wget/src/progress.c

/* Download progress.
   Copyright (C) 2001, 2002 Free Software Foundation, Inc.

This file is part of GNU Wget.

GNU Wget is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

GNU Wget is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Wget; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

In addition, as a special exception, the Free Software Foundation
gives permission to link the code of its release of Wget with the
OpenSSL project's "OpenSSL" library (or with modified versions of it
that use the same license as the "OpenSSL" library), and distribute
the linked executables.  You must obey the GNU General Public License
in all respects for all of the code used other than "OpenSSL".  If you
modify this file, you may extend this exception to your version of the
file, but you are not obligated to do so.  If you do not wish to do
so, delete this exception statement from your version.  */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif /* HAVE_STRING_H */
#include <assert.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#ifdef HAVE_SIGNAL_H
# include <signal.h>
#endif

#include "wget.h"
#include "progress.h"
#include "utils.h"
#include "retr.h"

struct progress_implementation {
  char *name;
  void *(*create) PARAMS ((long, long));
  void (*update) PARAMS ((void *, long, double));
  void (*finish) PARAMS ((void *, double));
  void (*set_params) PARAMS ((const char *));
};

/* Necessary forward declarations. */

static void *dot_create PARAMS ((long, long));
static void dot_update PARAMS ((void *, long, double));
static void dot_finish PARAMS ((void *, double));
static void dot_set_params PARAMS ((const char *));

static void *bar_create PARAMS ((long, long));
static void bar_update PARAMS ((void *, long, double));
static void bar_finish PARAMS ((void *, double));
static void bar_set_params PARAMS ((const char *));

static struct progress_implementation implementations[] = {
  { "dot", dot_create, dot_update, dot_finish, dot_set_params },
  { "bar", bar_create, bar_update, bar_finish, bar_set_params }
};
static struct progress_implementation *current_impl;
static int current_impl_locked;

/* Progress implementation used by default.  Can be overriden in
   wgetrc or by the fallback one.  */

#define DEFAULT_PROGRESS_IMPLEMENTATION "bar"

/* Fallnback progress implementation should be something that works
   under all display types.  If you put something other than "dot"
   here, remember that bar_set_params tries to switch to this if we're
   not running on a TTY.  So changing this to "bar" could cause
   infloop.  */

#define FALLBACK_PROGRESS_IMPLEMENTATION "dot"

/* Return non-zero if NAME names a valid progress bar implementation.
   The characters after the first : will be ignored.  */

int
valid_progress_implementation_p (const char *name)
{
  int i = 0;
  struct progress_implementation *pi = implementations;
  char *colon = strchr (name, ':');
  int namelen = colon ? colon - name : strlen (name);

  for (i = 0; i < ARRAY_SIZE (implementations); i++, pi++)
    if (!strncmp (pi->name, name, namelen))
      return 1;
  return 0;
}

/* Set the progress implementation to NAME.  */

void
set_progress_implementation (const char *name)
{
  int i, namelen;
  struct progress_implementation *pi = implementations;
  char *colon;

  if (!name)
    name = DEFAULT_PROGRESS_IMPLEMENTATION;

  colon = strchr (name, ':');
  namelen = colon ? colon - name : strlen (name);

  for (i = 0; i < ARRAY_SIZE (implementations); i++, pi++)
    if (!strncmp (pi->name, name, namelen))
      {
	current_impl = pi;
	current_impl_locked = 0;

	if (colon)
	  /* We call pi->set_params even if colon is NULL because we
	     want to give the implementation a chance to set up some
	     things it needs to run.  */
	  ++colon;

	if (pi->set_params)
	  pi->set_params (colon);
	return;
      }
  abort ();
}

static int output_redirected;

void
progress_schedule_redirect (void)
{
  output_redirected = 1;
}

/* Create a progress gauge.  INITIAL is the number of bytes the
   download starts from (zero if the download starts from scratch).
   TOTAL is the expected total number of bytes in this download.  If
   TOTAL is zero, it means that the download size is not known in
   advance.  */

void *
progress_create (long initial, long total)
{
  /* Check if the log status has changed under our feet. */
  if (output_redirected)
    {
      if (!current_impl_locked)
	set_progress_implementation (FALLBACK_PROGRESS_IMPLEMENTATION);
      output_redirected = 0;
    }

  return current_impl->create (initial, total);
}

/* Inform the progress gauge of newly received bytes.  DLTIME is the
   time in milliseconds since the beginning of the download.  */

void
progress_update (void *progress, long howmuch, double dltime)
{
  current_impl->update (progress, howmuch, dltime);
}

