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:

       •   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.

       •   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

       •   curses_trace, which selectively enables different tracing features, and

       •   _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:

       •   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.

       •   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(3NCURSES) 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:

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

       •   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:

       •   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.

       •   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.

       •   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

       ncurses(3NCURSES)