Bash-4.3 distribution sources and documentation

[platform/upstream/bash.git] / lib / readline / display.c

/* display.c -- readline redisplay facility. */

/* Copyright (C) 1987-2013 Free Software Foundation, Inc.

   This file is part of the GNU Readline Library (Readline), a library    
   for reading lines of text with interactive input and history editing.

   Readline 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 3 of the License, or
   (at your option) any later version.

   Readline 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 Readline.  If not, see <http://www.gnu.org/licenses/>.
*/

#define READLINE_LIBRARY

#if defined (HAVE_CONFIG_H)
#  include <config.h>
#endif

#include <sys/types.h>

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif /* HAVE_UNISTD_H */

#include "posixstat.h"

#if defined (HAVE_STDLIB_H)
#  include <stdlib.h>
#else
#  include "ansi_stdlib.h"
#endif /* HAVE_STDLIB_H */

#include <stdio.h>

#ifdef __MSDOS__
#  include <pc.h>
#endif

/* System-specific feature definitions and include files. */
#include "rldefs.h"
#include "rlmbutil.h"

/* Termcap library stuff. */
#include "tcap.h"

/* Some standard library routines. */
#include "readline.h"
#include "history.h"

#include "rlprivate.h"
#include "xmalloc.h"

#if !defined (strchr) && !defined (__STDC__)
extern char *strchr (), *strrchr ();
#endif /* !strchr && !__STDC__ */

static void update_line PARAMS((char *, char *, int, int, int, int));
static void space_to_eol PARAMS((int));
static void delete_chars PARAMS((int));
static void insert_some_chars PARAMS((char *, int, int));
static void open_some_spaces PARAMS((int));
static void cr PARAMS((void));

/* State of visible and invisible lines. */
struct line_state
  {
    char *line;
    int *lbreaks;
    int lbsize;
#if defined (HANDLE_MULTIBYTE)
    int *wrapped_line;
    int wbsize;
#endif
  };

/* The line display buffers.  One is the line currently displayed on
   the screen.  The other is the line about to be displayed. */
static struct line_state line_state_array[2];
static struct line_state *line_state_visible = &line_state_array[0];
static struct line_state *line_state_invisible = &line_state_array[1];
static int line_structures_initialized = 0;

/* Backwards-compatible names. */
#define inv_lbreaks     (line_state_invisible->lbreaks)
#define inv_lbsize      (line_state_invisible->lbsize)
#define vis_lbreaks     (line_state_visible->lbreaks)
#define vis_lbsize      (line_state_visible->lbsize)

#define visible_line    (line_state_visible->line)
#define invisible_line  (line_state_invisible->line)

#if defined (HANDLE_MULTIBYTE)
static int _rl_col_width PARAMS((const char *, int, int, int));
#else
#  define _rl_col_width(l, s, e, f)     (((e) <= (s)) ? 0 : (e) - (s))
#endif

/* Heuristic used to decide whether it is faster to move from CUR to NEW
   by backing up or outputting a carriage return and moving forward.  CUR
   and NEW are either both buffer positions or absolute screen positions. */
#define CR_FASTER(new, cur) (((new) + 1) < ((cur) - (new)))

/* _rl_last_c_pos is an absolute cursor position in multibyte locales and a
   buffer index in others.  This macro is used when deciding whether the
   current cursor position is in the middle of a prompt string containing
   invisible characters.  XXX - might need to take `modmark' into account. */
#define PROMPT_ENDING_INDEX \
  ((MB_CUR_MAX > 1 && rl_byte_oriented == 0) ? prompt_physical_chars : prompt_last_invisible+1)
  

/* **************************************************************** */
/*                                                                  */
/*                      Display stuff                               */
/*                                                                  */
/* **************************************************************** */

/* This is the stuff that is hard for me.  I never seem to write good
   display routines in C.  Let's see how I do this time. */

/* (PWP) Well... Good for a simple line updater, but totally ignores
   the problems of input lines longer than the screen width.

   update_line and the code that calls it makes a multiple line,
   automatically wrapping line update.  Careful attention needs
   to be paid to the vertical position variables. */

/* Keep two buffers; one which reflects the current contents of the
   screen, and the other to draw what we think the new contents should
   be.  Then compare the buffers, and make whatever changes to the
   screen itself that we should.  Finally, make the buffer that we
   just drew into be the one which reflects the current contents of the
   screen, and place the cursor where it belongs.

   Commands that want to can fix the display themselves, and then let
   this function know that the display has been fixed by setting the
   RL_DISPLAY_FIXED variable.  This is good for efficiency. */

/* Application-specific redisplay function. */
rl_voidfunc_t *rl_redisplay_function = rl_redisplay;

/* Global variables declared here. */
/* What YOU turn on when you have handled all redisplay yourself. */
int rl_display_fixed = 0;

int _rl_suppress_redisplay = 0;
int _rl_want_redisplay = 0;

/* The stuff that gets printed out before the actual text of the line.
   This is usually pointing to rl_prompt. */
char *rl_display_prompt = (char *)NULL;

/* Pseudo-global variables declared here. */

/* The visible cursor position.  If you print some text, adjust this. */
/* NOTE: _rl_last_c_pos is used as a buffer index when not in a locale
   supporting multibyte characters, and an absolute cursor position when
   in such a locale.  This is an artifact of the donated multibyte support.
   Care must be taken when modifying its value. */
int _rl_last_c_pos = 0;
int _rl_last_v_pos = 0;

static int cpos_adjusted;
static int cpos_buffer_position;
static int displaying_prompt_first_line;
static int prompt_multibyte_chars;

/* Number of lines currently on screen minus 1. */
int _rl_vis_botlin = 0;

/* Variables used only in this file. */
/* The last left edge of text that was displayed.  This is used when
   doing horizontal scrolling.  It shifts in thirds of a screenwidth. */
static int last_lmargin;

/* A buffer for `modeline' messages. */
static char *msg_buf = 0;
static int msg_bufsiz = 0;

/* Non-zero forces the redisplay even if we thought it was unnecessary. */
static int forced_display;

/* Default and initial buffer size.  Can grow. */
static int line_size = 1024;

/* Variables to keep track of the expanded prompt string, which may
   include invisible characters. */

static char *local_prompt, *local_prompt_prefix;
static int local_prompt_len;
static int prompt_visible_length, prompt_prefix_length;

/* The number of invisible characters in the line currently being
   displayed on the screen. */
static int visible_wrap_offset;

/* The number of invisible characters in the prompt string.  Static so it
   can be shared between rl_redisplay and update_line */
static int wrap_offset;

/* The index of the last invisible character in the prompt string. */
static int prompt_last_invisible;

/* The length (buffer offset) of the first line of the last (possibly
   multi-line) buffer displayed on the screen. */
static int visible_first_line_len;

/* Number of invisible characters on the first physical line of the prompt.
   Only valid when the number of physical characters in the prompt exceeds
   (or is equal to) _rl_screenwidth. */
static int prompt_invis_chars_first_line;

static int prompt_last_screen_line;

static int prompt_physical_chars;

/* set to a non-zero value by rl_redisplay if we are marking modified history
   lines and the current line is so marked. */
static int modmark;

/* Variables to save and restore prompt and display information. */

/* These are getting numerous enough that it's time to create a struct. */

static char *saved_local_prompt;
static char *saved_local_prefix;
static int saved_last_invisible;
static int saved_visible_length;
static int saved_prefix_length;
static int saved_local_length;
static int saved_invis_chars_first_line;
static int saved_physical_chars;

/* Return a character indicating the editing mode, for use in the prompt. */
static int
prompt_modechar ()
{
  if (rl_editing_mode == emacs_mode)
    return '@';
  else if (_rl_keymap == vi_insertion_keymap)
    return '+';         /* vi insert mode */
  else
    return ':';         /* vi command mode */
}

/* Expand the prompt string S and return the number of visible
   characters in *LP, if LP is not null.  This is currently more-or-less
   a placeholder for expansion.  LIP, if non-null is a place to store the
   index of the last invisible character in the returned string. NIFLP,
   if non-zero, is a place to store the number of invisible characters in
   the first prompt line.  The previous are used as byte counts -- indexes
   into a character buffer. */

/* Current implementation:
        \001 (^A) start non-visible characters
        \002 (^B) end non-visible characters
   all characters except \001 and \002 (following a \001) are copied to
   the returned string; all characters except those between \001 and
   \002 are assumed to be `visible'. */ 

static char *
expand_prompt (pmt, lp, lip, niflp, vlp)
     char *pmt;
     int *lp, *lip, *niflp, *vlp;
{
  char *r, *ret, *p, *igstart;
  int l, rl, last, ignoring, ninvis, invfl, invflset, ind, pind, physchars;

  /* Short-circuit if we can. */
  if ((MB_CUR_MAX <= 1 || rl_byte_oriented) && strchr (pmt, RL_PROMPT_START_IGNORE) == 0)
    {
      if (pmt == rl_prompt && _rl_show_mode_in_prompt)
        {
          l = strlen (pmt);
          r = (char *)xmalloc (l + 2);
          r[0] = prompt_modechar ();
          strcpy (r + 1, pmt);
        }
      else
        r = savestring (pmt);

      if (lp)
        *lp = strlen (r);
      if (lip)
        *lip = 0;
      if (niflp)
        *niflp = 0;
      if (vlp)
        *vlp = lp ? *lp : strlen (r);
      return r;
    }

  l = strlen (pmt);
  r = ret = (char *)xmalloc (l + 2);

  rl = physchars = 0;   /* move up here so mode show can set them */
  if (pmt == rl_prompt && _rl_show_mode_in_prompt)
    {
      *r++ = prompt_modechar ();
      rl = physchars = 1;
    }

  invfl = 0;    /* invisible chars in first line of prompt */
  invflset = 0; /* we only want to set invfl once */

  igstart = 0;
  for (ignoring = last = ninvis = 0, p = pmt; p && *p; p++)
    {
      /* This code strips the invisible character string markers
         RL_PROMPT_START_IGNORE and RL_PROMPT_END_IGNORE */
      if (ignoring == 0 && *p == RL_PROMPT_START_IGNORE)                /* XXX - check ignoring? */
        {
          ignoring = 1;
          igstart = p;
          continue;
        }
      else if (ignoring && *p == RL_PROMPT_END_IGNORE)
        {
          ignoring = 0;
          if (p != (igstart + 1))
            last = r - ret - 1;
          continue;
        }
      else
        {
#if defined (HANDLE_MULTIBYTE)
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            {
              pind = p - pmt;
              ind = _rl_find_next_mbchar (pmt, pind, 1, MB_FIND_NONZERO);
              l = ind - pind;
              while (l--)
                *r++ = *p++;
              if (!ignoring)
                {
                  /* rl ends up being assigned to prompt_visible_length,
                     which is the number of characters in the buffer that
                     contribute to characters on the screen, which might
                     not be the same as the number of physical characters
                     on the screen in the presence of multibyte characters */
                  rl += ind - pind;
                  physchars += _rl_col_width (pmt, pind, ind, 0);
                }
              else
                ninvis += ind - pind;
              p--;                      /* compensate for later increment */
            }
          else
#endif
            {
              *r++ = *p;
              if (!ignoring)
                {
                  rl++;                 /* visible length byte counter */
                  physchars++;
                }
              else
                ninvis++;               /* invisible chars byte counter */
            }

          if (invflset == 0 && rl >= _rl_screenwidth)
            {
              invfl = ninvis;
              invflset = 1;
            }
        }
    }

  if (rl < _rl_screenwidth)
    invfl = ninvis;

  *r = '\0';
  if (lp)
    *lp = rl;
  if (lip)
    *lip = last;
  if (niflp)
    *niflp = invfl;
  if  (vlp)
    *vlp = physchars;
  return ret;
}

