- The getcchar function gets a wide-character string and
- rendition from a cchar_t argument. When wch is not a null
- pointer, the getcchar function does the following:
+
+ The getcchar function gets a wide-character string and rendition from a
+ cchar_t argument. When wch is not a null pointer, the getcchar func-
+ tion does the following:
- - Stores the character attributes in the location
- pointed to by attrs
+ o Extracts information from a cchar_t value wcval
- - Stores the color-pair in the location pointed to by
- color_pair
+ o Stores the character attributes in the location pointed to by attrs
- - Stores the wide-character string, characters refer-
- enced by wcval, into the array pointed to by wch.
+ o Stores the color-pair in the location pointed to by color_pair
- When wch is a null pointer, the getcchar function does the
- following:
+ o Stores the wide-character string, characters referenced by wcval,
+ into the array pointed to by wch.
- - Obtains the number of wide characters pointed to by
- wcval
+ When wch is a null pointer, the getcchar function does the following:
- - Does not change the data referenced by attrs or
- color_pair
+ o Obtains the number of wide characters pointed to by wcval
- The setcchar function initializes the location pointed to
- by wcval by using:
+ o Does not change the data referenced by attrs or color_pair
- - The character attributes in attrs
- - The color pair in color_pair
+
+ The setcchar function initializes the location pointed to by wcval by
+ using:
- - The wide-character string pointed to by wch. The
- string must be L'\0' terminated, contain at most one
- character with strictly positive width, which must be
- the first, and contain no characters of negative
- width.
+ o The character attributes in attrs
+ o The color pair in color_pair
-
-
NOTES
- The opts argument is reserved for future use. Currently,
- an application must provide a null pointer as opts.
+ o The wide-character string pointed to by wch. The string must be
+ L'\0' terminated, contain at most one spacing character, which must
+ be the first.
- The wcval argument may be a value generated by a call to
- setcchar or by a function that has a cchar_t output argu-
- ment. If wcval is constructed by any other means, the
- effect is unspecified.
+ Up to CCHARW_MAX-1 nonspacing characters may follow. Additional
+ nonspacing characters are ignored.
+ The string may contain a single control character instead. In that
+ case, no nonspacing characters are allowed.
-
-
RETURN VALUES
- When wch is a null pointer, getcchar returns the number of
- wide characters referenced by wcval, including the null
- terminator.
- When wch is not a null pointer, getcchar returns OK upon
- successful completion, and ERR otherwise.
+
+ X/Open Curses documents the opts argument as reserved for future use,
+ saying that it must be null. This implementation uses that parameter
+ in ABI 6 for the functions which have a color-pair parameter to support
+ extended color pairs:
- Upon successful completion, setcchar returns OK. Other-
- wise, it returns ERR.
+ o For functions which modify the color, e.g., setcchar, if opts is
+ set it is treated as a pointer to int, and used to set the color
+ pair instead of the short pair parameter.
+ o For functions which retrieve the color, e.g., getcchar, if opts is
+ set it is treated as a pointer to int, and used to retrieve the
+ color pair as an int value, in addition retrieving it via the stan-
+ dard pointer to short parameter.
-
+ The wcval argument may be a value generated by a call to setcchar or by
+ a function that has a cchar_t output argument. If wcval is constructed
+ by any other means, the effect is unspecified.
+
+
+
+ When wch is a null pointer, getcchar returns the number of wide charac-
+ ters referenced by wcval, including one for a trailing null.
+
+ When wch is not a null pointer, getcchar returns OK upon successful
+ completion, and ERR otherwise.
+
+ Upon successful completion, setcchar returns OK. Otherwise, it returns
+ ERR.
+
+
+
+ The CCHARW_MAX symbol is specific to ncurses. X/Open Curses does not
+ provide details for the layout of the cchar_t structure. It tells what
+ data are stored in it:
+
+ o a spacing character (wchar_t, i.e., 32-bits).
+
+ o non-spacing characters (again, wchar_t's).
+
+ o attributes (at least 16 bits, inferred from the various ACS- and
+ WACS-flags).
+
+ o color pair (at least 16 bits, inferred from the unsignedshort
+ type).
+
+ The non-spacing characters are optional, in the sense that zero or more
+ may be stored in a cchar_t. XOpen/Curses specifies a limit:
+
+ Implementations may limit the number of non-spacing characters that
+ can be associated with a spacing character, provided any limit is
+ at least 5.
+
+ The Unix implementations at the time follow that limit:
+
+ o AIX 4 and OSF1 4 use the same declaration with an array of 5 non-
+ spacing characters z and a single spacing character c.
+
+ o HP-UX 10 uses an opaque structure with 28 bytes, which is large
+ enough for the 6 wchar_t values.
+
+ o Solaris xpg4 curses uses a single array of 6 wchar_t values.
+
+ This implementation's cchar_t was defined in 1995 using 5 for the total
+ of spacing and non-spacing characters (CCHARW_MAX). That was probably
+ due to a misreading of the AIX 4 header files, because the X/Open
+ Curses document was not generally available at that time. Later (in
+ 2002), this detail was overlooked when beginning to implement the func-
+ tions using the structure.
+
+ In practice, even four non-spacing characters may seem enough. X/Open
+ Curses documents possible uses for non-spacing characters, including
+ using them for ligatures between characters (a feature apparently not
+ supported by any curses implementation). Unicode does not limit the
+ (analogous) number of combining characters, so some applications may be
+ affected.
+
+
+