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2.\" $OpenBSD: curs_util.3,v 1.7 2023/10/17 09:52:08 nicm Exp $
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33.\" $Id: curs_util.3,v 1.7 2023/10/17 09:52:08 nicm Exp $
34.TH curs_util 3 2023-08-19 "ncurses 6.4" "Library calls"
35.ie \n(.g .ds `` \(lq
36.el .ds `` ``
37.ie \n(.g .ds '' \(rq
38.el .ds '' ''
39.de bP
40.ie n .IP \(bu 4
41.el .IP \(bu 2
42..
43.na
44.hy 0
45.SH NAME
46\fBdelay_output\fP,
47\fBfilter\fP,
48\fBflushinp\fP,
49\fBgetwin\fP,
50\fBkey_name\fP,
51\fBkeyname\fP,
52\fBnofilter\fP,
53\fBputwin\fP,
54\fBunctrl\fP,
55\fBuse_env\fP,
56\fBuse_tioctl\fP,
57\fBwunctrl\fP \- miscellaneous \fBcurses\fP utility routines
58.ad
59.hy
60.SH SYNOPSIS
61\fB#include <curses.h>\fP
62.sp
63\fBconst char *unctrl(chtype \fIc\fB);\fR
64.br
65\fBwchar_t *wunctrl(cchar_t *\fIc\fB);\fR
66.sp
67\fBconst char *keyname(int \fIc\fB);\fR
68.br
69\fBconst char *key_name(wchar_t \fIw\fB);\fR
70.sp
71\fBvoid filter(void);\fP
72.sp
73\fBvoid use_env(bool \fIf\fB);\fR
74.sp
75\fBint putwin(WINDOW *\fIwin\fB, FILE *\fIfilep\fB);\fR
76.br
77\fBWINDOW *getwin(FILE *\fIfilep\fB);\fR
78.sp
79\fBint delay_output(int \fIms\fB);\fR
80.br
81\fBint flushinp(void);\fP
82.sp
83/* extensions */
84.br
85\fBvoid nofilter(void);\fP
86.br
87\fBvoid use_tioctl(bool \fIf\fB);\fR
88.SH DESCRIPTION
89.SS unctrl
90The \fBunctrl\fP routine returns a character string which is a printable
91representation of the character \fIc\fP:
92.bP
93Printable characters are displayed as themselves,
94e.g., a one-character string containing the key.
95.bP
96Control characters are displayed in the \fB^\fIX\fR notation.
97.bP
98Printing characters are displayed as is.
99.bP
100DEL (character 127) is displayed as \fB^?\fP.
101.bP
102Values above 128 are either meta characters
103(if the screen has not been initialized,
104or if \fBmeta\fP(3) has been called with a \fBTRUE\fP parameter),
105shown in the \fBM\-\fIX\fR notation,
106or are displayed as themselves.
107In the latter case, the values may not be printable;
108this follows the X/Open specification.
109.PP
110The corresponding \fBwunctrl\fP returns a printable representation of
111a complex character \fIc\fP.
112.PP
113In both \fBunctrl\fP and \fBwunctrl\fP the attributes and color associated
114with the character parameter are ignored.
115.SS keyname/key_name
116The \fBkeyname\fP routine returns a character string
117corresponding to the key \fIc\fP.
118Key codes are different from character codes.
119.bP
120Key codes below 256 are characters.
121They are displayed using \fBunctrl\fP.
122.bP
123Values above 256 may be the codes for function keys.
124The function key name is displayed.
125.bP
126Otherwise (if there is no corresponding name and the key is not a character)
127the function returns null, to denote an error.
128X/Open also lists an \*(``UNKNOWN KEY\*('' return value,
129which some implementations return rather than null.
130.LP
131The corresponding \fBkey_name\fP returns
132a multibyte character string corresponding
133to the wide-character value \fIw\fP.
134The two functions (\fBkeyname\fP and \fBkey_name\fP)
135do not return the same set of strings:
136.bP
137\fBkeyname\fP returns null where \fBkey_name\fP would display a meta character.
