/*  $Id: window.pl,v 1.72 2006/04/11 16:52:09 jan Exp $

    Part of XPCE --- The SWI-Prolog GUI toolkit

    Author:        Jan Wielemaker and Anjo Anjewierden
    E-mail:        jan@swi.psy.uva.nl
    WWW:           http://www.swi.psy.uva.nl/projects/xpce/
    Copyright (C): 1985-2002, University of Amsterdam

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    As a special exception, if you link this library with other files,
    compiled with a Free Software compiler, to produce an executable, this
    library does not by itself cause the resulting executable to be covered
    by the GNU General Public License. This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

:- module(emacs_frame, []).
:- use_module(library(pce)).
:- use_module(prompt).
:- require([ between/3
	   , concat_atom/2
	   , default/3
	   , forall/2
	   , ignore/1
	   ]).

resource(pinned,	image, image('pinned.xpm')).
resource(not_pinned,	image, image('pin.xpm')).
resource(mode_x_icon,   image, image('32x32/doc_x.xpm')).


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@current_emacs_mode is a variable  pointing   to  the current emacs-mode
object.  Pushed by `emacs_key_binding  ->fill_arguments_and_execute' and
various others.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

:- pce_global(@current_emacs_mode, new(var)).

:- pce_begin_class(emacs_frame, frame, "Frame for the PceEmacs editor").

class_variable(confirm_done, bool, false,       "Donot confirm emacs-windows").
class_variable(size,         size, size(80,32), "Size of text-field").
class_variable(prompt_style, {mini_window,dialog}, dialog, "How to prompt").

variable(sticky_window, bool,   get,  "When @on, window won't be killed").
variable(pool,		[name], both, "Window pool I belong too").

initialise(F, B:emacs_buffer) :->
	"Create window for buffer"::
	send(F, send_super, initialise, B?name, application := @emacs),
	send(F, fix_colour_map),
	send(F, slot, sticky_window, @off),
	send(F, append, new(MBD, emacs_mode_dialog)),

	get(F, class_variable_value, size, Size),
	send(new(V, emacs_view(B, Size?width, Size?height)), below, MBD),
	send(new(MW, emacs_mini_window), below, V),
	get(V, editor, E),
	send(E, recogniser, handler(keyboard,
				    message(MW, editor_event, @arg1))),
	send(F, keyboard_focus, V),
	send(F, setup_mode, V),

	send(F, open),
	send(F, pool, B?pool),
	get(E, mode, Mode),
	ignore(send(Mode, new_buffer)).


fix_colour_map(F) :->
	"Set colour-map to @nil on mapped displays"::
	(   get(@display, depth, Depth),
	    Depth =< 8
	->  send(F, colour_map, @nil)
	;   true
	).


input_focus(F, Val:bool) :->
	"Activate the window"::
	send(F, send_super, input_focus, Val),
	(   send(F, unlinking)
	->  true
	;   send(F, active, Val)
	).


buffer(F, B:emacs_buffer) :->
	"Switch to the given emacs buffer"::
	get(F, editor, E),
	send(F, pool, B?pool),
	send(E, text_buffer, B).


view(F, View:emacs_view) :<-
	get(F, member, emacs_view, View).


editor(F, Editor:emacs_editor) :<-
	"Editor component of the frame"::
	get(F, member, emacs_view, V),
	get(V, editor, Editor).


menu_bar(F, MB:emacs_menu_bar) :<-
	"The menu_bar object at the top"::
	get(F, member, emacs_mode_dialog, D),
	get(D, member, emacs_menu_bar, MB).


mode(F, Mode:emacs_mode) :<-
	"Current mode object of the editor"::
	get(F, editor, E),
	get(E, mode, Mode).


setup_mode(F, V:emacs_view) :->
	"Setup the mode for indicated view"::
	get(V, mode, Mode),
	(   get(Mode, icon, Icon)
	->  send(F, icon, Icon)
	;   true
	),
	get(F, menu_bar, MB),
	ignore(send(V, fill_menu_bar, MB)).


active(F, Val:bool) :->
	"Indicate active status"::
	get(F, view, View),
	(   Val == @on
	->  send(@emacs, selection, View?text_buffer)
	;   send(@emacs, selection, @nil)
	).


sticky_window(F, Val:[bool]) :->
	"[toggle] sticky status"::
	default(Val, F?sticky_window?negate, V2),
	send(F, slot, sticky_window, V2),
	get(F, member, mini_window, WM),
	get(WM, member, sticky_indicator, Bitmap),
	(   get(F, sticky_window, @on)
	->  send(Bitmap, image, resource(pinned))
	;   send(Bitmap, image, resource(not_pinned))
	).


fit(F) :->
	"Request to fit the contents"::
	(   get(F, attribute, fitted, @on)
	->  send(F, resize)
	;   send(F, send_super, fit),
	    send(F, attribute, fitted, @on)
	).


keyboard_focus(F, W:window) :->
	(   send(W, instance_of, view),
	    get(F, member, mini_window, MW),
	    get(MW, prompter, Prompter), Prompter \== @nil
	->  send(F, send_super, keyboard_focus, MW)
	;   send(F, send_super, keyboard_focus, W)
	).

		 /*******************************
		 *	    PROMPTING		*
		 *******************************/

:- pce_global(@prompt_recogniser, make_prompt_binding).

make_prompt_binding(G) :-
	new(G, key_binding(emacs_mini_window_prompter, text_item)),
	send(G, function, 'TAB',  complete),
	send(G, function, 'SPC',  insert_self),
	send(G, function, 'RET',  if(message(@receiver, apply, @on))),
	send(G, function, '\\C-g', and(message(@receiver, keyboard_quit),
				      message(@receiver?frame, return,
					      canceled))).

prompt_using(F, Item:dialog_item, Rval:unchecked) :<-
	"Prompt for value in dialog using Item"::
	get(F, view, View),
	get(F, member, mini_window, W),
	get(F, menu_bar, MB),
	send(MB, active, @off),

	send(W, client, View),
	send(W, prompter, Item),
	send(Item, message, message(F, return, ok)),
	(   send(Item, instance_of, text_item)
	->  send(Item, recogniser, @prompt_recogniser),
	    send(Item, value_font, fixed)
	;   true
	),
	send(F, keyboard_focus, W),
	get(F, confirm, Return),
	object(F),			% may be freed!

