<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<HTML>
<HEAD>
<TITLE>Programming in XPCE/Prolog</TITLE><LINK REL=home HREF="index.html">
<LINK REL=contents HREF="Contents.html">
<LINK REL=index HREF="DocIndex.html">
<LINK REL=summary HREF="summary.html">
<LINK REL=previous HREF="sec-7.5.html">
<LINK REL=next HREF="classvaraccess.html">
<STYLE type="text/css">
/* Style sheet for SWI-Prolog latex2html
*/
dd.defbody
{ margin-bottom: 1em;
}
dt.pubdef
{ background-color: #c5e1ff;
}
pre.code
{ margin-left: 1.5em;
margin-right: 1.5em;
border: 1px dotted;
padding-top: 5px;
padding-left: 5px;
padding-bottom: 5px;
background-color: #f8f8f8;
}
div.navigate
{ text-align: center;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
}
div.title
{ text-align: center;
padding-bottom: 1em;
font-size: 200%;
font-weight: bold;
}
div.author
{ text-align: center;
font-style: italic;
}
div.abstract
{ margin-top: 2em;
background-color: #f0f0f0;
border: 1px dotted;
padding: 5px;
margin-left: 10%; margin-right:10%;
}
div.abstract-title
{ text-align: center;
padding: 5px;
font-size: 120%;
font-weight: bold;
}
div.toc-h1
{ font-size: 200%;
font-weight: bold;
}
div.toc-h2
{ font-size: 120%;
font-weight: bold;
margin-left: 2em;
}
div.toc-h3
{ font-size: 100%;
font-weight: bold;
margin-left: 4em;
}
div.toc-h4
{ font-size: 100%;
margin-left: 6em;
}
span.sec-nr
{
}
span.sec-title
{
}
span.pred-ext
{ font-weight: bold;
}
/* Footnotes */
sup.fn { color: blue; text-decoration: underline; }
span.fn-text: { display: none; }
sup.fn span {display: none;}
sup:hover span
{ display: block !important;
position: absolute; top: auto; left: auto; width: 80%;
color: #000; background: white;
border: 2px solid;
padding: 5px; margin: 10px; z-index: 100;
font-size: smaller;
}
</STYLE>
</HEAD>
<BODY BGCOLOR="white">
<DIV class="navigate"><A class="nav" href="index.html"><IMG SRC="home.gif" BORDER=0 ALT="Home"></A>
<A class="nav" href="Contents.html"><IMG SRC="index.gif" BORDER=0 ALT="Contents"></A>
<A class="nav" href="DocIndex.html"><IMG SRC="yellow_pages.gif" BORDER=0 ALT="Index"></A>
<A class="nav" href="summary.html"><IMG SRC="info.gif" BORDER=0 ALT="Summary"></A>
<A class="nav" href="sec-7.5.html"><IMG SRC="prev.gif" BORDER=0 ALT="Previous"></A>
<A class="nav" href="classvaraccess.html"><IMG SRC="next.gif" BORDER=0 ALT="Next"></A>
</DIV>
<H1><A NAME="sec:8"><SPAN class="sec-nr">8</SPAN> <SPAN class="sec-title">Class
Variables</SPAN></A></H1>
<A NAME="sec:classvar"></A>
<P>Class variables act as read-only storage for class-constants. They
are normally used for storing setting information, such as fonts,
colours etc. For this reason, the default value for a <A class="" href="summary.html#class:class_variable">class_variable</A>
is defined with the declaration of it, but this default my be overruled
using the <CODE>Defaults</CODE> file. The system defaults file is
located in the <font size=-1>XPCE</font> home directory (<A NAME="idx:objectnamepcegethome:263"></A>`<B><B>@pce</B><CODE><-</CODE>home</B>').
This file contains an
<EM>include</EM> statement, including the file <CODE> /.xpce/Defaults</CODE>,<SUP class="fn">10<SPAN class="fn-text">On
Windows systems, <CODE> </CODE> expands to <CODE>%HOME%</CODE>, <CODE>%USERPROFILE%</CODE>, <CODE>%HOMEDRIVE%/%HOMEPATH%</CODE>
or the root of the current drive. See <A NAME="idx:expandfilename2:264"></A><SPAN class="pred-ext">expand_file_name/2</SPAN>
of the SWI-Prolog manual.</SPAN></SUP> which may be used by the
developer and application user to specify defaults.
<P>Many <font size=-1>XPCE</font> built-in classes define
class-variables. These can be examined using the <STRONG>ClassBrowser</STRONG>
(see <A class="sec" href="sec-3.3.html">section 3.3.1</A>) from the
online manual tools.
<P>
<HR>
<CENTER>
<H2>Section Index</H2>
</CENTER>
<HR>
<DIV class="toc">
<DIV class="toc-h2"><A class="sec" href="classvaraccess.html"><SPAN class="sec-nr">8.1</SPAN> <SPAN class="sec-title">Accessing
Class Variables</SPAN></A></DIV>
<DIV class="toc-h2"><A class="sec" href="sec-8.2.html"><SPAN class="sec-nr">8.2</SPAN> <SPAN class="sec-title">Class
variable and instance variables</SPAN></A></DIV>
<DIV class="toc-h2"><A class="sec" href="sec-8.3.html"><SPAN class="sec-nr">8.3</SPAN> <SPAN class="sec-title">The
`Defaults' file</SPAN></A></DIV>
<DIV class="toc-h2"><A class="sec" href="sec-8.4.html"><SPAN class="sec-nr">8.4</SPAN> <SPAN class="sec-title">Class
variables in User Defined Classes</SPAN></A></DIV>
</DIV>
</BODY></HTML>
