# user_caps(5) - man - phpMan [user_caps(5)](https://www.chedong.com/phpMan.php/man/usercaps/5/markdown) File Formats Manual [user_caps(5)](https://www.chedong.com/phpMan.php/man/usercaps/5/markdown) ## NAME user_caps - user-defined terminfo capabilities ## SYNOPSIS ### tic -x, infocmp -x ## DESCRIPTION ### Background Before ncurses 5.0, terminfo databases used a _fixed_ _repertoire_ of terminal capabilities de‐ signed 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 _extensions_ in this fixed repertoire were additions to the tables of boolean, nu‐ meric and string capabilities. Rather than change the meaning of an existing capability, a new name was added. The terminfo database uses a binary format; binary compatibility was en‐ sured by using a header which gave the number of items in the tables for each type of capa‐ bility. The standardization was incomplete: • The _binary_ _format_ itself is not described in the X/Open Curses documentation. Only the _source_ _format_ is described. Library developers rely upon the SVr4 documentation, and reverse-engineering the compiled terminfo files to match the binary format. • Lacking a standard for the binary format, most implementations copy the SVr2 binary for‐ mat, 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. • The tables of capability names differ between implementations. Although they _may_ provide all of the standard capability names, the position in the ta‐ bles 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. For example, ncurses can be configured with tables which match the terminal databases for AIX, HP-UX or OSF/1, rather than the default Solaris-like configuration. • In SVr4 curses and ncurses, the terminal database is defined at compile-time using a text file which lists the different terminal capabilities. In principle, the text-file can be extended, but doing this requires recompiling and re‐ installing the library. The text-file used in ncurses for terminal capabilities includes details for various systems past the documented X/Open Curses features. For example, ncurses supports these capabilities in each configuration: memory_lock (meml) lock memory above cursor memory_unlock (memu) unlock memory box_chars_1 (box1) box characters primary set The memory lock/unlock capabilities were included because they were used in the X11R6 terminal description for **xterm**. The _box1_ capability is used in tic to help with terminal descriptions written for AIX. During the 1990s, some users were reluctant to use terminfo in spite of its performance ad‐ vantages over termcap: • The fixed repertoire prevented users from adding features for unanticipated terminal im‐ provements (or required them to reuse existing capabilities as a workaround). • The limitation to 16-bit signed integers was also mentioned. Because termcap stores ev‐ erything as a string, it could represent larger numbers. Although termcap's extensibility was rarely used (it was never the _speaker_ who had actually used the feature), the criticism had a point. ncurses 5.0 provided a way to detect nonstan‐ dard capabilities, determine their type and optionally store and retrieve them in a way which did not interfere with other applications. These are referred to as _user-defined_ _capabili__‐ _ties_ because no modifications to the toolset's predefined capability names are needed. The ncurses utilities **tic** and **infocmp** have a command-line option “-x” to control whether the nonstandard capabilities are stored or retrieved. A library function **use**___**extended**___**names** is provided for the same purpose. When compiling a terminal database, if “-x” is set, **tic** will store a user-defined capability if the capability name is not one of the predefined names. Because ncurses provides a termcap library interface, these user-defined capabilities may be visible to termcap applications: • 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 application, it is provided as a 2-character name. • 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 triv‐ ial expression support provided by termcap. For these, the terminfo database should have only capability names with 3 or more characters. • Some terminals can send distinct strings for special keys (cursor-, keypad- or function- keys) depending on modifier keys (shift, control, etc.). While terminfo and termcap have a set of 60 predefined function-key names, to which a series of keys can be assigned, that is insufficient for more than a dozen keys multiplied by more than a couple of modi‐ fier combinations. The ncurses database uses a convention based on **xterm** to provide ex‐ tended special-key names. Fitting that into termcap's limitation of 2-character names would be pointless. These extended keys are available only with terminfo. ### Recognized capabilities The ncurses library uses the user-definable capabilities. While the terminfo database may have other extensions, ncurses makes explicit checks for these: AX _boolean_, asserts that the terminal interprets SGR 39 and SGR 49 by resetting the fore‐ ground and background color, respectively, to the default. This is a feature recognized by the **screen** program as well. E3 _string_, tells how to clear the terminal's scrollback buffer. When present, the [**clear**(1)](https://www.chedong.com/phpMan.php/man/clear/1/markdown) program sends this before clearing the terminal. The command “**tput** **clear**” does the same thing. RGB _boolean_, _number_ **or** _string_, to assert that the **set**___**a**___**foreground** and **set**___**a**___**background** ca‐ pabilities correspond to _direct_ _colors_, using an RGB (red/green/blue) convention. This capability allows the **color**___**content** function to return appropriate values without re‐ quiring the application