	(   Return == ok
	->  get(Item, selection, Rval)
	;   true
	),

	send(Item, message, @nil),
	send(Item, lock_object, @on),	% Tricky, but we should leave the
	send(W, prompter, @nil),	% lifetime to the caller
	get(Item, unlock, Item),
	get(F, view, View),
	send(F, keyboard_focus, View),
	send(MB, active, @on),
	Return == ok.

reset(F) :->
	"Remove prompter"::
	send(F, send_super, reset),
	get(F, member, mini_window, W),
	send(W, prompter, @nil),
	get(F, menu_bar, MB),
	send(MB, active, @on).

show_line_number(F, Line:'int|{too_expensive}*') :->
	"Show current line in mini-window"::
	get(F, member, mini_window, W),
	send(W, show_line_number, Line).

:- pce_end_class(emacs_frame).


:- pce_begin_class(emacs_mode_dialog, dialog,
		   "Show menu-bar for mode options").

initialise(D) :->
	send_super(D, initialise),
	send(D, gap, size(0,0)),
	send(D, pen, 0),
	send(D, append, new(emacs_menu_bar)).

resize(D) :->
	send(D, layout, D?area?size).

assign_accelerators(_) :->
	"Accelerators are defined by the window"::
	true.

:- pce_end_class(emacs_mode_dialog).


:- pce_begin_class(emacs_menu_bar, menu_bar,
		   "Top menu bar of the editor").

assign_accelerators(_) :->
	"Accelerators are defined by the window"::
	true.

mode(MB, Mode:emacs_mode) :->
	"Prepare for given mode"::
	get(Mode, mode_menu, ModeMenu),
	send(MB, clear),
	send(ModeMenu, for_all,
	     message(MB, append_items, Mode, @arg1?name, @arg1?value)).

append_items(MB, Mode:emacs_mode, Name:name, Entries:chain) :->
	(   get(MB, member, Name, Popup)
	->  true
	;   new(Popup, emacs_popup(Name,
				   message(@emacs_mode, noarg_call, @arg1))),
	    (   Name == help
	    ->	send(MB, append, Popup, right)
	    ;   send(MB, append, Popup)
	    )
	),
	send(Entries, for_some, message(Popup, append_item, Mode, @arg1)).

:- pce_end_class(emacs_menu_bar).


:- pce_begin_class(emacs_popup, popup,
		   "Popup for the mode-menu").

class_variable(accelerator_font, font, small).

assign_accelerators(_) :->
	"Accelerators are defined by the window"::
	true.

append_item(P, Mode:emacs_mode, Item:any) :->
	"Append single menu item"::
	(   Item == -
	->  send(P, append, gap)
	;   atom(Item)
	->  send(P, append, new(MI, menu_item(Item))),
	    (	accelerator(Item, Mode, Accell)
	    ->	send(MI, accelerator, Accell)
	    ;   true
	    ),
	    (   get(Mode, send_method, Item, tuple(_, Impl))
	    ->  (   forall((between(1, 10, ArgN),
		    get(Impl, argument_type, ArgN, ArgType)),
		    send(ArgType, includes, default))
		->  true
		;   send(MI, label, string('%s ...', Item?label_name))
		)
	    ;   send(MI, active, @off)
	    )
	;   send(P, append, Item?clone)
	).

%	accelerator(+Command, +Mode, -Accelerator)
%	
%	Copy/cut are hacked due to the tricky combination of CUA and
%	native Emacs mode.

accelerator(copy, _, 'Control-c') :- !.
accelerator(cut,  _, 'Control-x') :- !.
accelerator(Cmd,  Mode, Accell) :-
	get(Mode, bindings, KeyBindings),
	get(KeyBindings, binding, Cmd, Key),
	human_accelerator(Key, Accell).

%	human_accelerator(+Key, -Human)
%
%	Translate XPCE key-sequences in conventional notation.  Should be
%	part of the XPCE kernel someday.

:- dynamic
	accel_cache/2.

human_accelerator(Key, Text) :-
	accel_cache(Key, Text), !.
human_accelerator(Key, Text) :-
	new(S, string('%s', Key)),
	send(regex('\\\\C-(.)'), for_all, S,
	     message(@arg1, replace, @arg2, 'Control-\\1 ')),
	send(regex('\\\\e'), for_all, S,
	     message(@arg1, replace, @arg2, 'Alt-')),
	get(S, value, Text),
	assert(accel_cache(Key, Text)).

:- pce_end_class(emacs_popup).


:- pce_begin_class(emacs_mini_window, dialog, "Prompt and feedback window").

variable(prompter, 	 dialog_item*,  get,	"Current prompter").
variable(report_count,	 number,	get,	"Count to erase report").
variable(report_type,	 name*,		both,	"Last type of report").

initialise(D) :->
	send(D, send_super, initialise),
	send(D, slot, report_count, number(0)),
	send(D, gap, size(10, 2)),
	send(D, pen, 0),
	send(D, display, new(StickyIndicator, bitmap(resource(not_pinned)))),
	send(StickyIndicator, name, sticky_indicator),
	send(StickyIndicator, recogniser,
	     click_gesture(left, '', single,
			   message(@receiver?frame, sticky_window))),
	send(D, display, label(reporter), point(25, 2)),
	send(D, display, new(T, text('', right, normal)), point(100, 2)),
	send(T, name, line),
	get(text_item(''), height, MH),
	send(D, height, MH),
	send(D, name, mini_window).

resize(D) :->
	get(D, member, line, Text),
	get(D?area, width, W),
	get(Text, width, TW),
	send(Text, x, W-TW-2).

'_compute_desired_size'(_) :->
	"We have fixed size"::
	true.

client(D, Client:emacs_view) :->
	"Register emacs_view as client"::
	send(D, delete_hypers, client),
	new(_, hyper(D, Client, client, mini_window)).
client(D, Client:emacs_view) :<-
	"Get client emacs_view"::
	get(D, hypered, client, Client).


show_line_number(D, Line:'int|{too_expensive}*') :->
	"Show number of current line"::
	get(D, member, line, Text),
	(   Line == @nil
	->  send(Text, string, '')
	;   Line == too_expensive
	->  send(Text, string, 'Line: ?')
	;   send(Text, string, string('Line: %d', Line))
	).


report(D, Type:name, Fmt:[char_array], Args:any ...) :->
	"Report"::
	(   get(D, report_type, ReportType),
	    ok_to_overrule(Type, ReportType)
	->  send(D, report_type, Type),
	    get(D, member, reporter, Label),
	    get(D, report_count, RC),
	    (   Fmt == '', Type == status	% clear
	    ->  send(Label, clear),
		send(RC, value, 0)
	    ;   (   get(D, prompter, Prompter), Prompter \== @nil
		->  send(Label, x, Prompter?width + 10)
		;   send(Label, x, 25)
		),
		send(Label, displayed, @on),
		Msg =.. [report, Type, Fmt|Args],
		send(Label, Msg),
		send(RC, value, 10)
	    )
	;   true
	).

ok_to_overrule(_, @nil).
ok_to_overrule(_, status).
ok_to_overrule(_, progress).
ok_to_overrule(_, done).
ok_to_overrule(warning, warning).
ok_to_overrule(inform, _).
ok_to_overrule(error, _).

