curs_trace 3x 2023-10-07 ncurses 6.4 Library calls

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


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


       #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);


       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.


       The principal parts of this interface are

       o   curses_trace, which selectively enables different tracing features,

       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

           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:

            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 user and system times of updates.

            trace tputs(3x) calls.

            trace update actions, old & new screens.

            trace cursor movement and scrolling.

            trace all character outputs.

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

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

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

            trace low-level input processing, including timeouts.

            trace state of TTY control bits.

            trace internal/nested calls.

            trace per-character calls.

            trace read/write of terminfo/termcap data.

            trace changes to video attributes and colors.

            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


       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.


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


       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

           _nc_tracebits, _tracedump, _tracemouse

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



ncurses 6.4                       2023-10-07                    curs_trace(3x)