138.bP
139\fBkey_name\fP does not return the name of a function key.
140.SS filter/nofilter
141The \fBfilter\fP routine, if used, must be called before \fBinitscr\fP or
142\fBnewterm\fP are called.
143Calling \fBfilter\fP causes these changes in initialization:
144.bP
145\fBLINES\fP is set to 1;
146.bP
147the capabilities
148\fBclear\fP,
149\fBcud1\fP,
150\fBcud\fP,
151\fBcup\fP,
152\fBcuu1\fP,
153\fBcuu\fP,
154\fBvpa\fP
155are disabled;
156.bP
157the capability \fBed\fP is disabled if \fBbce\fP is set;
158.bP
159and the \fBhome\fP string is set to the value of \fBcr\fP.
160.PP
161The \fBnofilter\fP routine cancels the effect of a preceding \fBfilter\fP
162call.
163That allows the caller to initialize a screen on a different device,
164using a different value of \fB$TERM\fP.
165The limitation arises because the \fBfilter\fP routine modifies the
166in-memory copy of the terminal information.
167.SS use_env
168The \fBuse_env\fP routine, if used,
169should be called before \fBinitscr\fP or
170\fBnewterm\fP are called
171(because those compute the screen size).
172It modifies the way \fBncurses\fP treats environment variables
173when determining the screen size.
174.bP
175Normally \fBncurses\fP looks first at the terminal database for the screen size.
176.IP
177If \fBuse_env\fP was called with \fBFALSE\fP for parameter,
178it stops here unless
179\fBuse_tioctl\fP was also called with \fBTRUE\fP for parameter.
180.bP
181Then it asks for the screen size via operating system calls.
182If successful,
183it overrides the values from the terminal database.
184.bP
185Finally (unless \fBuse_env\fP was called with \fBFALSE\fP parameter),
186\fBncurses\fP examines the \fBLINES\fP or \fBCOLUMNS\fP environment variables,
187using a value in those to override the results
188from the operating system or terminal database.
189.IP
190\fBNcurses\fP also updates the screen size in response to \fBSIGWINCH\fP,
191unless overridden by the \fBLINES\fP or \fBCOLUMNS\fP environment variables,
192.SS use_tioctl
193The \fBuse_tioctl\fP routine, if used,
194should be called before \fBinitscr\fP or \fBnewterm\fP are called
195(because those compute the screen size).
196After \fBuse_tioctl\fP is called with \fBTRUE\fP as an argument,
197\fBncurses\fP modifies the last step in its computation
198of screen size as follows:
199.bP
200checks if the \fBLINES\fP and \fBCOLUMNS\fP environment variables
201are set to a number greater than zero.
202.bP
203for each, \fBncurses\fP updates the corresponding environment variable
204with the value that it has obtained via operating system call
205or from the terminal database.
206.bP
207\fBncurses\fP re-fetches the value of the environment variables so that
208it is still the environment variables which set the screen size.
209.PP
210The \fBuse_env\fP and \fBuse_tioctl\fP routines combine as
211summarized here:
212.PP
213.TS
214center tab(/);
215l l l
216_ _ _
217lw7 lw7 lw40.
218\fBuse_env\fP/\fBuse_tioctl\fP/\fBSummary\fP
219TRUE/FALSE/T{
220This is the default behavior.
221\fBncurses\fP uses operating system calls
222unless overridden by $LINES or $COLUMNS environment variables.
223T}
224TRUE/TRUE/T{
225\fBncurses\fP updates $LINES and $COLUMNS based on operating system calls.
226T}
227FALSE/TRUE/T{
228\fBncurses\fP ignores $LINES and $COLUMNS,
229uses operating system calls to obtain size.
230T}
231FALSE/FALSE/T{
232\fBncurses\fP relies on the terminal database to determine size.
233T}
234.TE
235.SS putwin/getwin
236The \fBputwin\fP routine writes all data associated
237with window (or pad) \fIwin\fP into
238the file to which \fIfilep\fP points.