:- pce_global(@emacs_mini_window_bindings, make_emacs_mini_window_bindings).

make_emacs_mini_window_bindings(B) :-
	new(B, key_binding(emacs_mini_window)),
	send(B, function, '\\es', sticky_window),
	send(B, function, '\\en', m_x_next),
	send(B, function, '\\ep', m_x_previous).
	      
editor_event(D, Ev:event) :->
	"Process event typed in the editor"::
	(   get(D, prompter, Prompter),
	    Prompter \== @nil
	->  (   send(@emacs_mini_window_bindings, event, Ev)
	    ->  true
	    ;   get(D, member, reporter, Reporter),
		send(Reporter, displayed, @off),
		ignore(send(Ev, post, Prompter))
	    )
	;   send(D, report_type, @nil),
	    get(D, report_count, RC),
	    send(RC, minus, 1),
	    (   send(RC, equal, 0)
	    ->  send(D, report, status, '')
	    ),
	    fail
	).


event(D, Ev:event) :->
	"Process direct event"::
	(   get(D, prompter, Prompter),
	    Prompter \== @nil
	->  send(D, editor_event, Ev)
	;   send_super(D, event, Ev)
	).


m_x_next(D) :->
	"Handle M-n to get next value"::
	(   get(D?client?mode, m_x_next, NewDefault)
	->  send(D?prompter, displayed_value, NewDefault?print_name)
	;   send(D?prompter, restore)
	).


m_x_previous(D) :->
	"Handle M-p to get previous value"::
	get(D?client?mode, m_x_previous, NewDefault),
	send(D?prompter, displayed_value, NewDefault?print_name).


geometry(D, X:[int], Y:[int], W:[int], H:[int]) :->
	"Change size, center contents vertically"::
	send(D, send_super, geometry, X, Y, W, H),
	get(D, height, DH),
	DH2 is DH//2,
	send(D?graphicals, for_all,
	     message(@arg1, center_y, DH2)).


prompter(D, Prompter:dialog_item*) :->
	"Display the prompter"::
	get(D, member, reporter, Reporter),
	(   get(D, prompter, OldPrompter), OldPrompter \== @nil
	->  send(D, erase, OldPrompter)
	;   true
	),
	(   Prompter == @nil
	->  send(Reporter, clear),
	    send(Reporter, displayed, @on)
	;   send(Reporter, displayed, @off),
	    get(Prompter, height, H),
	    get(D, height, DH),
	    PY is (DH-H)//2,
	    send(D, display, Prompter, point(25, PY)),
	    get(Prompter, height, H),
	    MinH is H,
	    (	DH < MinH
	    ->	send(D, height, MinH)
	    ;	true
	    )
	),
	send(D, slot, prompter, Prompter).

:- pce_end_class.


:- pce_begin_class(emacs_view, view,
		   "View running an emacs_editor").

:- pce_global(@emacs_image_recogniser,
	      new(handler(button,
			  message(@receiver?device?(mode), event, @event)))).

class_variable(size,         size, size(80,32), "Size of text-field").

variable(reuse,		bool := @on,	both, "Re-use for opening buffers").

initialise(V, B:buffer=[emacs_buffer], W:width=[int], H:height=[int]) :->
	"Create for buffer"::
	get(V, class_variable_value, size, size(DW, DH)),
	default(W, DW, Width),
	default(H, DH, Height),
	(   B == @default
	->  new(Buffer, emacs_buffer(@nil, '*scratch*'))
	;   Buffer = B
	),
	send_super(V, initialise, @default, @default, @default,
		   new(E, emacs_editor(Buffer, Width, Height))),
	send(E?image, recogniser, @emacs_image_recogniser),
	get(Buffer, mode, ModeName),
	send(E, mode, ModeName),
	get(E, mode, Mode),		% the mode object
	ignore(send(Mode, new_buffer)).


drop_files(V, Files:chain, _At:point) :->
	"Accept files dropped on me"::
	send(V?editor, drop_files, Files).


:- pce_group(mode).

setup_mode(V) :->
	"Editor has changed mode; ask <-frame to do its part"::
	(   get(V, frame, Frame),
	    send(Frame, has_send_method, setup_mode)
	->  send(Frame, setup_mode, V)
	;   true
	).

fill_menu_bar(V, MB:menu_bar) :->
	"Setup menu-bar for current mode"::
	send(V?editor, fill_menu_bar, MB).

:- pce_group(prompt).

prompt_using(V, Item:dialog_item, Rval:unchecked) :<-
	"Prompt for one value using a dialog-item"::
	(   get(V, frame, Frame),
	    send(Frame, has_get_method, prompt_using)
	->  get(Frame, prompt_using, Item, Rval)
	;   new(D, dialog),		% very incomplete!
	    send(D, transient_for, V),
	    send(D, modal, transient),
	    send(D, append, Item),
	    get(D, confirm_centered, Rval)
	).

prompt(V, Label:char_array, Default:[any], Type:[type], History:[chain],
       Rval:any) :<-
	"Prompt for a value"::
	get(V, mode, Mode),
	make_item(Mode, Label, Default, Type, History, Item),
	(   send(Item, instance_of, text_item)
	->  send(Item, length, 60),
	    send(Item, pen, 0)
	),
	
	get(V, prompt_using, Item, RawRval),

	fix_rval(Type, RawRval, Rval),
	(   object(Rval),
	    get(Rval, lock_object, @off)
	->  send(Rval, lock_object, @on), 	% protect during deletion!
	    free(Item),
	    get(Rval, unlock, Rval)
	;   free(Item)
	).