/* Tell the progress gauge to clean up.  Calling this will free the
   PROGRESS object, the further use of which is not allowed.  */

void
progress_finish (void *progress, double dltime)
{
  current_impl->finish (progress, dltime);
}

/* Dot-printing. */

struct dot_progress {
  long initial_length;		/* how many bytes have been downloaded
				   previously. */
  long total_length;		/* expected total byte count when the
				   download finishes */

  int accumulated;

  int rows;			/* number of rows printed so far */
  int dots;			/* number of dots printed in this row */
  double last_timer_value;
};

/* Dot-progress backend for progress_create. */

static void *
dot_create (long initial, long total)
{
  struct dot_progress *dp = xmalloc (sizeof (struct dot_progress));

  memset (dp, 0, sizeof (*dp));

  dp->initial_length = initial;
  dp->total_length   = total;

  if (dp->initial_length)
    {
      int dot_bytes = opt.dot_bytes;
      long row_bytes = opt.dot_bytes * opt.dots_in_line;

      int remainder = (int) (dp->initial_length % row_bytes);
      long skipped = dp->initial_length - remainder;

      if (skipped)
	{
	  int skipped_k = (int) (skipped / 1024); /* skipped amount in K */
	  int skipped_k_len = numdigit (skipped_k);
	  if (skipped_k_len < 5)
	    skipped_k_len = 5;

	  /* Align the [ skipping ... ] line with the dots.  To do
	     that, insert the number of spaces equal to the number of
	     digits in the skipped amount in K.  */
	  logprintf (LOG_VERBOSE, _("\n%*s[ skipping %dK ]"),
		     2 + skipped_k_len, "", skipped_k);
	}

      logprintf (LOG_VERBOSE, "\n%5ldK", skipped / 1024);
      for (; remainder >= dot_bytes; remainder -= dot_bytes)
	{
	  if (dp->dots % opt.dot_spacing == 0)
	    logputs (LOG_VERBOSE, " ");
	  logputs (LOG_VERBOSE, ",");
	  ++dp->dots;
	}
      assert (dp->dots < opt.dots_in_line);

      dp->accumulated = remainder;
      dp->rows = skipped / row_bytes;
    }

  return dp;
}

static void
print_percentage (long bytes, long expected)
{
  int percentage = (int)(100.0 * bytes / expected);
  logprintf (LOG_VERBOSE, "%3d%%", percentage);
}

static void
print_download_speed (struct dot_progress *dp, long bytes, double dltime)
{
  logprintf (LOG_VERBOSE, " %s",
	     retr_rate (bytes, dltime - dp->last_timer_value, 1));
  dp->last_timer_value = dltime;
}

/* Dot-progress backend for progress_update. */

static void
dot_update (void *progress, long howmuch, double dltime)
{
  struct dot_progress *dp = progress;
  int dot_bytes = opt.dot_bytes;
  long row_bytes = opt.dot_bytes * opt.dots_in_line;

  log_set_flush (0);

  dp->accumulated += howmuch;
  for (; dp->accumulated >= dot_bytes; dp->accumulated -= dot_bytes)
    {
      if (dp->dots == 0)
	logprintf (LOG_VERBOSE, "\n%5ldK", dp->rows * row_bytes / 1024);

      if (dp->dots % opt.dot_spacing == 0)
	logputs (LOG_VERBOSE, " ");
      logputs (LOG_VERBOSE, ".");

      ++dp->dots;
      if (dp->dots >= opt.dots_in_line)
	{
	  long row_qty = row_bytes;
	  if (dp->rows == dp->initial_length / row_bytes)
	    row_qty -= dp->initial_length % row_bytes;

	  ++dp->rows;
	  dp->dots = 0;

	  if (dp->total_length)
	    print_percentage (dp->rows * row_bytes, dp->total_length);
	  print_download_speed (dp, row_qty, dltime);
	}
    }

  log_set_flush (1);
}

/* Dot-progress backend for progress_finish. */

static void
dot_finish (void *progress, double dltime)
{
  struct dot_progress *dp = progress;
  int dot_bytes = opt.dot_bytes;
  long row_bytes = opt.dot_bytes * opt.dots_in_line;
  int i;

  log_set_flush (0);

  if (dp->dots == 0)
    logprintf (LOG_VERBOSE, "\n%5ldK", dp->rows * row_bytes / 1024);
  for (i = dp->dots; i < opt.dots_in_line; i++)
    {
      if (i % opt.dot_spacing == 0)
	logputs (LOG_VERBOSE, " ");
      logputs (LOG_VERBOSE, " ");
    }
  if (dp->total_length)
    {
      print_percentage (dp->rows * row_bytes
			+ dp->dots * dot_bytes
			+ dp->accumulated,
			dp->total_length);
    }