/* Just strip out RL_PROMPT_START_IGNORE and RL_PROMPT_END_IGNORE from
   PMT and return the rest of PMT. */
char *
_rl_strip_prompt (pmt)
     char *pmt;
{
  char *ret;

  ret = expand_prompt (pmt, (int *)NULL, (int *)NULL, (int *)NULL, (int *)NULL);
  return ret;
}

void
_rl_reset_prompt ()
{
  rl_visible_prompt_length = rl_expand_prompt (rl_prompt);
}

/*
 * Expand the prompt string into the various display components, if
 * necessary.
 *
 * local_prompt = expanded last line of string in rl_display_prompt
 *                (portion after the final newline)
 * local_prompt_prefix = portion before last newline of rl_display_prompt,
 *                       expanded via expand_prompt
 * prompt_visible_length = number of visible characters in local_prompt
 * prompt_prefix_length = number of visible characters in local_prompt_prefix
 *
 * This function is called once per call to readline().  It may also be
 * called arbitrarily to expand the primary prompt.
 *
 * The return value is the number of visible characters on the last line
 * of the (possibly multi-line) prompt.
 */
int
rl_expand_prompt (prompt)
     char *prompt;
{
  char *p, *t;
  int c;

  /* Clear out any saved values. */
  FREE (local_prompt);
  FREE (local_prompt_prefix);

  local_prompt = local_prompt_prefix = (char *)0;
  local_prompt_len = 0;
  prompt_last_invisible = prompt_invis_chars_first_line = 0;
  prompt_visible_length = prompt_physical_chars = 0;

  if (prompt == 0 || *prompt == 0)
    return (0);

  p = strrchr (prompt, '\n');
  if (!p)
    {
      /* The prompt is only one logical line, though it might wrap. */
      local_prompt = expand_prompt (prompt, &prompt_visible_length,
                                            &prompt_last_invisible,
                                            &prompt_invis_chars_first_line,
                                            &prompt_physical_chars);
      local_prompt_prefix = (char *)0;
      local_prompt_len = local_prompt ? strlen (local_prompt) : 0;
      return (prompt_visible_length);
    }
  else
    {
      /* The prompt spans multiple lines. */
      t = ++p;
      local_prompt = expand_prompt (p, &prompt_visible_length,
                                       &prompt_last_invisible,
                                       &prompt_invis_chars_first_line,
                                       &prompt_physical_chars);
      c = *t; *t = '\0';
      /* The portion of the prompt string up to and including the
         final newline is now null-terminated. */
      local_prompt_prefix = expand_prompt (prompt, &prompt_prefix_length,
                                                   (int *)NULL,
                                                   (int *)NULL,
                                                   (int *)NULL);
      *t = c;
      local_prompt_len = local_prompt ? strlen (local_prompt) : 0;
      return (prompt_prefix_length);
    }
}

/* Initialize the VISIBLE_LINE and INVISIBLE_LINE arrays, and their associated
   arrays of line break markers.  MINSIZE is the minimum size of VISIBLE_LINE
   and INVISIBLE_LINE; if it is greater than LINE_SIZE, LINE_SIZE is
   increased.  If the lines have already been allocated, this ensures that
   they can hold at least MINSIZE characters. */
static void
init_line_structures (minsize)
      int minsize;
{
  register int n;

  if (invisible_line == 0)      /* initialize it */
    {
      if (line_size < minsize)
        line_size = minsize;
      visible_line = (char *)xmalloc (line_size);
      invisible_line = (char *)xmalloc (line_size);
    }
  else if (line_size < minsize) /* ensure it can hold MINSIZE chars */
    {
      line_size *= 2;
      if (line_size < minsize)
        line_size = minsize;
      visible_line = (char *)xrealloc (visible_line, line_size);
      invisible_line = (char *)xrealloc (invisible_line, line_size);
    }

  for (n = minsize; n < line_size; n++)
    {
      visible_line[n] = 0;
      invisible_line[n] = 1;
    }

  if (vis_lbreaks == 0)
    {
      /* should be enough. */
      inv_lbsize = vis_lbsize = 256;

#if defined (HANDLE_MULTIBYTE)
      line_state_visible->wbsize = vis_lbsize;
      line_state_visible->wrapped_line = (int *)xmalloc (line_state_visible->wbsize * sizeof (int));

      line_state_invisible->wbsize = inv_lbsize;
      line_state_invisible->wrapped_line = (int *)xmalloc (line_state_invisible->wbsize * sizeof (int));
#endif

      inv_lbreaks = (int *)xmalloc (inv_lbsize * sizeof (int));
      vis_lbreaks = (int *)xmalloc (vis_lbsize * sizeof (int));
      inv_lbreaks[0] = vis_lbreaks[0] = 0;
    }

  line_structures_initialized = 1;
}
  
/* Basic redisplay algorithm. */
void
rl_redisplay ()
{
  register int in, out, c, linenum, cursor_linenum;
  register char *line;
  int inv_botlin, lb_botlin, lb_linenum, o_cpos;
  int newlines, lpos, temp, n0, num, prompt_lines_estimate;
  char *prompt_this_line;
#if defined (HANDLE_MULTIBYTE)
  wchar_t wc;
  size_t wc_bytes;
  int wc_width;
  mbstate_t ps;
  int _rl_wrapped_multicolumn = 0;
#endif

  if (_rl_echoing_p == 0)
    return;

  /* Block keyboard interrupts because this function manipulates global
     data structures. */
  _rl_block_sigint ();  
  RL_SETSTATE (RL_STATE_REDISPLAYING);

  if (!rl_display_prompt)
    rl_display_prompt = "";

  if (line_structures_initialized == 0)
    {
      init_line_structures (0);
      rl_on_new_line ();
    }

  /* Draw the line into the buffer. */
  cpos_buffer_position = -1;

  prompt_multibyte_chars = prompt_visible_length - prompt_physical_chars;

  line = invisible_line;
  out = inv_botlin = 0;

  /* Mark the line as modified or not.  We only do this for history
     lines. */
  modmark = 0;
  if (_rl_mark_modified_lines && current_history () && rl_undo_list)
    {
      line[out++] = '*';
      line[out] = '\0';
      modmark = 1;
    }

  /* If someone thought that the redisplay was handled, but the currently
     visible line has a different modification state than the one about
     to become visible, then correct the caller's misconception. */
  if (visible_line[0] != invisible_line[0])
    rl_display_fixed = 0;

  /* If the prompt to be displayed is the `primary' readline prompt (the
     one passed to readline()), use the values we have already expanded.
     If not, use what's already in rl_display_prompt.  WRAP_OFFSET is the
     number of non-visible characters in the prompt string. */
  if (rl_display_prompt == rl_prompt || local_prompt)
    {
      if (local_prompt_prefix && forced_display)
        _rl_output_some_chars (local_prompt_prefix, strlen (local_prompt_prefix));

      if (local_prompt_len > 0)
        {
          temp = local_prompt_len + out + 2;
          if (temp >= line_size)
            {
              line_size = (temp + 1024) - (temp % 1024);
              visible_line = (char *)xrealloc (visible_line, line_size);
              line = invisible_line = (char *)xrealloc (invisible_line, line_size);
            }
          strncpy (line + out, local_prompt, local_prompt_len);
          out += local_prompt_len;
        }
      line[out] = '\0';
      wrap_offset = local_prompt_len - prompt_visible_length;
    }
  else
    {
      int pmtlen;
      prompt_this_line = strrchr (rl_display_prompt, '\n');
      if (!prompt_this_line)
        prompt_this_line = rl_display_prompt;
      else
        {
          prompt_this_line++;
          pmtlen = prompt_this_line - rl_display_prompt;        /* temp var */
          if (forced_display)
            {
              _rl_output_some_chars (rl_display_prompt, pmtlen);
              /* Make sure we are at column zero even after a newline,
                 regardless of the state of terminal output processing. */
              if (pmtlen < 2 || prompt_this_line[-2] != '\r')
                cr ();
            }
        }

      prompt_physical_chars = pmtlen = strlen (prompt_this_line);
      temp = pmtlen + out + 2;
      if (temp >= line_size)
        {
          line_size = (temp + 1024) - (temp % 1024);
          visible_line = (char *)xrealloc (visible_line, line_size);
          line = invisible_line = (char *)xrealloc (invisible_line, line_size);
        }
      strncpy (line + out,  prompt_this_line, pmtlen);
      out += pmtlen;
      line[out] = '\0';
      wrap_offset = prompt_invis_chars_first_line = 0;
    }

#define CHECK_INV_LBREAKS() \
      do { \
        if (newlines >= (inv_lbsize - 2)) \
          { \
            inv_lbsize *= 2; \
            inv_lbreaks = (int *)xrealloc (inv_lbreaks, inv_lbsize * sizeof (int)); \
          } \
      } while (0)

#if defined (HANDLE_MULTIBYTE)    
#define CHECK_LPOS() \
      do { \
        lpos++; \
        if (lpos >= _rl_screenwidth) \
          { \
            if (newlines >= (inv_lbsize - 2)) \
              { \
                inv_lbsize *= 2; \
                inv_lbreaks = (int *)xrealloc (inv_lbreaks, inv_lbsize * sizeof (int)); \
              } \
            inv_lbreaks[++newlines] = out; \
            if (newlines >= (line_state_invisible->wbsize - 1)) \
              { \
                line_state_invisible->wbsize *= 2; \
                line_state_invisible->wrapped_line = (int *)xrealloc (line_state_invisible->wrapped_line, line_state_invisible->wbsize * sizeof(int)); \
              } \
            line_state_invisible->wrapped_line[newlines] = _rl_wrapped_multicolumn; \
            lpos = 0; \
          } \
      } while (0)
#else
#define CHECK_LPOS() \
      do { \
        lpos++; \
        if (lpos >= _rl_screenwidth) \
          { \
            if (newlines >= (inv_lbsize - 2)) \
              { \
                inv_lbsize *= 2; \
                inv_lbreaks = (int *)xrealloc (inv_lbreaks, inv_lbsize * sizeof (int)); \
              } \
            inv_lbreaks[++newlines] = out; \
            lpos = 0; \
          } \
      } while (0)
#endif

  /* inv_lbreaks[i] is where line i starts in the buffer. */
  inv_lbreaks[newlines = 0] = 0;
  lpos = prompt_physical_chars + modmark;

#if defined (HANDLE_MULTIBYTE)
  memset (line_state_invisible->wrapped_line, 0, line_state_invisible->wbsize * sizeof (int));
  num = 0;
#endif

  /* prompt_invis_chars_first_line is the number of invisible characters in
     the first physical line of the prompt.
     wrap_offset - prompt_invis_chars_first_line is the number of invis
     chars on the second (or, more generally, last) line. */

  /* This is zero-based, used to set the newlines */
  prompt_lines_estimate = lpos / _rl_screenwidth;

  /* what if lpos is already >= _rl_screenwidth before we start drawing the
     contents of the command line? */
  while (lpos >= _rl_screenwidth)
    {
      int z;
      /* fix from Darin Johnson <darin@acuson.com> for prompt string with
         invisible characters that is longer than the screen width.  The
         prompt_invis_chars_first_line variable could be made into an array
         saying how many invisible characters there are per line, but that's
         probably too much work for the benefit gained.  How many people have
         prompts that exceed two physical lines?
         Additional logic fix from Edward Catmur <ed@catmur.co.uk> */
#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0 && prompt_multibyte_chars > 0)
        {
          n0 = num;
          temp = local_prompt_len;
          while (num < temp)
            {
              z = _rl_col_width  (local_prompt, n0, num, 1);
              if (z > _rl_screenwidth)
                {
                  num = _rl_find_prev_mbchar (local_prompt, num, MB_FIND_ANY);
                  break;
                }
              else if (z == _rl_screenwidth)
                break;
              num++;
            }
          temp = num;
        }
      else
#endif /* !HANDLE_MULTIBYTE */
        temp = ((newlines + 1) * _rl_screenwidth);