239This information can be later retrieved
240using the \fBgetwin\fP function.
241.PP
242The \fBgetwin\fP routine reads window related data stored in the file by
243\fBputwin\fP.
244The routine then creates and initializes a new window using that
245data.
246It returns a pointer to the new window.
247There are a few caveats:
248.bP
249the data written is a copy of the \fBWINDOW\fP structure,
250and its associated character cells.
251The format differs between the wide-character (\fBncursesw\fP) and
252non-wide (\fBncurses\fP) libraries.
253You can transfer data between the two, however.
254.bP
255the retrieved window is always created as a top-level window (or pad),
256rather than a subwindow.
257.bP
258the window's character cells contain the color pair \fIvalue\fP,
259but not the actual color \fInumbers\fP.
260If cells in the retrieved window use color pairs which have not been
261created in the application using \fBinit_pair\fP,
262they will not be colored when the window is refreshed.
263.SS delay_output
264The \fBdelay_output\fP routine inserts an \fIms\fP millisecond pause
265in output.
266This routine should not be used extensively because
267padding characters are used rather than a CPU pause.
268If no padding character is specified,
269this uses \fBnapms\fP to perform the delay.
270.SS flushinp
271The \fBflushinp\fP routine throws away any typeahead that has been typed by the
272user and has not yet been read by the program.
273.SH RETURN VALUE
274Except for \fBflushinp\fP, routines that return an integer return \fBERR\fP
275upon failure and \fBOK\fP (SVr4 specifies only "an integer value other than
276\fBERR\fP") upon successful completion.
277.PP
278Routines that return pointers return \fBNULL\fP on error.
279.PP
280X/Open does not define any error conditions.
281In this implementation
282.RS 3
283.TP 5
284\fBflushinp\fP
285returns an error if the terminal was not initialized.
286.TP 5
287\fBputwin\fP
288returns an error if the associated \fBfwrite\fP calls return an error.
289.RE
290.SH PORTABILITY
291.SS filter
292The SVr4 documentation describes the action of \fBfilter\fP only in the vaguest
293terms.
294The description here is adapted from the XSI Curses standard (which
295erroneously fails to describe the disabling of \fBcuu\fP).
296.SS keyname
297The \fBkeyname\fP function may return the names of user-defined
298string capabilities which are defined in the terminfo entry via the \fB\-x\fP
299option of \fBtic\fP.
300This implementation automatically assigns at run-time keycodes to
301user-defined strings which begin with \*(``k\*(''.
302The keycodes start at KEY_MAX, but are not guaranteed to be
303the same value for different runs because user-defined codes are
304merged from all terminal descriptions which have been loaded.
305The \fBuse_extended_names\fP(3) function controls whether this data is
306loaded when the terminal description is read by the library.
307.SS nofilter/use_tioctl
308The \fBnofilter\fP and \fBuse_tioctl\fP routines are specific to \fBncurses\fP.
309They were not supported on Version 7, BSD or System V implementations.
310It is recommended that any code depending on \fBncurses\fP extensions
311be conditioned using NCURSES_VERSION.
312.SS putwin/getwin file-format
313The \fBputwin\fP and \fBgetwin\fP functions have several issues with
314portability:
315.bP
316The files written and read by these functions
317use an implementation-specific format.
318Although the format is an obvious target for standardization,
319it has been overlooked.
320.IP
321Interestingly enough, according to the copyright dates in Solaris source,
322the functions (along with \fBscr_init\fP, etc.) originated with
323the University of California, Berkeley (in 1982)
324and were later (in 1988) incorporated into SVr4.
325Oddly, there are no such functions in the 4.3BSD curses sources.
326.bP
327Most implementations simply dump the binary \fBWINDOW\fP structure to the file.
328These include SVr4 curses, NetBSD and PDCurses,
329as well as older \fBncurses\fP versions.