  {
    long row_qty = dp->dots * dot_bytes + dp->accumulated;
    if (dp->rows == dp->initial_length / row_bytes)
      row_qty -= dp->initial_length % row_bytes;
    print_download_speed (dp, row_qty, dltime);
  }

  logputs (LOG_VERBOSE, "\n\n");
  log_set_flush (0);

  xfree (dp);
}

/* This function interprets the progress "parameters".  For example,
   if Wget is invoked with --progress=dot:mega, it will set the
   "dot-style" to "mega".  Valid styles are default, binary, mega, and
   giga.  */

static void
dot_set_params (const char *params)
{
  if (!params || !*params)
    params = opt.dot_style;

  if (!params)
    return;

  /* We use this to set the retrieval style.  */
  if (!strcasecmp (params, "default"))
    {
      /* Default style: 1K dots, 10 dots in a cluster, 50 dots in a
	 line.  */
      opt.dot_bytes = 1024;
      opt.dot_spacing = 10;
      opt.dots_in_line = 50;
    }
  else if (!strcasecmp (params, "binary"))
    {
      /* "Binary" retrieval: 8K dots, 16 dots in a cluster, 48 dots
	 (384K) in a line.  */
      opt.dot_bytes = 8192;
      opt.dot_spacing = 16;
      opt.dots_in_line = 48;
    }
  else if (!strcasecmp (params, "mega"))
    {
      /* "Mega" retrieval, for retrieving very long files; each dot is
	 64K, 8 dots in a cluster, 6 clusters (3M) in a line.  */
      opt.dot_bytes = 65536L;
      opt.dot_spacing = 8;
      opt.dots_in_line = 48;
    }
  else if (!strcasecmp (params, "giga"))
    {
      /* "Giga" retrieval, for retrieving very very *very* long files;
	 each dot is 1M, 8 dots in a cluster, 4 clusters (32M) in a
	 line.  */
      opt.dot_bytes = (1L << 20);
      opt.dot_spacing = 8;
      opt.dots_in_line = 32;
    }
  else
    fprintf (stderr,
	     _("Invalid dot style specification `%s'; leaving unchanged.\n"),
	     params);
}

/* "Thermometer" (bar) progress. */

/* Assumed screen width if we can't find the real value.  */
#define DEFAULT_SCREEN_WIDTH 80

/* Minimum screen width we'll try to work with.  If this is too small,
   create_image will overflow the buffer.  */
#define MINIMUM_SCREEN_WIDTH 45

static int screen_width = DEFAULT_SCREEN_WIDTH;

/* Size of the download speed history ring. */
#define DLSPEED_HISTORY_SIZE 30

/* The minimum time length of a history sample.  By default, each
   sample is at least 100ms long, which means that, over the course of
   30 samples, "current" download speed spans at least 3s into the
   past.  */
#define DLSPEED_SAMPLE_MIN 100

struct bar_progress {
  long initial_length;		/* how many bytes have been downloaded
				   previously. */
  long total_length;		/* expected total byte count when the
				   download finishes */
  long count;			/* bytes downloaded so far */

  double last_screen_update;	/* time of the last screen update,
				   measured since the beginning of
				   download. */

  int width;			/* screen width we're using at the
				   time the progress gauge was
				   created.  this is different from
				   the screen_width global variable in
				   that the latter can be changed by a
				   signal. */
  char *buffer;			/* buffer where the bar "image" is
				   stored. */
  int tick;			/* counter used for drawing the
				   progress bar where the total size
				   is not known. */

  /* The following variables (kept in a struct for namespace reasons)
     keep track of recent download speeds.  See bar_update() for
     details.  */
  struct bar_progress_hist {
    int pos;
    long times[DLSPEED_HISTORY_SIZE];
    long bytes[DLSPEED_HISTORY_SIZE];