      /* Now account for invisible characters in the current line. */
      /* XXX - this assumes that the invisible characters may be split, but only
         between the first and the last lines. */
      temp += (newlines == 0) ? prompt_invis_chars_first_line
                              : ((newlines == prompt_lines_estimate) ? wrap_offset : prompt_invis_chars_first_line);

      inv_lbreaks[++newlines] = temp;
#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0 && prompt_multibyte_chars > 0)
        lpos -= _rl_col_width (local_prompt, n0, num, 1);
      else
#endif
        lpos -= _rl_screenwidth;
    }

  prompt_last_screen_line = newlines;

  /* Draw the rest of the line (after the prompt) into invisible_line, keeping
     track of where the cursor is (cpos_buffer_position), the number of the line containing
     the cursor (lb_linenum), the last line number (lb_botlin and inv_botlin).
     It maintains an array of line breaks for display (inv_lbreaks).
     This handles expanding tabs for display and displaying meta characters. */
  lb_linenum = 0;
#if defined (HANDLE_MULTIBYTE)
  in = 0;
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    {
      memset (&ps, 0, sizeof (mbstate_t));
      /* XXX - what if wc_bytes ends up <= 0? check for MB_INVALIDCH */
      wc_bytes = mbrtowc (&wc, rl_line_buffer, rl_end, &ps);
    }
  else
    wc_bytes = 1;
  while (in < rl_end)
#else
  for (in = 0; in < rl_end; in++)
#endif
    {
      c = (unsigned char)rl_line_buffer[in];

#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          if (MB_INVALIDCH (wc_bytes))
            {
              /* Byte sequence is invalid or shortened.  Assume that the
                 first byte represents a character. */
              wc_bytes = 1;
              /* Assume that a character occupies a single column. */
              wc_width = 1;
              memset (&ps, 0, sizeof (mbstate_t));
            }
          else if (MB_NULLWCH (wc_bytes))
            break;                      /* Found '\0' */
          else
            {
              temp = WCWIDTH (wc);
              wc_width = (temp >= 0) ? temp : 1;
            }
        }
#endif

      if (out + 8 >= line_size)         /* XXX - 8 for \t */
        {
          line_size *= 2;
          visible_line = (char *)xrealloc (visible_line, line_size);
          invisible_line = (char *)xrealloc (invisible_line, line_size);
          line = invisible_line;
        }

      if (in == rl_point)
        {
          cpos_buffer_position = out;
          lb_linenum = newlines;
        }

#if defined (HANDLE_MULTIBYTE)
      if (META_CHAR (c) && _rl_output_meta_chars == 0)  /* XXX - clean up */
#else
      if (META_CHAR (c))
#endif
        {
          if (_rl_output_meta_chars == 0)
            {
              sprintf (line + out, "\\%o", c);

              if (lpos + 4 >= _rl_screenwidth)
                {
                  temp = _rl_screenwidth - lpos;
                  CHECK_INV_LBREAKS ();
                  inv_lbreaks[++newlines] = out + temp;
                  lpos = 4 - temp;
                }
              else
                lpos += 4;

              out += 4;
            }
          else
            {
              line[out++] = c;
              CHECK_LPOS();
            }
        }
#if defined (DISPLAY_TABS)
      else if (c == '\t')
        {
          register int newout;

#if 0
          newout = (out | (int)7) + 1;
#else
          newout = out + 8 - lpos % 8;
#endif
          temp = newout - out;
          if (lpos + temp >= _rl_screenwidth)
            {
              register int temp2;
              temp2 = _rl_screenwidth - lpos;
              CHECK_INV_LBREAKS ();
              inv_lbreaks[++newlines] = out + temp2;
              lpos = temp - temp2;
              while (out < newout)
                line[out++] = ' ';
            }
          else
            {
              while (out < newout)
                line[out++] = ' ';
              lpos += temp;
            }
        }
#endif
      else if (c == '\n' && _rl_horizontal_scroll_mode == 0 && _rl_term_up && *_rl_term_up)
        {
          line[out++] = '\0';   /* XXX - sentinel */
          CHECK_INV_LBREAKS ();
          inv_lbreaks[++newlines] = out;
          lpos = 0;
        }
      else if (CTRL_CHAR (c) || c == RUBOUT)
        {
          line[out++] = '^';
          CHECK_LPOS();
          line[out++] = CTRL_CHAR (c) ? UNCTRL (c) : '?';
          CHECK_LPOS();
        }
      else
        {
#if defined (HANDLE_MULTIBYTE)
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            {
              register int i;

              _rl_wrapped_multicolumn = 0;

              if (_rl_screenwidth < lpos + wc_width)
                for (i = lpos; i < _rl_screenwidth; i++)
                  {
                    /* The space will be removed in update_line() */
                    line[out++] = ' ';
                    _rl_wrapped_multicolumn++;
                    CHECK_LPOS();
                  }
              if (in == rl_point)
                {
                  cpos_buffer_position = out;
                  lb_linenum = newlines;
                }
              for (i = in; i < in+wc_bytes; i++)
                line[out++] = rl_line_buffer[i];
              for (i = 0; i < wc_width; i++)
                CHECK_LPOS();
            }
          else
            {
              line[out++] = c;
              CHECK_LPOS();
            }
#else
          line[out++] = c;
          CHECK_LPOS();
#endif
        }

#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          in += wc_bytes;
          /* XXX - what if wc_bytes ends up <= 0? check for MB_INVALIDCH */
          wc_bytes = mbrtowc (&wc, rl_line_buffer + in, rl_end - in, &ps);
        }
      else
        in++;
#endif

    }
  line[out] = '\0';
  if (cpos_buffer_position < 0)
    {
      cpos_buffer_position = out;
      lb_linenum = newlines;
    }

  inv_botlin = lb_botlin = newlines;
  CHECK_INV_LBREAKS ();
  inv_lbreaks[newlines+1] = out;
  cursor_linenum = lb_linenum;

  /* CPOS_BUFFER_POSITION == position in buffer where cursor should be placed.
     CURSOR_LINENUM == line number where the cursor should be placed. */

  /* PWP: now is when things get a bit hairy.  The visible and invisible
     line buffers are really multiple lines, which would wrap every
     (screenwidth - 1) characters.  Go through each in turn, finding
     the changed region and updating it.  The line order is top to bottom. */

  /* If we can move the cursor up and down, then use multiple lines,
     otherwise, let long lines display in a single terminal line, and
     horizontally scroll it. */
  displaying_prompt_first_line = 1;
  if (_rl_horizontal_scroll_mode == 0 && _rl_term_up && *_rl_term_up)
    {
      int nleft, pos, changed_screen_line, tx;

      if (!rl_display_fixed || forced_display)
        {
          forced_display = 0;

          /* If we have more than a screenful of material to display, then
             only display a screenful.  We should display the last screen,
             not the first.  */
          if (out >= _rl_screenchars)
            {
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                out = _rl_find_prev_mbchar (line, _rl_screenchars, MB_FIND_ANY);
              else
                out = _rl_screenchars - 1;
            }

          /* The first line is at character position 0 in the buffer.  The
             second and subsequent lines start at inv_lbreaks[N], offset by
             OFFSET (which has already been calculated above).  */

#define INVIS_FIRST()   (prompt_physical_chars > _rl_screenwidth ? prompt_invis_chars_first_line : wrap_offset)
#define WRAP_OFFSET(line, offset)  ((line == 0) \
                                        ? (offset ? INVIS_FIRST() : 0) \
                                        : ((line == prompt_last_screen_line) ? wrap_offset-prompt_invis_chars_first_line : 0))
#define W_OFFSET(line, offset) ((line) == 0 ? offset : 0)
#define VIS_LLEN(l)     ((l) > _rl_vis_botlin ? 0 : (vis_lbreaks[l+1] - vis_lbreaks[l]))
#define INV_LLEN(l)     (inv_lbreaks[l+1] - inv_lbreaks[l])
#define VIS_CHARS(line) (visible_line + vis_lbreaks[line])
#define VIS_LINE(line) ((line) > _rl_vis_botlin) ? "" : VIS_CHARS(line)
#define INV_LINE(line) (invisible_line + inv_lbreaks[line])

#define OLD_CPOS_IN_PROMPT() (cpos_adjusted == 0 && \
                        _rl_last_c_pos != o_cpos && \
                        _rl_last_c_pos > wrap_offset && \
                        o_cpos < prompt_last_invisible)

          /* For each line in the buffer, do the updating display. */
          for (linenum = 0; linenum <= inv_botlin; linenum++)
            {
              /* This can lead us astray if we execute a program that changes
                 the locale from a non-multibyte to a multibyte one. */
              o_cpos = _rl_last_c_pos;
              cpos_adjusted = 0;
              update_line (VIS_LINE(linenum), INV_LINE(linenum), linenum,
                           VIS_LLEN(linenum), INV_LLEN(linenum), inv_botlin);

              /* update_line potentially changes _rl_last_c_pos, but doesn't
                 take invisible characters into account, since _rl_last_c_pos
                 is an absolute cursor position in a multibyte locale.  See
                 if compensating here is the right thing, or if we have to
                 change update_line itself.  There are several cases in which
                 update_line adjusts _rl_last_c_pos itself (so it can pass
                 _rl_move_cursor_relative accurate values); it communicates
                 this back by setting cpos_adjusted.  If we assume that
                 _rl_last_c_pos is correct (an absolute cursor position) each
                 time update_line is called, then we can assume in our
                 calculations that o_cpos does not need to be adjusted by
                 wrap_offset. */
              if (linenum == 0 && (MB_CUR_MAX > 1 && rl_byte_oriented == 0) && OLD_CPOS_IN_PROMPT())
                _rl_last_c_pos -= prompt_invis_chars_first_line;        /* XXX - was wrap_offset */
              else if (linenum == prompt_last_screen_line && prompt_physical_chars > _rl_screenwidth &&
                        (MB_CUR_MAX > 1 && rl_byte_oriented == 0) &&
                        cpos_adjusted == 0 &&
                        _rl_last_c_pos != o_cpos &&
                        _rl_last_c_pos > (prompt_last_invisible - _rl_screenwidth - prompt_invis_chars_first_line))
                _rl_last_c_pos -= (wrap_offset-prompt_invis_chars_first_line);
                  
              /* If this is the line with the prompt, we might need to
                 compensate for invisible characters in the new line. Do
                 this only if there is not more than one new line (which
                 implies that we completely overwrite the old visible line)
                 and the new line is shorter than the old.  Make sure we are
                 at the end of the new line before clearing. */
              if (linenum == 0 &&
                  inv_botlin == 0 && _rl_last_c_pos == out &&
                  (wrap_offset > visible_wrap_offset) &&
                  (_rl_last_c_pos < visible_first_line_len))
                {
                  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                    nleft = _rl_screenwidth - _rl_last_c_pos;
                  else
                    nleft = _rl_screenwidth + wrap_offset - _rl_last_c_pos;
                  if (nleft)
                    _rl_clear_to_eol (nleft);
                }
#if 0
              /* This segment is intended to handle the case where the prompt
                 has invisible characters on the second line and the new line
                 to be displayed needs to clear the rest of the old characters
                 out (e.g., when printing the i-search prompt).  In general,
                 the case of the new line being shorter than the old.
                 Incomplete */
              else if (linenum == prompt_last_screen_line &&
                       prompt_physical_chars > _rl_screenwidth &&
                       wrap_offset != prompt_invis_chars_first_line &&
                       _rl_last_c_pos == out &&
#endif


