Programming in XPCE/Prolog

# 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.

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