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+<H1 class="no-header">user_caps 5</H1>
+<PRE>
+<STRONG><A HREF="user_caps.5.html">user_caps(5)</A></STRONG> <STRONG><A HREF="user_caps.5.html">user_caps(5)</A></STRONG>
+
+
+
+
+</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
+ user_caps - user-defined terminfo capabilities
+
+
+</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
+ <STRONG>tic</STRONG> <STRONG>-x,</STRONG> <STRONG>infocmp</STRONG> <STRONG>-x</STRONG>
+
+
+</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
+
+</PRE><H3><a name="h3-Background">Background</a></H3><PRE>
+ Before ncurses 5.0, terminfo databases used a <EM>fixed</EM> <EM>repertoire</EM> of ter-
+ minal capabilities designed for the SVr2 terminal database in 1984, and
+ extended in stages through SVr4 (1989), and standardized in the Single
+ Unix Specification beginning in 1995.
+
+ Most of the <EM>extensions</EM> in this fixed repertoire were additions to the
+ tables of boolean, numeric and string capabilities. Rather than change
+ the meaning of an existing capability, a new name was added. The ter-
+ minfo database uses a binary format; binary compatibility was ensured
+ by using a header which gave the number of items in the tables for each
+ type of capability. The standardization was incomplete:
+
+ <STRONG>o</STRONG> The <EM>binary</EM> <EM>format</EM> itself is not described in the X/Open Curses doc-
+ umentation. Only the <EM>source</EM> <EM>format</EM> is described.
+
+ Library developers rely upon the SVr4 documentation, and reverse-
+ engineering the compiled terminfo files to match the binary format.
+
+ <STRONG>o</STRONG> Lacking a standard for the binary format, most implementations copy
+ the SVr2 binary format, which uses 16-bit signed integers, and is
+ limited to 4096-byte entries.
+
+ The format cannot represent very large numeric capabilities, nor
+ can it represent large numbers of special keyboard definitions.
+
+ <STRONG>o</STRONG> The tables of capability names differ between implementations.
+
+ Although they <EM>may</EM> provide all of the standard capability names, the
+ position in the tables differs because some features were added as
+ needed, while others were added (out of order) to comply with
+ X/Open Curses.
+
+ While ncurses' repertoire of predefined capabilities is closest to
+ Solaris, Solaris's terminfo database has a few differences from the
+ list published by X/Open Curses.
+
+ During the 1990s, some users were reluctant to use terminfo in spite of
+ its performance advantages over termcap:
+
+ <STRONG>o</STRONG> The fixed repertoire prevented users from adding features for unan-
+ ticipated terminal improvements (or required them to reuse existing
+ capabilities as a workaround).
+
+ <STRONG>o</STRONG> The limitation to 16-bit signed integers was also mentioned.
+ Because termcap stores everything as a string, it could represent
+ larger numbers.
+
+ Although termcap's extensibility was rarely used (it was never the
+ <EM>speaker</EM> who had actually used the feature), the criticism had a point.
+ ncurses 5.0 provided a way to detect nonstandard capabilities, deter-
+ mine their type and optionally store and retrieve them in a way which
+ did not interfere with other applications. These are referred to as
+ <EM>user-defined</EM> <EM>capabilities</EM> because no modifications to the toolset's
+ predefined capability names are needed.
+
+ The ncurses utilities <STRONG>tic</STRONG> and <STRONG>infocmp</STRONG> have a command-line option "-x"
+ to control whether the nonstandard capabilities are stored or
+ retrieved. A library function <STRONG>use_extended_names</STRONG> is provided for the
+ same purpose.
+
+ When compiling a terminal database, if "-x" is set, <STRONG>tic</STRONG> will store a
+ user-defined capability if the capability name is not one of the prede-
+ fined names.
+
+ Because ncurses provides a termcap library interface, these user-
+ defined capabilities may be visible to termcap applications:
+
+ <STRONG>o</STRONG> The termcap interface (like all implementations of termcap)
+ requires that the capability names are 2-characters.
