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   ncurses.3x    ( 3 )

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Портативность (Portability)

The ncurses library is intended to be BASE-level conformant with XSI Curses. The EXTENDED XSI Curses functionality (including color support) is supported.

A small number of local differences (that is, individual differences between the XSI Curses and ncurses calls) are described in PORTABILITY sections of the library man pages.

Error checking In many cases, X/Open Curses is vague about error conditions, omitting some of the SVr4 documentation.

Unlike other implementations, this one checks parameters such as pointers to WINDOW structures to ensure they are not null. The main reason for providing this behavior is to guard against programmer error. The standard interface does not provide a way for the library to tell an application which of several possible errors were detected. Relying on this (or some other) extension will adversely affect the portability of curses applications.

Extensions versus portability Most of the extensions provided by ncurses have not been standardized. Some have been incorporated into other implementations, such as PDCurses or NetBSD curses. Here are a few to consider:

• The routine has_key is not part of XPG4, nor is it present in SVr4. See the curs_getch(3X) manual page for details.

• The routine slk_attr is not part of XPG4, nor is it present in SVr4. See the curs_slk(3X) manual page for details.

• The routines getmouse, mousemask, ungetmouse, mouseinterval, and wenclose relating to mouse interfacing are not part of XPG4, nor are they present in SVr4. See the curs_mouse(3X) manual page for details.

• The routine mcprint was not present in any previous curses implementation. See the curs_print(3X) manual page for details.

• The routine wresize is not part of XPG4, nor is it present in SVr4. See the wresize(3X) manual page for details.

• The WINDOW structure's internal details can be hidden from application programs. See curs_opaque(3X) for the discussion of is_scrollok, etc.

• This implementation can be configured to provide rudimentary support for multi-threaded applications. See curs_threads(3X) for details.

• This implementation can also be configured to provide a set of functions which improve the ability to manage multiple screens. See curs_sp_funcs(3X) for details.

Padding differences In historic curses versions, delays embedded in the capabilities cr, ind, cub1, ff and tab activated corresponding delay bits in the UNIX tty driver. In this implementation, all padding is done by sending NUL bytes. This method is slightly more expensive, but narrows the interface to the UNIX kernel significantly and increases the package's portability correspondingly.

Header files The header file <curses.h> automatically includes the header files <stdio.h> and <unctrl.h>.

X/Open Curses has more to say, but does not finish the story:

The inclusion of <curses.h> may make visible all symbols from the headers <stdio.h>, <term.h>, <termios.h>, and <wchar.h>.

Here is a more complete story:

• Starting with BSD curses, all implementations have included <stdio.h>.

BSD curses included <curses.h> and <unctrl.h> from an internal header "curses.ext" ("ext" was a short name for externs).

BSD curses used <stdio.h> internally (for printw and scanw), but nothing in <curses.h> itself relied upon <stdio.h>.

• SVr2 curses added newterm(3X), which relies upon <stdio.h>. That is, the function prototype uses FILE.

SVr4 curses added putwin and getwin, which also use <stdio.h>.

X/Open Curses documents all three of these functions.

SVr4 curses and X/Open Curses do not require the developer to include <stdio.h> before including <curses.h>. Both document curses showing <curses.h> as the only required header.

As a result, standard <curses.h> will always include <stdio.h>.

• X/Open Curses is inconsistent with respect to SVr4 regarding <unctrl.h>.

As noted in curs_util(3X), ncurses includes <unctrl.h> from <curses.h> (like SVr4).

• X/Open's comments about <term.h> and <termios.h> may refer to HP-UX and AIX:

HP-UX curses includes <term.h> from <curses.h> to declare setupterm in curses.h, but ncurses (and Solaris curses) do not.

AIX curses includes <term.h> and <termios.h>. Again, ncurses (and Solaris curses) do not.

• X/Open says that <curses.h> may include <term.h>, but there is no requirement that it do that.

Some programs use functions declared in both <curses.h> and <term.h>, and must include both headers in the same module. Very old versions of AIX curses required including <curses.h> before including <term.h>.

Because ncurses header files include the headers needed to define datatypes used in the headers, ncurses header files can be included in any order. But for portability, you should include <curses.h> before <term.h>.

• X/Open Curses says "may make visible" because including a header file does not necessarily make all symbols in it visible (there are ifdef's to consider).

For instance, in ncurses <wchar.h> may be included if the proper symbol is defined, and if ncurses is configured for wide-character support. If the header is included, its symbols may be made visible. That depends on the value used for _XOPEN_SOURCE feature test macro.

• X/Open Curses documents one required header, in a special case: <stdarg.h> before <curses.h> to prototype the vw_printw and vw_scanw functions (as well as the obsolete the vwprintw and vwscanw functions). Each of those uses a va_list parameter.

The two obsolete functions were introduced in SVr3. The other functions were introduced in X/Open Curses. In between, SVr4 curses provided for the possibility that an application might include either <varargs.h> or <stdarg.h>. Initially, that was done by using void* for the va_list parameter. Later, a special type (defined in <stdio.h>) was introduced, to allow for compiler type-checking. That special type is always available, because <stdio.h> is always included by <curses.h>.

None of the X/Open Curses implementations require an application to include <stdarg.h> before <curses.h> because they either have allowed for a special type, or (like ncurses) include <stdarg.h> directly to provide a portable interface.