%	If the user entered a directory while requested for a file,
%	start the finder in the specified directory to provide the file.

fix_rval(Type, RawRval, RVal) :-
	send(Type, instance_of, type),
	send(Type, includes, file),
	\+ send(Type, includes, directory),
	atom(RawRval),
	send(directory(RawRval), exists), !,
	get(@finder, file, @on, directory := RawRval, RVal).
fix_rval(_, Rval, Rval).


:- pce_global(@emacs_prompt_for,
	      new(constant(prompt, 'Prompt for value'))).

interactive_arguments(V, Impl:any, Times:[int], Argv:vector) :<-
	"Prompt for arguments for the given implementation"::
	get(V, mode, Mode),
	make_arg_vector(Impl, Times, Argv),
	(   get(Argv, index, @emacs_prompt_for, _)
	->  (   get(V, frame, Frame),
	        send(Frame, has_get_method, prompt_style),
		get(Frame, prompt_style, mini_window)
	    ->  fill_arg_vector(Mode, Impl, Argv)
	    ;	new(D, emacs_prompt_dialog(Mode, Impl, Argv)),
		send(D, prompt, V, Argv),
		send(D, destroy)
	    )
	;   true
	).

fill_arg_vector(Mode, Impl, Argv) :-
	fill_arg_vector(1, Mode, Impl, Argv).

fill_arg_vector(ArgN, Mode, Impl, Argv) :-
	get(Impl, argument_type, ArgN, ArgType),
	get(Argv, element, ArgN, @emacs_prompt_for), !,
	get(Mode, interactive_argument, Impl, ArgN, Arg),
	get(ArgType, check, Arg, CheckedArg),
	send(Argv, element, ArgN, CheckedArg),
	Next is ArgN + 1,
	fill_arg_vector(Next, Mode, Impl, Argv).
fill_arg_vector(ArgN, Mode, Impl, Argv) :-
	get(Impl, argument_type, ArgN, _), !,
	Next is ArgN + 1,
	fill_arg_vector(Next, Mode, Impl, Argv).
fill_arg_vector(_, _, _, _).
	

make_arg_vector(Impl, Times, Argv) :-
	new(Argv, code_vector),
	make_arg_vector(1, Impl, Times, Argv).

make_arg_vector(ArgN, Impl, Times, Argv) :-
	get(Impl, argument_type, ArgN, ArgType), !,
	(   integer(Times),
	    send(ArgType, includes, int)
	->  send(Argv, element, ArgN, Times),
	    NextTimes = @default
	;   NextTimes = Times,
	    (   send(ArgType, includes, default)
	    ->  send(Argv, element, ArgN, @default)
	    ;   send(Argv, element, ArgN, @emacs_prompt_for)
	    )
	),
	Next is ArgN + 1,
	make_arg_vector(Next, Impl, NextTimes, Argv).
make_arg_vector(_, _, _, _).


:- pce_end_class(emacs_view).


:- pce_begin_class(emacs_editor, editor, "Generic PceEmacs editor").

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
We use a pool of  modes  recorded  in   <-modes  to  avoid  the need for
destruction of mode objects during the livetime  of the editor.  This is
dangerous as the mode might still be `running' some command.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

variable(mode,		  emacs_mode*,	get, "Mode of operation").
variable(modes,		  chain,	get, "Modes part of this editor").

initialise(E, TB:[text_buffer], W:[int], H:[int]) :->
	send(E, send_super, initialise, TB, W, H),
	send(E, slot, modes, new(chain)).


unlink(E) :->
	"Unlink from mode object"::
	get(E, modes, Modes),
	send(Modes, for_all, message(@arg1, free)),
	send(E, send_super, unlink).

:- pce_global(@emacs_idle_timer, make_idle_timer).

make_idle_timer(T) :-
	new(T, timer(2)),
	send(T, message,
	     new(Msg, message(T, send_hyper, editor, editor_idle_event))),
	send(Msg, debug_class, service). 	% non-traceable


editor_idle_event(E) :->
	"Editor is idle"::
	get(E, mode, Mode),
	Mode \== @nil,
	send(Mode, has_send_method, idle),
	get(E, window, Window),
	get(Window, focus, @nil),	% only send event if no recognisers
	send(Mode, idle).		% are active


start_idle_timer(E, Interval:[real]) :->
	"Reset the idle timer to timeout after the specified time"::
	default(Interval, 2, Time),
	send(@emacs_idle_timer, interval, Time),
	send(@emacs_idle_timer, status, once),
	send(@emacs_idle_timer, delete_hypers),
	new(_, hyper(@emacs_idle_timer, E, editor, idle_timer)).


typed(E, Id:'event|event_id') :->
	"Handle typing via mode"::
	send(E, start_idle_timer),
	get(E, mode, Mode),
	(   send(Mode, typed, Id, E),
	    object(Mode)		% may disappear
	->  send(Mode, highlight_matching_bracket)
	;   true
	).


caret(E, Caret:[int]) :->
	"Deal with idle-timing and ->new_caret_position"::
	get(E, caret, Old),
	send_super(E, caret, Caret),
	send(E, start_idle_timer),
	get(E, mode, Mode),
	(				% Mode can be @nil
	    send(Mode, has_send_method, new_caret_position)
	->  (   Caret == @default
	    ->  get(E, caret, NewCaret)
	    ;   NewCaret = Caret
	    ),
	    (   Old \== NewCaret
	    ->  send(Mode, new_caret_position, NewCaret)
	    ;   true
	    )
	;   true
	).


event(E, Ev:event) :->
	(   send(Ev, is_a, area_enter)
	->  get(E, frame, Frame),
	    (	get(Frame, transients, Transients),
		Transients \== @nil,
		get(Transients, find, @arg1?modal == transient, _)
	    ->	format('We have a transient~n')
	    ;	send(Frame, keyboard_focus, E?window)
	    )
	;   send_super(E, event, Ev)
	).


paste(E) :->
	send(E, start_idle_timer),
	send_super(E, paste),
	send(E, highlight_matching_bracket).


highlight_matching_bracket(E) :->
	get(E, mode, Mode),
	(   send(Mode, highlight_matching_bracket)
	->  true
	;   true			% avoid delegation
	).