+
+ When the capability is simple enough for use in a termcap applica-
+ tion, it is provided as a 2-character name.
+
+ <STRONG>o</STRONG> There are other user-defined capabilities which refer to features
+ not usable in termcap, e.g., parameterized strings that use more
+ than two parameters or use more than the trivial expression support
+ provided by termcap. For these, the terminfo database should have
+ only capability names with 3 or more characters.
+
+ <STRONG>o</STRONG> Some terminals can send distinct strings for special keys (cursor-,
+ keypad- or function-keys) depending on modifier keys (shift, con-
+ trol, etc.). While terminfo and termcap have a set of 60 prede-
+ fined function-key names, to which a series of keys can be
+ assigned, that is insufficient for more than a dozen keys multi-
+ plied by more than a couple of modifier combinations. The ncurses
+ database uses a convention based on <STRONG>xterm</STRONG> to provide extended spe-
+ cial-key names.
+
+ Fitting that into termcap's limitation of 2-character names would
+ be pointless. These extended keys are available only with ter-
+ minfo.
+
+
+</PRE><H3><a name="h3-Recognized-capabilities">Recognized capabilities</a></H3><PRE>
+ The ncurses library uses the user-definable capabilities. While the
+ terminfo database may have other extensions, ncurses makes explicit
+ checks for these:
+
+ AX <EM>boolean</EM>, asserts that the terminal interprets SGR 39 and SGR 49
+ by resetting the foreground and background color, respectively,
+ to the default.
+
+ This is a feature recognized by the <STRONG>screen</STRONG> program as well.
+
+ E3 <EM>string</EM>, tells how to clear the terminal's scrollback buffer.
+ When present, the <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG> program sends this before clearing the
+ terminal.
+
+ The command "<STRONG>tput</STRONG> <STRONG>clear</STRONG>" does the same thing.
+
+ RGB
+ <EM>boolean</EM>, <EM>number</EM> <STRONG>or</STRONG> <EM>string</EM>, to assert that the <STRONG>set_a_foreground</STRONG>
+ and <STRONG>set_a_background</STRONG> capabilities correspond to <EM>direct</EM> <EM>colors</EM>,
+ using an RGB (red/green/blue) convention. This capability allows
+ the <STRONG>color_content</STRONG> function to return appropriate values without
+ requiring the application to initialize colors using <STRONG>init_color</STRONG>.
+
+ The capability type determines the values which ncurses sees:
+
+ <EM>boolean</EM>
+ implies that the number of bits for red, green and blue are
+ the same. Using the maximum number of colors, ncurses adds
+ two, divides that sum by three, and assigns the result to red,
+ green and blue in that order.
+
+ If the number of bits needed for the number of colors is not a
+ multiple of three, the blue (and green) components lose in
+ comparison to red.
+
+ <EM>number</EM>
+ tells ncurses what result to add to red, green and blue. If
+ ncurses runs out of bits, blue (and green) lose just as in the
+ <EM>boolean</EM> case.
+
+ <EM>string</EM>
+ explicitly list the number of bits used for red, green and
+ blue components as a slash-separated list of decimal integers.
+
+ U8 <EM>boolean</EM>, asserts that ncurses must use Unicode values for line-
+ drawing characters, and that it should ignore the alternate char-
+ acter set capabilities when the locale uses UTF-8 encoding. For
+ more information, see the discussion of <STRONG>NCURSES_NO_UTF8_ACS</STRONG> in
+ <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>.
+
+ Set this capability to a nonzero value to enable it.
+
+ XM <EM>string</EM>, override ncurses's built-in string which enables/disables
+ <STRONG>xterm</STRONG> mouse mode.
+
+
+</PRE><H3><a name="h3-Extended-key-definitions">Extended key-definitions</a></H3><PRE>
+ Several terminals provide the ability to send distinct strings for com-
+ binations of modified special keys. There is no standard for what
+ those keys can send.
