overlay string or a
                     string displayed via the `display' property,
                     consider `local-map' and `keymap' properties of
                     that string.  */
                  Lisp_Object pos, map, map2;

                  pos = XCDR (string);
                  string = XCAR (string);
                  if (XINT (pos) >= 0
                      && XINT (pos) < SCHARS (string))
                    {
                      map = Fget_text_property (pos, Qlocal_map, string);
                      if (!NILP (map))
                        orig_local_map = map;
                      map2 = Fget_text_property (pos, Qkeymap, string);
                      if (!NILP (map2))
                        orig_keymap = map2;

                      if (!NILP (map) || !NILP (map2))
                        {
                          from_string = string;
                          goto replay_sequence;
                        }
                    }
                }
            }

// Menu bar: seemingly does not require other maps.

          else if (CONSP (XCDR (key))
                   && CONSP (EVENT_START (key))
                   && CONSP (XCDR (EVENT_START (key))))
            {
              Lisp_Object posn;

              posn = POSN_POSN (EVENT_START (key));
              /* Handle menu-bar events:
                 insert the dummy prefix event `menu-bar'.  */
              if (EQ (posn, Qmenu_bar) || EQ (posn, Qtool_bar))
                {
                  if (t + 1 >= bufsize)
                    error ("Key sequence too long");
                  keybuf[t] = posn;
                  keybuf[t+1] = key;

                  /* Zap the position in key, so we know that we've
                     expanded it, and don't try to do so again.  */
                  POSN_SET_POSN (EVENT_START (key),
                                 Fcons (posn, Qnil));

                  mock_input = t + 2;
                  goto replay_sequence;
                }
              else if (CONSP (posn))
                {
                  /* We're looking at the second event of a
                     sequence which we expanded before.  Set
                     last_real_key_start appropriately.  */
                  if (last_real_key_start == t && t > 0)
                    last_real_key_start = t - 1;
                }
            }
        }


If it seems to you that your patch gets the same cases (and with the
same order of priorities), that would be great!

Another thing: I had proposed an additional optional "LOCATION"
argument for key-binding.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum