These routines are included as a conversion aid for pro-
grams that use the termcap library. Their parameters are
the same and the routines are emulated using the terminfo
@@ -70,34 +76,94 @@
bilities of entries for which a terminfo entry has been
compiled.
- The tgetent routine loads the entry for name. It returns
- 1 on success, 0 if there is no such entry, and -1 if the
- terminfo database could not be found. The emulation
- ignores the buffer pointer bp.
- The tgetflag routine gets the boolean entry for id, or
- zero if it is not available.
+
+ The tgetent routine loads the entry for name. It returns:
+
+ 1 on success,
+
+ 0 if there is no such entry (or that it is a generic
+ type, having too little information for curses ap-
+ plications to run), and
- The tgetnum routine gets the numeric entry for id, or -1
+ -1 if the terminfo database could not be found.
+
+ This differs from the termcap library in two ways:
+
+ o The emulation ignores the buffer pointer bp. The
+ termcap library would store a copy of the terminal
+ description in the area referenced by this pointer.
+ However, ncurses stores its terminal descriptions
+ in compiled binary form, which is not the same
+ thing.
+
+ o There is a difference in return codes. The termcap
+ library does not check if the terminal description
+ is marked with the generic capability, or if the
+ terminal description has cursor-addressing.
+
+
+
+ The tgetflag routine gets the boolean entry for id, or ze-
+ ro if it is not available.
+
+ The tgetnum routine gets the numeric entry for id, or -1
if it is not available.
- The tgetstr routine returns the string entry for id, or
- zero if it is not available. Use tputs to output the
- returned string. The return value will also be copied to
- the buffer pointed to by area, and the area value will be
- updated to point past the null ending this value.
+ The tgetstr routine returns the string entry for id, or
+ zero if it is not available. Use tputs to output the re-
+ turned string. The area parameter is used as follows:
+
+ o It is assumed to be the address of a pointer to a
+ buffer managed by the calling application.
+
+ o However, ncurses checks to ensure that area is not
+ NULL, and also that the resulting buffer pointer is
+ not NULL. If either check fails, the area parame-
+ ter is ignored.
+
+ o If the checks succeed, ncurses also copies the re-
+ turn value to the buffer pointed to by area, and
+ the area value will be updated to point past the
+ null ending this value.
+
+ o The return value itself is an address in the termi-
+ nal description which is loaded into memory.
Only the first two characters of the id parameter of tget-flag, tgetnum and tgetstr are compared in lookups.
- The tgoto routine instantiates the parameters into the
- given capability. The output from this routine is to be
- passed to tputs.
+
+
+ The tgoto routine expands the given capability using the
+ parameters.
+
+ o Because the capability may have padding characters,
+ the output of tgoto should be passed to tputs rather
+ than some other output function such as printf.
+
+ o While tgoto is assumed to be used for the two-parame-
+ ter cursor positioning capability, termcap applica-
+ tions also use it for single-parameter capabilities.
+
+ Doing this shows a quirk in tgoto: most hardware ter-
+ minals use cursor addressing with row first, but the
+ original developers of the termcap interface chose to
+ put the column parameter first. The tgoto function
+ swaps the order of parameters. It does this also for
+ calls requiring only a single parameter. In that
+ case, the first parameter is merely a placeholder.
+
+ o Normally the ncurses library is compiled with terminfo
+ support. In that case, tgoto uses tparm(3x) (a more
+ capable formatter).
The tputs routine is described on the curs_terminfo(3x)
manual page. It can retrieve capabilities by either term-
cap or terminfo name.
+
+
The variables PC, UP and BC are set by tgetent to the ter-
minfo entry's data for pad_char, cursor_up and
backspace_if_not_bs, respectively. UP is not used by
@@ -107,66 +173,107 @@
minal speed.
-
-
-
RETURN VALUE
- Except where explicitly noted, routines that return an
- integer return ERR upon failure and OK (SVr4 only speci-
- fies "an integer value other than ERR") upon successful
- completion.
