# curs_trace 3x 2023-12-23 ncurses 6.4 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 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)

    ncurses 6.4                       2023-12-23                    curs_trace(3x)