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

    Author:        Jan Wielemaker and Anjo Anjewierden
    E-mail:        J.Wielemaker@cs.vu.nl
    WWW:           http://www.swi-prolog.org/projects/xpce/
    Copyright (C): 1985-2013, University of Amsterdam
			      VU University 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  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(persistent_frame, []).
:- use_module(library(pce)).
:- use_module(library(pce_config)).

/** <module> Save/restore layout of XPCE windows

This library defines the class  persistent_frame,   a  subclass of class
frame remembering its geometry  and  optionally   (by  default  on)  the
subwindow layout.

This class cooperates with the   library(pce_config),  a generic package
for managing application preferences.  It collects the locations of user
frames in the file <profile-dir>/Geometry.cnf

Geometry information is stored in  the   internal  configuration DB (see
library(pce_config))  if  a  frame  is  closed   or  on  exit  from  the
application. The internal database is written   to  tehe above mentioned
file on exit from the application.

Somehow the system must identify the frame   to decide which geometry to
use. This is done using the  <->geometry_key.   If  not set, this is the
classname or, if the class is not subclassed   it  is the <-label of the
frame.

Exploiting this library is very simple,  just make your toplevel windows
for  which  you  want  the  geometry  remembered  a  subclass  of  class
persistent_frame rather than class frame.  Note   that  this implies you
have to create your frame explitely:

    ==
	...
	new(F, persistent_frame('Pretty Application')),
	send(F, geometry_key, pretty_app),
	send(F, append, new(D, dialog)),
	send(new(V, view), right, D),
	...
    ==
*/

:- pce_begin_class(persistent_frame, frame, "Frame remembering location").

variable(persistent_subwindow_layout, bool := @on, get,
	 "Remember the layout of the subwindows?").
variable(geometry_key,		      name*, send,
	 "Key used to identify this frame").

unlink(F) :->
	"Save layout and destroy"::
	send(F, save_layout),
	send_super(F, unlink).

create(F) :->
	"Create and restore layout"::
	send_super(F, create),
	ignore(send(F, load_layout)).

:- pce_group(config).

geometry_key(F, Key:name) :<-
	"Name to store geometry"::
	(   get(F, slot, geometry_key, Key),
	    Key \== @nil
	->  true
	;   get(F, class_name, Key),
	    Key \== persistent_frame
	->  true
	;   get(F, label, Key)
	).

save_layout(F) :->
	"Save current layout in config DB"::
	get(F, geometry, Geometry),
	get(F, geometry_key, Key),
	set_config(history/geometry/Key, Geometry),
	(   get(F, persistent_subwindow_layout, @on),
	    get(F, tile, RootTile),
	    get(RootTile, members, Members),
	    Members \== @nil,
	    get_tile_layout(RootTile, Layout),
	    Layout \== *
	->  set_config(history/subwindow_layout/Key, Layout)
	;   true
	).

load_layout(F) :->
	load_geometry_config,
	get(F, geometry_key, Key),
	(   get_config(history/geometry/Key, Geometry)
	->  send(F, geometry, Geometry)
	;   true
	),
	(   get(F, persistent_subwindow_layout, @on),
	    get_config(history/subwindow_layout/Key, Layout)
	->  get(F, tile, RootTile),
	    apply_tile_layout(RootTile, Layout)
	;   true
	).

%%	get_tile_layout(+Tile, -Layout)
%
%	Create a Prolog term representing the subwindow (tile) layout.
%	Note that we only save the width/height of resizeable subwindows,
%	leaving the others to the application.  This ensures proper behaviour
%	if the application is modified.

get_tile_layout(T, layout(Me, SubLayout)) :-
	get(T, members, Members),
	Members \== @nil,
	chain_list(Members, List),
	maplist(get_tile_layout, List, SubLayout),
	get_this_tile_layout(T, Me),
	has_specifier(layout(Me, SubLayout)), !.
get_tile_layout(T, Me) :-
	get_this_tile_layout(T, Me).

get_this_tile_layout(T, Size) :-
	get(T, can_resize, @on), !,
	get(T, area, A),
	(   get(T?super, orientation, horizontal)
	->  get(A, width, Size)
	;   get(A, height, Size)
	).
get_this_tile_layout(_, *).

%%	has_specifier(+Layout)
%
%	See whether there is a specification somewhere, otherwise there
%	is no use storing it.

has_specifier(layout(Size, _)) :-
	Size \== *, !.
has_specifier(layout(_, Subs)) :- !,
	has_specifier(Subs).
has_specifier(X) :-
	integer(X), !.
has_specifier(Subs) :-
	member(Sub, Subs),
	has_specifier(Sub), !.


%%	apply_tile_layout(+Tile, +Layout)
%
%	Apply a previously saved layout description, sending ->width
%	or ->height messages to resizeable tiles.

apply_tile_layout(T, layout(Me, SubLayout)) :- !,
	apply_this_tile_layout(T, Me),
	(   get(T, members, Members),
	    Members \== @nil
	->  chain_list(Members, List),
	    maplist(apply_tile_layout, List, SubLayout)
	;   true
	).
apply_tile_layout(T, Me) :-
	apply_this_tile_layout(T, Me).

apply_this_tile_layout(_, *) :- !.
apply_this_tile_layout(T, Size) :-
	get(T, super, Super),
	Super \== @nil, !,
	(   get(Super, orientation, horizontal)
	->  get(T?area, width, W0),
	    (	Size > W0
	    ->	get(T, hor_stretch, S)
	    ;	get(T, hor_shrink, S)
	    ),
	    (	S > 0
	    ->	send(T, width, Size)
	    ;	true
	    )
	;   get(T?area, height, H0),
	    (	Size > H0
	    ->	get(T, ver_stretch, S)
	    ;	get(T, ver_shrink, S)
	    ),
	    (	S > 0
	    ->	send(T, height, Size)
	    ;	true
	    )
	).
apply_this_tile_layout(_, _).

:- pce_end_class(persistent_frame).


		 /*******************************
		 *	    EXIT HOOKS		*
		 *******************************/

:- initialization
   send(@pce, exit_message,
	message(@display?frames,
		for_some,
		if(message(@arg1, instance_of, persistent_frame),
		   message(@arg1, save_layout)))).


		 /*******************************
		 *	   CONFIG HOOKS		*
		 *******************************/

config(config/file,
       [ default('Geometry')
       ]).
config(history/geometry/_Key,
       [ type(geometry),
	 editable(false),
	 comment('(X-)geometry for persistent frames')
       ]).
config(history/subwindow_layout/_Key,
       [ type(subwindow_layout),
	 editable(false),
	 comment('Sub-window layout for persistent frames')
       ]).

:- register_config(config).

load_geometry_config :-
	context_module(M),
	ensure_loaded_config(M:_).
