- You must also define <STRONG>_XOPEN_SOURCE_EXTENDED</STRONG> when compiling for the
- wide-character library to use the extended (wide-character) func-
- tions. The <STRONG>curses.h</STRONG> file which is installed for the wide-charac-
- ter library is designed to be compatible with the normal library's
- header. Only the size of the <STRONG>WINDOW</STRONG> structure differs, and very
- few applications require more than a pointer to <STRONG>WINDOW</STRONG>s. If the
- headers are installed allowing overwrite, the wide-character
- library's headers should be installed last, to allow applications
- to be built using either library from the same set of headers.
+ You must also enable the wide-character features in the header
+ file when compiling for the wide-character library to use the
+ extended (wide-character) functions. The symbol which enables
+ these features has changed since XSI Curses, Issue 4:
+
+ <STRONG>o</STRONG> Originally, the wide-character feature required the symbol
+ <STRONG>_XOPEN_SOURCE_EXTENDED</STRONG> but that was only valid for XPG4
+ (1996).
+
+ <STRONG>o</STRONG> Later, that was deemed conflicting with <STRONG>_XOPEN_SOURCE</STRONG> defined
+ to 500.
+
+ <STRONG>o</STRONG> As of mid-2018, none of the features in this implementation
+ require a <STRONG>_XOPEN_SOURCE</STRONG> feature greater than 600. However,
+ X/Open Curses, Issue 7 (2009) recommends defining it to 700.
+
+ <STRONG>o</STRONG> Alternatively, you can enable the feature by defining
+ <STRONG>NCURSES_WIDECHAR</STRONG> with the caveat that some other header file
+ than <STRONG>curses.h</STRONG> may require a specific value for <STRONG>_XOPEN_SOURCE</STRONG>
+ (or a system-specific symbol).
+
+ The <STRONG>curses.h</STRONG> file which is installed for the wide-character
+ library is designed to be compatible with the normal library's
+ header. Only the size of the <STRONG>WINDOW</STRONG> structure differs, and very
+ few applications require more than a pointer to <STRONG>WINDOW</STRONG>s.
+
+ If the headers are installed allowing overwrite, the wide-charac-
+ ter library's headers should be installed last, to allow applica-
+ tions to be built using either library from the same set of head-
+ ers.