              /* Since the new first line is now visible, save its length. */
              if (linenum == 0)
                visible_first_line_len = (inv_botlin > 0) ? inv_lbreaks[1] : out - wrap_offset;
            }

          /* We may have deleted some lines.  If so, clear the left over
             blank ones at the bottom out. */
          if (_rl_vis_botlin > inv_botlin)
            {
              char *tt;
              for (; linenum <= _rl_vis_botlin; linenum++)
                {
                  tt = VIS_CHARS (linenum);
                  _rl_move_vert (linenum);
                  _rl_move_cursor_relative (0, tt);
                  _rl_clear_to_eol
                    ((linenum == _rl_vis_botlin) ? strlen (tt) : _rl_screenwidth);
                }
            }
          _rl_vis_botlin = inv_botlin;

          /* CHANGED_SCREEN_LINE is set to 1 if we have moved to a
             different screen line during this redisplay. */
          changed_screen_line = _rl_last_v_pos != cursor_linenum;
          if (changed_screen_line)
            {
              _rl_move_vert (cursor_linenum);
              /* If we moved up to the line with the prompt using _rl_term_up,
                 the physical cursor position on the screen stays the same,
                 but the buffer position needs to be adjusted to account
                 for invisible characters. */
              if ((MB_CUR_MAX == 1 || rl_byte_oriented) && cursor_linenum == 0 && wrap_offset)
                _rl_last_c_pos += wrap_offset;
            }

          /* We have to reprint the prompt if it contains invisible
             characters, since it's not generally OK to just reprint
             the characters from the current cursor position.  But we
             only need to reprint it if the cursor is before the last
             invisible character in the prompt string. */
          nleft = prompt_visible_length + wrap_offset;
          if (cursor_linenum == 0 && wrap_offset > 0 && _rl_last_c_pos > 0 &&
#if 0
              _rl_last_c_pos <= PROMPT_ENDING_INDEX && local_prompt)
#else
              _rl_last_c_pos < PROMPT_ENDING_INDEX && local_prompt)
#endif
            {
#if defined (__MSDOS__)
              putc ('\r', rl_outstream);
#else
              if (_rl_term_cr)
                tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif
              if (modmark)
                _rl_output_some_chars ("*", 1);

              _rl_output_some_chars (local_prompt, nleft);
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                _rl_last_c_pos = _rl_col_width (local_prompt, 0, nleft, 1) - wrap_offset + modmark;
              else
                _rl_last_c_pos = nleft + modmark;
            }

          /* Where on that line?  And where does that line start
             in the buffer? */
          pos = inv_lbreaks[cursor_linenum];
          /* nleft == number of characters in the line buffer between the
             start of the line and the desired cursor position. */
          nleft = cpos_buffer_position - pos;

          /* NLEFT is now a number of characters in a buffer.  When in a
             multibyte locale, however, _rl_last_c_pos is an absolute cursor
             position that doesn't take invisible characters in the prompt
             into account.  We use a fudge factor to compensate. */

          /* Since _rl_backspace() doesn't know about invisible characters in the
             prompt, and there's no good way to tell it, we compensate for
             those characters here and call _rl_backspace() directly. */
          if (wrap_offset && cursor_linenum == 0 && nleft < _rl_last_c_pos)
            {
              /* TX == new physical cursor position in multibyte locale. */
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                tx = _rl_col_width (&visible_line[pos], 0, nleft, 1) - visible_wrap_offset;
              else
                tx = nleft;
              if (tx >= 0 && _rl_last_c_pos > tx)
                {
                  _rl_backspace (_rl_last_c_pos - tx);  /* XXX */
                  _rl_last_c_pos = tx;
                }
            }

          /* We need to note that in a multibyte locale we are dealing with
             _rl_last_c_pos as an absolute cursor position, but moving to a
             point specified by a buffer position (NLEFT) that doesn't take
             invisible characters into account. */
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            _rl_move_cursor_relative (nleft, &invisible_line[pos]);
          else if (nleft != _rl_last_c_pos)
            _rl_move_cursor_relative (nleft, &invisible_line[pos]);
        }
    }
  else                          /* Do horizontal scrolling. */
    {
#define M_OFFSET(margin, offset) ((margin) == 0 ? offset : 0)
      int lmargin, ndisp, nleft, phys_c_pos, t;

      /* Always at top line. */
      _rl_last_v_pos = 0;

      /* Compute where in the buffer the displayed line should start.  This
         will be LMARGIN. */

      /* The number of characters that will be displayed before the cursor. */
      ndisp = cpos_buffer_position - wrap_offset;
      nleft  = prompt_visible_length + wrap_offset;
      /* Where the new cursor position will be on the screen.  This can be
         longer than SCREENWIDTH; if it is, lmargin will be adjusted. */
      phys_c_pos = cpos_buffer_position - (last_lmargin ? last_lmargin : wrap_offset);
      t = _rl_screenwidth / 3;

      /* If the number of characters had already exceeded the screenwidth,
         last_lmargin will be > 0. */

      /* If the number of characters to be displayed is more than the screen
         width, compute the starting offset so that the cursor is about
         two-thirds of the way across the screen. */
      if (phys_c_pos > _rl_screenwidth - 2)
        {
          lmargin = cpos_buffer_position - (2 * t);
          if (lmargin < 0)
            lmargin = 0;
          /* If the left margin would be in the middle of a prompt with
             invisible characters, don't display the prompt at all. */
          if (wrap_offset && lmargin > 0 && lmargin < nleft)
            lmargin = nleft;
        }
      else if (ndisp < _rl_screenwidth - 2)             /* XXX - was -1 */
        lmargin = 0;
      else if (phys_c_pos < 1)
        {
          /* If we are moving back towards the beginning of the line and
             the last margin is no longer correct, compute a new one. */
          lmargin = ((cpos_buffer_position - 1) / t) * t;       /* XXX */
          if (wrap_offset && lmargin > 0 && lmargin < nleft)
            lmargin = nleft;
        }
      else
        lmargin = last_lmargin;

      displaying_prompt_first_line = lmargin < nleft;

      /* If the first character on the screen isn't the first character
         in the display line, indicate this with a special character. */
      if (lmargin > 0)
        line[lmargin] = '<';

      /* If SCREENWIDTH characters starting at LMARGIN do not encompass
         the whole line, indicate that with a special character at the
         right edge of the screen.  If LMARGIN is 0, we need to take the
         wrap offset into account. */
      t = lmargin + M_OFFSET (lmargin, wrap_offset) + _rl_screenwidth;
      if (t < out)
        line[t - 1] = '>';

      if (rl_display_fixed == 0 || forced_display || lmargin != last_lmargin)
        {
          forced_display = 0;
          o_cpos = _rl_last_c_pos;
          cpos_adjusted = 0;
          update_line (&visible_line[last_lmargin],
                       &invisible_line[lmargin],
                       0,
                       _rl_screenwidth + visible_wrap_offset,
                       _rl_screenwidth + (lmargin ? 0 : wrap_offset),
                       0);

          if ((MB_CUR_MAX > 1 && rl_byte_oriented == 0) &&
                displaying_prompt_first_line && OLD_CPOS_IN_PROMPT())
            _rl_last_c_pos -= prompt_invis_chars_first_line;    /* XXX - was wrap_offset */

          /* If the visible new line is shorter than the old, but the number
             of invisible characters is greater, and we are at the end of
             the new line, we need to clear to eol. */
          t = _rl_last_c_pos - M_OFFSET (lmargin, wrap_offset);
          if ((M_OFFSET (lmargin, wrap_offset) > visible_wrap_offset) &&
              (_rl_last_c_pos == out) && displaying_prompt_first_line &&
              t < visible_first_line_len)
            {
              nleft = _rl_screenwidth - t;
              _rl_clear_to_eol (nleft);
            }
          visible_first_line_len = out - lmargin - M_OFFSET (lmargin, wrap_offset);
          if (visible_first_line_len > _rl_screenwidth)
            visible_first_line_len = _rl_screenwidth;

          _rl_move_cursor_relative (cpos_buffer_position - lmargin, &invisible_line[lmargin]);
          last_lmargin = lmargin;
        }
    }
  fflush (rl_outstream);

  /* Swap visible and non-visible lines. */
  {
    struct line_state *vtemp = line_state_visible;

    line_state_visible = line_state_invisible;
    line_state_invisible = vtemp;

    rl_display_fixed = 0;
    /* If we are displaying on a single line, and last_lmargin is > 0, we
       are not displaying any invisible characters, so set visible_wrap_offset
       to 0. */
    if (_rl_horizontal_scroll_mode && last_lmargin)
      visible_wrap_offset = 0;
    else
      visible_wrap_offset = wrap_offset;
  }

  RL_UNSETSTATE (RL_STATE_REDISPLAYING);
  _rl_release_sigint ();
}

/* PWP: update_line() is based on finding the middle difference of each
   line on the screen; vis:

                             /old first difference
        /beginning of line   |        /old last same       /old EOL
        v                    v        v             v
old:    eddie> Oh, my little gruntle-buggy is to me, as lurgid as
new:    eddie> Oh, my little buggy says to me, as lurgid as
        ^                    ^  ^                          ^
        \beginning of line   |  \new last same     \new end of line
                             \new first difference

   All are character pointers for the sake of speed.  Special cases for
   no differences, as well as for end of line additions must be handled.

   Could be made even smarter, but this works well enough */
static void
update_line (old, new, current_line, omax, nmax, inv_botlin)
     register char *old, *new;
     int current_line, omax, nmax, inv_botlin;
{
  register char *ofd, *ols, *oe, *nfd, *nls, *ne;
  int temp, lendiff, wsatend, od, nd, twidth, o_cpos;
  int current_invis_chars;
  int col_lendiff, col_temp;
  int bytes_to_insert;
#if defined (HANDLE_MULTIBYTE)
  mbstate_t ps_new, ps_old;
  int new_offset, old_offset;
#endif

  /* If we're at the right edge of a terminal that supports xn, we're
     ready to wrap around, so do so.  This fixes problems with knowing
     the exact cursor position and cut-and-paste with certain terminal
     emulators.  In this calculation, TEMP is the physical screen
     position of the cursor. */
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    temp = _rl_last_c_pos;
  else
    temp = _rl_last_c_pos - WRAP_OFFSET (_rl_last_v_pos, visible_wrap_offset);
  if (temp == _rl_screenwidth && _rl_term_autowrap && !_rl_horizontal_scroll_mode
        && _rl_last_v_pos == current_line - 1)
    {
#if defined (HANDLE_MULTIBYTE)
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          wchar_t wc;
          mbstate_t ps;
          int tempwidth, bytes;
          size_t ret;

