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curs_trace(3)                                                    curs_trace(3)




NAME

       curses_trace, trace, _tracef, _traceattr, _traceattr2, _tracecchar_t,
       _tracecchar_t2, _tracechar, _tracechtype, _tracechtype2, _nc_tracebits,
       _tracedump, _tracemouse - curses debugging routines


SYNOPSIS

       #include <curses.h>

       unsigned curses_trace(const unsigned param);

       void _tracef(const char *format, ...);

       char *_traceattr(attr_t attr);
       char *_traceattr2(int buffer, chtype ch);
       char *_tracecchar_t(const cchar_t *string);
       char *_tracecchar_t2(int buffer, const cchar_t *string);
       char *_tracechar(int ch);
       char *_tracechtype(chtype ch);
       char *_tracechtype2(int buffer, chtype ch);

       void _tracedump(const char *label, WINDOW *win);
       char *_nc_tracebits(void);
       char *_tracemouse(const MEVENT *event);

       /* deprecated */
       void trace(const unsigned int param);


DESCRIPTION

       The curses trace routines are used for debugging the ncurses libraries,
       as well as applications which use the ncurses libraries.  Some
       limitations apply:

       o   Aside from curses_trace, the other functions are normally available
           only with the debugging library e.g., libncurses_g.a.

           All of the trace functions may be compiled into any model (shared,
           static, profile) by defining the symbol TRACE.

       o   Additionally, the functions which use cchar_t are only available with
           the wide-character configuration of the libraries.

   Functions
       The principal parts of this interface are

       o   curses_trace, which selectively enables different tracing features,
           and

       o   _tracef, which writes formatted data to the trace file.

           The other functions either return a pointer to a string-area
           (allocated by the corresponding function), or return no value (such
           as _tracedump, which implements the screen dump for TRACE_UPDATE).
           The caller should not free these strings, since the allocation is
           reused on successive calls.  To work around the problem of a single
           string-area per function, some use a buffer-number parameter, telling
           the library to allocate additional string-areas.

       The curses_trace function is always available, whether or not the other
       trace functions are available:

       o   If tracing is available, calling curses_trace with a nonzero
           parameter updates the trace mask, and returns the previous trace
           mask.

           When the trace mask is nonzero, ncurses creates the file "trace" in
           the current directory for output.  If the file already exists, no
           tracing is done.

       o   If tracing is not available, curses_trace returns zero (0).

   Trace Parameter
       The trace parameter is formed by OR'ing values from the list of TRACE_xxx
       definitions in <curses.h>.  These include:

       TRACE_DISABLE
            turn off tracing by passing a zero parameter.

            The library flushes the output file, but retains an open file-
            descriptor to the trace file so that it can resume tracing later if
            a nonzero parameter is passed to the curses_trace function.

       TRACE_TIMES
            trace user and system times of updates.

       TRACE_TPUTS
            trace tputs(3X) calls.

       TRACE_UPDATE
            trace update actions, old & new screens.

       TRACE_MOVE
            trace cursor movement and scrolling.

       TRACE_CHARPUT
            trace all character outputs.

       TRACE_ORDINARY
            trace all update actions.  The old and new screen contents are
            written to the trace file for each refresh.

       TRACE_CALLS
            trace all curses calls.  The parameters for each call are traced, as
            well as return values.

       TRACE_VIRTPUT
            trace virtual character puts, i.e., calls to addch.

       TRACE_IEVENT
            trace low-level input processing, including timeouts.

       TRACE_BITS
            trace state of TTY control bits.

       TRACE_ICALLS
            trace internal/nested calls.

       TRACE_CCALLS
            trace per-character calls.

       TRACE_DATABASE
            trace read/write of terminfo/termcap data.

       TRACE_ATTRS
            trace changes to video attributes and colors.

       TRACE_MAXIMUM
            maximum trace level, enables all of the separate trace features.

       Some tracing features are enabled whenever the curses_trace parameter is
       nonzero.  Some features overlap.  The specific names are used as a
       guideline.

   Initialization
       These functions check the NCURSES_TRACE environment variable, to set the
       tracing feature as if curses_trace was called:

           filter, initscr, new_prescr, newterm, nofilter, restartterm,
           ripoffline, setupterm, slk_init, tgetent, use_env,
           use_extended_names, use_tioctl

   Command-line Utilities
       The command-line utilities such as tic(1) provide a verbose option which
       extends the set of messages written using the curses_trace function.
       Both of these (-v and curses_trace) use the same variable (_nc_tracing),
       which determines the messages which are written.

       Because the command-line utilities may call initialization functions such
       as setupterm, tgetent or use_extended_names, some of their debugging
       output may be directed to the trace file if the NCURSES_TRACE environment
       variable is set:

       o   messages produced in the utility are written to the standard error.

       o   messages produced by the underlying library are written to trace.

       If ncurses is built without tracing, none of the latter are produced, and
       fewer diagnostics are provided by the command-line utilities.


RETURN VALUE

       Routines which return a value are designed to be used as parameters to
       the _tracef routine.


PORTABILITY

       These functions are not part of the XSI interface.  Some other curses
       implementations are known to have similar features, but they are not
       compatible with ncurses:

       o   SVr4 provided traceon and traceoff, to control whether debugging
           information was written to the "trace" file.  While the functions
           were always available, this feature was only enabled if DEBUG was
           defined when building the library.

           The SVr4 tracing feature is undocumented.

       o   PDCurses provides traceon and traceoff, which (like SVr4) are always
           available, and enable tracing to the "trace" file only when a debug-
           library is built.

           PDCurses has a short description of these functions, with a note that
           they are not present in X/Open Curses, ncurses or NetBSD.  It does
           not mention SVr4, but the functions' inclusion in a header file
           section labeled "Quasi-standard" hints at the origin.

       o   NetBSD does not provide functions for enabling/disabling traces.  It
           uses environment variables CURSES_TRACE_MASK and CURSES_TRACE_FILE to
           determine what is traced, and where the results are written.  This is
           available only when a debug-library is built.

           The NetBSD tracing feature is undocumented.

       A few ncurses functions are not provided when symbol versioning is used:

           _nc_tracebits, _tracedump, _tracemouse

       The original trace routine was deprecated because it often conflicted
       with application names.


SEE ALSO

       curses(3X).



                                                                  curs_trace(3)

ncurses 6.4 - Generated Tue Jan 3 15:02:11 CST 2023
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