/* 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 All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include static status forwardCreateConstraint(Constraint c); static status fromConstraint(Constraint c, Any obj); static status toConstraint(Constraint c, Any obj); /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - NOTE (Jan Wielemaker, 16/11/90): Using this implementation technique we cannot handle constraints with the same from and to. The problem is that we do not know which whether the constraint is to be executed forwards or backards. Consider the following calls: ?- new(@b, box(40,50)), new(@c, constraint(@b, @b, identity(width, height))). to construct a square. We now hope that sending ->width will also update ->height; and sending ->height will update ->width. To realise this, the constraint must know whether to invoke the relation with direction forwards or backwards. In this case the constraint would have to monitor the changes to the object resulting from sending the original message and analyse the relation. Constraints are not supposed to know about their relation and thus cannot perform this task. Furthermore, what do we do after the user sends ?- send(@b, size, size(30, 60)). Turn it into a square of 30x30 or 60x60? - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ static status initialiseConstraint(Constraint c, Any from, Any to, Relation relation, Name only) { Name lock; if ( from == to ) return errorPce(c, NAME_cannotConstraintSelf); assign(c, from, from); assign(c, to, to); assign(c, relation, relation); if ( isDefault(only) ) lock = NAME_none; else if ( equalName(only, NAME_forwards) ) lock = NAME_backwards; else lock = NAME_forwards; assign(c, locked, lock); constraintObject(from, c); constraintObject(to, c); forwardCreateConstraint(c); succeed; } static status unlinkConstraint(Constraint c) { toConstraint(c, NIL); fromConstraint(c, NIL); succeed; } status lockConstraint(Constraint c, Any obj) { if (c->locked == NAME_none) { assign(c, locked, obj == c->from ? NAME_back : NAME_front); succeed; } fail; } status unlockConstraint(Constraint c, Any obj) { if (c->locked == (obj == c->from ? NAME_back : NAME_front)) assign(c, locked, NAME_none); succeed; } static status relationConstraint(Constraint c, Relation relation) { if (c->relation == relation) succeed; assign(c, relation, relation); forwardCreateConstraint(c); succeed; } static status forwardCreateConstraint(Constraint c) { if ( notNil(c->from) && notNil(c->to) ) updateConstraintsObject(c->from); succeed; } status executeConstraint(Constraint c, Any obj) { if ( isNil(c->from) || isNil(c->to) ) fail; if ( obj == c->from && (equalName(c->locked, NAME_forwards) || equalName(c->locked, NAME_front)) ) fail; if ( obj == c->to && (equalName(c->locked, NAME_backwards) || equalName(c->locked, NAME_back)) ) fail; return send(c->relation, obj == c->from ? NAME_forwards : NAME_backwards, c->from, c->to, EAV); } static status fromConstraint(Constraint c, Any obj) { Instance old_from = c->from; if (old_from == obj) succeed; assign(c, from, obj); deleteConstraintObject(old_from, c); if (isNil(obj)) succeed; constraintObject(c->from, c); forwardCreateConstraint(c); succeed; } static status toConstraint(Constraint c, Any obj) { Instance old_to = c->to; if (old_to == obj) succeed; assign(c, to, obj); if ( notNil(old_to) ) deleteConstraintObject(old_to, c); if (isNil(obj)) succeed; constraintObject(c->to, c); forwardCreateConstraint(c); succeed; } /******************************* * CLASS DECLARATION * *******************************/ /* Type declarations */ static char *T_initialise[] = { "from=object", "to=object", "relation=relation", "propagate=[{forwards,backwards}]" }; /* Instance Variables */ static vardecl var_constraint[] = { SV(NAME_from, "object", IV_GET|IV_STORE, fromConstraint, NAME_client, "`From' side of the constraint"), SV(NAME_to, "object", IV_GET|IV_STORE, toConstraint, NAME_client, "`To' side of the constraint"), SV(NAME_relation, "relation", IV_GET|IV_STORE, relationConstraint, NAME_relation, "Relation that describes the constraint"), IV(NAME_locked, "{none,forwards,front,backwards,back}", IV_NONE, NAME_internal, "Avoid looping of propagation") }; /* Send Methods */ static senddecl send_constraint[] = { SM(NAME_initialise, 4, T_initialise, initialiseConstraint, DEFAULT, "Create from objects, relation and direction"), SM(NAME_unlink, 0, NULL, unlinkConstraint, DEFAULT, "Remove from to- and from-object") }; /* Get Methods */ #define get_constraint NULL /* static getdecl get_constraint[] = { }; */ /* Resources */ #define rc_constraint NULL /* static classvardecl rc_constraint[] = { }; */ /* Class Declaration */ static Name constraint_termnames[] = { NAME_from, NAME_to, NAME_relation, NAME_locked }; ClassDecl(constraint_decls, var_constraint, send_constraint, get_constraint, rc_constraint, 3, constraint_termnames, "$Rev$"); status makeClassConstraint(Class class) { declareClass(class, &constraint_decls); cloneStyleClass(class, NAME_relation); succeed; }