mode(E, ModeName:mode_name) :->
	"Associate argument mode"::
	get(E, mode, OldMode),
	(   get(OldMode, name, ModeName)
	->  send(E, syntax, OldMode?syntax)
	;   (	get(E?modes, find, @arg1?name == ModeName, Mode)
	    ->  send(E, slot, mode, Mode)
	    ;	send(E, slot, mode, ModeName),	% Converted to object
	        get(E, mode, Mode),		% The object
	        send(Mode, editor, E),
		send(E?modes, append, Mode)
	    ),
	    send(E?text_buffer, mode, ModeName),
	    send(E, syntax, Mode?syntax),
	    send(E, bindings, Mode?bindings),
	    send(E, setup_mode),
	    send(E?device, setup_mode),
	    send(E, report, status, 'Switched to ``%s'''' mode', ModeName)
	).

	
sticky_window(E, Val:[bool]) :->
	"Change sticky status of window"::
	send(E?frame, sticky_window, Val).


preview_drop(E, Obj:object*) :->
	"Delegate to mode"::
	get(E, mode, Mode),
	get(Mode?class, send_method, preview_drop, _), % avoid delegation
	send(Mode, preview_drop, Obj).


drop(E, Obj:object) :->
	"Delegate to mode"::
	get(E, mode, Mode),
	get(Mode?class, send_method, drop, _),	       % avoid delegation
	send(Mode, drop, Obj).


auto_fill(E, Caret:[int]) :->
	"Delegate to mode"::
	(   get(E, mode, Mode),
	    get(Mode?class, send_method, auto_fill, _)
	->  send(Mode, auto_fill, Caret)
	;   send_super(E, auto_fill)
	).


import_selection(E) :->
	"Import the (primary) selection or the cut_buffer"::
	get(E, display, Display),
	get(Display, selected_text, String),
	(   get(E, frame, Frame),
	    get(Frame, member, mini_window, MiniWindow),
	    get(MiniWindow, prompter, TI),
	    send(TI, instance_of, text_item)
	->  send(TI, insert, @default, String)
	;   send(E, insert, String)
	).


catch_all(E, Selector:name, Args:unchecked ...) :->
        "Delegate to mode"::
        get(E, mode, Mode),
	get(Mode?class, send_method, Selector, _),
        send(@pce, last_error, @nil),
	Msg =.. [Selector|Args],
        send(Mode, Msg).


text_buffer(E, B:emacs_buffer) :->
	"Switch to indicated buffer"::
	get(E, text_buffer, Last),
	(   B == Last
	->  true
	;   send_super(E, text_buffer, B),
	    get(B, mode, ModeName),
	    send(E, mode, ModeName),
	    send(B, update_label),
	    send(E, report, status, ''),
	    get(E, mode, Mode),
	    send(Mode, new_buffer),
	    (	send(Last, instance_of, emacs_buffer)
	    ->  send(E, delete_hypers, last_buffer),
		new(_, hyper(E, Last, last_buffer, last_editor))
	    ;	true
	    )
	).


last_buffer(E, TB:text_buffer) :<-
	"Text-buffer we came from (for default)"::
	get(E, hypered, last_buffer, TB).


		 /*******************************
		 *          UTILITIES		*
		 *******************************/

looking_at(E, Re:regex, Where:[int], End:[int]) :->
	"Test if regex macthes from the caret"::
	(   Where == @default
	->  get(E, caret, C)
	;   C = Where
	),
	get(E, text_buffer, TB),
	send(Re, match, TB, C, End).

:- pce_end_class.


		 /*******************************
		 *	    EMACS MODES		*
		 *******************************/

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PceEmacs  modes  are  tricky  stuff.   We    like  to  have  comfortable
programming, which implies we should  represent   a  PceEmacs  mode as a
class.   This  provides  us  with  a   good  programming  interface  and
inheritance as well as all the other goodies of OO programming.

We also would like to be able to   switch PceEmacs windows from one mode
to another.  This conflicts, as instances  cannot be migrated from class
to class.  Therefore, PceEmacs modes are objects  that are attached to a
emacs_editor.  An emacs_mode delegates to the   editor  in this mode and
editors delegate to their mode (with an explicit method to avoid endless
loops  if  the   method   is   defined    on   neither).    The   method
`pce_editor->mode' attaches a mode to an editor.

Next, we would like users to be able  to extend these classes to provide
custom methods and possibly redefine methods.  This has been implemented
using tricky meta-programming: class emacs_mode_class   is a subclass of
class `class' (representing classes).   This   class  defines the method
->load_user_extensions, which is called when an instance of the class is
created.   The  classes  defining  emacs_modes  are  instances  of  this
emacs_mode_class class.  To understand this, try:

	?- new(X, class(myclass, class)),
	   new(Y, myclass(myobject, object)),
	   new(Z, myobject).

and verify how the objects and classes are related.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */


:- pce_begin_class(emacs_mode_class, class,
		   "Class for emacs modes").

variable(user_extensions_loaded, bool := @off, get,
	 "Test if extensions are loaded").

load_user_extensions(C) :->
	"Load mode extensions from ~/lib/xpce/emacs/"::
	(   get(C, user_extensions_loaded, @on)
	->  true
	;   get(C, name, Name),
	    (   atom_concat(emacs_, Base, Name)
	    ->	true
	    ;	Base = Name
	    ),
	    send(@emacs, load_user_extension, Base),
	    send(C, slot, user_extensions_loaded, @on),
	    get(C, super_class, Super),
	    (	send(Super, has_send_method, load_user_extensions)
	    ->	send(Super, load_user_extensions)
	    ;	true
	    )
	).

:- pce_end_class(emacs_mode_class).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Finally, we have to tell pce_begin_class/3 the  meta-class we want to be
using.  If pce_begin_class/3 makes a subclass, it will make the subclass
of the same  meta-class  as  its   super-class.   Thus,  a  subclass  of
emacs_mode will be an instance   of  class(emacs_mode_class), instead of
class(class).
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

:- pce_begin_class(emacs_mode_class:emacs_mode(name), object,
		   "Generic PceEmacs mode class").

variable(name,		  name,		get,  "Name of the mode").
variable(syntax,	  syntax_table,	get,  "Syntax for this mode").
variable(bindings,	  key_binding,	get,  "Key-binding table").
variable(editor,	  editor*,	both, "Associated editor").
variable(m_x_history,	  chain*,	both, "Current M-x command history").
variable(m_x_index,	  int*,		both, "M-p/M-n current index").
variable(m_x_argn,	  int*,		both, "M-p/M-n current argument").
variable(keep_selection,  bool := @off, both, "Keep selection for this method").

delegate_to(editor).

