1user_caps(5) File Formats Manual user_caps(5)
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6 user_caps - user-defined terminfo capabilities
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9 tic -x, infocmp -x
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12 Background
13 Before ncurses 5.0, terminfo databases used a fixed repertoire of ter‐
14 minal capabilities designed for the SVr2 terminal database in 1984, and
15 extended in stages through SVr4 (1989), and standardized in the Single
16 Unix Specification beginning in 1995.
17 Most of the extensions in this fixed repertoire were additions to the
19 tables of boolean, numeric and string capabilities. Rather than change
20 the meaning of an existing capability, a new name was added. The ter‐
21 minfo database uses a binary format; binary compatibility was ensured
22 by using a header which gave the number of items in the tables for each
23 type of capability. The standardization was incomplete:
24 • The binary format itself is not described in the X/Open Curses doc‐
26 umentation. Only the source format is described.
27 Library developers rely upon the SVr4 documentation, and reverse-
29 engineering the compiled terminfo files to match the binary format.
30 • Lacking a standard for the binary format, most implementations copy
32 the SVr2 binary format, which uses 16-bit signed integers, and is
33 limited to 4096-byte entries.
34 The format cannot represent very large numeric capabilities, nor
36 can it represent large numbers of special keyboard definitions.
37 • The tables of capability names differ between implementations.
39 Although they may provide all of the standard capability names, the
41 position in the tables differs because some features were added as
42 needed, while others were added (out of order) to comply with
43 X/Open Curses.
44 While ncurses' repertoire of predefined capabilities is closest to
46 Solaris, Solaris's terminfo database has a few differences from the
47 list published by X/Open Curses. For example, ncurses can be con‐
48 figured with tables which match the terminal databases for AIX, HP-
49 UX or OSF/1, rather than the default Solaris-like configuration.
50 • In SVr4 curses and ncurses, the terminal database is defined at
52 compile-time using a text file which lists the different terminal
53 capabilities.
54 In principle, the text-file can be extended, but doing this re‐
56 quires recompiling and reinstalling the library. The text-file
57 used in ncurses for terminal capabilities includes details for var‐
58 ious systems past the documented X/Open Curses features. For exam‐
59 ple, ncurses supports these capabilities in each configuration:
60 memory_lock
62 (meml) lock memory above cursor
63 memory_unlock
65 (memu) unlock memory
66 box_chars_1
68 (box1) box characters primary set
69 The memory lock/unlock capabilities were included because they were
71 used in the X11R6 terminal description for xterm(1). The box1 ca‐
72 pability is used in tic to help with terminal descriptions written
73 for AIX.
74 During the 1990s, some users were reluctant to use terminfo in spite of
76 its performance advantages over termcap:
77 • The fixed repertoire prevented users from adding features for unan‐
79 ticipated terminal improvements (or required them to reuse existing
80 capabilities as a workaround).
81 • The limitation to 16-bit signed integers was also mentioned. Be‐
83 cause termcap stores everything as a string, it could represent
84 larger numbers.
85 Although termcap's extensibility was rarely used (it was never the
87 speaker who had actually used the feature), the criticism had a point.
88 ncurses 5.0 provided a way to detect nonstandard capabilities, deter‐
89 mine their type and optionally store and retrieve them in a way which
90 did not interfere with other applications. These are referred to as
91 user-defined capabilities because no modifications to the toolset's
92 predefined capability names are needed.
93 The ncurses utilities tic and infocmp have a command-line option “-x”
95 to control whether the nonstandard capabilities are stored or re‐
96 trieved. A library function use_extended_names is provided for the
97 same purpose.
98 When compiling a terminal database, if “-x” is set, tic will store a
100 user-defined capability if the capability name is not one of the prede‐
101 fined names.
102 Because ncurses provides a termcap library interface, these user-de‐
104 fined capabilities may be visible to termcap applications:
105 • The termcap interface (like all implementations of termcap) re‐
107 quires that the capability names are 2-characters.
108 When the capability is simple enough for use in a termcap applica‐
110 tion, it is provided as a 2-character name.
111 • There are other user-defined capabilities which refer to features
113 not usable in termcap, e.g., parameterized strings that use more
114 than two parameters or use more than the trivial expression support
115 provided by termcap. For these, the terminfo database should have
116 only capability names with 3 or more characters.
