wide vs. complex characters

[Neil Zanella]

Hello,

I have a question concerning Solaris curses (and hopefully this is
the right place to ask since after all ncurses aims at being much
like Solaris). My question has to do with data types:

While investigating the Solaris man pages I found the following two
functions among others: addwch and add_wch. According to the Solaris
man pages only the second one is part of the XSI Curses Standard
while the first one is part of pre-standard Solaris curses.

The addwch function works with wchar_t which is a standard C type called a
wide character. The add_wch on the other hand works with a type called
complex character and denoted by cchar_t

The following description is given for cchar_t:

A type that refers to a string consisting of a spacing wide character, up
to 5 non-spacing wide characters, and zero or more attributes of any
type. See Attributes, Color Pairs, and Renditions. A null cchar_t object
terminates arrays of cchar_t objects.

What is the point of cchar_t and why should cchar_t be so wide???
Does this have to do with encoding attributes into the characters
themselves? And what is the purpose of the spacing wide character?

Thanks,

Neil