curs_trace 3x

curs_trace(3x)                                                  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  limita-
       tions 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 (allo-
           cated 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 param-
           eter 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:

            turn off tracing by passing a zero parameter.

            The library flushes the output file, but retains an open  file-de-
            scriptor  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  func-
       tion.   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 debug-
       ging output may be directed to the trace file if the NCURSES_TRACE  en-
       vironment 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  al-
           ways  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   CURS-
           ES_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.