X-Git-Url: https://ncurses.scripts.mit.edu/?p=ncurses.git;a=blobdiff_plain;f=man%2Fcurs_termcap.3x;h=9b21505603b968b74af2ea357cd98d4129a06a9e;hp=7f6762798d09ffe7c2167c4cf017dd270fa51a9f;hb=9c110809dcc6246cb01544e9cb6c709795697a1a;hpb=cef50b3afcd58166f3541b701c97bce538844c76

diff --git a/man/curs_termcap.3x b/man/curs_termcap.3x
index 7f676279..9b215056 100644
--- a/man/curs_termcap.3x
+++ b/man/curs_termcap.3x
@@ -1,5 +1,5 @@
 .\"***************************************************************************
-.\" Copyright (c) 1998-2007,2010 Free Software Foundation, Inc.              *
+.\" Copyright (c) 1998-2015,2016 Free Software Foundation, Inc.              *
 .\"                                                                          *
 .\" Permission is hereby granted, free of charge, to any person obtaining a  *
 .\" copy of this software and associated documentation files (the            *
@@ -26,8 +26,11 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
-.\" $Id: curs_termcap.3x,v 1.25 2010/10/02 23:40:57 tom Exp $
+.\" $Id: curs_termcap.3x,v 1.32 2016/03/19 22:52:25 tom Exp $
 .TH curs_termcap 3X ""
+.de bP
+.IP \(bu 4
+..
 .na
 .hy 0
 .ds n 5
@@ -75,11 +78,39 @@ the \fItermcap\fR library.  Their parameters are the same and the
 routines are emulated using the \fIterminfo\fR database.  Thus, they
 can only be used to query the capabilities of entries for which a
 terminfo entry has been compiled.
+.SS INITIALIZATION
 .PP
 The \fBtgetent\fR routine loads the entry for \fIname\fR.
-It returns 1 on success, 0 if there is no such entry, and \-1 if the
-terminfo database could not be found.
+It returns:
+.RS 3
+.TP 3
+1
+on success,
+.TP 3
+0
+if there is no such entry
+(or that it is a generic type, having too little information for curses
+applications to run), and
+.TP 3
+\-1
+if the terminfo database could not be found.
+.RE
+.PP
+This differs from the \fItermcap\fP library in two ways:
+.RS 3
+.bP
 The emulation ignores the buffer pointer \fIbp\fR.
+The \fItermcap\fP 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.
+.bP
+There is a difference in return codes.
+The \fItermcap\fP library does not check if the terminal
+description is marked with the \fIgeneric\fP capability,
+or if the terminal description has cursor-addressing.
+.RE
+.SS CAPABILITY VALUES
 .PP
 The \fBtgetflag\fR routine gets the boolean entry for \fIid\fR,
 or zero if it is not available.
@@ -90,20 +121,55 @@ or \-1 if it is not available.
 The \fBtgetstr\fR routine returns the string entry for \fIid\fR,
 or zero if it is not available.
 Use \fBtputs\fR to output the returned string.
-The return value will also be copied to the buffer pointed to by \fIarea\fR,
+The \fIarea\fP parameter is used as follows:
+.RS 3
+.bP
+It is assumed to be the address of a pointer to a buffer managed by the
+calling application.
+.bP
+However, ncurses checks to ensure that \fBarea\fP is not NULL,
+and also that the resulting buffer pointer is not NULL.
+If either check fails, the \fIarea\fP parameter is ignored.
+.bP
+If the checks succeed, ncurses also copies the return value to
+the buffer pointed to by \fIarea\fR,
 and the \fIarea\fR value will be updated to point past the null ending
 this value.
+.bP
+The return value itself is an address in the terminal description which
+is loaded into memory.
+.RE
 .PP
 Only the first two characters of the \fBid\fR parameter of
 \fBtgetflag\fR,
 \fBtgetnum\fR and
 \fBtgetstr\fR are compared in lookups.
+.SS FORMATTING CAPABILITIES
 .PP
-The \fBtgoto\fR routine instantiates the parameters into the given capability.
-The output from this routine is to be passed to \fBtputs\fR.
+The \fBtgoto\fR routine expands the given capability using the parameters.
+.bP
+Because the capability may have padding characters,
+the output of \fBtgoto\fP should be passed to \fBtputs\fR
+rather than some other output function such as \fBprintf\fP.
+.bP
+While \fBtgoto\fP is assumed to be used for the two-parameter
+cursor positioning capability,
+termcap applications also use it for single-parameter capabilities.
+.IP
+Doing this shows a quirk in \fBtgoto\fP: most hardware
+terminals use cursor addressing with \fIrow\fP first,
+but the original developers of the termcap interface chose to
+put the \fIcolumn\fP parameter first.
+The \fBtgoto\fP 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.
+.bP
+Normally the ncurses library is compiled with terminfo support.
+In that case, \fBtgoto\fP uses \fBtparm\fP (a more capable formatter).
 .PP
 The \fBtputs\fR routine is described on the \fBcurs_terminfo\fR(3X) manual
 page.  It can retrieve capabilities by either termcap or terminfo name.
+.SS GLOBAL VARIABLES
 .PP
 The variables
 \fBPC\fR,
@@ -165,14 +231,28 @@ However, termcap applications' use of those variables is poorly documented,
 e.g., not distinguishing between input and output.
 In particular, some applications are reported to declare and/or
 modify \fBospeed\fR.
+.PP
+The comment that only the first two characters of the \fBid\fR 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 \fBtgetstr\fP, \fBtgetnum\fP and \fBtgetflag\fP.
+Some applications assume that the termcap interface does not require
+the trailing NUL for the parameter name.
+Taking into account these issues:
+.bP
+As a special case,
+\fBtgetflag\fP 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 implementation disallows matches against single-character capability names.
+.bP
+This implementation disallows matches by the termcap interface against
+extended capability names which are longer than two characters.
 .SH SEE ALSO
 \fBcurses\fR(3X),
 \fBterminfo\fR(\*n),
 \fBterm_variables\fR(3X),
 \fBputc\fR(3).
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
+.sp
+http://invisible-island.net/ncurses/tctest.html