		/********************************
		*         CREATE/REUSE		*
		********************************/

initialise(M) :->
	"Create"::
	get(M, class_name, ClassName),
	mode_name(ClassName, Name),
	send(@mode_name_type?context, add, Name), % make sure
	send(M, send_super, initialise),
	send(M, slot, name, Name),
	send(M, slot, syntax, Name),		  % converts to object
	send(M, bindings).


icon(_, I:image) :<-
	"Return icon for mode"::
	new(I, image(resource(mode_x_icon))).


mode_name(emacs_mode, default) :- !.
mode_name(Mode, Name) :-
	(   atom_concat(emacs_, M1, Mode)
	;   M1 = Mode
	), !,
	(   atom_concat(Name, '_mode', M1)
	;   Name = M1
	), !.


table_name(ClassName, TableName) :-
	atom_concat(TableName, '_mode', ClassName).


new_buffer(M) :->
	"Called if a new buffer is attached to this mode"::
	(   get(M, frame, Frame),
	    send(Frame, has_send_method, show_line_number)
	->  send(Frame, show_line_number, @nil)
	;   true
	),
	send(M, new_caret_position, M?caret).


new_caret_position(M, Caret:int) :->
	"Called after any caret movement"::
	get(M, text_buffer, TB),
	get(TB, find_all_fragments,
	    message(@arg1, overlap, Caret),
	    Fragments),
	(   send(Fragments, empty)
	->  send(M, report, status, '')
	;   send(Fragments, for_some,
		 message(M, in_fragment, @arg1))
	).


highlight_matching_bracket(_M, _At:[int]) :->
	"Virtual.  Statically highlight bracket matching caret"::
	true.


in_fragment(M, Fragment:fragment) :->
	"Called after a caret movement brings the caret in fragment"::
	(   send(Fragment, has_send_method, identify)
	->  send(Fragment, identify)
	;   (   get(Fragment, attribute, message, Message)
	    ->  get(Fragment, style, StyleName),
		send(M, report, status, '%s: %s', StyleName, Message)
	    ;   true
	    )
	).


bindings(M) :->
	"Associate key_binding table"::
	get(M, class_name, ClassName),
	binding_name(ClassName, Name),
	get(@key_bindings, member, Name, Table), !,
	send(M, slot, bindings, Table).


syntax(M) :->
	"Associate syntax table"::
	get(M, class_name, ClassName),
	binding_name(ClassName, Name),
	get(@syntax_tables, member, Name, Table), !,
	send(M, slot, syntax, Table).


binding_name(ClassName, Name) :-
	table_name(ClassName, Name).
binding_name(ClassName, Name) :-
	mode_name(ClassName, ModeName),
	key_binding_name(ModeName, Name).
binding_name(ClassName, Name) :-
	get(@pce, convert, ClassName, class, Class),
	get(Class, super_class, Super),
	send(Super, is_a, emacs_mode),
	get(Super, name, SuperName),
	binding_name(SuperName, Name).


convert(_, Name:name, Mode:emacs_mode) :<-
        "Convert name into a mode object"::
        concat_atom([emacs_, Name, '_mode'], ModeClassName),
	get(@pce, convert, ModeClassName, class, _), % fail silently
        new(Mode, ModeClassName).


		 /*******************************
		 *	   THE MODE MENU	*
		 *******************************/

:- pce_global(@emacs_mode, new(@event?window?(mode))).

mode_menu(M, MM:emacs_mode_menu) :<-
	"Return the mode-menu structure for this mode"::
	get(M, class_name, ClassName),
	mode_menu_name(ClassName, Name),
	get(@emacs_mode_menus, member, Name, MM), !.


mode_menu_name(ClassName, Name) :-
	mode_name(ClassName, Name).
mode_menu_name(ClassName, Name) :-
	get(@pce, convert, ClassName, class, Class),
	get(Class, super_class, Super),
	send(Super, is_a, emacs_mode),
	get(Super, name, SuperName),
	mode_menu_name(SuperName, Name).

fill_menu_bar(M, MB:menu_bar) :->
	"Fill the menu_bar"::
	send(MB, mode, M).


		 /*******************************
		 *	      HISTORY		*
		 *******************************/

%:- pce_global(@c_method, new(var)).	% debugging

open_history(M, Impl:behaviour, Force:[bool]) :->
	"(Initialise) history for behaviour"::
	(   (Force == @on ; get(M, m_x_history, @nil))
	->  (   get(Impl, attribute, emacs_history, History)
	    ->  true
	    ;   send(Impl, attribute, emacs_history, new(History, chain))
	    ),
%	    send(@c_method, assign, Impl, global),
	    send(M, m_x_history, History),
	    send(M, m_x_index, @nil)
	;   true
	).


close_history(M, Argv:[vector]) :->
	"Close open history adding Argv"::
	get(M, m_x_history, History),
	(   Argv \== @default,
	    History \== @nil
	->  get(Argv, copy, Save),
	    clean_argv(Save),
	    (	get(History, find,
		    message(@prolog, same_argv, Save, @arg1),
		    Old)
	    ->	send(History, move_after, Old)
	    ;	send(History, prepend, Argv)
	    )
	;   true
	),
	send(M, m_x_history, @nil),
	send(M, m_x_index, @nil).


same_argv(V1, V2) :-
	get(V1, size, S1),
	get(V2, size, S1),
	forall(between(1, S1, N),
	       (   get(V1, element, N, E1), get(E1, print_name, P1),
		   get(V2, element, N, E2), get(E2, print_name, P2),
		   send(P1, equal, P2)
	       )).


%	clean_argv(+Vector)
%	Replace vector elements with their written version to avoid the
%	risk of illegal-object references.

clean_argv(Vector) :-
	get(Vector, low_index, Low),
	get(Vector, high_index, High),
	(   between(Low, High, Index),
	    get(Vector, element, Index, E),
	    object(E),
	    get(E, protect, @off),
	    send(Vector, element, Index, E),
	    fail
	;   true
	).


noarg_call(M, Selector:name, Times:[int]) :->
	"Invoke method without arguments (prompt)"::
	(   get(M, send_method, Selector, tuple(_, Impl))
	->  send(@current_emacs_mode, assign, M),
	    send(M, open_history, Impl, @on),
	    get(M, interactive_arguments, Impl, Times, Argv),
	    send(M, report, status, ''),
	    send(M, close_history, Argv),
	    (	send(M, send_vector, Selector, Argv)
	    ->	(   object(M)
		->  send(M, mark_undo)
		;   true
		)
	    ;	(   object(M)
		->  send(M, report, status, '%s command failed', Selector)
		;   true
		)
	    )
	;   send(M, report, error, 'No implementation for ``%s''''', Selector)
	).


arg_call(M, Selector:name, Arg:any) :->
	"Invoke method from pullright menu"::
	send(M, Selector, Arg).