    /* The sum of times and bytes respectively, maintained for
       efficiency. */
    long total_time;
    long total_bytes;
  } hist;

  double recent_start;		/* timestamp of beginning of current
				   position. */
  long recent_bytes;		/* bytes downloaded so far. */

  /* create_image() uses these to make sure that ETA information
     doesn't flash. */
  double last_eta_time;		/* time of the last update to download
				   speed and ETA, measured since the
				   beginning of download. */
  long last_eta_value;
};

static void create_image PARAMS ((struct bar_progress *, double));
static void display_image PARAMS ((char *));

static void *
bar_create (long initial, long total)
{
  struct bar_progress *bp = xmalloc (sizeof (struct bar_progress));

  memset (bp, 0, sizeof (*bp));

  /* In theory, our callers should take care of this pathological
     case, but it can sometimes happen. */
  if (initial > total)
    total = initial;

  bp->initial_length = initial;
  bp->total_length   = total;

  /* - 1 because we don't want to use the last screen column. */
  bp->width = screen_width - 1;
  /* + 1 for the terminating zero. */
  bp->buffer = xmalloc (bp->width + 1);

  logputs (LOG_VERBOSE, "\n");

  create_image (bp, 0);
  display_image (bp->buffer);

  return bp;
}

static void update_speed_ring PARAMS ((struct bar_progress *, long, double));

static void
bar_update (void *progress, long howmuch, double dltime)
{
  struct bar_progress *bp = progress;
  int force_screen_update = 0;

  bp->count += howmuch;
  if (bp->total_length > 0
      && bp->count + bp->initial_length > bp->total_length)
    /* We could be downloading more than total_length, e.g. when the
       server sends an incorrect Content-Length header.  In that case,
       adjust bp->total_length to the new reality, so that the code in
       create_image() that depends on total size being smaller or
       equal to the expected size doesn't abort.  */
    bp->total_length = bp->initial_length + bp->count;

  update_speed_ring (bp, howmuch, dltime);

  if (screen_width - 1 != bp->width)
    {
      bp->width = screen_width - 1;
      bp->buffer = xrealloc (bp->buffer, bp->width + 1);
      force_screen_update = 1;
    }

  if (dltime - bp->last_screen_update < 200 && !force_screen_update)
    /* Don't update more often than five times per second. */
    return;

  create_image (bp, dltime);
  display_image (bp->buffer);
  bp->last_screen_update = dltime;
}

static void
bar_finish (void *progress, double dltime)
{
  struct bar_progress *bp = progress;

  if (bp->total_length > 0
      && bp->count + bp->initial_length > bp->total_length)
    /* See bar_update() for explanation. */
    bp->total_length = bp->initial_length + bp->count;

  create_image (bp, dltime);
  display_image (bp->buffer);

  logputs (LOG_VERBOSE, "\n\n");

  xfree (bp->buffer);
  xfree (bp);
}

/* This code attempts to maintain the notion of a "current" download
   speed, over the course of no less than 3s.  (Shorter intervals
   produce very erratic results.)

   To do so, it samples the speed in 0.1s intervals and stores the
   recorded samples in a FIFO history ring.  The ring stores no more
   than 30 intervals, hence the history covers the period of at least
   three seconds and at most 30 reads into the past.  This method
   should produce good results for both very fast and very slow
   downloads.

   The idea is that for fast downloads, we get the speed over exactly
   the last three seconds.  For slow downloads (where a network read
   takes more than 0.1s to complete), we get the speed over a larger
   time period, as large as it takes to complete thirty reads.  This
   is good because slow downloads tend to fluctuate more and a
   3-second average would be very erratic.  */

static void
update_speed_ring (struct bar_progress *bp, long howmuch, double dltime)
{
  struct bar_progress_hist *hist = &bp->hist;
  double recent_age = dltime - bp->recent_start;

  /* Update the download count. */
  bp->recent_bytes += howmuch;

  /* For very small time intervals, we return after having updated the
     "recent" download count.  When its age reaches or exceeds minimum
     sample time, it will be recorded in the history ring.  */
  if (recent_age < DLSPEED_SAMPLE_MIN)
    return;

  /* Store "recent" bytes and download time to history ring at the
     position POS.  */

  /* To correctly maintain the totals, first invalidate existing data
     (least recent in time) at this position. */
  hist->total_time  -= hist->times[hist->pos];
  hist->total_bytes -= hist->bytes[hist->pos];