          /* This fixes only double-column characters, but if the wrapped
             character consumes more than three columns, spaces will be
             inserted in the string buffer. */
          if (current_line < line_state_visible->wbsize && line_state_visible->wrapped_line[current_line] > 0)
            _rl_clear_to_eol (line_state_visible->wrapped_line[current_line]);

          memset (&ps, 0, sizeof (mbstate_t));
          ret = mbrtowc (&wc, new, MB_CUR_MAX, &ps);
          if (MB_INVALIDCH (ret))
            {
              tempwidth = 1;
              ret = 1;
            }
          else if (MB_NULLWCH (ret))
            tempwidth = 0;
          else
            tempwidth = WCWIDTH (wc);

          if (tempwidth > 0)
            {
              int count, i;
              bytes = ret;
              for (count = 0; count < bytes; count++)
                putc (new[count], rl_outstream);
              _rl_last_c_pos = tempwidth;
              _rl_last_v_pos++;
              memset (&ps, 0, sizeof (mbstate_t));
              ret = mbrtowc (&wc, old, MB_CUR_MAX, &ps);
              if (ret != 0 && bytes != 0)
                {
                  if (MB_INVALIDCH (ret))
                    ret = 1;
                  memmove (old+bytes, old+ret, strlen (old+ret));
                  memcpy (old, new, bytes);
                  /* Fix up indices if we copy data from one line to another */
                  omax += bytes - ret;
                  for (i = current_line+1; i <= inv_botlin+1; i++)
                    vis_lbreaks[i] += bytes - ret;
                }
            }
          else
            {
              putc (' ', rl_outstream);
              _rl_last_c_pos = 1;
              _rl_last_v_pos++;
              if (old[0] && new[0])
                old[0] = new[0];
            }
        }
      else
#endif
        {
          if (new[0])
            putc (new[0], rl_outstream);
          else
            putc (' ', rl_outstream);
          _rl_last_c_pos = 1;
          _rl_last_v_pos++;
          if (old[0] && new[0])
            old[0] = new[0];
        }
    }

      
  /* Find first difference. */
#if defined (HANDLE_MULTIBYTE)
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    {
      /* See if the old line is a subset of the new line, so that the
         only change is adding characters. */
      temp = (omax < nmax) ? omax : nmax;
      if (memcmp (old, new, temp) == 0)         /* adding at the end */
        {
          new_offset = old_offset = temp;
          ofd = old + temp;
          nfd = new + temp;
        }
      else
        {      
          memset (&ps_new, 0, sizeof(mbstate_t));
          memset (&ps_old, 0, sizeof(mbstate_t));

          if (omax == nmax && STREQN (new, old, omax))
            {
              old_offset = omax;
              new_offset = nmax;
              ofd = old + omax;
              nfd = new + nmax;
            }
          else
            {
              new_offset = old_offset = 0;
              for (ofd = old, nfd = new;
                    (ofd - old < omax) && *ofd &&
                    _rl_compare_chars(old, old_offset, &ps_old, new, new_offset, &ps_new); )
                {
                  old_offset = _rl_find_next_mbchar (old, old_offset, 1, MB_FIND_ANY);
                  new_offset = _rl_find_next_mbchar (new, new_offset, 1, MB_FIND_ANY);

                  ofd = old + old_offset;
                  nfd = new + new_offset;
                }
            }
        }
    }
  else
#endif
  for (ofd = old, nfd = new;
       (ofd - old < omax) && *ofd && (*ofd == *nfd);
       ofd++, nfd++)
    ;

  /* Move to the end of the screen line.  ND and OD are used to keep track
     of the distance between ne and new and oe and old, respectively, to
     move a subtraction out of each loop. */
  for (od = ofd - old, oe = ofd; od < omax && *oe; oe++, od++);
  for (nd = nfd - new, ne = nfd; nd < nmax && *ne; ne++, nd++);

  /* If no difference, continue to next line. */
  if (ofd == oe && nfd == ne)
    return;

#if defined (HANDLE_MULTIBYTE)
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0 && _rl_utf8locale)
    {
      wchar_t wc;
      mbstate_t ps = { 0 };
      int t;

      /* If the first character in the difference is a zero-width character,
         assume it's a combining character and back one up so the two base
         characters no longer compare equivalently. */
      t = mbrtowc (&wc, ofd, MB_CUR_MAX, &ps);
      if (t > 0 && UNICODE_COMBINING_CHAR (wc) && WCWIDTH (wc) == 0)
        {
          old_offset = _rl_find_prev_mbchar (old, ofd - old, MB_FIND_ANY);
          new_offset = _rl_find_prev_mbchar (new, nfd - new, MB_FIND_ANY);
          ofd = old + old_offset;       /* equal by definition */
          nfd = new + new_offset;
        }
    }
#endif

  wsatend = 1;                  /* flag for trailing whitespace */

#if defined (HANDLE_MULTIBYTE)
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    {
      ols = old + _rl_find_prev_mbchar (old, oe - old, MB_FIND_ANY);
      nls = new + _rl_find_prev_mbchar (new, ne - new, MB_FIND_ANY);

      while ((ols > ofd) && (nls > nfd))
        {
          memset (&ps_old, 0, sizeof (mbstate_t));
          memset (&ps_new, 0, sizeof (mbstate_t));

#if 0
          /* On advice from jir@yamato.ibm.com */
          _rl_adjust_point (old, ols - old, &ps_old);
          _rl_adjust_point (new, nls - new, &ps_new);
#endif

          if (_rl_compare_chars (old, ols - old, &ps_old, new, nls - new, &ps_new) == 0)
            break;

          if (*ols == ' ')
            wsatend = 0;

          ols = old + _rl_find_prev_mbchar (old, ols - old, MB_FIND_ANY);
          nls = new + _rl_find_prev_mbchar (new, nls - new, MB_FIND_ANY);
        }
    }
  else
    {
#endif /* HANDLE_MULTIBYTE */
  ols = oe - 1;                 /* find last same */
  nls = ne - 1;
  while ((ols > ofd) && (nls > nfd) && (*ols == *nls))
    {
      if (*ols != ' ')
        wsatend = 0;
      ols--;
      nls--;
    }
#if defined (HANDLE_MULTIBYTE)
    }
#endif

  if (wsatend)
    {
      ols = oe;
      nls = ne;
    }
#if defined (HANDLE_MULTIBYTE)
  /* This may not work for stateful encoding, but who cares?  To handle
     stateful encoding properly, we have to scan each string from the
     beginning and compare. */
  else if (_rl_compare_chars (ols, 0, NULL, nls, 0, NULL) == 0)
#else
  else if (*ols != *nls)
#endif
    {
      if (*ols)                 /* don't step past the NUL */
        {
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            ols = old + _rl_find_next_mbchar (old, ols - old, 1, MB_FIND_ANY);
          else
            ols++;
        }
      if (*nls)
        {
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            nls = new + _rl_find_next_mbchar (new, nls - new, 1, MB_FIND_ANY);
          else
            nls++;
        }
    }

  /* count of invisible characters in the current invisible line. */
  current_invis_chars = W_OFFSET (current_line, wrap_offset);
  if (_rl_last_v_pos != current_line)
    {
      _rl_move_vert (current_line);
      if ((MB_CUR_MAX == 1 || rl_byte_oriented) && current_line == 0 && visible_wrap_offset)
        _rl_last_c_pos += visible_wrap_offset;
    }

  /* If this is the first line and there are invisible characters in the
     prompt string, and the prompt string has not changed, and the current
     cursor position is before the last invisible character in the prompt,
     and the index of the character to move to is past the end of the prompt
     string, then redraw the entire prompt string.  We can only do this
     reliably if the terminal supports a `cr' capability.

     This is not an efficiency hack -- there is a problem with redrawing
     portions of the prompt string if they contain terminal escape
     sequences (like drawing the `unbold' sequence without a corresponding
     `bold') that manifests itself on certain terminals. */

  lendiff = local_prompt_len;
  od = ofd - old;       /* index of first difference in visible line */
  if (current_line == 0 && !_rl_horizontal_scroll_mode &&
      _rl_term_cr && lendiff > prompt_visible_length && _rl_last_c_pos > 0 &&
      od >= lendiff && _rl_last_c_pos < PROMPT_ENDING_INDEX)
    {
#if defined (__MSDOS__)
      putc ('\r', rl_outstream);
#else
      tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif
      if (modmark)
        _rl_output_some_chars ("*", 1);
      _rl_output_some_chars (local_prompt, lendiff);
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          /* We take wrap_offset into account here so we can pass correct
             information to _rl_move_cursor_relative. */
          _rl_last_c_pos = _rl_col_width (local_prompt, 0, lendiff, 1) - wrap_offset + modmark;
          cpos_adjusted = 1;
        }
      else
        _rl_last_c_pos = lendiff + modmark;
    }

  o_cpos = _rl_last_c_pos;

  /* When this function returns, _rl_last_c_pos is correct, and an absolute
     cursor position in multibyte mode, but a buffer index when not in a
     multibyte locale. */
  _rl_move_cursor_relative (od, old);

#if defined (HANDLE_MULTIBYTE)
  /* We need to indicate that the cursor position is correct in the presence of
     invisible characters in the prompt string.  Let's see if setting this when
     we make sure we're at the end of the drawn prompt string works. */
  if (current_line == 0 && MB_CUR_MAX > 1 && rl_byte_oriented == 0 &&
      (_rl_last_c_pos > 0 || o_cpos > 0) &&
      _rl_last_c_pos == prompt_physical_chars)
    cpos_adjusted = 1;
#endif

  /* if (len (new) > len (old))
     lendiff == difference in buffer (bytes)
     col_lendiff == difference on screen (columns)
     When not using multibyte characters, these are equal */
  lendiff = (nls - nfd) - (ols - ofd);
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    col_lendiff = _rl_col_width (new, nfd - new, nls - new, 1) - _rl_col_width (old, ofd - old, ols - old, 1);
  else
    col_lendiff = lendiff;

  /* If we are changing the number of invisible characters in a line, and
     the spot of first difference is before the end of the invisible chars,
     lendiff needs to be adjusted. */
  if (current_line == 0 && !_rl_horizontal_scroll_mode &&
      current_invis_chars != visible_wrap_offset)
    {
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          lendiff += visible_wrap_offset - current_invis_chars;
          col_lendiff += visible_wrap_offset - current_invis_chars;
        }
      else
        {
          lendiff += visible_wrap_offset - current_invis_chars;
          col_lendiff = lendiff;
        }
    }

  /* We use temp as a count of the number of bytes from the first difference
     to the end of the new line.  col_temp is the corresponding number of
     screen columns.  A `dumb' update moves to the spot of first difference
     and writes TEMP bytes. */
  /* Insert (diff (len (old), len (new)) ch. */
  temp = ne - nfd;
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    col_temp = _rl_col_width (new, nfd - new, ne - new, 1);
  else
    col_temp = temp;

  /* how many bytes from the new line buffer to write to the display */
  bytes_to_insert = nls - nfd;