		 /*******************************
		 *           SETUP		*
		 *******************************/

setup_mode(M) :->
	"Initialise mode (->load_user_extensions)"::
	send(M, load_user_extensions).


load_user_extensions(M) :->
	"Load mode extensions from ~/lib/xpce/emacs/"::
	send(M?class, load_user_extensions).


		/********************************
		*           TYPING		*
		********************************/

typed(M, Id:'event|event_id', Editor:editor) :->
	"Handle typed character for editor"::
	get(M, text_buffer, TB),
	send(TB, check_auto_save),
	
					% send to mode rather than editor
	(   get(M, focus_function, F), F \== @nil
 	->  (   send(M, F, Id)
	    ->  true
	    ;   send(M, focus_function, @nil),
		send(M, typed, Id, Editor)	  % failed: unfocus and resent
 	    )
	;   get(M, bindings, Binding),
	    send(Binding, typed, Id, M)
	).


		 /*******************************
		 *	     SELECTION		*
		 *******************************/

default(_E, _Type:type, _Default:unchecked) :<-
	"[virtual] Provide default for prompting"::
	fail.


		 /*******************************
		 *	     EVENTS		*
		 *******************************/

event(M, Ev:event) :->
	"Allow for gestures to be appended to modes"::
	(   get(M, all_recognisers, Chain),
		get(Chain, find,
		    message(@arg1, event, Ev), _)
	;   send(Ev, is_a, ms_right_down), % show fragment popup (if any)
	    get(M?image, index, Caret),
	    get(M?text_buffer, find_all_fragments,
		message(@arg1, overlap, Caret),
		Fragments),
	    send(Fragments, sort, ?(@arg1?length, compare, @arg2?length)),
	    get(Fragments, find, message(@arg1, has_get_method, popup), F),
	    get(F, popup, P), P \== @nil,
	    new(G, popup_gesture(P)),
	    send(G, context, F),	% make fragment available as @arg1
	    send(G, event, Ev)
	).


		 /*******************************
		 *	  FIX DELEGATION	*
		 *******************************/

file(M, File:file*) :<-
	"Return associated file"::
	get(M?text_buffer, file, File).


		 /*******************************
		 *	PROMPTING ARGUMENTS	*
		 *******************************/

prompt(M, Label:char_array, Default:[any], Type:[type], Rval:any) :<-
	"Prompt for a value in the mini-window"::
	get(M?window, prompt, Label, Default, Type, Rval).


prompt_using(M, Item:graphical, Rval:any) :<-
	"Prompt using dialog item in the mini-window"::
	get(M?window, prompt_using, Item, Rval).


interactive_arguments(M, Implementation:any, Times:[int], Argv:vector) :<-
	"Prompt for arguments for the given implementation"::
	get(M, window, View),
	get(View, interactive_arguments, Implementation, Times, Argv).


interactive_argument(M, Implementation:any, Which:int, Value:any) :<-
	"Prompt for interactive argument of specified type"::
	send(M, open_history, Implementation),
	get(M, window, EmacsWindow),
	get(Implementation, argument_type, Which, Type),
	send(M, m_x_argn, Which),
	get(M, m_x_history, History),
	(   get(M, m_x_index, Idx), Idx \== @nil % use M-x History!
	->  get(History, nth1, Idx, HistArgv),
	    get(HistArgv, element, Which, DefaultValue)
	->  true
	;   get(Implementation, name, ImplName),
	    \+ send(ImplName, suffix, selection), % not on *_selection
	    get(M, selected, Selection),
	    get(Type, check, Selection, DefaultValue)
	->  true
	;   DefaultValue = @default
	),
	(   get(Type, argument_name, Label), Label \== @nil
	->  true
	;   get(Type, name, Label)
	),
	(   (   History == @nil
	    ;	send(History, empty)
	    )
	->  ValueSet = @default
	;   get(History, map, ?(@arg1, element, Which), ValueSet)
	),
	get(EmacsWindow, prompt, Label, DefaultValue, Type, ValueSet, Value).


m_x_previous(M, Value:any) :<-
	"Read next value from the M-x history"::
	get(M, m_x_index, Idx),
	(   Idx == @nil
	->  Nidx = 1
	;   Nidx is Idx + 1
	),
	(   get(M, m_x_history, H), H \== @nil,
	    get(H, nth1, Nidx, ArgVector)
	->  get(ArgVector, element, M?m_x_argn, Value),
	    send(M, m_x_index, Nidx)
	;   send(M, report, warning, 'No (more) history'),
	    fail
	).

	
m_x_next(M, Value:any) :<-
	"Read previous value from the M-x history"::
	get(M, m_x_index, Idx),
	(   (Idx == @nil ; Idx =< 1)
	->  send(M, report, warning, 'Back at start'),
	    fail
	;   Nidx is Idx - 1
	),
	get(M?m_x_history, nth1, Nidx, ArgVector),
	get(ArgVector, element, M?m_x_argn, Value),
	send(M, m_x_index, Nidx).
	

		 /*******************************
		 *	      REPORT		*
		 *******************************/

report_to(M, E:editor) :<-
	"Send reports to the <-editor"::
	get(M, editor, E).

:- pce_end_class.


:- pce_begin_class(emacs_mode_menu(name), sheet).