117 • Some terminals can send distinct strings for special keys (cursor-,
119 keypad- or function-keys) depending on modifier keys (shift, con‐
120 trol, etc.). While terminfo and termcap have a set of 60 prede‐
121 fined function-key names, to which a series of keys can be as‐
122 signed, that is insufficient for more than a dozen keys multiplied
123 by more than a couple of modifier combinations. The ncurses data‐
124 base uses a convention based on xterm(1) to provide extended spe‐
125 cial-key names.
126 Fitting that into termcap's limitation of 2-character names would
128 be pointless. These extended keys are available only with ter‐
129 minfo.
130 Recognized capabilities
132 The ncurses library uses the user-definable capabilities. While the
133 terminfo database may have other extensions, ncurses makes explicit
134 checks for these:
135 AX boolean, asserts that the terminal interprets SGR 39 and SGR 49
137 by resetting the foreground and background color, respectively,
138 to the default.
139 This is a feature recognized by the screen program as well.
141 E3 string, tells how to clear the terminal's scrollback buffer.
143 When present, the clear(1) program sends this before clearing the
144 terminal.
145 The command “tput clear” does the same thing.
147 NQ used to suppress a consistency check in tic for the ncurses capa‐
149 bilities in user6 through user9 (u6, u7, u8 and u9) which tell
150 how to query the terminal's cursor position and its device at‐
151 tributes.
152 RGB
154 boolean, number or string, used to assert that the set_a_fore‐
155 ground and set_a_background capabilities correspond to direct
156 colors, using an RGB (red/green/blue) convention. This capabil‐
157 ity allows the color_content function to return appropriate val‐
158 ues without requiring the application to initialize colors using
159 init_color.
160 The capability type determines the values which ncurses sees:
162 boolean
164 implies that the number of bits for red, green and blue are
165 the same. Using the maximum number of colors, ncurses adds
166 two, divides that sum by three, and assigns the result to red,
167 green and blue in that order.
168 If the number of bits needed for the number of colors is not a
170 multiple of three, the blue (and green) components lose in
171 comparison to red.
172 number
174 tells ncurses what result to add to red, green and blue. If
175 ncurses runs out of bits, blue (and green) lose just as in the
176 boolean case.
177 string
179 explicitly list the number of bits used for red, green and
180 blue components as a slash-separated list of decimal integers.
181 Because there are several RGB encodings in use, applications
183 which make assumptions about the number of bits per color are un‐
184 likely to work reliably. As a trivial case, for example, one
185 could define RGB#1 to represent the standard eight ANSI colors,
186 i.e., one bit per color.
187 U8 number, asserts that ncurses must use Unicode values for line-
189 drawing characters, and that it should ignore the alternate char‐
190 acter set capabilities when the locale uses UTF-8 encoding. For
191 more information, see the discussion of NCURSES_NO_UTF8_ACS in
192 ncurses(3X).
193 Set this capability to a nonzero value to enable it.
195 XM string, override ncurses's built-in string which enables/disables
197 xterm(1) mouse mode.
198 ncurses sends a character sequence to the terminal to initialize
200 mouse mode, and when the user clicks the mouse buttons or (in
201 certain modes) moves the mouse, handles the characters sent back
202 by the terminal to tell it what was done with the mouse.
203 The mouse protocol is enabled when the mask passed in the mouse‐
205 mask function is nonzero. By default, ncurses handles the re‐
206 sponses for the X11 xterm mouse protocol. It also knows about
207 the SGR 1006 xterm mouse protocol, but must to be told to look
208 for this specifically. It will not be able to guess which mode
209 is used, because the responses are enough alike that only confu‐
210 sion would result.
211 The XM capability has a single parameter. If nonzero, the mouse
213 protocol should be enabled. If zero, the mouse protocol should
214 be disabled. ncurses inspects this capability if it is present,
215 to see whether the 1006 protocol is used. If so, it expects the
216 responses to use the SGR 1006 xterm mouse protocol.
217 The xterm mouse protocol is used by other terminal emulators.
219 The terminal database uses building-blocks for the various xterm
220 mouse protocols which can be used in customized terminal descrip‐
221 tions.
