This section describes Some of the predicates available from the XPCE/Prolog library.
The predicates in this section used to be XPCE principal predicates. Changes to XPCE, the interface and our current understanding about programming the XPCE/Prolog environment have made these predicates less important.
send_list(, _) :- !. send_list(_, ) :- !. send_list([Object|Objects], Selectors) :- !, send_list(Object, Selectors), send_list(Objects, Selectors). send_list(Object, [Selector|Selectors]) :- !, send_list(Object, Selector), send_list(Object, Selectors). send_list(Object, Selector) :- send(Object, Selector).
Note that, since send/2
Selector(Arg...) the following is now valid code:
..., send_list(Box, [ colour(red), fill_pattern(colour(greed)) ]),
topmost_graphical(Pict, Pos, Gr) :- get(Pict, graphicals, Grs0), chain_list(Grs0, Grs1), topmost(Grs1, Pos, @nil, Gr), Gr \== @nil. topmost(, _, Gr, Gr). topmost([H|T], Pos, _, Gr) :- send(H, overlap, Pos), !, topmost(T, Pos, H, Gr). topmost([_|T], Pos, Gr0, Gr) :- topmost(T, Pos, Gr0, Gr).
Or, using XPCE's list processing:
topmost_graphical(Dev, Pos, Gr) :- get(Dev, graphicals, Grs), get(Grs, find_all, message(@arg1, overlap, Pos), O), get(O, tail, Gr), send(O, done).
The second implementation is not only shorter, it also requires far less data conversions between Prolog and XPCE and is therefore much faster.
get_chain(Receiver, Selector, List) :- get(Receiver, Selector, Chain), chain_list(Chain, List).
See comments with chain_list/2.
The predicates in this section provide shorthands for common commands for debugging XPCE programs. See section 12 for more information on debugging XPCE/Prolog programs.
->), get- (
<-) method or variable (
-) and cause invocations thereof to be printed on the console.
Syntax note: (
->) is a standard Prolog operator with
priority > 1000. Therefore many Prolog systems require
1 ?- tracepce((graphical ->selected)).
In SWI-Prolog this is not necessary. To be able to trace get-methods
with this predicate (
<-) must be declared as an infix
->_check' on them. This performs various consistency checks on the objects and prints diagnostic messages if something is wrong. `object
->_check' checks all objects it can (recursively) find through slot-references, chains, vectors and hash-tables and deals properly with loops in the data-structure.
1 ?- new(@move_gesture, move_gesture). 2 ?- show_slots(@move_gesture). @move_gesture/move_gesture active @on/bool button middle modifier @810918/modifier condition @nil/constant status inactive cursor @default/constant offset @548249/point
A graphical tool for inspecting instance variables is described in section 12.5.
1 ?- manpce(box). 2 ?- manpce((view->caret)).