8 Class Variables

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 class_variable is defined with the declaration of it, but this default my be overruled using the Defaults file. The system defaults file is located in the XPCE home directory (`@pce<-home'). This file contains an include statement, including the file /.xpce/Defaults,10On Windows systems, expands to %HOME%, %USERPROFILE%, %HOMEDRIVE%/%HOMEPATH% or the root of the current drive. See expand_file_name/2 of the SWI-Prolog manual. which may be used by the developer and application user to specify defaults.

Many XPCE built-in classes define class-variables. These can be examined using the ClassBrowser (see section 3.3.1) from the online manual tools.

Section Index

8.1 Accessing Class Variables
8.2 Class variable and instance variables
8.3 The `Defaults' file
8.4 Class variables in User Defined Classes