+
+ Since 1999, <STRONG>xterm</STRONG> has supported <EM>shift</EM>, <EM>control</EM>, <EM>alt</EM>, and <EM>meta</EM> modifiers
+ which produce distinct special-key strings. In a terminal description,
+ ncurses has no special knowledge of the modifiers used. Applications
+ can use the <EM>naming</EM> <EM>convention</EM> established for <STRONG>xterm</STRONG> to find these spe-
+ cial keys in the terminal description.
+
+ Starting with the curses convention that <EM>key</EM> <EM>names</EM> begin with "k" and
+ that shifted special keys are an uppercase name, ncurses' terminal
+ database defines these names to which a suffix is added:
+
+ <EM>Name</EM> <EM>Description</EM>
+ ---------------------------------------------------------------
+ kDC special form of kdch1 (delete character)
+ kDN special form of kcud1 (cursor down)
+ kEND special form of kend (End)
+ kHOM special form of khome (Home)
+ kLFT special form of kcub1 (cursor-left or cursor-back)
+ kNXT special form of knext (Next, or Page-Down)
+ kPRV special form of kprev (Prev, or Page-Up)
+ kRIT special form of kcuf1 (cursor-right, or cursor-forward)
+ kUP special form of kcuu1 (cursor-up)
+
+ These are the suffixes used to denote the modifiers:
+
+ <EM>Value</EM> <EM>Description</EM>
+ ----------------------------------
+ 2 Shift
+ 3 Alt
+ 4 Shift + Alt
+ 5 Control
+ 6 Shift + Control
+ 7 Alt + Control
+ 8 Shift + Alt + Control
+ 9 Meta
+
+ 10 Meta + Shift
+ 11 Meta + Alt
+ 12 Meta + Alt + Shift
+ 13 Meta + Ctrl
+ 14 Meta + Ctrl + Shift
+ 15 Meta + Ctrl + Alt
+ 16 Meta + Ctrl + Alt + Shift
+
+ None of these are predefined; terminal descriptions can refer to <EM>names</EM>
+ which ncurses will allocate at runtime to <EM>key-codes</EM>. To use these keys
+ in an ncurses program, an application could do this:
+
+ <STRONG>o</STRONG> using a list of extended key <EM>names</EM>, ask <STRONG><A HREF="curs_terminfo.3x.html">tigetstr(3x)</A></STRONG> for their val-
+ ues, and
+
+ <STRONG>o</STRONG> given the list of values, ask <STRONG><A HREF="key_defined.3x.html">key_defined(3x)</A></STRONG> for the <EM>key-code</EM>
+ which would be returned for those keys by <STRONG><A HREF="curs_getch.3x.html">wgetch(3x)</A></STRONG>.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ The "-x" extension feature of <STRONG>tic</STRONG> and <STRONG>infocmp</STRONG> has been adopted in Net-
+ BSD curses. That implementation stores user-defined capabilities, but
+ makes no use of these capabilities itself.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <STRONG><A HREF="tic.1m.html">tic(1)</A></STRONG>, <STRONG><A HREF="infocmp.1m.html">infocmp(1)</A></STRONG>.
+
+
+</PRE><H2><a name="h2-AUTHORS">AUTHORS</a></H2><PRE>
+ Thomas E. Dickey
+ beginning with ncurses 5.0 (1999)
+
+
+
+ <STRONG><A HREF="user_caps.5.html">user_caps(5)</A></STRONG>
+</PRE>
+<div class="nav">
+<ul>
+<li><a href="#h2-NAME">NAME</a></li>
+<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
+<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
+<ul>
+<li><a href="#h3-Background">Background</a></li>
+<li><a href="#h3-Recognized-capabilities">Recognized capabilities</a></li>
+<li><a href="#h3-Extended-key-definitions">Extended key-definitions</a></li>
+</ul>
+</li>
+<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
+<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
+<li><a href="#h2-AUTHORS">AUTHORS</a></li>
+</ul>
+</div>
+</BODY>
+</HTML>
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