  /* col_lendiff > 0 if we are adding characters to the line */
  if (col_lendiff > 0)  /* XXX - was lendiff */
    {
      /* Non-zero if we're increasing the number of lines. */
      int gl = current_line >= _rl_vis_botlin && inv_botlin > _rl_vis_botlin;
      /* If col_lendiff is > 0, implying that the new string takes up more
         screen real estate than the old, but lendiff is < 0, meaning that it
         takes fewer bytes, we need to just output the characters starting
         from the first difference.  These will overwrite what is on the
         display, so there's no reason to do a smart update.  This can really
         only happen in a multibyte environment. */
      if (lendiff < 0)
        {
          _rl_output_some_chars (nfd, temp);
          _rl_last_c_pos += col_temp;   /* XXX - was _rl_col_width (nfd, 0, temp, 1); */
          /* If nfd begins before any invisible characters in the prompt,
             adjust _rl_last_c_pos to account for wrap_offset and set
             cpos_adjusted to let the caller know. */
          if (current_line == 0 && displaying_prompt_first_line && wrap_offset && ((nfd - new) <= prompt_last_invisible))
            {
              _rl_last_c_pos -= wrap_offset;
              cpos_adjusted = 1;
            }
          return;
        }
      /* Sometimes it is cheaper to print the characters rather than
         use the terminal's capabilities.  If we're growing the number
         of lines, make sure we actually cause the new line to wrap
         around on auto-wrapping terminals. */
      else if (_rl_terminal_can_insert && ((2 * col_temp) >= col_lendiff || _rl_term_IC) && (!_rl_term_autowrap || !gl))
        {
          /* If lendiff > prompt_visible_length and _rl_last_c_pos == 0 and
             _rl_horizontal_scroll_mode == 1, inserting the characters with
             _rl_term_IC or _rl_term_ic will screw up the screen because of the
             invisible characters.  We need to just draw them. */
          /* The same thing happens if we're trying to draw before the last
             invisible character in the prompt string or we're increasing the
             number of invisible characters in the line and we're not drawing
             the entire prompt string. */
          if (*ols && ((_rl_horizontal_scroll_mode &&
                        _rl_last_c_pos == 0 &&
                        lendiff > prompt_visible_length &&
                        current_invis_chars > 0) == 0) &&
                      (((MB_CUR_MAX > 1 && rl_byte_oriented == 0) &&
                        current_line == 0 && wrap_offset &&
                        ((nfd - new) <= prompt_last_invisible) &&
                        (col_lendiff < prompt_visible_length)) == 0) &&
                      (visible_wrap_offset >= current_invis_chars))
            {
              open_some_spaces (col_lendiff);
              _rl_output_some_chars (nfd, bytes_to_insert);
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                _rl_last_c_pos += _rl_col_width (nfd, 0, bytes_to_insert, 1);
              else
                _rl_last_c_pos += bytes_to_insert;
            }
          else if ((MB_CUR_MAX == 1 || rl_byte_oriented != 0) && *ols == 0 && lendiff > 0)
            {
              /* At the end of a line the characters do not have to
                 be "inserted".  They can just be placed on the screen. */
              _rl_output_some_chars (nfd, temp);
              _rl_last_c_pos += col_temp;
              return;
            }
          else  /* just write from first difference to end of new line */
            {
              _rl_output_some_chars (nfd, temp);
              _rl_last_c_pos += col_temp;
              /* If nfd begins before the last invisible character in the
                 prompt, adjust _rl_last_c_pos to account for wrap_offset
                 and set cpos_adjusted to let the caller know. */
              if ((MB_CUR_MAX > 1 && rl_byte_oriented == 0) && current_line == 0 && displaying_prompt_first_line && wrap_offset && ((nfd - new) <= prompt_last_invisible))
                {
                  _rl_last_c_pos -= wrap_offset;
                  cpos_adjusted = 1;
                }
              return;
            }

          if (bytes_to_insert > lendiff)
            {
              /* If nfd begins before the last invisible character in the
                 prompt, adjust _rl_last_c_pos to account for wrap_offset
                 and set cpos_adjusted to let the caller know. */
              if ((MB_CUR_MAX > 1 && rl_byte_oriented == 0) && current_line == 0 && displaying_prompt_first_line && wrap_offset && ((nfd - new) <= prompt_last_invisible))
                {
                  _rl_last_c_pos -= wrap_offset;
                  cpos_adjusted = 1;
                }
            }
        }
      else
        {
          /* cannot insert chars, write to EOL */
          _rl_output_some_chars (nfd, temp);
          _rl_last_c_pos += col_temp;
          /* If we're in a multibyte locale and were before the last invisible
             char in the current line (which implies we just output some invisible
             characters) we need to adjust _rl_last_c_pos, since it represents
             a physical character position. */
          if ((MB_CUR_MAX > 1 && rl_byte_oriented == 0) &&
                current_line == prompt_last_screen_line && wrap_offset &&
                displaying_prompt_first_line &&
                wrap_offset != prompt_invis_chars_first_line &&
                ((nfd-new) < (prompt_last_invisible-(current_line*_rl_screenwidth))))
            {
              _rl_last_c_pos -= wrap_offset - prompt_invis_chars_first_line;
              cpos_adjusted = 1;
            }
        }
    }
  else                          /* Delete characters from line. */
    {
      /* If possible and inexpensive to use terminal deletion, then do so. */
      if (_rl_term_dc && (2 * col_temp) >= -col_lendiff)
        {
          /* If all we're doing is erasing the invisible characters in the
             prompt string, don't bother.  It screws up the assumptions
             about what's on the screen. */
          if (_rl_horizontal_scroll_mode && _rl_last_c_pos == 0 &&
              displaying_prompt_first_line &&
              -lendiff == visible_wrap_offset)
            col_lendiff = 0;

          /* If we have moved lmargin and we're shrinking the line, we've
             already moved the cursor to the first character of the new line,
             so deleting -col_lendiff characters will mess up the cursor
             position calculation */
          if (_rl_horizontal_scroll_mode && displaying_prompt_first_line == 0 &&
                col_lendiff && _rl_last_c_pos < -col_lendiff)
            col_lendiff = 0;

          if (col_lendiff)
            delete_chars (-col_lendiff); /* delete (diff) characters */

          /* Copy (new) chars to screen from first diff to last match,
             overwriting what is there. */
          if (bytes_to_insert > 0)
            {
              /* If nfd begins at the prompt, or before the invisible
                 characters in the prompt, we need to adjust _rl_last_c_pos
                 in a multibyte locale to account for the wrap offset and
                 set cpos_adjusted accordingly. */
              _rl_output_some_chars (nfd, bytes_to_insert);
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                {
                  _rl_last_c_pos += _rl_col_width (nfd, 0, bytes_to_insert, 1);
                  if (current_line == 0 && wrap_offset &&
                        displaying_prompt_first_line &&
                        _rl_last_c_pos > wrap_offset &&
                        ((nfd - new) <= prompt_last_invisible))
                    {
                      _rl_last_c_pos -= wrap_offset;
                      cpos_adjusted = 1;
                    }
                }
              else
                _rl_last_c_pos += bytes_to_insert;

              if (_rl_horizontal_scroll_mode && ((oe-old) > (ne-new)))
                goto clear_rest_of_line;
            }
        }
      /* Otherwise, print over the existing material. */
      else
        {
          if (temp > 0)
            {
              /* If nfd begins at the prompt, or before the invisible
                 characters in the prompt, we need to adjust _rl_last_c_pos
                 in a multibyte locale to account for the wrap offset and
                 set cpos_adjusted accordingly. */
              _rl_output_some_chars (nfd, temp);
              _rl_last_c_pos += col_temp;               /* XXX */
              if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
                {
                  if (current_line == 0 && wrap_offset &&
                        displaying_prompt_first_line &&
                        _rl_last_c_pos > wrap_offset &&
                        ((nfd - new) <= prompt_last_invisible))
                    {
                      _rl_last_c_pos -= wrap_offset;
                      cpos_adjusted = 1;
                    }
                }
            }
clear_rest_of_line:
          lendiff = (oe - old) - (ne - new);
          if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
            col_lendiff = _rl_col_width (old, 0, oe - old, 1) - _rl_col_width (new, 0, ne - new, 1);
          else
            col_lendiff = lendiff;

          /* If we've already printed over the entire width of the screen,
             including the old material, then col_lendiff doesn't matter and
             space_to_eol will insert too many spaces.  XXX - maybe we should
             adjust col_lendiff based on the difference between _rl_last_c_pos
             and _rl_screenwidth */
          if (col_lendiff && ((MB_CUR_MAX == 1 || rl_byte_oriented) || (_rl_last_c_pos < _rl_screenwidth)))
            {     
              if (_rl_term_autowrap && current_line < inv_botlin)
                space_to_eol (col_lendiff);
              else
                _rl_clear_to_eol (col_lendiff);
            }
        }
    }
}

/* Tell the update routines that we have moved onto a new (empty) line. */
int
rl_on_new_line ()
{
  if (visible_line)
    visible_line[0] = '\0';

  _rl_last_c_pos = _rl_last_v_pos = 0;
  _rl_vis_botlin = last_lmargin = 0;
  if (vis_lbreaks)
    vis_lbreaks[0] = vis_lbreaks[1] = 0;
  visible_wrap_offset = 0;
  return 0;
}

/* Tell the update routines that we have moved onto a new line with the
   prompt already displayed.  Code originally from the version of readline
   distributed with CLISP.  rl_expand_prompt must have already been called
   (explicitly or implicitly).  This still doesn't work exactly right. */
int
rl_on_new_line_with_prompt ()
{
  int prompt_size, i, l, real_screenwidth, newlines;
  char *prompt_last_line, *lprompt;

  /* Initialize visible_line and invisible_line to ensure that they can hold
     the already-displayed prompt. */
  prompt_size = strlen (rl_prompt) + 1;
  init_line_structures (prompt_size);

  /* Make sure the line structures hold the already-displayed prompt for
     redisplay. */
  lprompt = local_prompt ? local_prompt : rl_prompt;
  strcpy (visible_line, lprompt);
  strcpy (invisible_line, lprompt);

  /* If the prompt contains newlines, take the last tail. */
  prompt_last_line = strrchr (rl_prompt, '\n');
  if (!prompt_last_line)
    prompt_last_line = rl_prompt;

  l = strlen (prompt_last_line);
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    _rl_last_c_pos = _rl_col_width (prompt_last_line, 0, l, 1); /* XXX */
  else
    _rl_last_c_pos = l;

  /* Dissect prompt_last_line into screen lines. Note that here we have
     to use the real screenwidth. Readline's notion of screenwidth might be
     one less, see terminal.c. */
  real_screenwidth = _rl_screenwidth + (_rl_term_autowrap ? 0 : 1);
  _rl_last_v_pos = l / real_screenwidth;
  /* If the prompt length is a multiple of real_screenwidth, we don't know
     whether the cursor is at the end of the last line, or already at the
     beginning of the next line. Output a newline just to be safe. */
  if (l > 0 && (l % real_screenwidth) == 0)
    _rl_output_some_chars ("\n", 1);
  last_lmargin = 0;

  newlines = 0; i = 0;
  while (i <= l)
    {
      _rl_vis_botlin = newlines;
      vis_lbreaks[newlines++] = i;
      i += real_screenwidth;
    }
  vis_lbreaks[newlines] = l;
  visible_wrap_offset = 0;

  rl_display_prompt = rl_prompt;        /* XXX - make sure it's set */

  return 0;
}

/* Actually update the display, period. */
int
rl_forced_update_display ()
{
  register char *temp;

  if (visible_line)
    {
      temp = visible_line;
      while (*temp)
        *temp++ = '\0';
    }
  rl_on_new_line ();
  forced_display++;
  (*rl_redisplay_function) ();
  return 0;
}

/* Move the cursor from _rl_last_c_pos to NEW, which are buffer indices.
   (Well, when we don't have multibyte characters, _rl_last_c_pos is a
   buffer index.)
   DATA is the contents of the screen line of interest; i.e., where
   the movement is being done. */
void
_rl_move_cursor_relative (new, data)
     int new;
     const char *data;
{
  register int i;
  int woff;                     /* number of invisible chars on current line */
  int cpos, dpos;               /* current and desired cursor positions */
  int adjust;

  woff = WRAP_OFFSET (_rl_last_v_pos, wrap_offset);
  cpos = _rl_last_c_pos;

  if (cpos == 0 && cpos == new)
    return;

#if defined (HANDLE_MULTIBYTE)
  /* If we have multibyte characters, NEW is indexed by the buffer point in
     a multibyte string, but _rl_last_c_pos is the display position.  In
     this case, NEW's display position is not obvious and must be
     calculated.  We need to account for invisible characters in this line,
     as long as we are past them and they are counted by _rl_col_width. */
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    {
      adjust = 1;
      /* Try to short-circuit common cases and eliminate a bunch of multibyte
         character function calls. */
      /* 1.  prompt string */
      if (new == local_prompt_len && memcmp (data, local_prompt, new) == 0)
        {
          dpos = prompt_physical_chars;
          cpos_adjusted = 1;
          adjust = 0;
        }
      /* 2.  prompt_string + line contents */
      else if (new > local_prompt_len && local_prompt && memcmp (data, local_prompt, local_prompt_len) == 0)
        {
          dpos = prompt_physical_chars + _rl_col_width (data, local_prompt_len, new, 1);
          cpos_adjusted = 1;
          adjust = 0;
        }
      else
        dpos = _rl_col_width (data, 0, new, 1);

      if (displaying_prompt_first_line == 0)
        adjust = 0;