  /* Now store the new data and update the totals. */
  hist->times[hist->pos] = recent_age;
  hist->bytes[hist->pos] = bp->recent_bytes;
  hist->total_time  += recent_age;
  hist->total_bytes += bp->recent_bytes;

  /* Start a new "recent" period. */
  bp->recent_start = dltime;
  bp->recent_bytes = 0;

  /* Advance the current ring position. */
  if (++hist->pos == DLSPEED_HISTORY_SIZE)
    hist->pos = 0;

#if 0
  /* Sledgehammer check to verify that the totals are accurate. */
  {
    int i;
    double sumt = 0, sumb = 0;
    for (i = 0; i < DLSPEED_HISTORY_SIZE; i++)
      {
	sumt += hist->times[i];
	sumb += hist->bytes[i];
      }
    assert (sumt == hist->total_time);
    assert (sumb == hist->total_bytes);
  }
#endif
}

#define APPEND_LITERAL(s) do {			\
  memcpy (p, s, sizeof (s) - 1);		\
  p += sizeof (s) - 1;				\
} while (0)

#ifndef MAX
# define MAX(a, b) ((a) >= (b) ? (a) : (b))
#endif

static void
create_image (struct bar_progress *bp, double dl_total_time)
{
  char *p = bp->buffer;
  long size = bp->initial_length + bp->count;

  char *size_legible = legible (size);
  int size_legible_len = strlen (size_legible);

  struct bar_progress_hist *hist = &bp->hist;

  /* The progress bar should look like this:
     xx% [=======>             ] nn,nnn 12.34K/s ETA 00:00

     Calculate the geometry.  The idea is to assign as much room as
     possible to the progress bar.  The other idea is to never let
     things "jitter", i.e. pad elements that vary in size so that
     their variance does not affect the placement of other elements.
     It would be especially bad for the progress bar to be resized
     randomly.

     "xx% " or "100%"  - percentage               - 4 chars
     "[]"              - progress bar decorations - 2 chars
     " nnn,nnn,nnn"    - downloaded bytes         - 12 chars or very rarely more
     " 1012.56K/s"     - dl rate                  - 11 chars
     " ETA xx:xx:xx"   - ETA                      - 13 chars

     "=====>..."       - progress bar             - the rest
  */
  int dlbytes_size = 1 + MAX (size_legible_len, 11);
  int progress_size = bp->width - (4 + 2 + dlbytes_size + 11 + 13);

  if (progress_size < 5)
    progress_size = 0;

  /* "xx% " */
  if (bp->total_length > 0)
    {
      int percentage = (int)(100.0 * size / bp->total_length);

      assert (percentage <= 100);

      if (percentage < 100)
	sprintf (p, "%2d%% ", percentage);
      else
	strcpy (p, "100%");
      p += 4;
    }
  else
    APPEND_LITERAL ("    ");

  /* The progress bar: "[====>      ]" */
  if (progress_size && bp->total_length > 0)
    {
      double fraction = (double)size / bp->total_length;
      int dlsz = (int)(fraction * progress_size);
      char *begin;

      assert (dlsz <= progress_size);

      *p++ = '[';
      begin = p;

      if (dlsz > 0)
	{
	  /* Draw dlsz-1 '=' chars and one arrow char.  */
	  while (dlsz-- > 1)
	    *p++ = '=';
	  *p++ = '>';
	}

      while (p - begin < progress_size)
	*p++ = ' ';

      *p++ = ']';
    }
  else if (progress_size)
    {
      /* If we can't draw a real progress bar, then at least show
	 *something* to the user.  */
      int ind = bp->tick % (progress_size * 2 - 6);
      int i, pos;

      /* Make the star move in two directions. */
      if (ind < progress_size - 2)
	pos = ind + 1;
      else
	pos = progress_size - (ind - progress_size + 5);

      *p++ = '[';
      for (i = 0; i < progress_size; i++)
	{
	  if      (i == pos - 1) *p++ = '<';
	  else if (i == pos    ) *p++ = '=';
	  else if (i == pos + 1) *p++ = '>';
	  else
	    *p++ = ' ';
	}
      *p++ = ']';

      ++bp->tick;
    }

  /* " 234,567,890" */
  sprintf (p, " %-11s", legible (size));
  p += strlen (p);