:- pce_global(@emacs_mode_menus, new(hash_table)). % name ---> mode_menu object

variable(name,		name,		get,	"Name of the menu").

initialise(MM, Name:name, Super:[emacs_mode_menu]) :->
	"Create from name and super (default) menu"::
	send(MM, send_super, initialise),
	send(MM, slot, name, Name),
	send(@emacs_mode_menus, append, Name, MM),
	send(MM, protect),
	(   Super \== @default
	->  send(Super, for_all,
		 message(MM, value, @arg1?name, @arg1?value?copy))
	;   true
	).


lookup(_, Name:name, _Super:[emacs_mode_menu], MM) :<-
	"Reuse existing mode menu"::
	get(@emacs_mode_menus, member, Name, MM).


convert(_, Name:name, MM:emacs_mode_menu) :<-
	"Convert name to mode-menu object"::
	(   get(@emacs_mode_menus, member, Name, MM)
	->  true
	;   get(@pce, convert, string('emacs_%s_mode', Name), class, Class),
	    get(Class, name, ClassName),
	    mode_menu_name(ClassName, MenuName),
	    get(@emacs_mode_menus, member, MenuName, MM)
	).


action_name(Name, Name) :-
	atomic(Name), !.
action_name(MenuItem, Name) :-
	get(MenuItem?value?print_name, value, Name).

locate_action(Chain, Action, Cell) :-
	action_name(Action, Name),
	get(Chain, find, message(@prolog, action_name, @arg1, Name), Cell).

append(MM, Name:name, Action:'name|menu_item', Before:[name]) :->
	"Append item for specified menu"::
	(   get(MM, value, Name, Chain)
	->  true
	;   send(MM, value, Name, new(Chain, chain))
	),
	(   Action == -
	->  send(Chain, append, Action)
	;   locate_action(Chain, Action, Old)
	->  send(Chain, replace, Old, Action)
	;   send(Chain, append, Action),
	    (   Before \== @default,
		locate_action(Chain, Before, CellValue),
		send(Chain, move_before, Action, CellValue)
	    ->	true
	    ;   true
	    )
	).

delete(MM, Menu:name, Action:name) :->
	"Delete item from inherited menu"::
	(   get(MM, value, Menu, Chain),
	    send(Chain, delete, Action)
	->  true
	;   true
	).

:- pce_end_class.


		 /*******************************
		 *	   KEY-BINDINGS		*
		 *******************************/

:- pce_begin_class(emacs_key_binding, key_binding,
		   "Specialised key_binding for history").

key_binding_name(@default, @default) :- !.
key_binding_name(@nil, @nil) :- !.
key_binding_name(KB, Name) :-
	object(KB),
	get(KB, name, KBName), !,
	key_binding_name(KBName, Name).
key_binding_name(editor, editor) :- !.
key_binding_name(X, Internal) :-
	atom_concat('emacs$', X, Internal).


initialise(KB, Name:[name]*, Super:[key_binding]) :->
	default(Super, editor, S),
	key_binding_name(Name, IName),
	key_binding_name(S, IS),
	send(KB, send_super, initialise, IName, IS).

convert(_, IName:name, KB:emacs_key_binding) :<-
	"Handle mapped names"::
	key_binding_name(Name, IName),
	get(type(key_binding), convert, Name, KB).

lookup(_, Name:name, _Super:[key_binding], KB:emacs_key_binding) :<-
	"Find existing mappings"::
	key_binding_name(Name, IName),
	get(@key_bindings, member, IName, KB).

:- pce_group(execute).

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
These methods define  argument-filling  and   execution  from  arbitrary
methods from a keyboard command.  As  we   want  to  do  fairly advanced
prompting we need to do redefine some things from class key_binding.

First we check whether there is  need   for  prompting.  If so, we check
whether we use the miniwindow or  not.   The  miniwindow prompts for one
argument  at  a  time.  The  system  ->fill_arguments_and_execute  calls
<-interactive_argument on Receiver for each missing argument.

If we are in prompt mode we simply   use  ->noarg_call on the mode, just
like commands comming from the menus.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

fill_arguments_and_execute(KB, EvId:event_id, Receiver:emacs_mode,
			   Selector:name, Argv:any ...) :->
	"Open/close the argument processing"::
	 Message =.. [ fill_arguments_and_execute,
		       EvId, Receiver, Selector | Argv],

	(   get(Receiver, send_method, Selector, tuple(_, Impl))
	->  (   length(Argv, Before),
	        First is Before + 1,
		args_available(First, Impl, KB, EvId)
	    ->  send_super(KB, Message)			% no need to prompt
	    ;   get(Receiver, frame, Frame),
		send(Frame, has_get_method, prompt_style),
		get(Frame, prompt_style, mini_window)
	    ->  send(@current_emacs_mode, assign, Receiver),
		send(Receiver, open_history, Impl, @on),
		send_super(KB, Message)			% miniwindow
	    ;   send(Receiver, noarg_call, Selector)	% prompting
	    )
	;   send_super(KB, Message)			% generate error
	).

%	args_available(+I, +Implementation, +KeyBinding, +EventId)
%
%	See whether all arguments are around that allow us to execute
%	the command without prompting.  See the implementation of
%	`key_binding->fill_arguments_and_execute' for reference.

args_available(N, Impl, KB, EvId) :-
	get(Impl, argument_type, N, ArgType), !,
	(   send(ArgType, includes, event_id)
	;   send(ArgType, includes, char),
	    integer(EvId)
	;   send(ArgType, includes, int),
	    get(KB, argument, Arg),
	    integer(Arg)
	;   send(ArgType, includes, default)
	), !,
	NN is N + 1,
	args_available(NN, Impl, KB, EvId).
args_available(_, _, _, _).
	
execute(KB, Receiver:emacs_mode, Selector:name, Argv:any ...) :->
	"Push history if available"::
	(   get(Receiver, m_x_history, @nil)
	->  true
	;   VectorTerm =.. [code_vector|Argv], % do not create references!
	    send(Receiver, close_history, new(VectorTerm))
	),
	Message =.. [execute, Receiver, Selector | Argv],
	send_super(KB, Message).

:- pce_end_class.


		 /*******************************
		 *	   ARGUMENT ITEM	*
		 *******************************/

:- pce_begin_class(emacs_argument_item, menu_item,
		   "Item with pullright for args").

initialise(I, Name:name, ValueSet:'chain|function') :->
	send(I, send_super, initialise, Name),
	send(I, popup,
	     new(P, emacs_argument_popup(Name,
					 message(@emacs_mode, arg_call,
						 Name, @arg1)))),
	(   send(ValueSet, '_instance_of', chain)
	->  send(P, members, ValueSet)
	;   send(P, update_message,
		 message(@receiver, members, ValueSet))
	).

:- pce_end_class.


:- pce_begin_class(emacs_argument_popup, popup,
		   "Emacs mode menu pullright popup").

members(I, Members:chain) :->
	"->clear and attach new members (do not capitalise)"::
	get(Members, map,
	    create(menu_item, @arg1, @default, @arg1?print_name),
	    Items),
	send(I, send_super, members, Items).

:- pce_end_class.
