# curs_trace 3x

    curs_trace(3x)                                                  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  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.

### 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 (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:

           TRACE_DISABLE
                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_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  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.

## 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  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
           used:

               _nc_tracebits, _tracedump, _tracemouse

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

## SEE ALSO

           curses(3x).

                                                                    curs_trace(3x)