  /* " 1012.45K/s" */
  if (hist->total_time && hist->total_bytes)
    {
      static char *short_units[] = { "B/s", "K/s", "M/s", "G/s" };
      int units = 0;
      long bytes = hist->total_bytes + bp->recent_bytes;
      double tm = hist->total_time + dl_total_time - bp->recent_start;
      double dlrate = calc_rate (bytes, tm, &units);
      sprintf (p, " %7.2f%s", dlrate, short_units[units]);
      p += strlen (p);
    }
  else
    APPEND_LITERAL ("   --.--K/s");

  /* " ETA xx:xx:xx" */
  if (bp->total_length > 0 && dl_total_time > 3000)
    {
      long eta;
      int eta_hrs, eta_min, eta_sec;

      /* Don't change the value of ETA more than approximately once
	 per second; doing so would cause flashing without providing
	 any value to the user. */
      if (dl_total_time - bp->last_eta_time < 900
	  && bp->last_eta_value != 0)
	eta = bp->last_eta_value;
      else
	{
	  /* Calculate ETA using the average download speed to predict
	     the future speed.  If you want to use a speed averaged
	     over a more recent period, replace dl_total_time with
	     hist->total_time and bp->count with hist->total_bytes.
	     I found that doing that results in a very jerky and
	     ultimately unreliable ETA.  */
	  double time_sofar = (double)dl_total_time / 1000;
	  long bytes_remaining = bp->total_length - size;
	  eta = (long) (time_sofar * bytes_remaining / bp->count);
	  bp->last_eta_value = eta;
	  bp->last_eta_time = dl_total_time;
	}

      eta_hrs = eta / 3600, eta %= 3600;
      eta_min = eta / 60,   eta %= 60;
      eta_sec = eta;

      if (eta_hrs > 99)
	goto no_eta;

      if (eta_hrs == 0)
	{
	  /* Hours not printed: pad with three spaces. */
	  APPEND_LITERAL ("   ");
	  sprintf (p, " ETA %02d:%02d", eta_min, eta_sec);
	}
      else
	{
	  if (eta_hrs < 10)
	    /* Hours printed with one digit: pad with one space. */
	    *p++ = ' ';
	  sprintf (p, " ETA %d:%02d:%02d", eta_hrs, eta_min, eta_sec);
	}
      p += strlen (p);
    }
  else if (bp->total_length > 0)
    {
    no_eta:
      APPEND_LITERAL ("             ");
    }

  assert (p - bp->buffer <= bp->width);

  while (p < bp->buffer + bp->width)
    *p++ = ' ';
  *p = '\0';
}

/* Print the contents of the buffer as a one-line ASCII "image" so
   that it can be overwritten next time.  */

static void
display_image (char *buf)
{
  int old = log_set_save_context (0);
  logputs (LOG_VERBOSE, "\r");
  logputs (LOG_VERBOSE, buf);
  log_set_save_context (old);
}

static void
bar_set_params (const char *params)
{
  int sw;
  char *term = getenv ("TERM");

  if (params
      && 0 == strcmp (params, "force"))
    current_impl_locked = 1;

  if ((opt.lfilename
#ifdef HAVE_ISATTY
       /* The progress bar doesn't make sense if the output is not a
	  TTY -- when logging to file, it is better to review the
	  dots.  */
       || !isatty (fileno (stderr))
#else
       1
#endif
       /* Normally we don't depend on terminal type because the
	  progress bar only uses ^M to move the cursor to the
	  beginning of line, which works even on dumb terminals.  But
	  Jamie Zawinski reports that ^M and ^H tricks don't work in
	  Emacs shell buffers, and only make a mess.  */
       || (term && 0 == strcmp (term, "emacs"))
       )
      && !current_impl_locked)
    {
      /* We're not printing to a TTY, so revert to the fallback
	 display.  #### We're recursively calling
	 set_progress_implementation here, which is slightly kludgy.
	 It would be nicer if we provided that function a return value
	 indicating a failure of some sort.  */
      set_progress_implementation (FALLBACK_PROGRESS_IMPLEMENTATION);
      return;
    }

  sw = determine_screen_width ();
  if (sw && sw >= MINIMUM_SCREEN_WIDTH)
    screen_width = sw;
}

#ifdef SIGWINCH
RETSIGTYPE
progress_handle_sigwinch (int sig)
{
  int sw = determine_screen_width ();
  if (sw && sw >= MINIMUM_SCREEN_WIDTH)
    screen_width = sw;
  signal (SIGWINCH, progress_handle_sigwinch);
}
#endif