+
+ Except where explicitly noted, routines that return an in-
+ teger return ERR upon failure and OK (SVr4 only specifies
+ "an integer value other than ERR") upon successful comple-
+ tion.
Routines that return pointers return NULL on error.
-
If you call tgetstr to fetch ca or any other parameterized
- string, be aware that it will be returned in terminfo
- notation, not the older and not-quite-compatible termcap
- notation. This won't cause problems if all you do with it
- is call tgoto or tparm, which both expand terminfo-style
- strings as terminfo. (The tgoto function, if configured
- to support termcap, will check if the string is indeed
- terminfo-style by looking for "%p" parameters or "$<..>"
- delays, and invoke a termcap-style parser if the string
- does not appear to be terminfo).
+ string, be aware that it will be returned in terminfo no-
+ tation, not the older and not-quite-compatible termcap no-
+ tation. This will not cause problems if all you do with
+ it is call tgoto or tparm, which both expand terminfo-
+ style strings as terminfo. (The tgoto function, if con-
+ figured to support termcap, will check if the string is
+ indeed terminfo-style by looking for "%p" parameters or
+ "$<..>" delays, and invoke a termcap-style parser if the
+ string does not appear to be terminfo).
Because terminfo conventions for representing padding in
string capabilities differ from termcap's, tputs("50");
will put out a literal "50" rather than busy-waiting for
50 milliseconds. Cope with it.
+ Note that termcap has nothing analogous to terminfo's sgr
+ string. One consequence of this is that termcap applica-
+ tions assume me (terminfo sgr0) does not reset the alter-
+ nate character set. This implementation checks for, and
+ modifies the data shown to the termcap interface to accom-
+ modate termcap's limitation in this respect.
-
-
PORTABILITY
- The XSI Curses standard, Issue 4 describes these func-
- tions. However, they are marked TO BE WITHDRAWN and may
+
+
+ The XSI Curses standard, Issue 4 describes these func-
+ tions. However, they are marked TO BE WITHDRAWN and may
be removed in future versions.
- Neither the XSI Curses standard nor the SVr4 man pages
- documented the return values of tgetent correctly, though
- all three were in fact returned ever since SVr1. In par-
- ticular, an omission in the XSI Curses documentation has
- been misinterpreted to mean that tgetent returns OK or
+ Neither the XSI Curses standard nor the SVr4 man pages
+ documented the return values of tgetent correctly, though
+ all three were in fact returned ever since SVr1. In par-
+ ticular, an omission in the XSI Curses documentation has
+ been misinterpreted to mean that tgetent returns OK or
ERR. Because the purpose of these functions is to provide
- compatibility with the termcap library, that is a defect
+ compatibility with the termcap library, that is a defect
in XCurses, Issue 4, Version 2 rather than in ncurses.
- External variables are provided for support of certain
- termcap applications. However, termcap applications' use
+ External variables are provided for support of certain
+ termcap applications. However, termcap applications' use
of those variables is poorly documented, e.g., not distin-
- guishing between input and output. In particular, some
+ guishing between input and output. In particular, some
applications are reported to declare and/or modify ospeed.
+ The comment that only the first two characters of the id
+ parameter are used escapes many application developers.
+ The original BSD 4.2 termcap library (and historical
+ relics thereof) did not require a trailing null NUL on the
+ parameter name passed to tgetstr, tgetnum and tgetflag.
+ Some applications assume that the termcap interface does
+ not require the trailing NUL for the parameter name. Tak-
+ ing into account these issues:
+ o As a special case, tgetflag matched against a single-
+ character identifier provided that was at the end of
+ the terminal description. You should not rely upon
+ this behavior in portable programs. This implementa-
+ tion disallows matches against single-character capa-
+ bility names.
+
+ o This implementation disallows matches by the termcap
+ interface against extended capability names which are
+ longer than two characters.
+
+
+