to initialize colors using **init**___**color**. The capability type determines the values which ncurses sees: _boolean_ 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. _number_ 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 _boolean_ case. _string_ explicitly list the number of bits used for red, green and blue components as a slash-separated list of decimal integers. Because there are several RGB encodings in use, applications which make assumptions about the number of bits per color are unlikely to work reliably. As a trivial case, for example, one could define **RGB#1** to represent the standard eight ANSI colors, i.e., one bit per color. U8 _number_, asserts that ncurses must use Unicode values for line-drawing characters, and that it should ignore the alternate character set capabilities when the locale uses UTF-8 encoding. For more information, see the discussion of **NCURSES**___**NO**___**UTF8**___**ACS** in [**ncurses**(3X)](https://www.chedong.com/phpMan.php/man/ncurses/3X/markdown). Set this capability to a nonzero value to enable it. XM _string_, override ncurses's built-in string which enables/disables **xterm** mouse mode. ncurses sends a character sequence to the terminal to initialize mouse mode, and when the user clicks the mouse buttons or (in certain modes) moves the mouse, handles the characters sent back by the terminal to tell it what was done with the mouse. The mouse protocol is enabled when the _mask_ passed in the **mousemask** function is non‐ zero. By default, ncurses handles the responses for the X11 xterm mouse protocol. It also knows about the _SGR_ _1006_ xterm mouse protocol, but must to be told to look for this specifically. It will not be able to guess which mode is used, because the re‐ sponses are enough alike that only confusion would result. The **XM** capability has a single parameter. If nonzero, the mouse protocol should be en‐ abled. If zero, the mouse protocol should be disabled. ncurses inspects this capabil‐ ity if it is present, to see whether the 1006 protocol is used. If so, it expects the responses to use the _SGR_ _1006_ xterm mouse protocol. The xterm mouse protocol is used by other terminal emulators. The terminal database uses building-blocks for the various xterm mouse protocols which can be used in custom‐ ized terminal descriptions. The terminal database building blocks for this mouse feature also have an experimental capability _xm_. The “xm” capability describes the mouse response. Currently there is no interpreter which would use this information to make the mouse support completely data-driven. _xm_ shows the format of the mouse responses. In this experimental capability, the pa‐ rameters are _p1_ y-ordinate _p2_ x-ordinate _p3_ button _p4_ state, e.g., pressed or released _p5_ y-ordinate starting region _p6_ x-ordinate starting region _p7_ y-ordinate ending region _p8_ x-ordinate ending region Here are examples from the terminal database for the most commonly used xterm mouse protocols: xterm+x11mouse|X11 xterm mouse protocol, kmous=\E[M, XM=\E[?1000%?%p1%{1}%=%th%el%;, xm=\E[M %?%p4%t%p3%e%{3}%;%' '%+%c %p2%'!'%+%c %p1%'!'%+%c, xterm+sm+1006|xterm SGR-mouse, kmous=\E[<, XM=\E[?1006;1000%?%p1%{1}%=%th%el%;, xm=\E[<%i%p3%d; %p1%d; %p2%d; %?%p4%tM%em%;, ### Extended key-definitions Several terminals provide the ability to send distinct strings for combinations of modified special keys. There is no standard for what those keys can send. Since 1999, **xterm** has supported _shift_, _control_, _alt_, and _meta_ modifiers which produce dis‐ tinct special-key strings. In a terminal description, ncurses has no special knowledge of the modifiers used. Applications can use the _naming_ _convention_ established for **xterm** to find these special keys in the terminal description. Starting with the curses convention that _key_ _names_ begin with “k” and that shifted special keys are an uppercase name, ncurses' terminal database defines these names to which a suffix is added: _Name_ _Description_ ─────────────────────────────────────────────────────────────── 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: _Value_ _Description_ ────────────────────────────────── 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 _names_ which ncurses will al‐ locate at runtime to _key-codes_. To use these keys in an ncurses program, an application could do this: • using a list of extended key _names_, ask [**tigetstr**(3X)](https://www.chedong.com/phpMan.php/man/tigetstr/3X/markdown) for their values, and • given the list of values, ask **key**___**[defined**(3X)](https://www.chedong.com/phpMan.php/man/defined/3X/markdown) for the _key-code_ which would be returned for those keys by [**wgetch**(3X)](https://www.chedong.com/phpMan.php/man/wgetch/3X/markdown). ## PORTABILITY The “-x” extension feature of **tic** and **infocmp** has been adopted in NetBSD curses. That imple‐ mentation stores user-defined capabilities, but makes no use of these capabilities itself. ## SEE ALSO [**infocmp**(1)](https://www.chedong.com/phpMan.php/man/infocmp/1/markdown), [**tic**(1)](https://www.chedong.com/phpMan.php/man/tic/1/markdown). The terminal database section _NCURSES_ _USER-DEFINABLE_ _CAPABILITIES_ summarizes commonly-used user-defined capabilities which are used in the terminal descriptions. Some of those fea‐ tures are mentioned in [**screen**(1)](https://www.chedong.com/phpMan.php/man/screen/1/markdown) or [**tmux**(1)](https://www.chedong.com/phpMan.php/man/tmux/1/markdown). _XTerm_ _Control_ _Sequences_ provides further information on the **xterm** features which are used in these extended capabilities. ## AUTHORS Thomas E. Dickey beginning with ncurses 5.0 (1999) [user_caps(5)](https://www.chedong.com/phpMan.php/man/usercaps/5/markdown)