      /* Use NEW when comparing against the last invisible character in the
         prompt string, since they're both buffer indices and DPOS is a
         desired display position. */
      if (adjust && ((new > prompt_last_invisible) ||           /* XXX - don't use woff here */
          (prompt_physical_chars >= _rl_screenwidth &&
           _rl_last_v_pos == prompt_last_screen_line &&
           wrap_offset >= woff && dpos >= woff &&
           new > (prompt_last_invisible-(_rl_screenwidth*_rl_last_v_pos)-wrap_offset))))
           /* XXX last comparison might need to be >= */
        {
          dpos -= woff;
          /* Since this will be assigned to _rl_last_c_pos at the end (more
             precisely, _rl_last_c_pos == dpos when this function returns),
             let the caller know. */
          cpos_adjusted = 1;
        }
    }
  else
#endif
    dpos = new;

  /* If we don't have to do anything, then return. */
  if (cpos == dpos)
    return;

  /* It may be faster to output a CR, and then move forwards instead
     of moving backwards. */
  /* i == current physical cursor position. */
#if defined (HANDLE_MULTIBYTE)
  if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
    i = _rl_last_c_pos;
  else
#endif
  i = _rl_last_c_pos - woff;
  if (dpos == 0 || CR_FASTER (dpos, _rl_last_c_pos) ||
      (_rl_term_autowrap && i == _rl_screenwidth))
    {
#if defined (__MSDOS__)
      putc ('\r', rl_outstream);
#else
      tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif /* !__MSDOS__ */
      cpos = _rl_last_c_pos = 0;
    }

  if (cpos < dpos)
    {
      /* Move the cursor forward.  We do it by printing the command
         to move the cursor forward if there is one, else print that
         portion of the output buffer again.  Which is cheaper? */

      /* The above comment is left here for posterity.  It is faster
         to print one character (non-control) than to print a control
         sequence telling the terminal to move forward one character.
         That kind of control is for people who don't know what the
         data is underneath the cursor. */

      /* However, we need a handle on where the current display position is
         in the buffer for the immediately preceding comment to be true.
         In multibyte locales, we don't currently have that info available.
         Without it, we don't know where the data we have to display begins
         in the buffer and we have to go back to the beginning of the screen
         line.  In this case, we can use the terminal sequence to move forward
         if it's available. */
      if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
        {
          if (_rl_term_forward_char)
            {
              for (i = cpos; i < dpos; i++)
                tputs (_rl_term_forward_char, 1, _rl_output_character_function);
            }
          else
            {
              tputs (_rl_term_cr, 1, _rl_output_character_function);
              for (i = 0; i < new; i++)
                putc (data[i], rl_outstream);
            }
        }
      else
        for (i = cpos; i < new; i++)
          putc (data[i], rl_outstream);
    }

#if defined (HANDLE_MULTIBYTE)
  /* NEW points to the buffer point, but _rl_last_c_pos is the display point.
     The byte length of the string is probably bigger than the column width
     of the string, which means that if NEW == _rl_last_c_pos, then NEW's
     display point is less than _rl_last_c_pos. */
#endif
  else if (cpos > dpos)
    _rl_backspace (cpos - dpos);

  _rl_last_c_pos = dpos;
}

/* PWP: move the cursor up or down. */
void
_rl_move_vert (to)
     int to;
{
  register int delta, i;

  if (_rl_last_v_pos == to || to > _rl_screenheight)
    return;

  if ((delta = to - _rl_last_v_pos) > 0)
    {
      for (i = 0; i < delta; i++)
        putc ('\n', rl_outstream);
#if defined (__MSDOS__)
      putc ('\r', rl_outstream);
#else
      tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif
      _rl_last_c_pos = 0;
    }
  else
    {                   /* delta < 0 */
#ifdef __DJGPP__
      int row, col;

      fflush (rl_outstream);
      ScreenGetCursor (&row, &col);
      ScreenSetCursor (row + delta, col);
      i = -delta;
#else
      if (_rl_term_up && *_rl_term_up)
        for (i = 0; i < -delta; i++)
          tputs (_rl_term_up, 1, _rl_output_character_function);
#endif /* !__DJGPP__ */
    }

  _rl_last_v_pos = to;          /* Now TO is here */
}

/* Physically print C on rl_outstream.  This is for functions which know
   how to optimize the display.  Return the number of characters output. */
int
rl_show_char (c)
     int c;
{
  int n = 1;
  if (META_CHAR (c) && (_rl_output_meta_chars == 0))
    {
      fprintf (rl_outstream, "M-");
      n += 2;
      c = UNMETA (c);
    }

#if defined (DISPLAY_TABS)
  if ((CTRL_CHAR (c) && c != '\t') || c == RUBOUT)
#else
  if (CTRL_CHAR (c) || c == RUBOUT)
#endif /* !DISPLAY_TABS */
    {
      fprintf (rl_outstream, "C-");
      n += 2;
      c = CTRL_CHAR (c) ? UNCTRL (c) : '?';
    }

  putc (c, rl_outstream);
  fflush (rl_outstream);
  return n;
}

int
rl_character_len (c, pos)
     register int c, pos;
{
  unsigned char uc;

  uc = (unsigned char)c;

  if (META_CHAR (uc))
    return ((_rl_output_meta_chars == 0) ? 4 : 1);

  if (uc == '\t')
    {
#if defined (DISPLAY_TABS)
      return (((pos | 7) + 1) - pos);
#else
      return (2);
#endif /* !DISPLAY_TABS */
    }

  if (CTRL_CHAR (c) || c == RUBOUT)
    return (2);

  return ((ISPRINT (uc)) ? 1 : 2);
}
/* How to print things in the "echo-area".  The prompt is treated as a
   mini-modeline. */
static int msg_saved_prompt = 0;

#if defined (USE_VARARGS)
int
#if defined (PREFER_STDARG)
rl_message (const char *format, ...)
#else
rl_message (va_alist)
     va_dcl
#endif
{
  va_list args;
#if defined (PREFER_VARARGS)
  char *format;
#endif
#if defined (HAVE_VSNPRINTF)
  int bneed;
#endif

#if defined (PREFER_STDARG)
  va_start (args, format);
#else
  va_start (args);
  format = va_arg (args, char *);
#endif

  if (msg_buf == 0)
    msg_buf = xmalloc (msg_bufsiz = 128);

#if defined (HAVE_VSNPRINTF)
  bneed = vsnprintf (msg_buf, msg_bufsiz - 1, format, args);
  if (bneed >= msg_bufsiz - 1)
    {
      msg_bufsiz = bneed + 1;
      msg_buf = xrealloc (msg_buf, msg_bufsiz);
      va_end (args);

#if defined (PREFER_STDARG)
      va_start (args, format);
#else
      va_start (args);
      format = va_arg (args, char *);
#endif
      vsnprintf (msg_buf, msg_bufsiz - 1, format, args);
    }
#else
  vsprintf (msg_buf, format, args);
  msg_buf[msg_bufsiz - 1] = '\0';       /* overflow? */
#endif
  va_end (args);

  if (saved_local_prompt == 0)
    {
      rl_save_prompt ();
      msg_saved_prompt = 1;
    }
  else if (local_prompt != saved_local_prompt)
    {
      FREE (local_prompt);
      FREE (local_prompt_prefix);
      local_prompt = (char *)NULL;
    }
  rl_display_prompt = msg_buf;
  local_prompt = expand_prompt (msg_buf, &prompt_visible_length,
                                         &prompt_last_invisible,
                                         &prompt_invis_chars_first_line,
                                         &prompt_physical_chars);
  local_prompt_prefix = (char *)NULL;
  local_prompt_len = local_prompt ? strlen (local_prompt) : 0;
  (*rl_redisplay_function) ();

  return 0;
}
#else /* !USE_VARARGS */
int
rl_message (format, arg1, arg2)
     char *format;
{
  if (msg_buf == 0)
    msg_buf = xmalloc (msg_bufsiz = 128);

  sprintf (msg_buf, format, arg1, arg2);
  msg_buf[msg_bufsiz - 1] = '\0';       /* overflow? */

  rl_display_prompt = msg_buf;
  if (saved_local_prompt == 0)
    {
      rl_save_prompt ();
      msg_saved_prompt = 1;
    }
  else if (local_prompt != saved_local_prompt)
    {
      FREE (local_prompt);
      FREE (local_prompt_prefix);
      local_prompt = (char *)NULL;
    }
  local_prompt = expand_prompt (msg_buf, &prompt_visible_length,
                                         &prompt_last_invisible,
                                         &prompt_invis_chars_first_line,
                                         &prompt_physical_chars);
  local_prompt_prefix = (char *)NULL;
  local_prompt_len = local_prompt ? strlen (local_prompt) : 0;
  (*rl_redisplay_function) ();
      
  return 0;
}
#endif /* !USE_VARARGS */

/* How to clear things from the "echo-area". */
int
rl_clear_message ()
{
  rl_display_prompt = rl_prompt;
  if (msg_saved_prompt)
    {
      rl_restore_prompt ();
      msg_saved_prompt = 0;
    }
  (*rl_redisplay_function) ();
  return 0;
}

int
rl_reset_line_state ()
{
  rl_on_new_line ();

  rl_display_prompt = rl_prompt ? rl_prompt : "";
  forced_display = 1;
  return 0;
}

void
rl_save_prompt ()
{
  saved_local_prompt = local_prompt;
  saved_local_prefix = local_prompt_prefix;
  saved_prefix_length = prompt_prefix_length;
  saved_local_length = local_prompt_len;
  saved_last_invisible = prompt_last_invisible;
  saved_visible_length = prompt_visible_length;
  saved_invis_chars_first_line = prompt_invis_chars_first_line;
  saved_physical_chars = prompt_physical_chars;

  local_prompt = local_prompt_prefix = (char *)0;
  local_prompt_len = 0;
  prompt_last_invisible = prompt_visible_length = prompt_prefix_length = 0;
  prompt_invis_chars_first_line = prompt_physical_chars = 0;
}

void
rl_restore_prompt ()
{
  FREE (local_prompt);
  FREE (local_prompt_prefix);

  local_prompt = saved_local_prompt;
  local_prompt_prefix = saved_local_prefix;
  local_prompt_len = saved_local_length;
  prompt_prefix_length = saved_prefix_length;
  prompt_last_invisible = saved_last_invisible;
  prompt_visible_length = saved_visible_length;
  prompt_invis_chars_first_line = saved_invis_chars_first_line;
  prompt_physical_chars = saved_physical_chars;

  /* can test saved_local_prompt to see if prompt info has been saved. */
  saved_local_prompt = saved_local_prefix = (char *)0;
  saved_local_length = 0;
  saved_last_invisible = saved_visible_length = saved_prefix_length = 0;
  saved_invis_chars_first_line = saved_physical_chars = 0;
}

char *
_rl_make_prompt_for_search (pchar)
     int pchar;
{
  int len;
  char *pmt, *p;

  rl_save_prompt ();

  /* We've saved the prompt, and can do anything with the various prompt
     strings we need before they're restored.  We want the unexpanded
     portion of the prompt string after any final newline. */
  p = rl_prompt ? strrchr (rl_prompt, '\n') : 0;
  if (p == 0)
    {
      len = (rl_prompt && *rl_prompt) ? strlen (rl_prompt) : 0;
      pmt = (char *)xmalloc (len + 2);
      if (len)
        strcpy (pmt, rl_prompt);
      pmt[len] = pchar;
      pmt[len+1] = '\0';
    }
  else
    {
      p++;
      len = strlen (p);
      pmt = (char *)xmalloc (len + 2);
      if (len)
        strcpy (pmt, p);
      pmt[len] = pchar;
      pmt[len+1] = '\0';
    }  

