curs_trace(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | PORTABILITY | SEE ALSO | COLOPHON

curs_trace(3X)                                            curs_trace(3X)

NAME         top

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

SYNOPSIS         top

       #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         top

       The  curses trace routines are used for debugging the ncurses li‐
       braries, 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., libncurs‐
           es_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 avail‐
           able 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 allo‐
           cate 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 al‐
           ready 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 curs‐
            es_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 fea‐
            tures.

       Some tracing features are enabled whenever the curses_trace para‐
       meter 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  op‐
       tion  which  extends  the set of messages written using the curs‐
       es_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  func‐
       tions  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 pro‐
       duced, and fewer diagnostics are provided by the command-line
       utilities.

RETURN VALUE         top

       Routines which return a value are designed to be used as parame‐
       ters to the _tracef routine.

PORTABILITY         top

       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 debug‐
           ging information was written to the “trace” file.  While the
           functions were always available, this feature was only en‐
           abled 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' inclu‐
           sion 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-li‐
           brary 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 con‐
       flicted with application names.

SEE ALSO         top

       curses(3X).

COLOPHON         top

       This page is part of the ncurses (new curses) project.  Informa‐
       tion about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
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                                                          curs_trace(3X)