# curs_trace 3x 2025-01-18 ncurses 6.6 Library calls

    curs_trace(3x)                   Library calls                  curs_trace(3x)

## 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 trace-mask);

           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 c);
           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 trace-mask);

## 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 logically  "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.

### 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.

## ENVIRONMENT

### NCURSES_TRACE

           A positive integral value stored in this variable causes the  following
           functions to enable the tracing feature as if curses_trace were called.

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

## PORTABILITY

           These  functions  are  not  part  of the X/Open Curses 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)

    ncurses 6.6                       2025-01-18                    curs_trace(3x)