330This implementation
331(as well as the X/Open variant of Solaris curses, dated 1995)
332uses textual dumps.
333.IP
334The implementations which use binary dumps use block-I/O
335(the \fBfwrite\fP and \fBfread\fP functions).
336Those that use textual dumps use buffered-I/O.
337A few applications may happen to write extra data in the file using
338these functions.
339Doing that can run into problems mixing block- and buffered-I/O.
340This implementation reduces the problem on writes by flushing the output.
341However, reading from a file written using mixed schemes may not be successful.
342.SS unctrl/wunctrl
343The XSI Curses standard, Issue 4 describes these functions.
344It states that \fBunctrl\fP and \fBwunctrl\fP will return a null pointer if
345unsuccessful, but does not define any error conditions.
346This implementation checks for three cases:
347.bP
348the parameter is a 7-bit US\-ASCII code.
349This is the case that X/Open Curses documented.
350.bP
351the parameter is in the range 128\-159, i.e., a C1 control code.
352If \fBuse_legacy_coding\fP(3) has been called with a \fB2\fP parameter,
353\fBunctrl\fP returns the parameter, i.e., a one-character string with
354the parameter as the first character.
355Otherwise, it returns \*(``~@\*('', \*(``~A\*('', etc.,
356analogous to \*(``^@\*('', \*(``^A\*('', C0 controls.
357.IP
358X/Open Curses does not document whether \fBunctrl\fP can be called before
359initializing curses.
360This implementation permits that,
361and returns the \*(``~@\*('', etc., values in that case.
362.bP
363parameter values outside the 0 to 255 range.
364\fBunctrl\fP returns a null pointer.
365.PP
366The strings returned by \fBunctrl\fP in this implementation are determined
367at compile time,
368showing C1 controls from the upper-128 codes
369with a \*(``~\*('' prefix rather than \*(``^\*(''.
370Other implementations have different conventions.
371For example, they may show both sets of control characters with \*(``^\*('',
372and strip the parameter to 7 bits.
373Or they may ignore C1 controls and treat all of the upper-128 codes as
374printable.
375This implementation uses 8 bits but does not modify the string to reflect
376locale.
377The \fBuse_legacy_coding\fP(3) function allows the caller to
378change the output of \fBunctrl\fP.
379.PP
380Likewise, the \fBmeta\fP(3) function allows the caller to change the
381output of \fBkeyname\fP, i.e.,
382it determines whether to use the \*(``M\-\*('' prefix
383for \*(``meta\*('' keys (codes in the range 128 to 255).
384Both \fBuse_legacy_coding\fP(3) and \fBmeta\fP(3) succeed only after
385curses is initialized.
386X/Open Curses does not document the treatment of codes 128 to 159.
387When treating them as \*(``meta\*('' keys
388(or if \fBkeyname\fP is called before initializing curses),
389this implementation returns strings \*(``M\-^@\*('', \*(``M\-^A\*('', etc.
390.PP
391X/Open Curses documents \fBunctrl\fP as declared in \fB<unctrl.h>\fP,
392which \fBncurses\fP does.
393However, \fBncurses\fP' \fB<curses.h>\fP includes \fB<unctrl.h>\fP,
394matching the behavior of SVr4 curses.
395Other implementations may not do that.
396.SS use_env/use_tioctl
397If \fBncurses\fP is configured to provide the sp-functions extension,
398the state of \fBuse_env\fP and \fBuse_tioctl\fP may be updated before
399creating each \fIscreen\fP rather than once only
400(\fBcurs_sp_funcs\fP(3)).
401This feature of \fBuse_env\fP
402is not provided by other implementations of curses.
403.SH SEE ALSO
404\fBcurses\fP(3),
405\fBcurs_initscr\fP(3),
406\fBcurs_inopts\fP(3),
407\fBcurs_kernel\fP(3),
408\fBcurs_scr_dump\fP(3),
409\fBcurs_sp_funcs\fP(3),
410\fBcurs_variables\fP(3),
411\fBlegacy_coding\fP(3).