|-||Printable characters are displayed as themselves, e.g., a one-character string containing the key.|
|-||Control characters are displayed in the ^X notation.|
|-||DEL (character 127) is displayed as ^?.|
|-||Values above 128 are either meta characters (if the screen has not been initialized, or if meta has been called with a TRUE parameter), shown in the M-X notation, or are displayed as themselves. In the latter case, the values may not be printable; this follows the X/Open specification.|
|-||Values above 256 may be the names of the names of function keys.|
|-||Otherwise (if there is no corresponding name) the function returns null, to denote an error. X/Open also lists an "UNKNOWN KEY" return value, which some implementations return rather than null.|
The corresponding key_name returns a character string corresponding to the wide-character value w. The two functions do not return the same set of strings; the latter returns null where the former would display a meta character.
The filter routine, if used, must be called before initscr or newterm are called. The effect is that, during those calls, LINES is set to 1; the capabilities clear, cup, cud, cud1, cuu1, cuu, vpa are disabled; and the home string is set to the value of cr.
The nofilter routine cancels the effect of a preceding filter call. That allows the caller to initialize a screen on a different device, using a different value of $TERM. The limitation arises because the filter routine modifies the in-memory copy of the terminal information.
The use_env routine, if used, is called before initscr or newterm are called. When called with FALSE as an argument, the values of lines and columns specified in the terminfo database will be used, even if environment variables LINES and COLUMNS (used by default) are set, or if curses is running in a window (in which case default behavior would be to use the window size if LINES and COLUMNS are not set). Note that setting LINES or COLUMNS overrides the corresponding size which may be obtained from the operating system.
The putwin routine writes all data associated with window win into the file to which filep points. This information can be later retrieved using the getwin function.
The getwin routine reads window related data stored in the file by putwin. The routine then creates and initializes a new window using that data. It returns a pointer to the new window.
The delay_output routine inserts an ms millisecond pause in output. This routine should not be used extensively because padding characters are used rather than a CPU pause. If no padding character is specified, this uses napms to perform the delay.
The flushinp routine throws away any typeahead that has been typed by the user and has not yet been read by the program.
Except for flushinp, routines that return an integer return ERR upon failure and OK (SVr4 specifies only "an integer value other than ERR") upon successful completion.
Routines that return pointers return NULL on error.
X/Open does not define any error conditions. In this implementation
flushinp returns an error if the terminal was not initialized. meta returns an error if the terminal was not initialized. putwin returns an error if the associated fwrite calls return an error.
The XSI Curses standard, Issue 4 describes these functions. It states that unctrl and wunctrl will return a null pointer if unsuccessful, but does not define any error conditions. This implementation checks for three cases:
- the parameter is a 7-bit US-ASCII code. This is the case that X/Open Curses documented. - the parameter is in the range 128-159, i.e., a C1 control code. If use_legacy_coding has been called with a 2 parameter, unctrl returns the parameter, i.e., a one-character string with the parameter as the first character. Otherwise, it returns ~@, ~A, etc., analogous to ^@, ^A, C0 controls. X/Open Curses does not document whether unctrl can be called before initializing curses. This implementation permits that, and returns the ~@, etc., values in that case. - parameter values outside the 0 to 255 range. unctrl returns a null pointer.
The SVr4 documentation describes the action of filter only in the vaguest terms. The description here is adapted from the XSI Curses standard (which erroneously fails to describe the disabling of cuu).
The strings returned by unctrl in this implementation are determined at compile time, showing C1 controls from the upper-128 codes with a ~ prefix rather than ^. Other implementations have different conventions. For example, they may show both sets of control characters with ^, and strip the parameter to 7 bits. Or they may ignore C1 controls and treat all of the upper-128 codes as printable. This implementation uses 8 bits but does not modify the string to reflect locale. The use_legacy_coding function allows the caller to change the output of unctrl.
Likewise, the meta function allows the caller to change the output of keyname, i.e., it determines whether to use the M- prefix for meta keys (codes in the range 128 to 255). Both use_legacy_coding and meta succeed only after curses is initialized. X/Open Curses does not document the treatment of codes 128 to 159. When treating them as meta keys (or if keyname is called before initializing curses), this implementation returns strings M-^@, M-^A, etc.
The keyname function may return the names of user-defined string capabilities which are defined in the terminfo entry via the -x option of tic. This implementation automatically assigns at run-time keycodes to user-defined strings which begin with "k". The keycodes start at KEY_MAX, but are not guaranteed to be the same value for different runs because user-defined codes are merged from all terminal descriptions which have been loaded. The use_extended_names function controls whether this data is loaded when the terminal description is read by the library.
The nofilter routine is specific to ncurses. It was not supported on Version 7, BSD or System V implementations. It is recommended that any code depending on ncurses extensions be conditioned using NCURSES_VERSION.
legacy_coding(3X), curses(3X), curs_initscr(3X), curs_kernel(3X), curs_scr_dump(3X), legacy_coding(3X).