222 The terminal database building blocks for this mouse feature also
224 have an experimental capability xm. The “xm” capability de‐
225 scribes the mouse response. Currently there is no interpreter
226 which would use this information to make the mouse support com‐
227 pletely data-driven.
228 xm shows the format of the mouse responses. In this experimental
230 capability, the parameters are
231 p1 y-ordinate
233 p2 x-ordinate
235 p3 button
237 p4 state, e.g., pressed or released
239 p5 y-ordinate starting region
241 p6 x-ordinate starting region
243 p7 y-ordinate ending region
245 p8 x-ordinate ending region
247 Here are examples from the terminal database for the most com‐
249 monly used xterm mouse protocols:
250 xterm+x11mouse|X11 xterm mouse protocol,
252 kmous=\E[M, XM=\E[?1000%?%p1%{1}%=%th%el%;,
253 xm=\E[M
254 %?%p4%t%p3%e%{3}%;%' '%+%c
255 %p2%'!'%+%c
256 %p1%'!'%+%c,
257 xterm+sm+1006|xterm SGR-mouse,
259 kmous=\E[<, XM=\E[?1006;1000%?%p1%{1}%=%th%el%;,
260 xm=\E[<%i%p3%d;
261 %p1%d;
262 %p2%d;
263 %?%p4%tM%em%;,
264 Extended key-definitions
266 Several terminals provide the ability to send distinct strings for com‐
267 binations of modified special keys. There is no standard for what
268 those keys can send.
269 Since 1999, xterm(1) has supported shift, control, alt, and meta modi‐
271 fiers which produce distinct special-key strings. In a terminal de‐
272 scription, ncurses has no special knowledge of the modifiers used. Ap‐
273 plications can use the naming convention established for xterm to find
274 these special keys in the terminal description.
275 Starting with the curses convention that key names begin with “k” and
277 that shifted special keys are an uppercase name, ncurses' terminal
278 database defines these names to which a suffix is added:
279 Name Description
281 ───────────────────────────────────────────────────────────────
282 kDC special form of kdch1 (delete character)
283 kDN special form of kcud1 (cursor down)
284 kEND special form of kend (End)
285 kHOM special form of khome (Home)
286 kLFT special form of kcub1 (cursor-left or cursor-back)
287 kNXT special form of knext (Next, or Page-Down)
288 kPRV special form of kprev (Prev, or Page-Up)
289 kRIT special form of kcuf1 (cursor-right, or cursor-forward)
290 kUP special form of kcuu1 (cursor-up)
291 These are the suffixes used to denote the modifiers:
293 Value Description
295 ──────────────────────────────────
296 2 Shift
297 3 Alt
298 4 Shift + Alt
299 5 Control
300 6 Shift + Control
301 7 Alt + Control
302 8 Shift + Alt + Control
303 9 Meta
304 10 Meta + Shift
305 11 Meta + Alt
306 12 Meta + Alt + Shift
307 13 Meta + Ctrl
308 14 Meta + Ctrl + Shift
309 15 Meta + Ctrl + Alt
310 16 Meta + Ctrl + Alt + Shift
311 None of these are predefined; terminal descriptions can refer to names
313 which ncurses will allocate at runtime to key-codes. To use these keys
314 in an ncurses program, an application could do this:
315 • using a list of extended key names, ask tigetstr(3X) for their val‐
317 ues, and
318 • given the list of values, ask key_defined(3X) for the key-code
320 which would be returned for those keys by wgetch(3X).
321
323 The “-x” extension feature of tic and infocmp has been adopted in Net‐
324 BSD curses. That implementation stores user-defined capabilities, but
325 makes no use of these capabilities itself.
326
328 infocmp(1M), tic(1M).
329 The terminal database section NCURSES USER-DEFINABLE CAPABILITIES sum‐
331 marizes commonly-used user-defined capabilities which are used in the
332 terminal descriptions. Some of those features are mentioned in
333 screen(1) or tmux(1).
334 XTerm Control Sequences provides further information on the xterm(1)
336 features which are used in these extended capabilities.
337
339 Thomas E. Dickey
340 beginning with ncurses 5.0 (1999)
341 user_caps(5)