  /* will be overwritten by expand_prompt, called from rl_message */
  prompt_physical_chars = saved_physical_chars + 1;
  return pmt;
}

/* Quick redisplay hack when erasing characters at the end of the line. */
void
_rl_erase_at_end_of_line (l)
     int l;
{
  register int i;

  _rl_backspace (l);
  for (i = 0; i < l; i++)
    putc (' ', rl_outstream);
  _rl_backspace (l);
  for (i = 0; i < l; i++)
    visible_line[--_rl_last_c_pos] = '\0';
  rl_display_fixed++;
}

/* Clear to the end of the line.  COUNT is the minimum
   number of character spaces to clear, */
void
_rl_clear_to_eol (count)
     int count;
{
#ifndef __MSDOS__
  if (_rl_term_clreol)
    tputs (_rl_term_clreol, 1, _rl_output_character_function);
  else
#endif
    if (count)
      space_to_eol (count);
}

/* Clear to the end of the line using spaces.  COUNT is the minimum
   number of character spaces to clear, */
static void
space_to_eol (count)
     int count;
{
  register int i;

  for (i = 0; i < count; i++)
   putc (' ', rl_outstream);

  _rl_last_c_pos += count;
}

void
_rl_clear_screen ()
{
#ifndef __DJGPP__
  if (_rl_term_clrpag)
    tputs (_rl_term_clrpag, 1, _rl_output_character_function);
  else
    rl_crlf ();
#else
  ScreenClear ();
  ScreenSetCursor (0, 0);
#endif /* __DJGPP__ */
}

/* Insert COUNT characters from STRING to the output stream at column COL. */
static void
insert_some_chars (string, count, col)
     char *string;
     int count, col;
{
  open_some_spaces (col);
  _rl_output_some_chars (string, count);
}

/* Insert COL spaces, keeping the cursor at the same position.  We follow the
   ncurses documentation and use either im/ei with explicit spaces, or IC/ic
   by itself.  We assume there will either be ei or we don't need to use it. */
static void
open_some_spaces (col)
     int col;
{
#if !defined (__MSDOS__) && !defined (__MINGW32__)
  char *buffer;
  register int i;

  /* If IC is defined, then we do not have to "enter" insert mode. */
  if (_rl_term_IC)
    {
      buffer = tgoto (_rl_term_IC, 0, col);
      tputs (buffer, 1, _rl_output_character_function);
    }
  else if (_rl_term_im && *_rl_term_im)
    {
      tputs (_rl_term_im, 1, _rl_output_character_function);
      /* just output the desired number of spaces */
      for (i = col; i--; )
        _rl_output_character_function (' ');
      /* If there is a string to turn off insert mode, use it now. */
      if (_rl_term_ei && *_rl_term_ei)
        tputs (_rl_term_ei, 1, _rl_output_character_function);
      /* and move back the right number of spaces */
      _rl_backspace (col);
    }
  else if (_rl_term_ic && *_rl_term_ic)
    {
      /* If there is a special command for inserting characters, then
         use that first to open up the space. */
      for (i = col; i--; )
        tputs (_rl_term_ic, 1, _rl_output_character_function);
    }
#endif /* !__MSDOS__ && !__MINGW32__ */
}

/* Delete COUNT characters from the display line. */
static void
delete_chars (count)
     int count;
{
  if (count > _rl_screenwidth)  /* XXX */
    return;

#if !defined (__MSDOS__) && !defined (__MINGW32__)
  if (_rl_term_DC && *_rl_term_DC)
    {
      char *buffer;
      buffer = tgoto (_rl_term_DC, count, count);
      tputs (buffer, count, _rl_output_character_function);
    }
  else
    {
      if (_rl_term_dc && *_rl_term_dc)
        while (count--)
          tputs (_rl_term_dc, 1, _rl_output_character_function);
    }
#endif /* !__MSDOS__ && !__MINGW32__ */
}

void
_rl_update_final ()
{
  int full_lines;

  full_lines = 0;
  /* If the cursor is the only thing on an otherwise-blank last line,
     compensate so we don't print an extra CRLF. */
  if (_rl_vis_botlin && _rl_last_c_pos == 0 &&
        visible_line[vis_lbreaks[_rl_vis_botlin]] == 0)
    {
      _rl_vis_botlin--;
      full_lines = 1;
    }
  _rl_move_vert (_rl_vis_botlin);
  /* If we've wrapped lines, remove the final xterm line-wrap flag. */
  if (full_lines && _rl_term_autowrap && (VIS_LLEN(_rl_vis_botlin) == _rl_screenwidth))
    {
      char *last_line;

      last_line = &visible_line[vis_lbreaks[_rl_vis_botlin]];
      cpos_buffer_position = -1;        /* don't know where we are in buffer */
      _rl_move_cursor_relative (_rl_screenwidth - 1, last_line);        /* XXX */
      _rl_clear_to_eol (0);
      putc (last_line[_rl_screenwidth - 1], rl_outstream);
    }
  _rl_vis_botlin = 0;
  rl_crlf ();
  fflush (rl_outstream);
  rl_display_fixed++;
}

/* Move to the start of the current line. */
static void
cr ()
{
  if (_rl_term_cr)
    {
#if defined (__MSDOS__)
      putc ('\r', rl_outstream);
#else
      tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif
      _rl_last_c_pos = 0;
    }
}

/* Redraw the last line of a multi-line prompt that may possibly contain
   terminal escape sequences.  Called with the cursor at column 0 of the
   line to draw the prompt on. */
static void
redraw_prompt (t)
     char *t;
{
  char *oldp;

  oldp = rl_display_prompt;
  rl_save_prompt ();

  rl_display_prompt = t;
  local_prompt = expand_prompt (t, &prompt_visible_length,
                                   &prompt_last_invisible,
                                   &prompt_invis_chars_first_line,
                                   &prompt_physical_chars);
  local_prompt_prefix = (char *)NULL;
  local_prompt_len = local_prompt ? strlen (local_prompt) : 0;

  rl_forced_update_display ();

  rl_display_prompt = oldp;
  rl_restore_prompt();
}
      
/* Redisplay the current line after a SIGWINCH is received. */
void
_rl_redisplay_after_sigwinch ()
{
  char *t;

  /* Clear the last line (assuming that the screen size change will result in
     either more or fewer characters on that line only) and put the cursor at
     column 0.  Make sure the right thing happens if we have wrapped to a new
     screen line. */
  if (_rl_term_cr)
    {
      _rl_move_vert (_rl_vis_botlin);

#if defined (__MSDOS__)
      putc ('\r', rl_outstream);
#else
      tputs (_rl_term_cr, 1, _rl_output_character_function);
#endif
      _rl_last_c_pos = 0;
#if defined (__MSDOS__)
      space_to_eol (_rl_screenwidth);
      putc ('\r', rl_outstream);
#else
      if (_rl_term_clreol)
        tputs (_rl_term_clreol, 1, _rl_output_character_function);
      else
        {
          space_to_eol (_rl_screenwidth);
          tputs (_rl_term_cr, 1, _rl_output_character_function);
        }
#endif
      if (_rl_last_v_pos > 0)
        _rl_move_vert (0);
    }
  else
    rl_crlf ();

  /* Redraw only the last line of a multi-line prompt. */
  t = strrchr (rl_display_prompt, '\n');
  if (t)
    redraw_prompt (++t);
  else
    rl_forced_update_display ();
}

void
_rl_clean_up_for_exit ()
{
  if (_rl_echoing_p)
    {
      _rl_move_vert (_rl_vis_botlin);
      _rl_vis_botlin = 0;
      fflush (rl_outstream);
      rl_restart_output (1, 0);
    }
}

void
_rl_erase_entire_line ()
{
  cr ();
  _rl_clear_to_eol (0);
  cr ();
  fflush (rl_outstream);
}

/* return the `current display line' of the cursor -- the number of lines to
   move up to get to the first screen line of the current readline line. */
int
_rl_current_display_line ()
{
  int ret, nleft;

  /* Find out whether or not there might be invisible characters in the
     editing buffer. */
  if (rl_display_prompt == rl_prompt)
    nleft = _rl_last_c_pos - _rl_screenwidth - rl_visible_prompt_length;
  else
    nleft = _rl_last_c_pos - _rl_screenwidth;

  if (nleft > 0)
    ret = 1 + nleft / _rl_screenwidth;
  else
    ret = 0;

  return ret;
}

#if defined (HANDLE_MULTIBYTE)
/* Calculate the number of screen columns occupied by STR from START to END.
   In the case of multibyte characters with stateful encoding, we have to
   scan from the beginning of the string to take the state into account. */
static int
_rl_col_width (str, start, end, flags)
     const char *str;
     int start, end, flags;
{
  wchar_t wc;
  mbstate_t ps;
  int tmp, point, width, max;

  if (end <= start)
    return 0;
  if (MB_CUR_MAX == 1 || rl_byte_oriented)
    /* this can happen in some cases where it's inconvenient to check */
    return (end - start);

  memset (&ps, 0, sizeof (mbstate_t));

  point = 0;
  max = end;

  /* Try to short-circuit common cases.  The adjustment to remove wrap_offset
     is done by the caller. */
  /* 1.  prompt string */
  if (flags && start == 0 && end == local_prompt_len && memcmp (str, local_prompt, local_prompt_len) == 0)
    return (prompt_physical_chars + wrap_offset);
  /* 2.  prompt string + line contents */
  else if (flags && start == 0 && local_prompt_len > 0 && end > local_prompt_len && local_prompt && memcmp (str, local_prompt, local_prompt_len) == 0)
    {
      tmp = prompt_physical_chars + wrap_offset;
      /* XXX - try to call ourselves recursively with non-prompt portion */
      tmp += _rl_col_width (str, local_prompt_len, end, flags);
      return (tmp);
    }

  while (point < start)
    {
      tmp = mbrlen (str + point, max, &ps);
      if (MB_INVALIDCH ((size_t)tmp))
        {
          /* In this case, the bytes are invalid or too short to compose a
             multibyte character, so we assume that the first byte represents
             a single character. */
          point++;
          max--;

          /* Clear the state of the byte sequence, because in this case the
             effect of mbstate is undefined. */
          memset (&ps, 0, sizeof (mbstate_t));
        }
      else if (MB_NULLWCH (tmp))
        break;          /* Found '\0' */
      else
        {
          point += tmp;
          max -= tmp;
        }
    }

  /* If START is not a byte that starts a character, then POINT will be
     greater than START.  In this case, assume that (POINT - START) gives
     a byte count that is the number of columns of difference. */
  width = point - start;

  while (point < end)
    {
      tmp = mbrtowc (&wc, str + point, max, &ps);
      if (MB_INVALIDCH ((size_t)tmp))
        {
          /* In this case, the bytes are invalid or too short to compose a
             multibyte character, so we assume that the first byte represents
             a single character. */
          point++;
          max--;

          /* and assume that the byte occupies a single column. */
          width++;

          /* Clear the state of the byte sequence, because in this case the
             effect of mbstate is undefined. */
          memset (&ps, 0, sizeof (mbstate_t));
        }
      else if (MB_NULLWCH (tmp))
        break;                  /* Found '\0' */
      else
        {
          point += tmp;
          max -= tmp;
          tmp = WCWIDTH(wc);
          width += (tmp >= 0) ? tmp : 1;
        }
    }

  width += point - end;

  return width;
}
#endif /* HANDLE_MULTIBYTE */