xpce(1) Prolog with graphical user interface (GUI)


xpce prolog-option ...


XPCE is a language independant library for GUI (Graphical User Interfaces). This manual page discusses XPCE/Prolog: the combination of a Prolog environment and XPCE.

XPCE is an object-oriented engine that can have methods defined in various languages. XPCE has about 150 predefined classes that deal mainly with GUI's. The object engine of XPE is made available to Prolog using the following predicates:


new(?Ref, +Term)
Create an XPCE object from Term and bind the object to the reference Ref. The functor-name of Term describes the class from which to create an instance. The arguments of Term are used as initialisation arguments for the new object. If the object was created successfully and Ref is a variable, Ref will be unified with the term @<RefNumber>. If Ref is a term of the form @<Atom>, this term will serve as a reference for the new object.

For example ?- new(@p, picture('Hello World'). Creates a graphical window object with title "Hello World".

send(+Ref, +Selector, +Args...)
Ref is a reference to an existing XPCE object. Selector is the name of a (send-)method defined on (the class of) this object and Args are terms that describe arguments to be passed to the method.

send/[2-12] will convert the arguments to XPCE data objects, resolve the procedure (C-function, Prolog predicate) implementing the method and run the implementation. If the execution is successful, send succeeds, otherwise send fails.

For example ?- send(@p, open, point(400,100)). opens the picture created above at position 400,100 on the display.

get(+Ref, +Selector, +Args ..., -Value)
Ref is a reference to an existing XPCE object. Selector is the name of a (get-)method defined on (the class of) this object and Args are terms to provide additional arguments. get/[3-13] works similar as send/[2-12] but returns a value rather than succeeding/failing (boolean operation).

For example get(@p, height, H). Unifies H with the height of the graphical window.

If Ref is a reference to an XPCE object, invoke send(Ref, free). to the object. Otherwise succeed silently.


XPCE is distributed under the General Public Licence version 2, also known as the GPL-2 licence. The license terms are in the file COPYING or on the GNU website at http://www.gnu.org.

In a nutshell, you can modify and use XPCE as long as you clearly indicate changes, don't change copyright messages and distribute the complete source of your work with every binary copy or make the source in some other form available for free to your users

Especially if you do not wish to distribute the source of your work you may wish to consider optaining a commercial license. Please visit the SWI-Prolog home-page for details.


Copyright (c) 1985-2001 University of Amsterdam.


Jan Wielemaker and Anjo Anjewierden